Exoplanet Geology: What Can We Learn From Current And Future Observations?

By Keith Cowing
Status Report
April 26, 2024
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Exoplanet Geology: What Can We Learn From Current And Future Observations?
The cosmic shoreline proposed by Zahnle & Catling (2017) in terms of present-day stellar flux (A), I ∝ v4 esc, and integrated XUV flux (B), Ixuv ∝ v4 esc, with regions where planets should be airless and should retain their atmospheres labelled. The four planets interpreted to be airless based on thermal emission are plotted. Depending on the chosen formulation for the cosmic shoreline, the two Trappist planets may fall into either the regime where they would be predicted to still retain atmospheres or to be airless. — astro-ph.EP

Nearly 30 years after the discovery of the first exoplanet around a main sequence star, thousands of planets have now been confirmed.

These discoveries have completely revolutionized our understanding of planetary systems, revealing types of planets that do not exist in our solar system but are common in extrasolar systems, and a wide range of system architectures. Our solar system is clearly not the default for planetary systems.

The community is now moving beyond basic characterization of exoplanets (mass, radius, and orbits) towards a deeper characterization of their atmospheres and even surfaces. With improved observational capabilities there is potential to now probe the geology of rocky exoplanets; this raises the possibility of an analogous revolution in our understanding of rocky planet evolution. However, characterizing the geology or geological processes occurring on rocky exoplanets is a major challenge, even with next generation telescopes.

This chapter reviews what we may be able to accomplish with these efforts in the near-term and long-term. In the near-term, the James Webb Space Telescope (JWST) is revealing which rocky planets lose versus retain their atmospheres.

This chapter discusses the implications of such discoveries, including how even planets with no or minimal atmospheres can still provide constraints on surface geology and long-term geological evolution. Longer-term possibilities are then reviewed, including whether the hypothesis of climate stabilization by the carbonate-silicate cycle can be tested by next generation telescopes. New modeling strategies sweeping through ranges of possibly evolutionary scenarios will be needed to use the current and future observations to constrain rocky exoplanet geology and evolution.

Bradford J. Foley

Comments: Chapter 15 accepted for publication in the Reviews in Mineralogy and Geochemistry (RiMG) Volume 90 on “Exoplanets: Compositions, Mineralogy, and Evolution” edited by Natalie Hinkel, Keith Putirka, and Siyi Xu; 31 pages, 8 figures, and 5 equations
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR); Geophysics (physics.geo-ph)
Cite as: arXiv:2404.15433 [astro-ph.EP] (or arXiv:2404.15433v1 [astro-ph.EP] for this version)
Submission history
From: Brad Foley [via Natalie Hinkel as proxy]
[v1] Tue, 23 Apr 2024 18:19:54 UTC (810 KB)

Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) 🖖🏻