The PLANETARYPLANETARY REPORT REPORT Volume XXV Number 3 May/June 2005 Saturn’Saturn’ss IcyIcy MoonsMoons Volume XXV Table of Number 3 Contents May/June 2005 A PUBLICATION OF From Features The The Moon: What We Know and Want to Know Editor 6 After decades of neglect, the Moon has once again become a popular destination—six space agencies have plans for missions to the Moon, totaling n 1980, as the two Voyager spacecraft 10 spacecraft set to explore our nearest neighbor. We’ve been to the Moon I were on their way to Saturn, we started numerous times before, so why go back? What more is there to learn? Planetary an organization dedicated to ensuring that Report Technical Editor James Burke summarizes our current lunar knowledge humanity’s exploration of the solar system and what we hope to learn from future missions, looking ahead to the possibil- did not end at the sixth planet from the ity of returning one day with human explorers. Sun. There was, at that time, a real danger that the political will to explore the universe Cassini’s Cornucopia of Moons: around us had failed. With The Planetary 12 7 Satellites in 7 Months at Saturn Society, we were able to demonstrate that Twenty five years ago, Voyager 1 and 2 gave us our first close-up look at the popular will to see what lay beyond the Saturn’s diverse and intriguing moons. Now, we have returned to the Saturnian next planet was still strong and kicking. system with Cassini for a four-year tour, filled with close flybys of all the The popular will prevailed, and we reap major satellites. In just 7 months, Cassini has returned more data about Saturn’s the results today. Just look at all the moons moons than the Voyagers did in the 1980s. Here, planetary scientists Amanda we cover in this issue of The Planetary Re- Hendrix and Jonathan Lunine present the latest views of 7 of Saturn’s icy port! In 1980, there were 11 known moons moons—Phoebe, Tethys, Dione, Iapetus, Mimas, Rhea, and Enceladus. of Saturn; in 2005, Saturn boasts 34 named moons, with 12 more waiting in the queue. Every day, Cassini returns more images of the Saturnian system, following Departments the trail blazed by Voyager 25 years ago. 3 Members’ Dialogue We are looking at Earth’s own Moon again, with an eye to returning there in 4 We Make It Happen! person. We are not just wondering if there are any planetary systems besides ours; 18 World Watch we are searching for and finding them. We are reveling in the overwhelming richness 20 Questions and Answers of nature and its potential to awe us with every new discovery. 22 Society News In a very real way, The Planetary Soci- ety focused the public will to make all this happen. Let’s hope our next 25 years are just as successful! —Charlene M. Anderson Contact Us Mailing Address: The Planetary Society, 65 North Catalina Avenue, Pasadena, CA 91106-2301 On the Cover: General Calls: 626-793-5100 Sales Calls Only: 626-793-1675 Cassini images taken on December 31, 2004 were combined to E-mail: [email protected] World Wide Web: http://planetary.org make this near-true-color view of Saturn’s moon Iapetus. This im- age, taken at a distance of about 172,900 kilometers (107,400 The Planetary Report (ISSN 0736-3680) is published bimonthly at the editorial offices of The Planetary Society, 65 North Catalina Avenue, Pasadena, CA 91106-2301, 626-793-5100. It is available to members of The Planetary Society. Annual dues in the US are $30 (US dollars); in Canada, $40 (Canadian dollars). Dues in miles) shows the northern part of the moon’s dark Cassini Regio. other countries are $45 (US dollars). Printed in USA. Third-class postage at Pasadena, California, and at an additional mailing office. Canada Post Agreement Number 87424. The large impact basin visible here is 400 kilometers (250 miles) in Editor, CHARLENE M. ANDERSON Copy Editor, A. J. SOBCZAK diameter. This image has been rotated so that north is to the right. Associate Editor, DONNA ESCANDON STEVENS Proofreader, LOIS SMITH Managing Editor, JENNIFER VAUGHN Art Director, BARBARA S. SMITH Technical Editor, JAMES D. BURKE Science Editor, BRUCE BETTS Image: NASA/JPL/Space Science Institute Viewpoints expressed in columns and editorials are those of the authors and do not necessarily represent positions of The Planetary Society, its officers, or its advisers. ©2005 by The Planetary Society. Cofounder CARL SAGAN 1934–1996 Board of Directors Chairman of the Board Members’ NEIL deGRASSE TYSON Astrophysicist and Director, Hayden Planetarium, American Museum of Natural History Dialogue President WESLEY T. HUNTRESS JR. Director, Geophysical Laboratory, Carnegie Institution of Washington Vice President BILL NYE Refreshing nation of the Project Daedalus great success was, in fact, science educator Executive Director Reminder craft, and even if it had been, nearly a disastrous failure. LOUIS D. FRIEDMAN Thank you for publishing it would have taken almost Combined with the error ANN DRUYAN author and producer “Miranda: