- --_.- .. .. _-- The Volume XIV On the Cover : Skywatchers will be poised to observe the heavenly Table of Number 1 stri ng of pearls kn own as comet Shoemaker-Levy 9 January/February 1994 thi s July when it crashes into Jupi te r's swirling atmo­ Contents sphere. This is an en largement of an image captured by the Hubble Space Tel escope (HSl) on July 1,1993, showing the reg ion of the brig htest nucleus of the comet, torn apart when it came too cl ose to Jupiter in 1992. This "bright nucleus " is actually a group of at least four separate pieces. The span of th is enti re Features image covers abou t 64,000 kilomete rs (40,000 miles). North is at the lower right. Image: H.A. Weaver and Bodies at the 16 Readers' T.E. Smith, Space Te lescope Science Institute, NASA 4 Brink Service Decades ago legendary planetary scientist The new mathematical field of chaos is Gerard P. Kuiper theorized that a band of difficult to penetrate, yet its somewhat comets orbited at the edge of our solar whimsical name and surprising predic­ From system. Telescopes of his time couldn't tions intrigue even the mathematically test this hypothesis, but now, working unsophisticated. Our featured book looks The with new equipment, astronomers have at chaos' applications to understanding discovered the first evidence that Kuiper our solar system. Editor was right. World Jupiter Watch: 17 Watch es, we have changed the 8 The Celestial Necklace It's a time of birth and death for NASA: Y design of The Planetary Breaks Its program to search for extraterrestrial Report; your eyes do not deceive This July, comet Shoemaker-Levy 9 will radio signals has been canceled by Congress, you. We have opened up space collide with Jupiter. The Planetary Society which at nearly the same time awarded between lines of type and unified is already planning events and activities to new starts to two spacecraft missions. the design of our regular depart­ bring this "once-in-a-thousand-lifetimes" Recovery from the loss of Mars Observer ments. happening to as many people as possible is under way, while NASA's space station The endeavor of planetary around the world. is reborn in a new partnership with Russia. exploration is, by its very nature, extremely challenging: To send 10 A Rover's Journey: 18 Nevvs and robots and, when we are very Linking Tvvo Worlds Revievvs daring, humans into hostile alien Our great rover adventure continues with Clark Chapman reviews a recent book environments requires a willing­ another chapter in the development of a about the Magellan mission (and an offer­ ness to undertake hard work. But, mobile robot designed to explore Mars. ing of our Readers' Service) from the per­ when new worlds are revealed We travel back to the challenging volcanic spective of a working planetary scientist. for the first time, the hard work terrain of Kamchatka, this time to test new is worth the cost. Each planet technologies- telepresence and virtual Society explored widens our understand­ reality-that may significantly advance 19 Nevvs ing of the universe around us. our exploratory abilities. We have more opportunities for you to It is our challenge, on the edito­ get involved with Society activities. rial staff of The Planetary Report, to make those discoveries acces­ 20 Questions and sible to all of our members. It is Departments Ansvvers a difficult task to, for example, One of the benefits of planetary explo­ make an arcane point of celestial 3 Members' ration is that it shows us other worlds to mechanics readily understand­ Dialogue which we can compare our own. For able. I know we don't always The staff here has been overwhelmed by example, is there an ozone layer on Mars? succeed. But, with your support, your response to our plans to put the name The answer to that question and a discus­ we keep trying. of every Planetary Society member, as of sion of the spokes in Saturn's rings fill With this redesign, we hope October 15, 1993, on Mars. Here we share this column. you will find it easier to "access" a sampling of letters with the entire mem­ the information contained in our bership. We also discuss the loss of Mars '. pages. As always, I ask you to let Observer, and the coming millennium. us know if we have succeeded. -Charlene M. Anderson

The Planetary Report (ISSN 0736-3680) is published bimonthly at the editorial offices of The Planetary Society. 65 North Catalina Avenue, Pasadena, CA 91 106, (818) 793-5100. It is available to members ofThe Planetary Society. Annual dues in the US or Canada are $25 US dollars or $30 Canadian. Dues outside the US or Canada are $35 (US). Printed in USA. Second-class postage pending at Pasadena, Californ ia, and at an additional mailing office. Postmaster: Send address changes to The Planetary Society, 65 North Catalina Avenue, Pasadena, CA 91106. Canada Post Agreement Number 87424. A Publication of Editor, CHARLENE M. ANDERSON Technical Editor, JAMES D. BURKE SOCIE TY Assistant Editor, DONNA ESCANDON STEVENS Copy Editor, GLORIA JOYCE THE-PL.A~T1RY Production Editor, MICHAEL HAGGERTY Art Director, BARBARA S. SMITH o -B- 0 Viewpoints expressed in columns or editorials are those of the authors and do not necessarily represent positions of The Planetary Society, .~ -e- ¢ its officers or advisors. © 1994 by The Planetary Society. o Board of Directors CARL SAGAN Presiden t Director, Laboratory for Planetary Studies, Members' CorneflUniversity BRU CE MURRAY Vice President Professor of Planetary Science, Dialogue California Institute of Technology LOUIS FRIEDMAN Executive Director NORMAN R. AU GUSTI NE Chairman and CEO, Martin Marietta Corporation JOHN E. BRYS ON Melnbers on Mars the Mars mission in 1994. pushed by people who really care Chairman and CEO, Southern California Edison I don't know if anyone else had I was part of the past, now I'll can do much more than befuddled JOSEPH RYAN this reaction, but I read Charlene be part of the future. Thank you, politicians. O'Melveny & Myers STEVEN SPIELBERG Anderson's article, "Awaiting the Planetary Society. -JEROME A. MUSILLO, director and producer Anaconda, Bayside, New York First Explorers: Society Members' -JOHN ALTIERI, Board of Advisors Names to Be Archived on Mars," Montana DIANE ACKERMAN through tears of joy. The COining poet and author BUZZ ALDRIN Born without the means for a Spacecraft's Milienni uln Apollo 11 astronaut RICHARD BERENDZEN college education and without the Tough Job As a member of the New Millen­ educator and astrophysicist physical constitution that would I'm writing in response to David nium Committee, I believe that I JACQUES BLAMONT Chief Scientist, Centre National allow space travel, I have had to Budda's letter in the November/ am not alone in thinking that The d'Etudes Spatiales, France content myself with the knowledge December 1993 issue of The Planetary Society is working on RAY BRADBURY poet and author that my tax dollars have ridden Planetary Report. While VCRs ideas that are critical to the future ARTHUR C. CLARKE into orbit with Mercury and may get "banged around" more of humanity. Furthermore, as we author CORNELIS DE JAGER Gemini, and to the Moon with than interplanetary spacecraft, are about to embark into the new Professor of Space Research, The Astronomical Institute at Utrecht, Apollo. To find out that my name they do not operate in the same millennium, our Society is emi­ the Ne therlands FRANK DR AKE will be on board the Mars landers conditions. Spacecraft have to nently qualified to help define a Professor of Astronomy and Astrophysics, when they arrive at Mars in 1995 endure temperatures well below powerful set of visions, plans and University of California, Santa Cruz LEE A. DUBRIDGE means more to me than anyone room temperature and are subject­ programs for our planet. former presidential science advisor JOHN GARDNER will ever know. ed to magnetic fields, solar winds I propose that our Society's founder, Common Cause Many thanks for the article and causing communication interfer­ directors, staff, advisors and MARC GARNEAU the good tidings it brought. ence, particles traveling at tens of 100,000 members together develop Canadian astronaut GEORG IY GOLITSYN -JERRY L. BOCKMaN, thousands of kilometers per hour, a document laying out one possi­ Institute of Atmospheric Physics, Russian Academy of Sciences Farmington, New Mexico and even unknown conditions. In ble road to a destination promising THEODORE M. HESBURGH President Emeritus, addition, spacecraft cannot be the possibility of adventure, pros­ University of Notre Dame I have been a member of the redesigned and "remarketed" with perity, harmony, knowledge and SHIRLEY M. HUFSTEDLER educator and jurist Society for a good many years. the relative ease, speed and low hope. Ultimately, the world com­ GARRY E. HUNT During that time I've celebrated cost that consumer products are munity will decide whether and space scientist, United Kingdom SERGEI KAPITSA many space exploration triumphs afforded. how to act upon these ideas. At the Institute for Physical Problems, and mourned many more space As for the public's image of the very least, this document should Russian Academy of SCiences GEN. DONALD J. KUTYNA (RET.) technology failures. I've felt per­ space program, I think it has less stimulate the development of other former Commander, US Space Command JOHN M. LOGSDON sonally humiliated by NASA. I've to do with project failures than ideas coming from other regions, Director, Space Policy Institute, been reduced to watching Star with the public's almost apathetic interests or biases. The free inter­ George Washington University HANS MARK Trek: The Next Generation for its attitude toward science. Many are change of ideas could form the The University of Texas at Austin JAMES MICHENER pitiful ability to comfort with its quick to call Mars Observer a fail­ basis for the agenda for the new author visions of the future, but I have ure, as if getting to Mars is a walk millennium. MARVIN MI NSKY Toshiba Professor of not sunk so low as to live in mem­ down the street. How many know I see an urgent need now for a Media Arts and SCiences, Massach usetts Institute of Technology ories of past space program glo­ how far away Mars is? Or even global, citizen-based, science­ PHILIP MO RRI SON Institute Professor, ries. Humans walking on the where Mars is? The unknown is grounded independent leadership Massachusetts Institute of Technology Moon is a painful thought, since too easy to criticize. to come forward. I think The Plan­ PAUL NEWMAN it's never been equaled. I couldn't -MIKE KERNA, Pittsburgh, etary Society is one of the best actor JUN NISHIMURA former Director General, even open the NovemberlDecember Pennsylvania qualified groups to begin that Institute of Space and 1993 issue of the Report at first­ process. Astronautical Science, Japan BERNARD M. OLIVER the cover said it all. But when I Take the Initiative -ABE GaMEL, Montreal, Chief, SETI Program, finally read it and saw that mem­ If the cause is to succeed, then we Quebec NASA/Ames Research Center SALLY RIDE Director, California Space Institute, bers' names would be going to must think of alternative means University of California, San Diego, . Mars on a microdot, I burst into with which to reach the goal. The Editor's Note: The New Millennium and former astronaut ROALD Z. SAGDEEV tears. If only as an inscription on a Society's effort to further space Committee is a group of individuals former Director, Institute for Space Research, microdot, I'm going to Mars. exploration is the finest example who have pledged $2,000 per year Russian Academy of Sciences HARRISON H. SCHMtn Thank you. of civilian power and initiative. So or have given donations of$20,000 form er US Senator, New Mexico, -VALERIE CASSES, maybe it is time to let NASA fade or more in support of The Planetary and Apollo 17 astronaut S. ROSS TAYLOR Johnstown, Pennsylvania away to be replaced by an organi­ Society's efforts to achieve its goals Professorial Fellow, Australian National UniverSity, Canberra zation supported by an endowment. for the next century. LEWIS THOMAS Chancellor, As an old Arctic explorer, I'm The National Endowment for the Memorial Sloan Kettering Cancer Center thrilled by the fact that my name Arts is a fairly successful group Please send your letters to Members' JAMES VAN ALLEN will be with those of other mem­ that has great lobbying power Dialogue, The Planetary SOCiety, 65 North Professor of Physics, University of Iowa bers of The Planetary Society on and influence. The private sector Catalina Avenue, Pasadena, CA 91106. 3 he solar system just got a little bit bigger. The Big Break: Finding 199i! IlB1 The discovery of two objects beyond the Astronomers David Jewitt of the University of Hawaii and orbit of Pluto has extended the heliocentric Jane Luu of Stanford University had been searching for five range of the planetary system (the distance years for objects in distant orbits around the Sun. Their ef­ outward from the Sun) and provided tantalizing hints that forts were rewarded on the night of August 30, 1992, during a large swarm of comets may exist in similarly distant an observing run on Mauna Kea, when they found a slow­ orbits. This discovery has important implications for moving, 23rd-magnitude object in Pisces. (The faintest star understanding both the origin of the solar system and the you can see without a telescope on a clear night far from 4 origin of the short-period comets. city lights is 6th magnitude; 23rd magnitude is about 6 mil- by Paul Wei!i!iman l

