Seeing Titan Mapping Saturn’S Moon with Infrared Technology Jason W

the art + science of seeing

volume 2 issue 4

Cosmos

Gl mpsevolume 2 issue 4 the art + science of seeing TM Cosmos is an interdisciplinary journal that examines vol 2.4 features articles, visual spreads,reviews interviews spanning and the sciences, arts and humanities. physical sciences, social Glimpse the functions, processes, constructing and and effects knowing of being, vision for and implications vision’s our world(s). Each theme-focused journal issue Contents The Cosmos Issue

11 Unberührtes Muster 24 Maya Ethnoastronomy Arto Vaun Susan Milbrath

Exploring Mars and the Moon Dimming the Lights 38 12 Using Google Earth Astronomy and light pollution Ross A. Beyer Scott Kardel 52 The Use of Color 18 What the Wise Men Saw In Interstellar Message Design In the Sky Kimberly A. Jameson & Jon Lomberg Michael R. Molnar 61 Seeing Titan Mapping Saturn’s moon with infrared technology Jason W. Barnes

68 RetroSpect: 1880-1911 Carolyn Arcabascio

70 RetroSpect: 1757 Gl

mpse 71 Seeing the Universe online The COSMOS Through a Straw ISSUE PLAYLIST The Hubble Space Telescope Christie Marie Bielmeier

81 $25 Million a Ride A real view of space tourism C.J. Wallington

84 (Re)views A Trip to the Moon & Moon

Ivy Moylan TM Contributors emotion. N in the environment. worlds’ cultures name and conceptualize color comparative investigations of the ways the genetic underpinnings of color perception; and human color cognition and perception; the agents; individual variation and universals in evolution amongcommunicatingartificial mathematical modeling of color category work, which includes research on the prominent role in her empirical and theoretical edu/~kjameson/kjameson.html). Color plays a University ofCalifornia, Irvine(http://aris.ss.uci. Mathematical Behavioral Sciences, atthe conducting research attheInstitutefor Kimberly A.Jamesonisacognitivescientist y A.jameson Kimberl of severalactivespacecraft. way. interested inwhatit’slikeandhowitgotthat S photogrammetry of the solid bodies in our surface processes,remote sensingand Cruz. P for the He isalsoaResearchFellowwiththeCenter B Astrobiology Division(Planetary Systems out his research in the S Dr. Beyerisaplanetary scientistwiththeCarl ROSS A.BEYER 2004. spacecraft’s arrivalintotheSaturnsystemin the Cassini F NASA’s AmesResearchCenterinMoffett as apostdocfor theKeplermissionat starting at the University of the University of Arizona in 2004. 1998 and a a growing upinSt.Louis,Missouri,hereceived physics at the University of Jason W. JASON W.BARNES lanets at the University of California, olar agan Center at the ield, California. ranch) at the ancy Alvarado on the cognitive processing of BS degree in Astronomy from Caltech in B S H eyer also serves on the science teams ystem—if you can stand on it, he’s e studies surface geomorphology, O rigin, Dynamics and Evolution of B arnes is an assistant professor of VI P h.D. in M N S A H science team since the S e has worked closely with

A Ames S P S he also collaborates with lanetary E S TI pace

I nstitute. R I esearch Center. I daho. After daho he worked S S cience and cience from P H rior to e carries S

