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The Sustainability of Habitability on Terrestrial Planets: Insights, Questions, and Needed Measurements from Mars for Understanding the Evolution of Earth-like Worlds

Ehlmann, B. L. and Anderson, F. S. and Andrews-Hanna, J. and Catling, D. C. and Christensen, P. R. and Cohen, B. A. and Dressing, C. D. and Edwards, C. S. and Elkins-Tanton, L. T. and Farley, K. A. and Fassett, C. I. and Fischer, W. W. and Fraeman, A. A. and Golombek, M. P. and Hamilton, V. E. and Hayes, A. G. and Herd, C. D. K. and Horgan, B. and Hu, R. and Jakosky, B. M. and Johnson, J. R. and Kasting, J. F. and Kerber, L. and Kinch, K. M. and Kite, E. S. and Knutson, H. A. and Lunine, J. I. and Mahaffy, P. R. and Mangold, N. and McCubbin, F. M. and Mustard, J. F. and Niles, P. B. and Quantin-Nataf, C. and Rice, M. S. and Stack, K. M. and Stevenson, D. J. and Stewart, S. T. and Toplis, M. J. and Usui, T. and Weiss, B. P. and Werner, S. C. and Wordsworth, R. D. and Wray, J. J. and Yingst, R. A. and Yung, Y. L. and Zahnle, K. J. (2016) The Sustainability of Habitability on Terrestrial Planets: Insights, Questions, and Needed Measurements from Mars for Understanding the Evolution of Earth-like Worlds. Journal of Geophysical Research. Planets, 121 (10). pp. 1927-1961. ISSN 2169-9097.

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What allows a planet to be both within a potentially habitable zone and sustain habitability over long geologic time? With the advent of exoplanetary astronomy and the ongoing discovery of terrestrial-type planets around other stars, our own solar system becomes a key testing ground for ideas about what factors control planetary evolution. Mars provides the solar system's longest record of the interplay of the physical and chemical processes relevant to habitability on an accessible rocky planet with an atmosphere and hydrosphere. Here we review current understanding and update the timeline of key processes in early Mars history. We then draw on knowledge of exoplanets and the other solar system terrestrial planets to identify six broad questions of high importance to the development and sustaining of habitability (unprioritized): (1) Is small planetary size fatal? (2) How do magnetic fields influence atmospheric evolution? (3) To what extent does starting composition dictate subsequent evolution, including redox processes and the availability of water and organics? (4) Does early impact bombardment have a net deleterious or beneficial influence? (5) How do planetary climates respond to stellar evolution, e.g., sustaining early liquid water in spite of a faint young Sun? (6) How important are the timescales of climate forcing and their dynamical drivers? Finally, we suggest crucial types of Mars measurements (unprioritized) to address these questions: (1) in situ petrology at multiple units/sites; (2) continued quantification of volatile reservoirs and new isotopic measurements of H, C, N, O, S, Cl, and noble gases in rocks that sample multiple stratigraphic sections; (3) radiometric age dating of units in stratigraphic sections and from key volcanic and impact units; (4) higher-resolution measurements of heat flux, subsurface structure, and magnetic field anomalies coupled with absolute age dating. Understanding the evolution of early Mars will feed forward to understanding the factors driving the divergent evolutionary paths of the Earth, Venus, and thousands of small rocky extrasolar planets yet to be discovered.

Item Type:Article
Related URLs:
URLURL TypeDescription
Ehlmann, B. L.0000-0002-2745-3240
Cohen, B. A.0000-0001-5896-5903
Dressing, C. D.0000-0001-8189-0233
Farley, K. A.0000-0002-7846-7546
Fassett, C. I.0000-0001-9155-3804
Fischer, W. W.0000-0002-8836-3054
Fraeman, A. A.0000-0003-4017-5158
Golombek, M. P.0000-0002-1928-2293
Hamilton, V. E.0000-0001-8675-2083
Johnson, J. R.0000-0002-5586-4901
Kasting, J. F.0000-0003-4042-2067
Kinch, K. M.0000-0002-4629-8880
Kite, E. S.0000-0002-1426-1186
Knutson, H. A.0000-0002-0822-3095
Lunine, J. I.0000-0003-2279-4131
Mahaffy, P. R.0000-0003-1896-1726
Mangold, N.0000-0002-0022-0631
Rice, M. S.0000-0002-8370-4139
Stack, K. M.0000-0003-3444-6695
Stevenson, D. J.0000-0001-9432-7159
Wordsworth, R. D.0000-0003-1127-8334
Yingst, R. A.0000-0002-0628-4265
Yung, Y. L.0000-0002-4263-2562
Additional Information:© 2016 American Geophysical Union. This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made. Accepted manuscript online: 15 September 2016; Manuscript Accepted: 13 September 2016; Manuscript Revised: 12 September 2016; Manuscript Received: 16 July 2016. One of us (Y.L.Y.) thanks Vlada Stamenkovic for illuminating discussions of the Martian atmosphere at the KISS Workshop on Methane on Mars. As per AGU's data availability policy, this paper is a review paper and contains no new data. Thanks to two reviewers and the editor for comments that improved this manuscript.
Subject Keywords:Mars history; Planetary evolution; Habitability; Sustainability; Terrestrial exoplanets
Issue or Number:10
Record Number:CaltechAUTHORS:20160916-124841566
Persistent URL:
Official Citation:Ehlmann, B. L., et al. (2016), The sustainability of habitability on terrestrial planets: Insights, questions,and needed measurements from Mars for understanding the evolution of Earth-like worlds, J. Geophys. Res. Planets, 121, 1927–1961, doi:10.1002/2016JE005134
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:70402
Deposited By: Tony Diaz
Deposited On:16 Sep 2016 20:03
Last Modified:09 Mar 2020 13:19

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