the dark surfaces of cometary nuclei. Comets are dirty snow­ balls in space, icy conglomerates of primordial ices, dust and organic molecules that accreted in the distant reaches of the solar nebula. A large carbon content gives comets their very low reflectivity, and the organics often give them a reddish tint. Jewitt and Luu' s observations showed that 1992 QB J was reddish in color. QB J was so far from the Sun, and moving so slowly, that it would take many months before an accurate orbit could be determined. Astronomers speculated that the object might be a giant long-period comet-one whose orbital period is greater than 200 years-on its way in from the Oort cloud, the distant spherical cloud of some 1012 to 1013 comets in orbits 3,000 to 100,000 AU from the Sun. Or it might be a comet traveling in a low-inclination, low-eccentricity orbit beyond the known planets, as had been suggested by astron­ omer Gerard Kuiper years before. (A low-inclination orbit is one in approximately the same plane as Earth and the other planets-the ecliptic plane-as they move around the Sun; a low-eccentricity orbit is close to circular in shape.) By December, there were finally enough observations for a preliminary orbit determination. Brian Marsden of the Smithsonian Astrophysical Observatory found that 1992 QB J revolved around the Sun once every 290 years at an average distance of 44 AU, in a near-circular orbit inclined only 2.2 degrees to the ecliptic plane. The large distance, low incli­ nation and low eccentricity matched Kuiper's hypothesis.

Kuiper's Hypothesis: An Idea Takes Hold In a classic paper published in 1951, Gerard Kuiper of the University of Chicago speculated on the nature of comets and where they might have formed. Kuiper recognized that the icy nature of comets, pointed out by Fred Whipple of Har­ vard University the year before, required that they be formed in the outer reaches of the solar nebula, where temperatures were low enough to allow volatile ices to condense. Kuiper suggested that, as the giant planets began to grow in the niidst of this swarm of icy bodies, some of the comets would have been gravitationally scattered to very distant orbits in the Oort cloud. But beyond Pluto, where no planet had formed, there was nothing big enough to scatter the comets. Orbit periods are so long beyond Pluto, and the density of material so low, that there simply was not enough time to grow a planet within the age of the solar system. Kuiper predicted that there would be a huge swarm or belt of comets in low-inclination, near-circular orbits beyond Pluto. lion times fainter.) Observations over the next few days Kuiper's idea was taken up by other astronomers. In 1964 showed that the object had to be very far from the Sun, about Fred Whipple suggested that a disk of comets beyond Pluto 41 astronomical units (an astronomical unit, or AU, is the av­ might perturb the orbits of the outer planets and comets. By erage distance from Earth to the Sun and is equal to about studying the orbits of short-period comets having large aph­ 150 million kilometers or 93 million miles). For comparison, elion distances (an orbiting object's maximum distance from Pluto's average distance from the Sun is just over 39 AU. the Sun)-comet Halley is an example-Whipple and col­ At a distance of 41 AU, the object, officially designated leagues showed that the disk could not total more than about 1992 QBJ' would be about 200 to 250 kilometers (125 to 155 0.8 Earth masses of material if it was located at 40 AU, or 1.3 miles) in diameter if it reflects sunlight in a similar fashion to Earth masses if it was at 50 AU. 5 thought that high-inclination comets might The inner edge of be preferentially destroyed during their evo­ the Kuiper belt lution to short-period orbits, leaving only (darker shaded area) begins at the low-inclination comets to be observed. about 42 astro­ Because planetary perturbations are larger nomical units (or AU; 1 AU is the for the low-inclination comets (they have a average distance higher probability of encountering one of from Earth to the the planets in the ecliptic plane), they evolve Sun, equal to about 150 million to short-period orbits faster than their high­ kilometers or 93 inclination cousins. This shorter evolution million miles). The outer edge is un­ time may be the key to their survival, while known, but scien­ the high-inclination comets die out or disrupt tists suspect that before they can get to short-period orbits. it is at least 100 AU. 1992 QB1 and Some short-period comets, such as Halley 1993 FW orbit the and Swift-Tuttle (the parent of the Perseid Sun just at the meteor shower, which occurs in August belt's inner edge and the planetary every year), are in high-inclination orbits. system's outer Almost all of the high-inclination short­ boundary. period comets also have relatively longer Chart courtesy of Kevin Yau, JPLINASA; orbital periods, between 20 and 200 years. drawn by B.S. Smith Dynamicists speculated that these comets came from the Oort cloud, whereas the low­ inclination comets having periods of less than 20 years came from the Kuiper belt. Thus, the short-period comets may actually come from two entirely different sources.

As astronomers recognized that Pluto was not a very big [:lues in a Disk planet and thus could not perturb the orbits of comets, they Other evidence for disks of comets like the Kuiper belt began to regard Neptune as the real outer boundary of the around other stars has come from studies of star formation. planetary system. In 1980 Julio Fernandez of the University Astronomers have begun to image disks of material in orbit of Uruguay proposed that a comet belt beyond Neptune around protostars, young planetary systems in the process could be the source of the short-period comets. Unlike the of formation. (If there are planets forming in these disks, long-period comets, whose orbits are randomly oriented on they are too small or too far away to be seen with Earth­ the sky, most of the short-period comets are in low-inclina­ based telescopes.) These disks are typically several hundred tion orbits like those of the planets. The best way to get such astronomical units in diameter, much larger than our own an inclination distribution is for the comets to come from a planetary system. Could the solar system's original disk of source with that distribution. Also, because the Kuiper belt is material have extended to similar distances? much closer to the planetary system than is the distant Oort Data from the Infrared Astronomical Satellite (IRAS) cloud, it would be easier for the planets to perturb the orbits suggested that such disks are fairly common. In 1983 IRAS of comets in the Kuiper belt down to short-period orbits, discovered thermal (heat) radiation from dust clouds around where we can observe them. Fernandez calculated that the many main-sequence stars (regular stars like the Sun) in the Kuiper belt would be 300 times more efficient than the Oort solar neighborhood. Some of the IRAS data indicated that cloud in producing short-period comets. the clouds of dust might be flattened disks. The largest of these was around a star called Beta Pictoris. The Dynamil:ists Debate Astronomers Brad Smith of the University of Arizona The key paper came in 1988 when Martin Duncan and and Richard Terrile of the Jet Propulsion Laboratory photo­ colleagues at the University of Toronto showed that the graphed the Beta Pictoris cloud by using a coronagraphic Oort cloud was probably not the source of most of the short­ technique, in which the light of the central star is masked out. period comets. Duncan and his colleagues ran computer­ (A coronagraph is normally used to photograph the Sun's based simulations of cometary dynamics. They found that, corona, or outer atmosphere, even when there is no solar when Oort cloud comets were captured to short-period orbits eclipse occurring.) The image showed a thin disk of material after repeated perturbations by the planets-that is, when seen edge on, extending up to 800 AU on either side of the their periods were reduced to less than 200 years-the star. Also, the IRAS data showed that the disk did not extend comets still tended to have very high orbital inclinations. all the way to the central star but had a hole in the middle But when the comets came from a belt beyond Neptune­ extending out to about 20 to 30 AU. This area may have the Kuiper belt-they kept their low inclinations and looked already been swept clean by planets forming around Beta just like the observed short-period comets. Duncan and his Pictoris. Estimates of the total mass of the Beta Pictoris colleagues estimated that there would have to be between disk range between 15 and 300 Earth masses of material. 108 and 1010 comets in the Kuiper belt for it to account for In fact, our own planetary system could be surrounded by the observed number of short-period comets. a disk like that around Beta Pictoris and we would not know Cometary dynamicists excitedly debated these results. it. IRAS observations in the ecliptic plane are dominated by 6 Some, such as Mark Bailey of the University of Liverpool, radiation from the zodiacal cloud, the vast interplanetary cloud of dust from comets and asteroids. Because IRAS was most sensitive to warm dust, cold dust hundreds of astronomical units from the Sun would be very difficult for it to detect. Future infrared satellites with better sensi­ tivity and resolution than IRAS will be required to settle the question.