Atom ic Num ber of Elem ent (num ber of protons ) anta 10 20 30 40 50 60 70 80 90 0 Gd Co Os Na Nb Ag Sb Cs Yb Br Li H K Mg Mo Ca Cd Be Ba Tb e T Lu Kr Ni Ir Number Cu Rb Pb Dy Sc c T La Hf Pt Al B Ce Th Zn Si Ti C of Kinds (number of Atoms of isotopes) for Each Ga Pr U N P V Palomar Observatory.There hedirects P S SCO edu research isathttp://solarsystem.wustl. her about More 2010. in appear will System new bookonthe Companion books; two and journals scientific in papers 80 than more (co-)authored has Lodders inside andoutsidethesolarsystem. in stellarenvironmentsandplanets chemistry on focuses research current Chemistry inMainz,Germany.Her Max- and University Johannes- the at 1991 Missouri. in University Washington Center for theSpaceciencesat P professor intheDepartmentofEarth& K KATHARINA LODDERS Association. member of the Arizona Universityandisalifetime secondary education from Bachelor’s degree inphysicalscience/ from theUniversityofArizonaanda holds a Masters degree in astronomy the historyofPalomarObservatory.He general astronomy,lightpollution,and across the United program. the observatory’s public outreach Element ublic Affairs Coordinator for Caltech’s lanetary lanetary ince 2003 atharina Lodders is a research research a is Lodders atharina Ge Nd Ho Ru Au a T Cr Sr Bi O S Sm Mn Hg Rh As Er W Cl TT KARDEL In Y F I The Planetary Scientist’s Scientist’s Planetary The for the the for He. Tm Re Ne Se Eu Pd Sn Xe Fe Ar Zr Tl H S S e has been a featured speaker ( he received her doctorate in in doctorate her received he ciences and the McDonnell McDonnell the and ciences S O cott xford Univ. Univ. xford I nternational Dark- R oyal Chemical Chemical oyal Chemistry of the Solar Solar the of Chemistry K S ardel has been the tates giving talks on P lanck- G utenberg utenberg P S N

ress 1998). A 1998). ress aint Louis, Louis, aint orthern I nstitute for nstitute S ociety ociety S ky volume 2.4 winter 2010 Cosmos 7 chool chool tation, tation, S S irgin irgin ’s ’s V ochester ochester R RIT tar of pace pace utan won the the won utan . Molnar now S S R Space Tourism R ) and the next next the and ) h.D. from the the from h.D. urt urt P

B RIT ervice Management, and and Management, ervice pace Center as a summer summer a as Center pace S nternational nternational S I flight or in line for for line in or flight outhern California and blames blames and California outhern G S echnology ( echnology . All of this was prior to Dennis Dennis to prior was this of All . eorge Lucas who was in cinema cinema in was who Lucas eorge T G . e currently teaches in in teaches currently e f he had the money (college (college money the had he f I H ravity’s commercial weightlessness weightlessness commercial ravity’s G A’s Johnson Johnson A’s ospitality and and ospitality rize. rize. S H P alactic’s suborbital flights (blatant hint for for hint (blatant flights suborbital alactic’s A ito’s trip to the the to trip ito’s ethlehem can be learned from his website: - etired astronomer Michael nstitute of of nstitute selected consumers’ interests in space selected consumers’ interests tourism. would he much), that make don’t professors Zero- a on be G a has Wallington funding). of University on this all making time same the about at school THX-1138 MICHAEL R. MOLNAR R makes violins to accompany the music of the spheres. More about the B www.michaelmolnar.com. ON LLINGT C.J. WA the knows) he as far (as is Wallington C.J. tourism space university first world’s at sessions two After teacher. development N the to returned he fellow, faculty I year initiated a course called Development T Zero- before years and flights, X of has even taught the course in Croatia, leading about thesis Master’s student’s Croatian a to ational ational N Milky Milky or the past past the or nterstellar nterstellar istory, and an an and istory, I F

