New Frontiers in the Solar System An Integrated Exploration Strategy (2003) / Chapter Skim
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5 Large Satellites: Active Worlds and Extreme Environments
5 Large Satellites: Active Worlds and Extreme Environments
Pages 118-150
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From page 119... ...
Io. who' surfed is constantly renewed by active volcanoes tinged with sulfur allotropes; Europe which pronely possums ~ liquid wear omen beneath its rustily in skin; Oanym~, ~ moon bigger On the planet Mercury, possessing ~ rump surfed of dire id and an internally generated magnetic field; and Cellists, ~ moon with an ancient cratered surfed who' interior is only weakly differentiate~l.
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From page 120... ...
Water is essential to life as we know it, md He large icy satellites may contain He largest reservoirs of liquid water in the solar system. Outside Earth Europa may be the best place in the solar system to search for extant life.
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From page 121... ...
The imported of tidal dissipation in ~e origin arid evolution of resonar~t configurations is apparent in the Jovian system' where Io' Europa' arid Gar~ymede interact through multiple resonates, arid where tidal dissipation drives Ions volcar~ism arid may maintain art ocem within Europa. At Saturn, resonances currently exist between ~e sa~lli~ pairs Mimas-Tethys' En~ladus-Dione, arid Titar~-H~rion; arid ~ Urmus, paired resonar~es likely once existed among the sa~lli~s Mirar~da' Ariel, arid Umbriel.
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From page 122... ...
Galileo imaging of the large Jovian satellites has revolutionized our understanding of large-satellite Ebonies. Io has mountains that soar to 17 km ~11, probably formed as volemie materials piled onto the surface, placing He entire lithosphere into compression.> C~listo shows enormous multiringed structures' which ~ high resolution consist of normal fault sharps md graben.~7 These md similar concentric structures on C~ymede md Europa probably formed when large impacts penetrated through the smelliest bridle lithospheres to mobile material below plausibly liquid wear.
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From page 123... ...
LATHE SA=~S FIGURE 5.2 Europa displays ~ win varicose of curfew forms, including the' so-=ll~1 ridged plains. Them features Connie of many parallel.
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From page 124... ...
D~ap'r'~m Interior material also em be brought to Me surface of ~ satellite though diapirism, in which buoyancy forces due to ~ density inversion cause mobile material to pierce md rise Trough ~ higher-density overburden. ~ the icy satellites, Tritonts piked ``em~loupe,' terrain offers the most dramatic example of ~ surface apparently turned inside out by diapirism' perhaps owing to compositions layering of various frozen volatiles.
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From page 125... ...
The darken regions, having margins similar to thou formed by fluid Ma flows on Earth, are ~lic~e<1 to ~ relatively young l~u' they are not yet covere<1 with plume fallout and are, perhaps No warm for bright gas rich in sulfur dioxin to coning. The old brigh~r plains to the upper right are co~7er~1 6y ridges formals possibly, by the folding of the surfed or by deposition or erosion.
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From page 126... ...
Tim receives ~100 times less solar insolation' Me energy that fuels terrestrial weather. In Contact, Tim has roughly 100 times more latent hem available for fueling weaner than does Earn.
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From page 127... ...
Laboratory simulations of this satellites photoehemis~ produce solid residues having optical properties similar to Hose of Titans hue. Their elements composition hints ~~ alkalies' aromatic compounds' heteropolymers, md amino acids, key initial compounds in lifers chemist' are constituent of Titans h~e.4 ~ Chemical reactions ~ Times surface proceed very slowly' potentially in cold 194 K)
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From page 128... ...
This non-iee component presumably represents ~ mixture of material originally secreted with He smelliest subsequent comet md Steroid impacts, md components implanted mdior modified by magnetospherie environments. On Europa' the presence of heavily hydrated sulfurs has been inferred, including sulfuric acid md sulfate Salk.
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From page 129... ...
Sput~dmp~'on M&gnet~pheric Prowesses and Alterations The large sullies of ~e gaseous gimt planets spend all or most of their time in ~e coro~ting magnetospheres of Base plumb. The interaction of sa~lli~ arid coro~ting plume modifies ~e sa~lli~' surfaces arid atmospheres arid leads to ~ net loss of vol~ile materials to ~e magnetospheres.
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From page 130... ...
, to future mission concepts win varying degrees of design md study (e.g., Tim Explorer' Europa Landers' Neptune Orbiter)
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From page 131... ...
The primp objectives of He mission, as defiled by He Europa Orbiter Science Definition Team, em be split into two groups in terms of their privily. The highest-priority, or Group I' objectives are as follows: Determine the presence or absence of ~ ocem; Char aeterize the ~ree-dimensiona1 distribution of my subsurface liquid wear md its overlying fee layer; Understand the formation of surface features, including sips of recent or current activity; md Identify Redid lading sites for future lander missions.
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From page 132... ...