l\IE!p"tunE! "thE! PE!r"turbE!r Just about the same time that 1992 QB t was discovered, Harold Levison of Southwest Research Institute and Martin Duncan were studying the stability of orbits in the Kuiper belt. Pluto is too small to significantly perturb the comets, unless they come especially close to it, a far too rare event. Thus, Neptune was the planet that was really controlling the comets' destiny. Levison and Duncan showed that even comets relatively distant from Neptune could be per­ turbed out of the Kuiper belt in less than a billion years. But beyond an average distance of about 42 AU, the orbits appeared to be stable-and 1992 QBt 's average distance was 44 AU. Thus, it had probably been in a similar orbit The slow motion of 1992 QB, (circled) can be discerned relative to distant, since the formation of the solar system. fixed galaxies. These discovery images were captured the night of August 30, 1992, by David Jewitt and Jane Luu using the University of Hawaii's 2.2-meter telescope. The elongated object that moves from lower right in I:ompany ~or 199i! OBI the top image to upper left in the bottom image is the trail of a main-belt One object beyond Pluto was a tantalizing piece of evi­ asteroid that was moving during each exposure. dence. But could it be a fluke, just one of a few bodies out Images courtesy of David Jewitt, University of Hawaii there? Jewitt and Luu pointed out that they had searched less than 1 square degree of sky to find 1992 QB,. Either objects like QB t were fairly common, or the observers had been extremely lucky to find this one object. Jewitt and Luu will be dynamically ejected from the solar system by a close predicted that there should be about 10,000 objects similar to encounter with one of the giant planets. 1992 QB t, and many more that were smaller, in the Kuiper belt. Unlocking "thE! !iE!crE!"t!i in While astronomers tried to comprehend the meaning of the Primordial icE! and DU!i"t new discovery, Jewitt and Luu were at the telescope searching All the discoveries cited here have gone a long way in pro­ for more Kuiper belt objects. In a surprisingly short time, in viding evidence for a cometary swarm beyond Neptune. March 1993, their efforts were rewarded a second time with That swarm, which may extend out to several hundred as­ the discovery of 1993 FW. Once again, it quickly become ob­ tronomical units from the Sun and contain many tens of vious that the object was very far from the Sun. After several Earth masses of comets, is a remnant population of primor­ months, a preliminary orbit for 1993 FW showed it to be at dial icy bodies from the solar nebula. They preserve the an average distance just under 44 AU, with a low eccentricity cosmochemical record of the original interstellar gas cloud and an inclination of only 7.7 degrees-again, a fairly low out of which the solar system formed. Some of those bodies value. Interestingly, 1993 FW is about the same size as 1992 find their way to short-period comet orbits where we can QB,. More observations will be required before the orbit of observe them. And if we could go out and study one of 1993 FW is known precisely, but for the moment it appears those objects at close range, or even bring a sample back to' to be the second member of the Kuiper belt to be discovered. Earth for detailed analysis, we might unlock some of the Jewitt and Luu were not done yet. In September 1993 they secrets of how our solar system formed. found two objects, 1993 RO and 1993 RP, at about 32 and The European Space Agency has been working on a 35 AU from the Sun, respectively. Soon, they had company. mission called Rosetta, to be launched in 2003, which will Iwan Williams (Queen Mary and Westfield College, London) rendezvous with a short-period comet and perform onboard and colleagues observing from La Palma in the Canary Is­ analyses of cometary materials. Rosetta may carry a package lands found two more objects, 1993 SB and 1993 SC, at 33 of instruments, perhaps provided by NASA, that will land on and 34 AU, respectively. The four objects range from 22nd to the comet to make direct measurements of the composition 24th magnitude; because they are closer to the Sun than 1992 and physical properties of the nucleus. 'QB, and 1993 FW, which are both 23rd magnitude, they are Like its namesake, Rosetta will unlock the secrets of our probably of comparable size or somewhat smaller. past. Gerard Kuiper would have been pleased to see where Also, because all four objects are in orbits much closer to his speculating about comets has led. Neptune's orbit, their orbits may not be stable over the age of the solar system. These four objects may have been perturbed Paul Weissman is a planetary scientist at the Jet Propulsion out of the Kuiper belt and are now beginning the evolution Laboratory, specializing in studies of the physics and dynam­ toward short-period orbits. However, there is only about a 10 ics of comets, and their interactions with the planetary system. to 15 percent probability that they will make it all the way to He is also a member of the Near Infrared Mapping Spectrom- short-period status. The more likely eventuality is that they eter team on the Galileo mission to Jupiter. 7 t could be a once-in-a-thousand­ tronomer David Levy. The team imme­ termined that in July of 1992 the unlucky lifetimes event. It could blow a hole diately notified a colleague at the Uni­ comet passed too close to the giant planet, in Jupiter's atmosphere, changing versity of Arizona's Lunar and Planetary coming within its Roche limit. (Named the planet's face for millennia. It could Institute, James Scotti, who uses the for 19th-century French mathematician be the biggest celestial show in human Space watch telescope at Kitt Peak E.A. Roche, this is the distance from the history. Or, for those of us from a small Observatory. With this larger telescope, planet within which a small, solid object blue planet hundreds of millions of kilo­ equipped with sensitive charge-coupled will be torn to pieces by tidal forces from meters away, it could be a dud. devices (CCDs), he was able to deter­ the planet's gravity.) This close encounter No one knows for certain what will mine that the object was actually a string ripped the comet into at least 20 frag­ happen in July when comet Shoemaker­ of comet fragments. (See page 28 of the ments, which astronomers now refer to Levy 9 collides with the planet Jupiter. July/August 1993 Planetary Report.) as a "necklace" or a "string of pearls." We do know that it will be an unprece­ Excited by the discovery, astronomers Moving forward in time, the analysts dented event. Whatever happens, The around the world trained their telescopes made the most exciting discovery of all: Planetary Society will be working to on the object. With a series of positions On or about July 21,1994, comet Shoe­ make sure that the greatest possible recorded, orbital analysts were able to plot maker-Levy 9 is doomed to collide with number of people around the world its orbit and predict the path of the comet Jupiter. share the excitement of this extraordi­ both backward and forward in time. We don't yet know what we will see nary occurrence. They learned that the comet is actual­ when the comet fragments encounter the Here's a little background on comet ly in orbit about Jupiter, not about the largest planet in our solar system. Early Shoemaker-Levy 9. On March 25, 1993, Sun, as are most of the comets we know estimates had put the size of the biggest during an observing run at Palomar of. This intriguing fmding indicates that fragment at about 10 kilometers (6 miles) Mountain Observatory in California, comet Shoemaker-Levy 9 may have in diameter-the size of the object that Carolyn Shoemaker noticed what ap­ begun life as a very small, volatile-rich struck Earth 65 million years ago and is peared to be a "squashed comet" on a satellite of Jupiter, as a so-called Trojan believed to have wiped out the dinosaurs. photograph she had exposed while asteroid locked into Jupiter's orbit or as But James Scotti and colleague H. Jay working with her husband, United States a comet captured by the planet's great Melosh now estimate that the comet Geological Survey planetary scientist gravitational attraction. was less than about 2.5 kilometers (1.5 B Eugene Shoemaker, and amateur as- Going back in time, the analysts de- miles) in diameter before its breakup, Left: This image was taken with the University of Arizona's Spacewatch camera. Although not discernible here, the bright "streak" near the center con­ tains many individual nuclei with their comae and tails. Light scattered from fine dust particles extends for large distances beyond the region of the streak. Image: Jim Scotti,