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agan’s principal artistic artistic principal agan’s H S and the TV series atural atural N , commissioned by the the by commissioned , rofessor of Anthropology at the the at Anthropology of rofessor , for which the artist won an which the artist , for P usan Milbrath is Curator of Latin Latin of Curator is Milbrath usan CONTACT -funded traveling exhibit featuring her her featuring exhibit traveling -funded S H E lorida Museum of of Museum lorida or 25 years Jon Lomberg was was Lomberg Jon years 25 or ecord, Lomberg designed the cover and and cover the designed Lomberg ecord, where she has continued working on on working continued has she where exhibits, including several exhibits that nationally. toured and archaeology the on focuses Maya last the Mayapan, of ethnohistory capital in Mexico, and astronomical imagery in Mesoamerican art. a number of major exhibits including an an including exhibits major of number a N American the at opened that research of Museum at curator a been has Milbrath years 20 the Florida Museum of Natural History American Art and Archaeology at the F Affiliate herUniversity of Florida. She received Ph.D. from Columbia University in Art History and Archaeology, and has curated A spacecraft. An asteroid aboard 3 NASA spacecraft. near Mars has been officially named Asteroid Lomberg in his honor. SUSAN MILBRATH Dr. Director of NASA’s Director R the of contents pictorial years. million 1000 of lifetime estimated his of artifacts message three Also, of Mars now on the surface design are Way Galaxy the iconic Air and Space Museum, remains of generation this for galaxy the of image astronomers. He has worked in with partnership interdisciplinary and physicists, astronomers, prominent Design As perception. of psychologists astronomer Carl Carl astronomer collaborator in books, magazines, the including projects film and television, film COSMOS is portrait of the H EMMY Award. JON LOMBERG F w 8 images usedinthisissueare Creative Commons private collectors.Thefont usedinthisissueis

Commons licensesfor theirworks.Manyofthe Glimpse www.glimpsejournal.com Glimpse acknowledgescreators’ copyright,and licensed imagesfromFlickr.commembers, and encourages contributorstoconsiderCreative Staff Poet, ContributingPoetry Editor others are publicdomainimagescourtesyof Copyright andAcknowledgements Contributing ScienceWriter Contributor, Film Christie MarieBielmeier Founder, ManagingEditor Design Intern,llustrator Tuffy, afreely available font. www.glimpsejournal.com Marketing +Communications Co-Founder, Editor(urope) Carolyn Arcabascio Matthew StevenCarlos Editorial Assistant Adjunct +Alumni Acquisitions Editor Nicholas Munyan Salem, MA01970 ISSN 1945-3906 Glimpse Team Editorial Intern Wayne Kleppe Christine Madsen Megan Hurst Rachel Sapin Editorial Advisor Anthony Owens Jamie Ahlstedt Art Director Ivy Moylan Angie Mah Arto Vaun Photographer PO Box 44 Logo Design Reviews Glimpse EmComm

From theEditor the with collaborating himself busy quickly would he suspect we then and telescopy and digital imaging technology today, he might be awestruck, objects. celestial of observations published F by looking. learned they’ve what and upwards, intently look that us among those emerged. beforelanguage written might have been the first text to which humans ascribed meaning, long up. looked always have Humans human of engagement withtheobservableuniverse overmillennia. representation broader and deeper much a is by pocket-protectors tempered and headsets wearing men of stereotype the image, we advise you to look beyond this cover where you will find that the 20 typifies that Control Mission of image an features cover issue’s This during thetimesofChristandMaya,respectively. events celestial of context cultural the of understanding an to inquiry Michael Dr. stars. the of patterns the to relate they as practices and customs civilizations’ at human history. Skills of acute observation serve astronomers just as well when looking imaging digital of theknownuniverse. in advances light, edges the to deeper, haveprobe technologies to astronomers enabled invisible of visualization the or magnification greater for allowing Whether seeing. of technologies with linked inextricably is Astronomy away. far very very, from ago, ancient light (both visible and invisible) that tells us stories of long, long stationed on Earth’s high points or floating in space, lenses open, record We see more clearly by looking to the past. best advice). Wallington’s C.J. Dr. (heeding vacation space million $25 a for angle Dr. by detail in described surface of the Moon and Mars in the latest versions of of imaging infrared Earth. terrestrial beyond and of re-framing of the sky. the of picture clearer K our hundred years ago this month, in March 1610, 1610, March in month, this ago years hundred our re fr imr atl lgt s ter bevtre cud e a get could observatories their so lights earthly dimmer for ardel Glimpse vol 2.4 issue contributors. th -century lore of space exploration. While we couldn’t resist this Sidereus P Two contributors to this issue piece together ancient eriodic N T uncius itan’s surface. surface. itan’s . Molnar and Dr. and Molnar R. T oss A. Ross able to better reflect the chemical elements , the first printed treatise on telescopic telescopic on treatise printed first the , H e might promote Dr. Dr. promote might e [email protected] Megan Hurst, e might join Dr. Jason W. Jason Dr. join might He If his issue, This Beyer. alilei could witness the power of power the witness could Galilei H He might be lobbying with e might virtually fly over the the over fly virtually might e usan Milbrath devote their devote Milbrath Susan O Perhaps ur telescopes and cameras,

