CaltechAUTHORS
Published October 2016 | Version Published
Journal Article Open

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

Creators

  • 1. ROR icon Jet Propulsion Lab
  • 2. ROR icon Southwest Research Institute
  • 3. ROR icon University of Washington
  • 4. ROR icon Arizona State University
  • 5. ROR icon Marshall Space Flight Center
  • 6. ROR icon California Institute of Technology
  • 7. ROR icon Northern Arizona University
  • 8. ROR icon Cornell University
  • 9. ROR icon University of Alberta
  • 10. ROR icon Purdue University West Lafayette
  • 11. ROR icon Laboratory for Atmospheric and Space Physics
  • 12. ROR icon Johns Hopkins University Applied Physics Laboratory
  • 13. ROR icon Pennsylvania State University
  • 14. ROR icon University of Copenhagen
  • 15. ROR icon University of Chicago
  • 16. ROR icon Goddard Space Flight Center
  • 17. ROR icon Laboratoire de Planétologie et Géodynamique de Nantes
  • 18. ROR icon Johnson Space Center
  • 19. ROR icon Brown University
  • 20. ROR icon Laboratoire de Géologie de Lyon : Terre, Planètes et Environnement
  • 21. ROR icon Western Washington University
  • 22. ROR icon University of California, Davis
  • 23. ROR icon Research Institute in Astrophysics and Planetology
  • 24. ROR icon Massachusetts Institute of Technology
  • 25. ROR icon University of Oslo
  • 26. ROR icon Harvard University
  • 27. ROR icon Georgia Institute of Technology
  • 28. ROR icon Planetary Science Institute

Abstract

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.

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.

Attached Files

Published - Ehlmann_et_al-2016-Journal_of_Geophysical_Research-_Planets.pdf

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Ehlmann_et_al-2016-Journal_of_Geophysical_Research-_Planets.pdf

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Additional details

Identifiers

Eprint ID
70402
Resolver ID
CaltechAUTHORS:20160916-124841566

Dates

Created
2016-09-16
Created from EPrint's datestamp field
Updated
2021-11-11
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Caltech Custom Metadata

Caltech groups
Division of Geological and Planetary Sciences (GPS)