The lakes and seas of Titan are a sink of products of photolysis in the atmosphere, and a crucial component in Titan's active methane cycle. In situ exploration of the seas is necessary to understand their intriguing prebiotic organic chemistry

Aharonson, O.

Bierhaus, E.

Clark, B.

Griffith, C.

Harri, A.-M.

Kantsiper, B.

Karkoschka, E.

Kirk, R.

Lorenz, R. D.

Lunine, J. I.

Mahaffy, P.

Newman, C.

Ravine, M.

Stofan, E. R.

Trainer, M.

Waite, H

Zarnecki, J.

English

Open Research Online (The Open University)

Open Research OnlineThe Open University’s repository of research publicationsand other research outputsTitan Mare Explorer (TiME): first in situ exploration ofan extraterrestrial seaConference or Workshop ItemHow to cite:Stofan, E. R.; Lorenz, R. D.; Lunine, J. I.; Aharonson, O.; Bierhaus, E.; Clark, B.; Griffith, C.; Harri, A.-M.;Karkoschka, E.; Kirk, R.; Kantsiper, B.; Mahaffy, P.; Newman, C.; Ravine, M.; Trainer, M.; Waite, H and Zarnecki,J. (2010). Titan Mare Explorer (TiME): first in situ exploration of an extraterrestrial sea. In: Astrobiology ScienceConference 2010: Evolution and Life: Surviving Catastrophes and Extremes on Earth and Beyond, 26-29 Apr 2010,League City, Texas, USA.For guidance on citations see FAQs.c© 2010 The AuthorsVersion: Version of RecordLink(s) to article on publisher’s website:http://www.lpi.usra.edu/meetings/abscicon2010/pdf/5270.pdfCopyright and Moral Rights for the articles on this site are retained by the individual authors and/or other copyrightowners. For more information on Open Research Online’s data policy on reuse of materials please consult the policiespage.oro.open.ac.ukTITAN MARE EXPLORER (TiME): FIRST IN SITU EXPLORATION OF AN EXTRATERRESTRIALSEA.  E.R. Stofan1, R.D. Lorenz2, J.I. Lunine3, O. Aharonson4, E. Bierhaus5, B. Clark6, C. Griffith7, A-M. Harri8, E.Karkoschka7, R. Kirk9, B. Kantsiper2, P. Mahaffy10, C. Newman4,14, M. Ravine11, M. Trainer10, H. Waite12, and J.Zarnecki13. 1Proxemy Research, Rectortown, VA 20140; 2Applied Physics Laboratory, Johns Hopkins University,Laurel MD 20723; 3Dipartimento di Fisica, Università degli Studi di Roma “Tor Vergata",  Rome, Italy, 4CaliforniaInstitute of Technology, Pasadena, CA 91125; 5Lockheed Martin, Denver, CO; 6Space Science Institute, Boulder CO80301; 7LPL, U. Arizona, Tucson, AZ 85721;  8Finnish Meteorological Institute, Finland; 9U.S.G.S. Flagstaff, AZ86001; 9NASA Goddard SFC, Greenbelt, MD 20771; 11Malin Space Science Systems, San Diego, CA 92191;12SWRI, San Antonio, TX 78228; 13PSSRI, The Open University, Milton Keynes, UK MK7 6BJ.14Ashima Research,Pasadena, CA 91106Introduction: Prior to Cassini, oceans of liquidhydrocarbons were thought to cover much of the sur-face of Titan.  Initial data from Cassini-Huygens in-stead found the equatorial and mid-latitude regions tobe dry, characterized by riverbeds and ‘seas’ of dunes[1-3]. The discovery of lakes in Titan’s northern hemi-sphere established that liquid hydrocarbons exist on thesurface of the haze-shrouded moon [4], and the detec-tion of the presence of ethane in Ontario Lacus nearthe South Pole confirmed that lakes are liquid-filled[5]. Near the north pole, more than 400 lakes havebeen identified, predominantly north of ~ 70°N, withsizes that range from a few square kilometers to in ex-cess of 100,000 km2 [7, 8].  The lakes and seas fillthrough rainfall and/or intersection with the subsurfaceliquid methane table, and providing the first evidencefor an active condensable-liquid hydrological cycle onanother planetary body. The Titan Mare Explorer(TiME) is a Discovery-class mission that lands in aTitan sea, and provides in situ measurements to con-strain Titan’s active methane cycle as well as its in-triguing prebiotic organic chemistry.Many aspects of the lakes and seas of Titan are un-known, including their composition, physical proper-ties, depths, and shoreline characteristics, but are keyparameters for constraining the liquid cycle, and thusare the key targets for the TiME mission.  Titan’s lakesand seas are likely to contain some combination ofliquid methane and liquid ethane, with admixtures ofnitrogen and organic species. Titan’s methane cycle isdominated by evaporation in equatorial regions andprecipitation near the poles, allowing the lakes andseas to persist in polar regions [9].  Therefore, the sta-bility of lakes and seas on Titan’s surface is dependentupon the abundance of methane in the atmosphere-surface system, as well as liquid methane in subsurfacealkanifers. Ethane, a dominant product of methanestratospheric photochemistry, is liquid under Titansurface conditions, and its presence in the lakes andseas would add to their stability against evaporation[10]. The methane/ethane ratio in the lakes cannot beconstrained with current data, but both methane andethane were detected evaporating into the Huygensprobe mass spectrometer after landing [11], ethane hasbeen detected in Ontario Lacus [5], and late wintertropospheric clouds (which must be largely methane)appeared above the lakes region [12].  