Editor T Cosmos he sky’s constellations constellations sky’s he K alilei would even would Galilei atharina Lodders’ Lodders’ atharina , is by and about and by is , Google Earth G alileo alileo arnes in Barnes G Scott alilei alilei TM by Jason W. Barnes

t seems incredible now, but at the dawn of the Space Age, equipping I interplanetary spacecraft with cameras was not a foregone conclusion. NASA planned no cameras for its first Venus mission, Mariner 2 in 1962, because astronomers inferred from images collected by Earth-based telescopes that a camera wouldn’t see anything through the planet’s thick clouds. Carl Sagan, a planetary scientist perhaps best known for co-writing the PBS television series Cosmos: A Personal Voyage in the early 1980s, lobbied to have a camera installed despite this anticipated futility. The camera’s purpose, Sagan mused, would not be to image the clouds that we knew were there, but rather to be on the lookout for the “unexpected.”

Carl Sagan lost the Mariner 2 battle. Instruments were sent to test previously existing hypotheses instead. But his approach of using cameras to discover new phenomena and processes—in essence, to look for the questions that we did not know enough to ask—won out in the long run. Over the past fifty years, imaging has developed into a critical tool for planetary exploration. These pictures of planets, asteroids and moons are more accessible and more easily interpreted scientifically than other datasets, in part because they piggyback on the human brain’s built-in hardware for assimilating information from images.

Figure 1. A true-color image of Titan, like what human eyes would see. Scattering off of atmospheric smog particles smears out all light from the surface, leaving Titan looking like a featureless grapefruit. This image is from Cassini’s Imaging Science Subsystem (ISS), but Voyager 1’s cameras from 1980 showed much the same picture. All images courtesy of the author. www.glimpsejournal.com

Glimpse

Figure 2. This color scheme emphasizes Titan’s atmospheric features. In this view from the VIMS instrument on Cassini’s T34 fly-by on July 19, 2007, surface features look green. The pinkish color near the limb shows scattering off of the smoggy haze particles. The bright bluish-white patches near the south pole are methane storm clouds. volume 2.4 winter 2010 Cosmos

Figure 3. This is the same VIMS image cube from Figure 2, but it uses images from different wavelengths to bring out the surface instead of the atmosphere. The dark brown areas near the center show where the sand dunes are located; the composition of the brighter areas has not yet been definitively identified. Areas that look bluer have more water ice. 64

64 Glimpse www.glimpsejournal.com Glimpse www.glimpsejournal.com tidally locked just like our our like just locked tidally the equator running from from running equator the linear features within the the within features linear degrees south (the south south (the south degrees middle of the image. The The image. the of middle kilometer-per-pixel V kilometer-per-pixel degrees north (the north north (the north degrees left-to-right through the the through left-to-right Saturn, because Titan is is Titan because Saturn, Figure 4. view from the T9 fly-by fly-by T9 the from view pole) at the bottom, and and bottom, the at pole) Cassini 31, the bright green terrain terrain green bright the on December26, moon), while the edges edges the while moon), that correspond to dry dry to correspond that Figure 6. wavelengths. This is a is This wavelengths. Titan at near-infrared near-infrared at Titan you canseedarkblue linear markings within within markings linear always points toward toward points always degrees longitude on on longitude degrees Titan (thepointthat 2005 center of the image image the of center sand dunes as long, long, as dunes sand pole) atthetop,90 Figure 5. projection with 90 90 with projection dark brownareas. view from the T4 T4 the from view corresponds to 0 to corresponds simple cylindrical cylindrical simple fly-by on March March on fly-by are 180degrees river channels. shows Titan’s Titan’s shows Global mapof