Europa Astrobiology 1~r A more ambitious Europa mission concept involves ~ study of orgar~ie ehemis~y md possible biosignatures from ~ landed station. The science rationale md some of He experiment concepts for such ~ mission have developed recently in ~ series of workshops sponsored by the Europa Focus Group of He NASA Astrobiology Institute' md are eomplemen~ry to objectives developed by He 1999 NASA Campaign Science Working Group for Prebiotie Chemistry in the Outer Solar System, but no complete system mission studies of He concept have been performed.
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From page 133... ...
A suite of remote-sensing experiments is assumed' with emphasis on the monitoring of Iots active volemism md relend processes. Laymen 0~r The C~ymede Orbiter mission is similar in concept to the Europa Geophysical Explorer, but He impraetieable goal of measuring C~ymedets very small tides is replaced by ~ increased emphasis on C~ymedets internally generated magnetic field md id interaction win thy of Jupiter.
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From page 134... ...
reside in extremely high radiation environments. Improvements in radiation-hard component Id design are essential to future exploration of these worlds.
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From page 135... ...
Tim orbiters arid Ionospheric explorers are one highly promising use of this Ethnology. One of the po~ntia1 missions of brew interest for both large sa~lli~ md gimt pit research ~e Neptune Orbiter requires eider solar-electric propulsion combined with advanced aerocapture capability or nuclear-electric propulsion to achieve art acceptable payload md mission capability.
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From page 136... ...
The advantage of ~ GSMT, win ~ aceomp~yin$ advance in adaptive optics'
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From page 137... ...
The following key questions emerge as He most important next sups toward underfunding He origin md evolution of satellite systems: ~ How do conditions in He protoplmet~ nebula influence the compositions' orbits' md sizes of He resulting satellites: ~ How do factors such as sing composition, orbital evolution, md tidal hewing influence the differentiation md ouches sing processes in large md midsized satellites: In particular' why is Tim the only large satellite win thick atmosphere: To what extent are the surfaces of icy satellites coupled to Heir interiors (chemically md physieally) 9 ~ How has the impaetor population in the outer solar system evolved Trough time, md how is it different from He inner solar system: ~ What does the magnetic field of C~ymede tell us about its Herman evolution, md do over large s~elli~s have intrinsic magnetic fields:
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From page 138... ...
Titan illuminates the organic chemistry that proceeds in more reduced environments than Earths. It is ~ intact chemical laboratory where ultraviolet photolysis md electron bombardment initial the synthesis of carbon md nib open that ultimately forms complex organic solids in He s~ato sphere.
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From page 139... ...
This analysis also illustrates that ~ flyby-lype mission such as the Neptune Flyby fairs poorly in the ruing matrix because mmy important measurement objectives em only be met from He global mdior Import coverage provided by ~ orbiting spaceport or from in situ surface measurements from ~ lander. It should be mood that the Uranus Orbiter also fares poorly compared win the Neptune Orbiter' because dynamic Triton is especially interesting.
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From page 141... ...
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From page 142... ...
749 .~ Con /10~109~]
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From page 144... ...
How does tidal heating affect the evolution of worldly Cassini-Huygerls, Europa Geophysical Explorer' Nepturle Orbiter' Uranus Orbiter Europa Geophysical Explorer' Europa Pathfirl~r Lo dry Europa Astrobiology Lear Cassini-Huygerls, Titan Explorer Cassini-Huygerls' lo Observer' Titan Explorer' Nepturle Orbiter Europa Astrobiology Lo der Titan Explorer Tritor~' Titan Er~mladus' Callisto' G~ymede' Europa Io' Europa' G~yme~' Tritorl' Erlm ladu s' h] irarlda Cassini-Huygerls, Europa Geophysical Explorer' Nepturle Orbiter' G~ymede Orbiter To Observer' Europa Geophysical Explorer' Nepturle Orbiter' G~ymede Orbiter' Cassini-Huygerls, Uranus Orbiter
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From page 145... ...
Tim is ~ unique natural laboratory for orgar~ic chemistry, unlike my over environment in ~e solar system' arid clearly the prime Argot for theme ~ exploring orgar~ic-rich environments arid high-priority question 2' How far toward life does orgar~ic chemistry proceed in extreme environmental Titar~'s atmosphere not only crews this scientifically interesting environment, but also filings future exploration via aerocapture arid airborne mobility. Titm may also have ~ subsurface wear layer md could prove to ~ ~ promising location to search for past or exit life or its precursor chemistry, md it is importmt to several over Demos md questions (s~ Table Sib.
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From page 146... ...
4. Neptune Orbiter
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From page 147... ...
Although the Ethnology recommendations above follow logically from the parcels science arid mission rankings, technologies may ~ developed for over reasons. For example' ~e administrations FY ZWS budget proposal includes funding for nuclear-electric propulsion.
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From page 148... ...
Appian Spe odometer (NIBS) Resu lts from the Galileo Flays ire ~ ?
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From page 149... ...
Sagan 1lOrg~ic Chemistry on Titar~urfam Trier ire Proceeded of ~e ~mpostam o~ ~~' Europear1 Spam A~rl~ Specia1 Public~iorl, SP-338> Europe~ Spam A~rl~. Noordwijk' Netherl~ds' ~ ?
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