Left: These composite images of comet Shoemaker-Levy 9 were captured over five months in 1993. David Jewitt and Jane Luu obtained them using a charge-coupled-device camera with the University of Hawaii's 2.2-meter telescope atop Mauna Kea. The images have been cor­ rected for the changing distance to the comet and show the real expansion of the "string of pearls" over time. A total of 21 Above: Here's how the comet looked components are visible in the on March 28, 1993, from the Steward digital images; some are lost in Observatory's 2.3-meter telescope at the photographic reproduction the University of Arizona. This close­ here. Images courtesy of David Jewill, up of the nuclear train shows about 12 University of Hawaii individual nuclei embedded within the coma. The bright spot at the left is an Left: Like a series of multimegaton bombs, comet Shoemaker-Levy 9 could unnamed star. Image: Wieslaw Wisniewski, University of Arizona sow a row of mushroom clouds on the face of Jupiter. Painting: Michael Carroll

which has considerably reduced the time, we have begun to get ready. and to celebrate another histOlic event estimates of the energy that will be Under the title of "Jupiter Watch," that occun'ed 25 years almost to the day released on impact with Jupiter. we are planning several different types before the Jupiter impacts: the Apollo 11 . Still, it could be an impressive event. of activities: landing on the Moon. The fragments will hit Jupiter's atmo­ • Setting up a worldwide network of These projects will be just the begin­ sphere at about 216,000 kilometers observers, to ensure that some telescope ning of the Society's Jupiter Watch. The (135,000 miles) per hour and vaporize, on Earth is always pointing toward Galileo spacecraft is now on its way to possibly causing the eruption of plumes Jupiter during the string of impacts. the jovian system, and it will arrive 17 of debris from its deep, hidden recesses. • Establishing liaisons between months after the comet fragments. The Unfortunately, this will be hidden professional and amateur astronomers spacecraft should be able to see the im­ from observers on Earth. The comet's so that the amateurs can make valid pacts directly and detect the effects of trajectory will carry it into the far side contributions to understancling the im­ the explosions through several of its of the planet. From Earth, we will be pact events. instruments, then relay the data back to able to see the effects of the collisions • Publishing Jupiter Watch observers' Earth. Between the impact date and only indirectly-for example, from guides so that viewers can get the most Galileo's arrival at Jupiter, we will light reflected off Jupiter's large out of this rare opportunity. continue to build support for and raise Galilean satellites. • Providing video links from tele­ awareness of planetary exploration with The string of explosions may disrupt scopes to auditoriums, classrooms and an ongoing series of special events. Jupiter's banded atmosphere. Although television stations so that even those We have set ambitious goals for the impacts will occur on the far side, without access to a telescope can watch Jupiter Watch, and we will need your the affected regions will swing into view the collisions as they happen. help to achieve them. If you are interest­ in a few hours due to the planet's rapid • Organizing Jupiter Watch parties ed in helping with any of our activities, rotation, and we may be able to see the around the world to encourage people please contact us by writing: Jupiter atmospheric effects. We may even wit­ to go outside, look up into the sky and Watch, The Planetary Society, 65 North ness the birth of a new Great Red Spot. see something that will probably never Catalina Avenue, Pasadena, CA 91106. Scientists will continue to refine their occur again during their lifetimes. calculations to predict what observers • Holding a gala party in Washington, Charlene M. Anderson is Director of can expect to see next July. In the mean- DC, to honor the comet's discoverers- Publications of The Planetary Society. 9 ~--,.------

. -

RIGHT: ON THIS

MORNING THE

CLOUDS PARTED

BRIEFLY TO RE-

VEAL THE TOP

OF TObBACHIK the airliner's captain announced our final approach into Moscow's interna­ tional airport on the morning of August 19, 1993, I pulled out a fax I had VOLCANO ON THE slipped into my notebook some 16 hours earlier as I was leaving the Space KAMCHATKA Dynamics Laboratory at Utah State University for the Salt Lake City airport. PENINSULA.THE Ai It was from Charlene Anderson, editor of The Planetary Report. She informed me RAINCOAT-CLAD that part of my job on this trip to Russia was to write an article for the magazine. The

MARS ROVER SITS fax was filled with admonitions to try to take good photographs (no backs of heads,

ON THE VOLCANO'S no fingers in front of the lens, and so on). It ended with these words: "Be personal. You're sharing the excitement of these tests with the members who paid your way." FLANKS, READY Well, here goes. What happened to me in Russia certainly was an adventure, and FOR A DAY OF I'd like to think that this story will bring you a taste of what it was like to be part of TESTS. the Russian team, and to watch as the rover began to move in response to a con­

10 PHOTO: GEORGE POWELL troller working a computer keyboard thousands of miles away. ~---~--... -.- ...- .. ------

· had been sent to Russia as The Planetary Society's rep~ to cold showers. It seems that Petropavlovsk has a central­ resentative at tests of the Mars Rover, a critical part of ized hot water system to supply the entire city, and there t the Russian Mars '96 mission. The rover will provide a was no fuel for the plant. mobile robotic platform for studies of the martian terrain. The next day, at 8:00 a.m. sharp, we all met in the hotel In 1992, the Society sponsored an expedition to Death lobby, ready to begin a lO-hour drive to Kosyrevsk, the Valley, California, to test the rover's mobility and naviga­ small town near our first test site. We were told that one tional capabilities and to check out the overall system. (See of the trucks had a water pump problem and there would the NovemberlDecember 1992 and January/February 1993 be a short delay. At 6:30 p.m., we finally loaded up our issues of The Planetary Report.) For these follow-up tests, gear and set out. We traveled through the night, stopping we were going to the forbidding volcanic terrain of the only for rest, vodka and a midnight bonfire. Kamchatka Peninsula, and we would concentrate more on EB:l navigation and on testing a French stereo video system. The Russians have a very impressive test facility at We were also going to conduct a major experiment in Kosyrevsk. The main house has many rooms, each with telepresence: A team of scientists and engineers in Califor­ two or three beds. There is one bathroom with running nia would attempt to operate the rover through a satellite water and a shower. A wood-fueled water heater supplies telephone link. We wanted to investigate whether the de­ both the bathroom and a kitchen. There are three other veloping computer technologies of telepresence and virtual small houses for sleeping. reality could be used to explore Mars. The main kitchen is in a separate building about 40 Operating the rover from California would be a good yards from the main house. The Russians had hired a cook simulation of the planned method of operation of the vehicle from the area to prepare three meals a day for us. We had on Mars, although it would lack the Earth- Mars communi­ fresh salmon, piles of vegetables and wonderful Russian cations time delay of about 20 minutes. The operators in potatoes. Though I did have some problems with the fish­ California would not know the test site beforehand; they head soup, I hadn't eaten so well in a long time. would have to gather data strictly from instruments on the On our first day in Kosyrevsk, we assembled the rover rover. This scenario would provide the first realistic test of chassis and fixed some minor problems with one of the the remote control of the Russian Mars Rover. wheels. We worked into the evening so that we would be & prepared for our first test with the US, scheduled for 9:30 My main responsibility on the Kamchatka expedition was to a.m. the next day. Fortunately, this test would be held near supply the communications link between the United States the house in Kosyrevsk. and Russia. Thus, I was carrying a rented $45,000 Inmarsat mobile communications ground station in an 80-pound metal We were only a few minutes late in beginning the test, suitcase. I was also lugging a smaller metal suitcase, weigh­ and everything went well. The team in the US was able ing only 70 pounds, that held a laptop computer and other to direct the rover, giving it simple commands, such as test equipment. I had one piece of personal luggage. forward, right, left. More important, they were able to take This was my fIrst trip to Russia, and I was relieved to fInd video images of the rover's surroundings. There were a my good friend Katya Linkina waiting for me at the airport. few miscommunications, but by the end of the one-hour I'd met Katya at Planetary Society headquarters just before test everything was running smoothly. the Death Valley expedition, and this year she was in charge After lunch we headed out to find a site where we could of organizing the tests in Kamchatka. She's a scientist at the test the rover over rough terrain. One of our trucks had Russian Institute for Space Research, which is known by its returned to Petropavlovsk, so all 13 of us, the rover, the Russian initials as IKI. It is one of three centers working on power generator and all the other equipment were stuffed the Mars '96 mission; the other two are the Babakin Center into one truck. Getting to know the other team members in Moscow, responsible for building the spacecraft, and the was now very easy. Mobile Vehicle Engineering Institute (VNIITransmash), After a 30-minute drive, we stopped in what looked like a which designs the Russian rovers, in St. Petersburg. nearly dry 11verbed, lined not with white sand but with black EB:l ash that had been washed down from the Tolbachik volcano, I spent four days with the Russian team members-lO scien­ 50 kilometers (30 miles) away from us. We found a good test tists and engineers from IKI and VNIITransmash-checking site, set up the rover and took a few stereo images. I planned out the equipment, making sure that the various components to send these images to the US in the morning so team mem­ (the Russian rover, the French cameras and the American bers there could use them to produce the three-dimensional communications link) all worked together. Then we packed images needed for the virtual reality environment. up the equipment and began our journey to Kamchatka. EB:l It was a nine-hour, nonstop flight to Petropavlovsk-Kam­ The following morning, I was the first person up. It was chatskii, a city of about 300,000 people on the Kamchatka 6:00 a.m. and I had to send the stereo images to the US Peninsula. The city had previously been off-limits to foreign­ before we moved out to the test site. As I set up the satellite ers because it was the location of an extremely secret Soviet link, I sighed in relief, for it was the first clear day we had military base. As we landed, I got my first close-up look at a seen in Kamchatka. But my optimism was short-lived. MiG fighter, parked on the tarmac. For the next three hours, I tried to establish a satellite mo­ At the hotel, I rendezvoused with two other Americans, dem link with the US, and I couldn't get anything to work. whose participation in the tests had been suggested and ar­ I finally had to quit trying so we could leave for the test site. ranged for by The Planetary Society: Michael Sims from We arrived late and had some problems with the equipment. NASA Ames Research Center and Carl Ruoff from the Jet Editor's note: Back in balmy Southern California, the Propulsion Laboratory. They told me that I'd better get used US portion of the team had gathered in an air-conditioned 11 ------

Above: The rover's camera "eyes" are on top, so the Russians had to make a visor to protect its vision, and a raincoat to cover the control and navigation equipment. Photo: George Powell

Left: The team had to create obstacles for the rover in a new test area after a storm flooded the dry riverbed (photo above) they'd planned on using.