I n this V this n longitude. T his 1.4 2005 I I MS MS MS MS ronically, the atmosphere also frustrated also atmosphere the Ironically, scientists. air that drew the attention of the thick of blanket this was it a And atmosphere. with system solar the in moon only the Mercury, planet the as big T world- p S u - a single e of s exploration o l c I 1 Voyager itself ontoUranusandNeptuneaswell. fling to gravity planets’ the using Saturn, spacecraft, moons. fifty than more their (Jupiter, planets giant four the of reconnaissance T aperture. main the of front in out filters colored differently with images multiple detectors. photomultiplier old with cameras device) instruments were pre-CCD (charge coupled now-obsolete with equipped were 1977 planetsin outer and two The nstead, it was tasked with the only only the with tasked was it nstead, aturn’s moon, moon, aturn’s itan. Almost as as Almost itan. hese cameras made the initial initial the made cameras hese Voyager 2 Voyager Saturn, Uranus and could havecould tour. same the done Voyager They acquired color from taking T Voyager 2 Voyager itan is is itan ) that were launched to the to launched were that ) V idicon cameras. cameras. idicon pccat ( spacecraft flew by Jupiter and Jupiter by flew pinball machine as ifinagiant... around endlessly photons bounce Neptune) and O oae 1 Voyager f the two two the f Voyager T hese hese of allowing us to view through and directly illuminating the surface. off of the ubiquitous haze particles instead of passing around 0.5 microns (like than the particle diameter, the waves are able to pass the same time, when the wavelength of light is longer at waves and particles both mechanically quantum themselves. particles haze the to wavelength in smaller are that photons blocking smog, L.A.’s Like that infestsMexicoCityandtheLosAngelesbasin. atmosphere. rich the of by nitrogen—created and molecules—consisting hydrogen oxygen, carbon, organic complex of up surface, and not the surface itself. its obscures that haze atmospheric the only show 1). to be a nearly featureless, orange billiard ball (Figure 1980 close-up, high-resolution pictures showed similar to that on 1 Voyager Titan looks smooth in these images because they un’s ultraviolet light in light ultraviolet Sun’s ’s exploratory efforts. efforts. exploratory ’s

V T enus back in 1962, the spacecraft’s T visible-light wavelengths of of wavelengths visible-light hair. human a of diameter the than smaller times fifty or meter, a of millionth micron—one in T or absorbed direction. different a in deflected either are and themselves than larger particles encounter wavelengths,however, all. at deflected through the particle without being he result is not unlike the smog smog the unlike not is result he itan’s haze inhibits visibility by by visibility inhibits haze itan’s he average diameter of a particle T itan’s surface directly, photons T Voyager 1 tns ae s rud 1 around is haze itan’s itan’s cold, methane- cold, Titan’s ecause photons are photons Because used) are deflected I n a development development a n The haze is made T he shorter shorter he Instead Hence, T itan volume 2.4 winter 2010 Cosmos 65 n particular, In itan at longer at Titan itan’s atmosphere at atmosphere Titan’s igure 2). Looking outside F he T itan’s T hese wavelengths are called “atmospheric nstead of consisting of water though, the clouds are made out of methane. liquid temperature in lower atmosphere is near the triple point of methane, similar to the way thatwater is near its infrared wavelengths. We can only see the surface surface the see only can We wavelengths. infrared at wavelengths that methane does not T absorb. windows.” use of Creative the windows can highlight aspects delineate to helps that way a in atmosphere the of its various attributes ( the windows yields only haze (red/pink); looking within the windows shows mostly surface (green); can you window, a of edges the at looking then, and (blue/white). surface the above are that clouds see These clouds are giant convective thunderstorms, like those on Earth. I like 352 different images, each corresponding to a to corresponding each images, different 352 like microns. 5.2 and 0.3 between wavelength different Earth observers call this type of “hyperspectral,” imaging data but planetary scientists “spectral mapping.” call it Color information is the real power that we get from spectral view we mapping.as diminishes interference Although the and longer wavelengths, haze the atmospheric gases well. as surface the block themselves in present methane, gaseous the 5 percent level, absorbs light at most near- Titan’s isual and and isual is not a V S M VI itan in 1655, Hence, the way T ).

