Migrating Scarps as a Significant Driver for Cometary Surface Evolution


(Georeferenced images of the Hapi region. (a) On February 28, 2015 the smooth plains are uniform and featureless. Depressions (yellow arrows in all panels) began to appear in this region in March 2015 (b/c), and then coalesced into larger features over a 2+ month period (d/e). Images 12 months later (after perihelion; panel f) show a similar surface prior to depression formation (a), with featureless smooth terrains. Underlying boulders, however, have been excavated (cyan arrows) as a result of the changes in panels b-e. Note that artifacts in the images are due to image projections, and they do not alter our interpretations.

Rosetta observations of 67P/Churyumov-Gerasimenko (67P) reveal that most changes occur in the fallback-generated smooth terrains, vast deposits of granular material blanketing the comet's northern hemisphere.

These changes express themselves both morphologically and spectrally across the nucleus, yet we lack a model that describes their formation and evolution. Here we present a self-consistent model that thoroughly explains the activity and mass loss from Hapi's smooth terrains. Our model predicts the removal of dust via re-radiated solar insolation localized within depression scarps that are substantially more ice-rich than previously expected. We couple our model with numerous Rosetta observations to thoroughly capture the seasonal erosion of Hapi's smooth terrains, where local scarp retreat gradually removes the uppermost dusty mantle.

As sublimation-regolith interactions occur on rocky planets, comets, icy moons and KBOs, our coupled model and observations provide a foundation for future understanding of the myriad of sublimation-carved worlds.

Samuel Birch, Alexander Hayes, Orkan Umurhan, Yuhui Tang, Jean-Baptiste Vincent, Nilda Oklay, Dennis Bodewits, Bjorn Davidsson, Raphael Marschall, Jason Soderblom, Jeff Moore, Paul Corlies, Steven Squyres
(Submitted on 9 Sep 2019)

Comments: 14 pages, 4 figures, accepted GRL
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:1909.03853 [astro-ph.EP] (or arXiv:1909.03853v1 [astro-ph.EP] for this version)
Submission history
From: Samuel Birch
[v1] Mon, 9 Sep 2019 13:39:50 UTC (2,370 KB)
https://arxiv.org/abs/1909.03853

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