Right: The Kamchatka team waits patiently as the group in Huntington Beach, California, controls the rover. Photos: Carl Ruoff

facility in Huntington Beach owned by the McDonnell watching to see how we would do. We finally found, and Douglas Corporation. A "Mac Dac" team, led by John solved, the problem-it was an obscure software setting on Garvey, was working with us and with NASA Ames to test the US side of the link. We managed to transmit a few im­ telepresence as a way to navigate and control the rover. ages before the rover was scheduled to begin other testing. This was our first official test day, and we had invited Then it began to rain. We packed up all the gear and drove high-ranking managers, engineers and scientists from back to Kosyrevsk. around the world to witness the tests. While George was ·r struggling in frigid Kamchatka with the equipment, we It rained through the night, and I woke up several times, were drinking cold sodas, eating chocolate chip cookies wondering ifit was ever going to stop. Finally, it let up at and wondering where our wandering engineer could be. daybreak. We were all a little quieter at breakfast, wonder­ We were running about an hour late when I made the ing if the day would be a repeat of the day before. first communications link with the US. It was only a partial When we got to the test site, we found that our broad link and they were receiving garbled data. To make things riverbed had been engulfed by a raging torrent. We had to 12 worse, I knew that people from around the world were find another site. We managed to find a still-dry streambed, Above: This was the camp on Tolbachik. The building on the left was the kitchen and dining hal/; on the right were the sleeping quarters. The scraps of firewood littering the ground explain how the team cooked and kept warm. Photo: Carl Ruoff

Above: As the team worked with the rover, George struggled . (successful/y) to overcome a software problem that was garbling . communications between him and the group at M9Donnel/ Douglas. Photo: Carl Ruoff

but it was mostly uninteresting sand and ash. We had to Once the link was established, the computer in Hunting­ gather up boulders to construct a worthy test bed. ton Beach was able to talk to my laptop in Kamchatka. We were about an hour behind schedule when I made The laptop simulated the flight computer on the rover. The my first contact with the group in California. They were plan was for the US team to issue commands to the laptop, very happy to hear my voice. and it in tum would control the wheel movements, acquire I hooked up my laptop computer to the Inmarsat system. images from the cameras and take measurements of the The computer modem connects to a small control box on rover's position. the Inmarsat terminal. The box has many function keys and On this day the modem link worked perfectly, and I a lO-key pad. could see our months of preparations paying off. Viacheslav The function keys allow the user to scroll through menus "Slava" Linkin, chief scientist on the project, was in Cali­ to select such things as longitude and latitude, satellite and fornia supervising the test, along with Planetary Society ground station. The terminal, in tum, tells the operator where Executive Director Louis Friedman. The team there studied to point the parabolic antenna. Then the user can make either the images returned by the rover, analyzed the terrain and a voice call or a modem call. All in all, it is quite simple. decided how to move the rover. When the course was laid 13 ------

out, Greg Loboda, a McDonnell Douglas engineer sitting a Ping-Pong room and an outhouse. Windblown ash had at a computer terminal in Huntington Beach, executed the covered up the lower doors, and we had to shovel it away command. to get into the buildings. Over in Kamchatka, we sat and watched the rover move Weather on the volcano was very erratic, with wind and forward, turn and avoid obstacles. We were not in direct rain coming and going several times a day. With this in communication with the US at this time, and we were im­ mind, we outfitted the rover with its own plastic raincoat. pressed as we watched the rover navigate the terrain. We One of the Russians made it a hat to protect the cameras. could see how the US operators were feeling their way The test site was about 150 yards from the camp. It was around the boulders. It's too bad I won't be able to watch filled with obstacles that the rover could not overcome, and the rover explore Mars from a similar vantage point! there were only two possible paths around them. The site The tests went on for about two hours, and then I had was much more treacherous than the Viking landing sites to break the computer link so that the rover could move on Mars, and the next day's test would be the most difficult on to other tests scheduled by the Russian engineers. we had yet attempted. L'.IEI!I That night we lay swathed in mummy bags on our plank On August 31, we began our move out onto the flanks of beds, and we listened to the wind howl. Tolbachik volcano for more tests. The main road had been L'.IEI!I washed out in the rainstorm. We had hoped to travel to our The morning broke picture-perfect. We could actually see camp by helicopter, but couldn't get one. We ended up tak­ the top of Tolbachik. After breakfast we set up for the tests. ing the long way round, a four-hour ride. The entire team, I called the US half an hour before the telepresence tests all the technical equipment, sleeping bags, pots and pans, were scheduled to begin and told them that we'd made it to and food for three days were piled into one truck. It was the volcano and things were going well. Greg told me that all we could do to keep from being buried alive as the truck the room at McDonnell Douglas was packed with people, lumbered across the landscape. including members of the press. That worried me a bit be­ Rain poured down most of the way, but we finally made cause the test area was much more difficult than anything it to the volcano. In every direction we looked, there were we'd attempted so far. cinder cones. Four kilometers away were two cinder cones Editor's note: George was right to worry: CNN was created in 1975. We visited them on another day and could taping our end of the telepresence test as it happened. still feel the heat and smell the sulfur. Within afew hours his success-or failure-would be The camp consisted of one large, two-storied structure broadcast around the world. used for sleeping, a small separate kitchen and dining hall, The first command the US team sent to the rover was

he term virtual reality is used the three-dimensional environment. vittual reality techniques to see not only to describe highly interactive, Telepresence refers to an application from the United States to Kamchatka three-dimensional computer of virtual reality principles using real but also from Earth to Mars. We may graphics systems that give users the images instead of computer-generated soon have missions to Mars that are illusion of being immersed in a simu­ graphics. Telepresence projects the controlled-virtually-through the lated environment. This simulated en­ human sensory apparatus into a remote vital link of telepresence. vironment is variously referred to as a location. The tests George Powell de­ At The Planetary Society, we are virtual environment or a virtual world. sClibes here use telepresence technology. excited by the possibilities these tech­ Simulators used in training airplane The stereo cameras on the rover cap­ nologies offer. We are working with pilots and space shuttle astronauts em­ tured scenes of Kamchatka that were our partners in the rover project on the ploy virtual reality to make trainees then transmitted to distant Huntington idea of mobile virtual reality stations feel as if they are actually airborne. Beach, California, and displayed for that may one day give people around Users can enter many of the newer the viewers. the world the experience of driving a virtual environments by means of Both virtual reality and telepresence rover across another planet. We can systems that require goggles having a will probably playa large role in future envision schoolchildren everywhere small display screen for each eye (to planetary exploration. NASA has been using their personal computers to link simulate three-dimensional effects) developing a virtual environment sim­ up with a spacecraft on Mars. and a glove equipped with sensors that ulator that uses data from flybys like The confluence of computers, detect the user's movements and trans­ Voyager's to let the user "fly" over a robotics and the coming "information late them into the person's motion planet's surface. Scientists and students superhighway" will change the way through the virtual world. For instance, may eventually be able to work with we conduct planetary exploration. As to move forward in a virtual environ­ actual data and carry out experiments yet we can only imagine this future, ment, users simply point forward. The on a remote planet without ever leav­ but The Planetary Society is working computer then updates the screens' dis­ ing their offices and classrooms. In the hard to help shape it. 14 plays to simulate movement through future, explorers may be able to use - Charlene M. Anderson r--~--~------