Shattering an Im- 75 years for it to reach Sirius. over the Doppler frequency DAN GERACI President and Chief Executive Officer, age” in the March/April 2005 —ERIK ZAVREL, changes, which were forgotten Phoenix Investment Partners, Ltd. LAURIE LESHIN issue of The Planetary Report. Kenosha, Wisconsin in the receiver design, and the planetary scientist Many people (myself included) need to redesign the Cassini JOHN M. LOGSDON Director, Space Policy Institute, are not old enough to remember Fragrance Free flyby to have any chance of George Washington University Advisory Council Chair the Voyager missions, so it is The otherwise excellent “A returning useful data, it shows CHRISTOPHER P. McKAY planetary scientist, NASA Ames Research Center refreshing to be reminded of World Revealed: Huygens’ that mission designers and BRUCE MURRAY Professor of Planetary Science and Geology, some of the more obscure Images of Titan,” in the March/ planners are still unable to California Institute of Technology ELON MUSK locales they visited. April 2005 issue of The Plane- ensure that the really basic Chairman, CEO, SpaceX Galileo has since been sent ary Report, makes reference things, like testing to confirm JOSEPH RYAN Executive Vice President and to Jupiter, and Cassini to Sat- to methane as a “smelly” or all commands are correct, General Counsel, Marriott International STEVEN SPIELBERG urn, so the beauty and mys- “noxious” compound. Actually, are done. Given the Genesis director and producer MARIA T. ZUBER tery of those systems are still pure methane gas is essentially (sensors upside down), Mars Professor, Massachusetts Institute of Technology fresh in mind, but we have not odorless, and it is poisonous Climate Orbiter (metric to Advisory Council JIHEI AKITA yet dedicated any [new] mis- only in the sense that it can act English unit muddle), and Executive Director, The Planetary Society, Japan sions to Uranus’ or Neptune’s as an asphyxiant, displacing Mars Polar Lander (landing BUZZ ALDRIN Apollo 11 astronaut systems. Articles like “Miran- oxygen in the air. test sequence) failures, the NORTON BELKNAP da” help keep up awareness The odors we detect in con- pattern is easy to see. Human President, Paul Taylor Dance Company RICHARD BERENDZEN about the amazing places still nection with naturally occur- error is the main cause. educator and astrophysicist JACQUES BLAMONT waiting to be explored. ring methane in swamps, in If the taxpayers in Europe Chief Scientist, Centre National d'Etudes Spatiales, France RAY BRADBURY —BRIAN ALTMEYER, dumps, and in agriculture are and the United States are going poet and author DAVID BRIN Rancho Cucamonga, contaminants resulting from to support expensive missions, author California biological processes. The human error must be reduced. FRANKLIN CHANG-DIAZ NASA, Astronaut Office strong smell we associate with It is simply not good enough ARTHUR C. CLARKE Project Daedalus natural gas, which is roughly to hold an investigation after- author FRANK DRAKE President, SETI Institute; Professor of Astronomy and As- In the Members’ Dialogue 95 percent methane, is from wards. I am a dedicated sup- trophysics, University of California,Santa Cruz section of your March/April ethyl mercaptan, an odiferous porter of such missions, but OWEN GARRIOTT former astronaut; Professor, 2005 issue, Fabian Stretton compound deliberately added mistakes like these will lose University of Alabama, Huntsville GARRY E. HUNT states that the Project Daedalus to make a gas leak detectable. public support, which cannot space scientist, United Kingdom BRUCE JAKOSKY spacecraft was designed to Titan might well be a smelly be regained. planetary scientist THOMAS D. JONES reach Sirius in 12 years. This place, thanks to the complex —LORD KIMBERLEY, planetary scientist, former astronaut, and author is not true. hydrocarbon chemistry going Buntingford, Herts, England SERGEI KAPITSA Institute for Physical Problems, The objective of Project on in its atmosphere, but it Russian Academy of Sciences CHARLES E. KOHLHASE JR. Daedalus, which was devel- won’t be because of the pres- In General mission designer, author, and digital artist JON LOMBERG oped by members of the ence of methane. Great job on the March/April artist British Interplanetary Society —CHARLES GALE, issue. Once again you’ve pro- HANS MARK University of Texas at Austin from 1973 through 1978, was Roswell, Georgia vided insightful information YASUNORI MATOGAWA to travel to Bernard’s Star, a on both recent and historical Associate Executive Director, JAXA JOHN MINOGUE red dwarf 5.9 light-years Reduce events. President, DePaul University PHILIP MORRISON away. The projected mission Human Error —CHRIS MARTEL, Institute Professor, Massachusetts Institute of Technology time, using helium-3 mined It was wonderful to hear the Plymouth, Michigan ADRIANA OCAMPO planetary scientist, European Space Agency from the atmosphere of news that Huygens was suc- RISTO PELLINEN Jupiter, was 50 years.