S he best global and M T VI acquires spectra from S M VI The resulting data cube looks Subsystem ) (ISS is a conventional he best spatial resolution on the ISS uses a narrow-band color filter pectrometer ( T S nstead, I nformation about the surface properties properties surface the about nformation I Titan’s haze is similar to the way that a Science Imaging talian astronomer who discovered nfrared Mapping n designing a follow-up mission, named Cassini, after the the after Cassini, named mission, follow-up a designing n course of a few minutes. 0.3-5.2 microns wavelength of a single spot at a time. different on focus to mirror programmable a uses it Then spots on the surface, building a 64x64 image over the Cassini’s other near-infrared instrument is the the is instrument near-infrared other Cassini’s I normal camera. surface is no better than one kilometer, and the contrast the and kilometer, one than better no is surface is only a few percent. wavelengths of light in order to penetrate the haze. While While haze. the penetrate to order in light of wavelengths the haze is partially invisible at this wavelength, some deflection off of atmospheric haze particles smears the resulting pictures. for its detector (like the one used in digital cameras that cameras digital in used one the (like detector its for you can buy today). at 0.938 microns wavelength that rejects other The visible-light camera with a 1024x1024 pixel CCD array photographer on Earth a might clear get view of distant two has Cassini filter. near-infrared a using by mountains instruments that use this technique. different photons with wavelengths larger than the size of size the than larger wavelengths with photons haze particles pass right through them. to see through enigmatic moon’s elusive surface. the in launched was which mission, this for views regional mid-1980s and is ongoing today, cameras would that see come at near-infrared from wavelengths, since I spacecraft engineers and planetary scientists sought a mechanism to see through the haze and glimpse the gets lost in the hubbub. lost gets I bounce around endlessly as if in a giant three-dimensional three-dimensional giant a in if as endlessly around bounce machine. pinball “atmospheric windows.” windows.” “atmospheric These wavelengths are called are These wavelengths surface at wavelengths that surface at wavelengths methane does not absorb. We can only see the We reflectivity of a surface—hence coal has a very low albedo, while freshly fallen snow has a very high albedo. The red channel, at 5 microns, has the least atmospheric scattering from haze, and shows the best contrast to 2 microns, revealing compositional variations across the surface, only some of which we understand. The blue channel is assigned to 1.3 microns, where areas that are richer in water ice are brighter. Because Titan is so cold, the light we see is always reflected sunlight, and not thermal emission. www.glimpsejournal.com

As you can see from Figure 3 and from the map in Figure 4, Titan’s surface as revealed by this