a 'request for stereo video images. As the images were being relayed over the satellite, which took about 10 minutes, clouds began to roll in over the site. Within those 10 min­ utes, visibility dropped to 20 meters (about 65 feet). We watched as the rover moved forward 1 meter and started to take another set of images for the US team. Then it began to rain. The laptop computer was sitting on a portable table, and we covered it with a canvas tarp to keep it dry. The rover's raincoat seemed to be working pretty well. The rover turned right and started taking another image, and the rain became intense. I looked over to the satellite ground station and water was pouring off it like a waterfall. I wondered how long it would be until something shorted out. The US team was navigating past the obstacles extremely well. As the weather got worse, I was amazed that all elements of the rover system continued to operate. There were only 2S meters (about 80 feet) of cable be­ tween the cameras on the rover and the laptop computer linking it to the US. The rover was negotiating the terrain The Kamchatka expedition team. Back row: Igor Blokchintzev (I), Alexei Gasperovich (I), more quickly than we had anticipated, and we realized that Carl Ruoff (J), George Powell (U), Valeri Gromov (V), Vladimir Nosik (V) and Alexander Popov (V). Middle row: Leonid Kasperovich (I), Konstantin Be/ovsov (I), Michael Sims (N) the cable was not going to be long enough. and Alexander Pomin (V). Front row: Marina Kolesnik (I), Katya Linkina (I) and Nikolai So, someone had the bright idea that we could pick up Kuznetsov (V). Image: Mars Rover KEY-I: Russian Institute for Space Research; J: Jet Propulsion the table the laptop was on and move it closer to the rover. Laboratory; U: Utah State University; V: Mobile Vehicle Engineering Institute; N: NASA Ames Research Center. With luck we could do it without disconnecting the power or disrupting the communications link. The US people wouldn't even know we'd moved the table, right? We picked up the table and water began to splash off the cold, wet and huddled together in front of the rover's canvas tarp in big waves. We had actually managed to move camera. (See photo, above.) They had done a great job the table close to the rover and set it down when someone and, over the computer link, we thanked them. bumped the power cord, and the link went down. rmm Within a few minutes we were able to reestablish the Our last test was finished, and we realized that the expedition link. The US team resumed command of the rover and had been a complete success. The US side of the team had operated it for another hour. controlled the rover through teleoperation, under conditions Editor's note: Back in California, we were having a closely simulating a real Mars mission. The remote operators great time. Slava Linkin and the Planetary Society-Mac were able to understand the rover's immediate environment Dac team quickly got the knack of driving the rover and by using images and telemetry relayed by satellite, and they gained confidence as they drove it across the volcanic then successfully navigated through difficult terrain. We Kamchatka terrain. couldn't have asked for more from these field tests. As the images came, we relayed them to a team of geolo­ There is still a lot of work to be done before the rover is gists at Brown University in Rhode Island and to the tele­ ready for Mars. The Russians are proceeding on an aggres­ robotics scientists at Ames Research Center in Mountain sive schedule, and their progress is impressive. View, California. The Brown geologists were interested in The entire team, both in California and in Kamchatka, seeing if they could correctly analyze the landscape from the worked incredibly hard to achieve this success. Through the rover images. The Ames scientists were taking the stereo SUpp0l1 and contributions of Planetary Society members, an pairs, running them through their virtual reality program important step was taken in exploring the worlds around us. and transmitting them back to us in Huntington Beach. As for me, I only had to get home, and that trip proved There, a Silicon Graphics workstation displayed a three­ more of an adventure than anything that had happened so dimensional map of the terrain through which we could far. Let's just say that I did make it home to Logan, Utah, "drive" the rover. Using the first pictures returnedfrom on September 6. My luggage- with all that very expensive Kamchatka, the Ames people even created a limited virtual electronics equipment-did not arrive until the next day. environment complete with a virtual rover. We could watch Editor's note: Our final day of testing was so extraordinarily the rover as it moved or view the virtual landscape through successful that the entire Planetary Society~McDonnell the rover's eyes. Douglas~NASA Ames-IKI team, along with press people With state-of-the-art computers and software to play who'd gathered to watch, were stunned by what we'd accom­ with, trays of cold cuts and bowls offresh fruit to eat, and plished. We had proven that, in partnership with robots and a sunny California day awaiting us outside, we could ask computers, we can extend our reach and our vision to distant for nothing more than afew extra minutes with the rover. continents, and, using the same technology, we will eventually But the Kamchatka team signaled us that the rain was be able to reach and see even further-to distant worlds. getting heavier and the temperature was dropping. There was one more picture they thought we could get before we George Powell is an electronics engineer at Utah State declared the 1993 rover test program over. University's Space Dynamics Laboratory, and has been It took a few minutes for the computer to process the last working for The Planetary Society on the Mars Rover and image, and then we saw our compatriots in Kamchatka, on the Snake for the Mars Balloonfor six years. 15 ---.-ers' system balanced so precariously-with just the right number of planets-that - a major perturbation would blow it all ce apart? Or is it resilient enough to absorb unpredictable events? Peterson leaves us with the disquiet­ ing thought that the future of the solar system is as unknowable in the very long run as is the future of the universe. For those who love mathematics, Newton's Clock will be a treat. And for those who usually skip the equations, ur Readers' Service is an easy way bodies 100 million years into the past this excellent read will leave them more for Society members to obtain newly or into the future. mathematically savvy than they ever Opublished books about the sCience Peterson is eager to explain how thought they could be. and adventure of voyages to other worlds. computers like the Digital Orrery have -Reviewed by Bettyann Kevles We make these books available at the revolutionized astronomy. For example, lowest possible prices. Each title is offered for they have been instrumental in solving Still Available: six months, or three issues of The Planetary old problems, such as the long-standing The Evening Star: Report. We keep rotating our stock so that mystery of the Moon's irregular move­ Venus Observed the titles we offer are always fresh. ment, and, with data from the Voyager By Henry S.F. Cooper, JT. missions, new problems, such as the One of the best space science writers odd movements of Hyperion, "a frigid of our time chronicles the Magellan Newton's Clock: misshapen chunk of ice and rock orbit­ mission to Venus. Chaos in the Solar ing Saturn," which tumbles in its orbit (Reviewed September/October 1993.) System instead of spinning like a top. Retail price: $22.00 Peterson paints colorful word-pictures Member price: $19.00 By Ivars Peterson; W.H. Freeman, about historical greats, like Kepler, who New York, 1993,317 pages. had to interrupt his work in 1617 to Tales of the Earth: Retail price: $22.95 help his mother, who was on trial for ParoxysllUs and Member price: $20.00 witchcraft. Perturbations of the An excellent guide to mathematics Blue Planet ough winds blew Columbus' as well as to mathematicians, Peterson By Charles Officer and Jake Page. R threadbare armada to Jamaica in comments that Newton was too brilliant Reader-friendly, with just the right 1504. Since his crew had pillaged the in the Principia because he convinced mix of solid data, anecdote and humor, island on an earlier visit, Columbus generations of astronomers that the uni­ this well-illustrated volume examines was in a bind. He had to convince the verse is both coherent and predictable. some of the cataclysmic events in understandably hostile islanders to This is where chaos theory enters the Earth's tumultuous history. help provision his ships. story. Chaos is as hard for the general (Reviewed NovemberfDecember 1993.) Desperate, he consulted his naviga­ public to grasp as the math at the core Retail price: $24.00 tional tables and saw that a lunar of Newton's theory. But just as New­ Member price: $21.00 eclipse would soon occur. Gambling ton's public worshipped his theory that the tables were accurate, he gath­ without understanding it, many people To Place Your Order: ered the island's leaders together and today like the idea of chaos theory but Please send a check or money order, made warned them that if they did not help understand only one part of it: the con­ out to The Planetary Society, for the price of him, the Moon would disappear from cept that even within a seemingly regu­ the book (in US dollars) plus, for each book, the sky the next night. There was an lar system some things just cannot be a shipping and handling charge of $2.50 for eclipse, and the rest is history. predicted. the US, Canada and Mexico, $5.00 for other In Newton's Clock, Ivars Peterson In Newton's Clock, Peterson shows countries. Address your envelope to Readers' includes Columbus' gamble in his how chaos theory explains the irregu­ Service, 65 North Catalina Avenue, Pasadena, two-thousand-year sweep of efforts to larities that stymied Newton, such as CA 91106. predict celestial movements. Along the the Moon's tilting and wobbling as it is For faster service, order by telephone with way he describes some of the instru­ pulled by both the Sun and Earth. And your Visa, MasterCard or American Express ments used to track the planets, from a he shows that the Moon and Hyperion card. Call (818) 793-1675 from 9:00 a.m. first-century Be mechanism found by can both be understood today even to 5:00 p.m. Pacific time. deep-sea divers off the Greek island though their celestial locations in the All books sent postpaid. Please allow 4 of Antikythera in 1900 to the Digital distant future cannot be predicted. to 6 weeks for delivery in the US, Canada Orrery-a computer built in 1984 This brings him to another question, and Mexico, 12 weeks for delivery to other 16 that could trace the orbits of planetary which he does not answer. Is the solar countries. World

1Natch by Louis D. Friedman

Washington, DC-The Unit­ the use of Russian capabilities. Space that the article was written in old-style ed States Congress took final action station Alpha (the name Freedom has nationalistic tones and concluded with on the NASA appropriations bill two been officially dropped by NASA, these words: "Apple trees will blossom weeks after the start of fiscal 1994. along with its design) includes a modu­ on Mars. Ours. Russian!" Anachro­ Of major interest to Planetary Society lar design and development plan able nisms apparently abound in all arenas. members are the two new starts for to accommodate the Russian Mir 2 or planetary missions. Both are in the a US module should the agreement to Pasadena -Following the loss Discovery program and are subject to a incorporate Mir 2 fail. of Mars Observer in August 1993, $150 million limit on development cost The Planetary Society was invited to NASA organized several teams to de­ (launch and operations not included). testify before both the Senate and the termine the causes of failure and to in­ Sadly, however, Congress canceled the House committees during the debate vestigate the question of a reflight or High-Resolution Microwave Survey on the space station. We were particu­ follow-on mission. At the time we go (HRMS), NASA's entry in the Search larly asked to comment about the to press, the conclusions of the teams for Extraterrestrial Intelligence, almost implications of the new Russian role. dealing with the spacecraft failure are one year to the day after the project The full transcript of the Society' s not yet available. began its observations. statement before Congress can be As for recovering from the loss of One of the planetary new starts is obtained upon request. Mars Observer, emphasis was initially MESUR Pathfinder, which will send a The administration's new program is put on a quick reflight, either with a small lander with a 9-kilogram micro­ a three-phase approach. The first phase second Mars Observer spacecraft, built rover to Mars in 1996. The mission is includes several shuttle-Mir rendez­ from spare parts, or with a smaller and a technological precursor to the full vous and American astronauts flying less costly defense satellite being MESUR (Mars Environmental Survey) extended-duration missions on Mir (see developed by the Ballistic Missile mission, which will put a number of next report). The second phase calls for Defense Organization (BMDO). small landers on Mars. the development of a US human-tended After an intensive one-month reView, The other planetary new start is the facility connected to a Mir module, and it was decided that the 1994 mission Near Earth Asteroid Rendezvous the third phase moves on to the perma­ wasn't feasible due to a combination (NEAR). Its launch is scheduled for nent-presence capability and adds the of financial, technical and schedule February 1996. NEAR' s primary mis­ European and Japanese modules. issues, and that efforts should be sion is a close-up investigation of the This phased approach permits a "go concentrated on 1996. asteroid Eros, but additional asteroid as you pay" philosophy, advocated by Planetary Society officers Carl flybys, including one to Iliya, are the Augustine committee in 1990. Sagan and Bruce Murray were made planned. A third mission approved in part of the special team consulting with concept, with $10 million initial fund­ MoscolN-In January 1994, Rus­ JPL about the proper recovery plan. It ing, is a to-be-defined Mars Observer sian cosmonaut Valeriy Polyakov is to is still too early to say definitely what recovery mission, presumably with a begin an 18-month flight on Mir. This NASA will do. A broad range of 1996 launch also. will be the longest flight ever by a hu­ possibilities is being considered as to man in space. A Russian news report how to meet Mars Observer objectives Washington, DC - The ad­ stated that the rationale of the upcom­ and for the whole US Mars program, ministration's space station budget was ing flight was to gather data for "a from 1996 to the tum of the century. approved, although some restrictions flight for Mars, which could be carried were put on expenditures pending a out through the joint efforts of Russia Louis D. Friedman is Executive Direc­ full report on the station redesign and and the United States." It is noteworthy tor of The Planetary Society. 17 News and l