Constrainingthis ratio is critical to determining the significance ofthe sources of methane. In addition to likely seasonalchanges in lake composition and depth [10,13], Titan’slakes and seas may participate in longer-term pole-poletransport forced by the changing astronomical configu-ration of the seasons, much like the Croll-Milankovichforcing of glacial cycles on Earth and Mars [14].In addition to ethane, methane and nitrogen Titan’sseas will likely contain dissolved amounts of manyother compounds – the seas represent a sink for theproducts of photolysis in the atmosphere. It is not in-conceivable that further chemistry may take place onthe surface, yielding prebiotic molecules impossible toform in the gas phase. It has even been suggested thatautocatalytic chemical cycles might yield far-from-equilibrium abundance patterns or mimic the function-ality of biological systems [15,16]. Only in-situ chemi-cal analysis can yield insight into these speculativepossibilities.Mission Description:  The target for the TiMEmission is Ligeia Mare, at 78°N, 250°W.  It is one ofthe largest seas identified to date on Titan, with a sur-face area of ~100,000 km2.  Kraken Mare, to the southof Ligeia, is a potential backup target.  The mission isdirectly responsive to goals from the 2003 Solar Sys-tem Decadal Survey [17], including the goal of under-standing volatiles and organics in the solar system, bydirectly measuring the organics on another planetaryobject, and understanding planetary processes, by per-forming the first active measurement of a liquid cyclebeyond Earth. This Discovery concept would test theAdvanced Stirling Radioisotope Generators (ASRGs)in both a deep space and non-terrestrial atmosphereenvironments, and would pioneer low-cost, outer solarsystem missions.Science objectives for the mission include meas-uring the chemistry of the sea to determine their role asa source and sink of methane and its chemical prod-ucts, determining the depth of the sea to help constrain5270.pdfAstrobiology Science Conference 2010 (2010)organic inventory, ascertaining marine processes in-cluding the nature of the sea surface and sea circula-tion, determining sea surface meteorology, and con-straining prebiotic chemistry in the sea. Instrumentsinclude a mass spectrometer, imaging systems and aphysical properties and meteorology package. Launchopportunities include January 2015 and 2016, witharrivals in 2022 and 2023, respectively.  The Earth andsun remain above the horizon for the three monthminimum lifetime, during which TiME collects andtransmits data on the sea.  Therefore, a launch prior to2020 is enabling for this mission, as launch dates afterthat date arrive in northern winter, after the sun andEarth have set, making direct to Earth transmissioninfeasible, and minimizing science observations.TiME’s high heritage instruments, GFE power andlaunch systems, simple surface operations and benignentry, descent and landing conditions make a lakelander mission to Titan achievable in Discovery.TiME science is fundamental, and will provide the firstin situ exploration of an extraterrestrial sea, the first insitu measurements of an active liquid cycle beyondEarth, and aid in understanding the limits of life in oursolar system.Acknowledgents: For JIL, this work was financedwith in the scope of the program "Incentivazione alla mo-bilita' di studiosi straineri e italiani residenti all'estero."References: [1] Elachi, C. et al. (2006) Nature, 441,709–713. [2] Lorenz R.D. et al. (2006) Science, 312,724–727. [3] Lunine, J.I. et al. (2008) Icarus, 195, 415–433.[4] Stofan, E.R. et al. (2007) Nature, 445,doi:10.1038/nature05438. [5] Brown, R.H. et al. (2008) Na-ture, 454, 607-610. [6] [7] Hayes, A. et al. (2008) Geophys.Res. Lett., 35, doi:10.1029/2008GL033409. [8] Mitchell, K.et al. (2009), J. Geophys. Res., in review. [9] Rannou, P. etal. (2006) Science, 311, 201-205. [10] Mitri, G. et al. (2007)Icarus, 186, 385-394. [11] Niemann, H.B. et al. (2005)Nature, 438, 779- 784. [12] Brown, R.H., et al. (2008) AGU,89(53), Fall Meet. Suppl., Abstract P12A-03. [13]. Tokano,T. (2009), Astrobiology, 9, 147-164   [14] Aharonson, O. etal. (2009) Nature Geoscience, 2, 851-854   [15] ‘Limits ofOrganic Life in Planetary Systems’, (2007) National Re-search Council,116pp.  [16]  Lunine, J. I. (2009), Proceed-ings of the American Philosophical Society, in press [17]‘New Frontiers in the Solar System: An Integrated Explora-tion Strategy’ (2003) National Research Council, 248pp.5270.pdfAstrobiology Science Conference 2010 (2010)

Titan Mare Explorer (TiME): first in situ exploration of an extraterrestrial sea

Titan Mare Explorer (TiME): first in situ exploration of an extraterrestrial sea

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