Glimpse color scheme changes markedly with latitude. Near Titan’s equator, dark and bright areas Figure 7. The bright and triple point on Earth and can be present in alternate. On Earth, our areas near the equator 66 unusual spectrum of this solid (ice), liquid and gaseous (vapor) form. are hot, wet tropical rainforests. But on Titan, area, along with its shape, has lead Titan scientists Methane therefore plays a similar role on most of the dark areas, spectral units that Titan to think that it might be a Titan that water does on Earth- it scientists call “dark brown,” correspond to huge cryovolcano. Volcanoes on evaporates into the air, forms clouds and fields of sand dunes (Figure 5). Though there are Earth are places where liquid rock bubbles up from rains on the surface. The effects of methane rainstorms and clouds on Titan- it the interior to cover the methane make Titan the place in the solar evidently must not rain much in these equatorial surface. Since it is so cold system that looks most like Earth. deserts! on Titan that water behaves like rock, when liquid water is forced up By looking in different windows, all from Our best resolution imaging of the dunes, taken and out onto the surface the same VIMS observation, we can build when Cassini was closest to Titan in the course of there we call it a cryovolcano. up a color image of Titan’s surface. This is its mission, showed that they are around 70 not true color, of course. True-color is meters high with 2 kilometers between dune defined as what your eyes would naturally crests. The spectrum of the dunes indicates that see. Your eyes cannot see near-infrared— they are made of organic compounds, and not and remember that in the visible, all you water ice like most of Titan’s crust. A mental Ten atmospheric would see would be haze. But the resulting analog for these might be mountains of coffee colors are real, if invisible to the human grounds almost as tall as a football field is wide. windows... eye, and they help to tell us about Titan’s The areas between dunes are free of sand; hence, surface properties. There are ten the dunes are probably still actively moving sand can be combined in atmospheric windows total due to the around today. specifics of how the methane molecule many different ways, absorbs light, and they can be combined in In other near-equatorial areas, we see long, many different ways, each of which tells a sinuous, dark albedo markings that designate the each of which tells a different story about Titan’s composition location of channels (Figure 6). Liquid methane and history. must have carved these, as they show branching different story about patterns just like rivers and streams on the Earth. Figure 3 shows a particularly useful color The channels show that, like Earth, but like no Titan’s composition combination. The green channel, at 2 other planet that we know, erosion on Titan is microns, contains the cleanest view of dominated by rainfall runoff. and history Titan’s surface albedo features. Albedo is what planetary scientists call the The geology of Titan has some fundamental differences from a rocky planet like lakestands in the geologic past. It is clear Earth, though. Instead of Earth’s that the methane cycle on Titan is active silicate rock crust, the crust of Titan is and dynamic, and will be of great interest made out of water ice. On Earth, heat for future studies. from the planet’s interior melts rock, volume 2.4 winter 2010 which is then extruded onto the surface The Cassini mission will continue until Because Titan is so and spewed out of volcanoes. The the end of this Titan season in 2017. equivalent of lava spewing forth on Near-infrared imaging provides an cold, the light we see Titan, then, would be interior heat opportunity for many new discoveries melting crustal ice and spewing out when we look into unexplored territory. is always reflected water. We call this “cryovolcanism.” Several exciting follow-ons have been The near-infrared imagers on Cassini proposed for when Cassini’s remarkable sunlight, and not have shown tantalizing evidence of mission ends. The next Titan mission may Cosmos possible cryovolcanism in a few places be an orbiter capable of global 25-meter thermal emission. on Titan (Figure 7). The shape of the resolution imaging, or a lander to sploosh albedo patterns shows finger-like structures that resemble terrestrial lava flows. These still need further 67 study, but if proven genuine, would show that Titan’s interior remains active today.

At Titan’s north and south poles, Cassini found one of the most exciting discoveries in the space program’s history- lakes of liquid methane. Liquid water is ubiquitous on Earth, but no liquid had been seen anywhere else before. Figure 8 shows a combined VIMS and ISS view of the lake called Ontario Lacus near Titan’s south pole. The lake is around the same size as Lake Ontario of North America’s Great Lakes on Earth. A mixture of liquid ethane and methane fills the lake.

Surrounding the lake are two rings: the inner dark and the outer bright. They into one of the northern lakes, or a seem to be remnants from when the propeller-driven airplane to take license- Figure 8. Here is a closeup view of a liquid methane- and ethane-filled lake lake level was higher in the past. The plate scale pictures of the surface. With named Ontario Lacus near Titan’s inner ring looks like mudflats that are any luck, what we find will continue to south pole. The background black-and- inundated seasonally. Titan’s seasons exemplify the kind of flexible science that white view is from ISS; the color view in the southeast corner is from VIMS. are about as strong as those of Earth an imaging system can do. With the This view starts to show shoreline since its axis tilt is similar, but the detailed information gleaned from features that may be similar to seasons there last twenty-eight years Cassini’s imaging exploration in particular, mudflats and salty playas on Earth. instead of one here on Earth. The most people would now agree that Carl outer ring may be evaporite deposits, Sagan was right all along. w like salt flats on Earth, from higher