RevielNs by Clark R. Chaplnan

he Magellan mission began spacecraft was valiantly attempting part I already know-as a practicing plane­ as a gleam in someone's eye of its extended mission on a shoestring tary scientist-with Cooper's account. T two decades ago. Somehow, budget. Even when Magellan's trans­ For me, Cooper's writing works won­ it gained real funding (called a "new mitters fall forever silent, there will be derfully well. But a neophyte to Venus, start") during the budget-cutting much left to tell about Magellan's un­ I suspect, will get hopelessly lost amid decade of the eighties, and actually veiling of Venus. The exquisite maps the ever-changing hypotheses of the got launched toward Venus. of our neighboring planet will continue Magellan geophysicists. (Some pictures Then, as chronicled by veteran sci­ yielding secrets to researchers for years would surely help any book about a ence writer Henry S.F. Cooper, Jr. (The to come-provided, of course, that planetary imaging project; there are Evening Star, Farrar Straus Giroux, funds don't dry up entirely. none in this book.) 1993), Magellan faced two continuing Cooper's book reads like Volume 1 I fear that Cooper is himself struggling threats. One was mechanical or electron­ of a two-volume work. Yet I suspect with his admittedly difficult scientific ic failure of the complex, remote-con­ that Volume 2 will never be written, topic and, therefore, occasionally falls trolled machine, operating millions of even if Magellan research continues. short. For me, the major venusian mys­ miles from the nearest mechanic. The Cooper, after all, has chronicled NASA tery revealed by Magellan after a few second was the equally omnipresent planetary missions before, in New months of mapping concerned the re­ threat of funding cuts, which can kill a Yorker articles and in several books, markable "freshness" of nearly all the mission as surely as hardware failure. but neither he nor other science writers craters on Venus. This key geological The hapless Mars Observer-the have written much about the continuing observation continues to fuel the major only other NASA planetary mission to progress of planetary research: the in­ scientific debate about Venus: Did the get securely out of the starting gate in sights gleaned years or decades after planet undergo a sudden, fundamental the 1980s-fell victim to the first the exciting missions have flown. change, or oscillation, several hundred threat. And Magellan, too, faced re­ million years ago in how it gets rid of peated crises of "loss of signal." But Identifying With its internal heat? Yet Cooper senses the Magellan did eventually phone home, Magellan topic's importance belatedly: He intro­ and clever engineers found work­ In reading The Evening Star, I think I duces it, obscurely, less than 40 pages arounds that let the Magellan team sense why there is such focus on en­ from the end of the book. However, he sleep more easily at night as the mis­ counters. Cooper's major topic is the devotes many pages to the more super­ sion progressed. ever-evolving interplay between data ficial (and inevitable) cases when the More relentless were shortsighted and hypothesis, as the multidisciplinary cold, hard facts from Magellan debunked Washington budget cutters, focused Magellan scientists struggled to learn several fleeting, speCUlative theories on doing things flashily and cheaply about a new world from a sudden, enor­ about Venus. rather than on capitalizing on invest­ mous data-dump. Yet the ongoing Maybe the intellectual drama of sci­ ments and on completing a project drama that serves as the book's back­ ence is just too difficult to prop up unless well. For artificial accounting reasons, bone, and gives it the feeling of a novel, it is accompanied by the more immedi­ Magellan's "primary" mission was de­ revolves around the dangers to the space­ ate appeal of an ongoing mission of fined as preparing a single map of craft and its mission. Magellan itself is exploration. As a practicing planetary Venus through its clouds. Making a the prime character, and it was continu­ scientist, I would like to think that the gravity map and searching for ongoing ally in jeopardy. Whether the threat trials and tribulations of my world of geological activity had been left to the came from a software glitch, faulty research would be interesting fodder for "extended" phase of the mission-just hardware or an official in NASA's Of­ a popular writer. But when the best of as Uranus and Neptune were encoun­ fice of Space Science, Cooper is at top them (and Cooper is) needs the harrow­ tered during the "extended" phase of form portraying Magellan engineers as ing thrills of a spacecraft encounter to "Voyager's mission. Scotland Yard detectives, saving the sustain his story, I think my wishes mission from predators. may be in vain. The Continuing Despite excellent metaphors and Scientific Drama turns of phrase, Cooper's handling of Clark R. Chapman understands the ex­ By the end of Cooper's narrative, most the scientific drama is less convincing. hilaration of a planetary encounter, and of Magellan's scientists and engineers Maybe I'm wrong. I cannot read the has written a not-yet-published book on 18 had been laid off or reassigned, but the science objectively, since I merge what Voyager's encounter with Neptune. Society l I Ne1NS

Making Space for Developing Countries Washington.. DC: The Space to Be Scientists from all over the world at­ tended the United Nations Workshop n July 1994, Washington, DC, will members are scheduled to visit many on Basic Space Sciences for Developing I be the place for Planetary Society of the space-related and historic sites Countties October 18-22, 1993, in activities that celebrate two historic in the Washington area, including the Lagos, Nigeria. occasions-the 25th anniversary of National Air and Space Museum, Cosponsored by The Planetary Soci­ the Apollo 11 Moon landing on July NASA Goddard Space Flight Center ety and the European Space Agency, this 20 and the expected collision of and George Washington's Mount third annual workshop focused on how comet Shoemaker-Levy 9 with Vemonhome. space science and its associated tech­ Jupiter, an event that will be observ­ For a tour brochure, call Sam Shah nologies can be useful to developing able from Earth over a five-day peri­ at Advanced Travel, 1-800-248-0388, countries. The workshop provided an od from July 19 through July 23. or write to Cindy Jalife at The Plane­ opportunity for scientists from African To coincide with these events, The tary Society, 65 North Catalina Ave­ countties to interact with colleagues Planetary Society has organized a nue, Pasadena, CA 91106. Advanced from Europe, Asia and the Amelicas. tour of the District of Columbia area Travel will also be able to help you To maintain this interaction, a consor­ for Society members, families arid with airline reservations. tium of groups, induding the UN and The friends July 16-23, 1994. Tour mem­ Tour space is limited, and discounts Planetary Society, is proposing extending bers are guaranteed tickets to Society are available for early reservations. the science Internet-the electronic com­ activities that will celebrate the For those considering travel to Wash­ munication link for many scientists-to Apollo 11 anniversary and monitor ington, DC, for the public events, but Africa. Planetary science applications the comet's collision with Jupiter. not the tour, Advanced Travel can also will be the basis for this pilot electronic The tour group will also attend help you with hotel accommodations. communications project. - Christopher private lectures on the comet and - Susan Lendroth, Manager of Events P. McKay, NASA Ames Research Center on other planetary topics. And tour and Communications

Seeing Planetary Society Stars in Anaheiln For the fourth year in a row, The Plane­ technology of telepresence. longer visits other worlds, no longer tary Society will present a series of spe­ For a registration packet, call The provides an opportunity for brave ex­ cial sessions at the National Science Planetary Society at 1-800-969-MARS, plorer-scientists to blaze new trails for Teachers Association's annual conven­ or write to NSTA Convention at the human species. Fittingly buried on tion. Cosponsored by the Society, the Planetary Society headquarters. - SL his last mountain, Karl Henize will be 1994 convention will be held in Anaheim, sorely missed. - Carl Sagan, President. California, March 30 through April 2. Melnorial to the First (Memorial read at a service in Houston The Planetary Society's sessions will Astronolner Astronaut for Henize, who died while scaling Mount be held on Friday, Aprill. David Levy, Karl Henize, scientist and explorer, was Everest on October 5, 1993.) one of the co-discoverers of comet Shoe­ the first astronomer of any nation to be maker-Levy 9, and planetary scientist chosen as an astronaut. His selection David Morrison will discuss the comet's seemed then to indicate that fundamental upcoming collision with Jupiter. Michael science would be an important part of Keep in Touch Klein, a scientist at the Jet Propulsion the US human space program. Henize is Laboratory, will examine the search for the latest of a number of astronauts, as­ Our mailing address: . planets around other Sun-like stars. tronaut candidates and space scientists to The Planetary Society Also present will be Robert Staehle of lose their lives in exploration- often on 65 North Catalina Avenue JPL, speaking about the Pluto mission; inaccessible mountains, as close to the Pasadena, CA 91106 science fiction author Larry Niven, dis­ planets as they were able to climb. Call for an events calendar: cussing the CD-ROM library of science They were willing to take risks in the (818) 793-4294 fiction being launched to Mars; and cause of exploration, space program or Louis Friedman, Executive Director of no space program. It is a pity that the General calls: (818) 793-5100 The Planetary Society, who will discuss human space program of the US and Sales calls only: (818) 793-1675 the Russian rover and the fascinating other nations no longer explores, no 19 -;------.------~------~

Questions and AnslNers

Could those mysterious spokes that ager viewed the rings from a different flyby, it was suggested that such tiny appear in Saturn's rings be attribut­ angle, the spokes appeared brighter particles could be produced in the ed to nothing more than a "strobo­ than the background rings. Also, we sporadic fashion observed, with scopic slip effect," similar to the then saw that they were actually associated electrostatic charging, by way the wagon wheels in a Western wedge-shaped, being narrowest at interplanetary debris hitting the rings. film beat in time with the movie the location where ring material orbits The meteorite impact trigger idea is camera's shutter speed to give an at the same rate as the planet's mag­ supported by the fact that most of the illusion of the wheel slowing down netic field. spoke-creation episodes seem to occur or even reversing? These changes in relative bright­ in the region where the impact veloci­ -Alistair Murch, Worthington, ness, and the observation that the ty and flux (the rate of particle flow) United Kingdom spoke structure was tied to the motion would be the highest. The huge cross and strength of Saturn's magnetic section of the rings provides an impact Before I answer your question, let me field, led us to believe that they were rate that could agree fairly well with give you some background. Voyagers regions of abundant micron- and sub­ the observations, although the flux of 1 and 2 discovered a new form of micron-sized ice grains, probably projectiles is something we don't brightness variation in the main rings puffed up off the surfaces of the nor­ know much about. of Saturn. These radially elongated, mal centimeter- to meter-sized icy Another theory describes a form of fuzzy-looking features appeared dark ring particles. Such small particles are magnetic instability that can occur as against the bright rings. They quickly easily affected by otherwise tiny mag­ a result of a meteorite impact, or even got the name "spokes" because they netic forces, and their light-scattering an unrelated fluctuation in the plasma seemed to rotate like the spokes of a properties agree with the observa­ surrounding the rings. wheel. Shortly afterward, when Voy- tions. Several years after Voyager's A strobe light works by freezing

One of the most surprising discoverilts ofVoysger 1's 1980 encounter with Saturn was the dark "spokes" that seemed to rotate like the spokes on a wheel. In this sequence of images, you can follow their progress around the planet. The spokes are probably tiny ice grains, knocked. loose by meteorite im­ pacts on ring particles, which are caught up in Saturn's magnetic field and accelerated around the planet. Images: JPLfNASA Factinos ______~ I the motion of a very rapidly mov­ layer" at equatorial and midlati­ l ing object; for repetitive patterns tudes, much as Earth does. such as the spokes of a wheel, the In those regions, Mars' ozone Examining the role of bubbles in the origin of speed can be measured by adjust­ concentrations are highest at an life on Earth is one of the newest approaches to ing the light's flash rate to mimic altitude of around 30 to 40 kilo­ solving the scientific mystery that is probably the time it takes for one spoke to meters (19 to 25 miles), with a second in importance only to the puzzle of how advance exactly to the position of maximum concentration of about the universe itself began. another. This effect would not 0.5 parts per million (ppm). For No one is saying that bubbles might explain apply here because sunlight has comparison, ozone concentrations everything. But a new theory receiving close no such regular (or even irregular) on Earth reach a maximum of attention suggests that the multitudes of bubbles flickering. Neither are the Voyager about 5 ppm. However, the verti­ forming on the surface of the primordial seas cameras susceptible to this sort of cally mixed amount of ozone is may have collected chemicals and concentrated effect. many, many times less than it is them for synthesis into complex molecules. There is surely a lot that we on Earth. Eventually, through multistage reactions con­ don' t understand about Saturn's Hence, while ozone on Earth stantly repeated by uncounted generations of spokes and about the rings in gen­ shields the surface from much of bubbles, the molecules grew in size and ambi­ eral. When Cassini arrives at Sat­ the Sun's harmful ultraviolet radia­ tion, until they were ready for the transition to urn in 2004, it will observe the flux tion, the ozone on Mars does not. living, reproducing cells. of interplanetary material with its Furthermore, while the ozone in Louis Lerman, a geophysicist from Lawrence dust detector, observe the changes Earth's stratosphere exerts a strong Berkeley Laboratory in California, is the origi­ in the magnetic fields near the control on the temperatures there, nator of the concept. Biologists have said that rings with charged-particle detec­ Mars' ozone exerts only a negligi­ the concept seems sound and is based on well­ tors, and observe the structure, for­ ble control on the planet's atmo­ established physical principles, and is certainly mation, color and evolution of the spheric temperatures. worth detailed study. Sherwood Chang, a spe­ spokes. It will discover whether At Mars' poles in winter; ozone cialist in the origin of life at NASA's Ames the distribution of spokes varies does not form a "layer," since it Research Center, said, "Clearly the ocean­ with time and tilt of the rings, as also exists in high quantities near atmosphere interface is a dynamic environment might be expected based upon a the surface. The vertically inte­ worthy of much future study and simulation as meteoroid impact hypothesis. grated amount of ozone is higher a site for chemical evolution." Cassini will also answer many at the poles than at equatoriallati­ One attraction of the new hypothesis is that it other questions about the rings: tudes in winter. Thus, ozone on offers a mechanism for a rapid chemical evolu­ how the composition varies from Mars fluctuates much more than tion. "Lerman is suggesting how the primordial dark, grayish material in the C ring what we've observed on Earth, soup might have been stirred up," said James P. and Cassini Division to bright, red­ but for different reasons. Ferris, a chemist at Rensselaer Polytechnic Insti­ dish material in the B and A rings; Earth's ozone hole is related in tute in Troy, New York, and editor of the journal whether small moonlets reside in part to human-made chemicals Origins of Life and Evolution of the Biosphere. the many empty gaps in the rings that are not present on Mars. There, -from John Noble Wilford in (other than the one lO-kilometer concentrations are more strongly The New York Times object discovered recently in the influenced by the amount of water A ring's Encke gap); whether new vapor, and the wide variability of ring features have appeared or water vapor on the planet results in For the first time, scientists have detected poly­ whether some of the features a large fluctuation in the amount cyclic aromatic hydrocarbons, an important Voyager saw have since evolved of ozone. family of organic molecules, in interplanetary into different forms. This explains why ozone on dust. This dust may be some of the oldest matter -JEFF CUZZI, NASA Ames Mars is more abundant at the very in the solar system. The discovery gives weight Research Center cold wintertime poles, where water to the theory that tiny dust particles from outer vapor is frozen out of the atmo­ space helped seed Earth with the chemicals Does Mars have an ozone layer sphere. In fact, observations by necessary for life to begin. similar to that of Earth? If so, Mariner 9 in 1972 showed that Two research teams collaborated on analyz­ are there fluctuations in the layer ozone rose and fell in conjunction ing the dust, which was collected by a NASA (presumably due to natural causes) with the passage of meteorological aircraft. At Washington University in St. Louis, similar to those resulting in the cold fronts, due in part to the re­ Robert M. Walker and colleagues measured the ozone hole(s) currently causing duction in water vapor in colder air abundance of different isotopes of the same ele­ so much concern on Earth? and in part to the obscuration of ment and concluded that the dust did originate - Mike Cleary, Jefferson City, ozone by clouds and dust. outside Earth. At Stanford University, a group Missouri Our group is proposing to including Simon J. Clemett and Richard N. Zare NASA that a balloon-borne ozone first vaporized, then ionized organic molecules Mars' ozone has been studied detector be sent to Mars to study in the dust. After using a mass spectrometer to from Earth-based observatories this variability more closely, as a sort the ions, the researchers concluded that and from Russian and American possible Discovery-class mission. they had indeed detected polycyclic aromatic spacecraft, most notably Mariner 9. -B. LEE LINDNER, Atmospheric hydrocarbons. Mars does in fact have an "ozone and Environmental Research, Inc. - from Ron Cowen in Science News 21 ------~-----~----

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Dinosaurs were driven into extinction by a Oive Europa T-Shirt members, submit your order for large comet or asteroid impact on Earth 65 Star Theater M, L, XL. 1 lb. #568 $14.00 any item offered on these pages million years ago. The dinosaur bone was 2 lb. #669 $32.00 on your school letterhead and collected from the Morrison Formation of Surf Titan T-Shirt enjoy a 20% discount! the Jurassic Period and is approximately NightStar Legend Long sleeve. S, M, L, XL. 1 lb. 140 million years old. 2 lb. #215 2 lb. #559 $26.95 #651 $20.00 tereoscopic vision will be a valuable tool for navigating the rover on Mars. During the August 1993 S telepresencelvirtual reality tests performed whi le the rover was in Kamchatka, the American team used a Silicon Graph ics workstation and specially deSigned glasses to view the rover's images in three dimensions. We can't reproduce that high-technology effect on the page of a magazine, but th is is an attempt to partly simulate the experience for all our members. This is one of the im ages from the stereo pairs taken by the rover. Hold it about 30 centimeters (12 inches) from your face and stare at the left image with your left eye and the right image with your right eye. It might help to hold a piece of cardboard upright between the images. As you stare, a stereoscopic image should appear in the space between the two printed images, Fortunately, when we attempt to drive the rover across Mars, we will have computer tools to make stereoscopic vision easier to achieve. And this new technology should significantly advance our ab iliti es to explore other worl ds, Image: Mars Rover

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