![\"Transport](\"https:\/\/www.newsbeep.com\/nz\/wp-content\/uploads\/2026\/06\/Transport-of-Water.png\")
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\n Initial structure of the Impact Plume 60 s post impact. The impactor strikes from the left, at a 60\u00b0 angle from horizontal, with the sun located to the right.There is a visible asymmetry in the plume due to the direction of impact; the \u201chole\u201d on the right side of the plume is a bubble in this 2D slice of a fully 3D plume due to the removal of water vapor-rock mixtures from the simulation during the sampling from SOVA into DSMC codes (Prem et al. 2015). (Top) the plume contains a region of high density (~1022 molecules\/m3 ) just above the point of impact, which rapidly drops toward the edges of the plume. (Bottom, left) The high plume densities correspond to short mean free paths for the vapor molecules. (Bottom, right) Comparing this mean free path with the length scale of the density gradient reveals very small Knudsen numbers throughout; the entire plume (except for the very outermost edges) is clearly within the continuum flow regime at this time, rather than the slip-flow, Knudsen, or Free Molecular regimes. \u2014 astro-ph.EP <\/p>\n
Mercury\u2019s polar cold traps host water ice deposits that are likely populated with impact-delivered water via Mercury\u2019s exosphere.<\/p>\n
However, Mercury\u2019s near-sun location experiences an extremely high photodestruction rate that rapidly destroys water with a timescale of only ~3.5 hours. Here we use the PLANET DSMC code to investigate the fate of water from a single 1 km radius comet impact striking Mercury\u2019s North Pole (30 km\/s at angle of 60\u00b0).<\/p>\n
We find that the evolving plume separates into four distinct phases:<\/p>\n
1) an early plume phase in which ballistic escape and photodestruction reach their peaks,<\/p>\n
2) a reentry phase in which water falling back toward the surface forms a self-shielded shock-topped atmosphere that migrates across the surface and ballistic loss ceases,<\/p>\n
3) a quasi-steady phase in which a self-shielding dawn atmospheric enhancement (DAE) forms and drives, a tenuous migration of exospheric water to the cold traps with a longitudinal dependence, and finally<\/p>\n
4) a late phase in which self-shielding ends and photodestruction dominates, effectively ending substantial water migration.<\/p>\n
In this work, we quantify the fates of the arriving water molecules, and describe some of the more important features of this highly unsteady, evolving three-dimensional atmosphere.<\/p>\n
We find that 23% of the initial water is photodestroyed, 65% of the water ballistically escapes the system (of which, 79% photodissociates prior to reaching the Hill radius), and 14% ends up in Mercury\u2019s cold traps, which is significantly more than the ~5% that migrates to the Moon\u2019s cold traps during an equivalent impact.<\/p>\n
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<\/p>\n
Mass density of deposited ices into Mercury\u2019s discrete cold traps. The comet impact deposits significant water into Mercury\u2019s cold traps; The discrete cold traps collect (top) ~6-26 kg\/m2 in the North and (bottom)~4-7 kg\/m2 of comet ice throughout the impact process; with cold trap densities generally increasing with increasing latitude; highest densities are found closest to the impact site at the north pole. The sizes of these circles correspond to their surficial extent. Note different scale bars for north and south poles. Diffuse cold traps are not plotted in these figures, as they would cover the discrete cold traps. Cold trap densities plotted above a subset of the USGS maps of the Borealis quadrangle in the north (top) and the Bach Quadrangle in the south (bottom) \u2014 astro-ph.EP<\/p>\n
Jordan K. Steckloff, David B. Goldstein, Philip L. Varghese, Laurence M. Trafton, Parvathy Prem<\/p>\n
Subjects: Earth and Planetary Astrophysics (astro-ph.EP) Astrobiology, Astrogeology, Astrochemistry,<\/p>\n","protected":false},"excerpt":{"rendered":"Initial structure of the Impact Plume 60 s post impact. The impactor strikes from the left, at a…\n","protected":false},"author":2,"featured_media":462785,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[7],"tags":[162684,28195,234577,234578,234579,22669,138255,57302,234580,10138,111,139,69,234581,78383,147,376],"class_list":["post-462784","post","type-post","status-publish","format-standard","has-post-thumbnail","category-science","tag-astro-ph-ep","tag-atmosphere","tag-bach-quadrangle","tag-borealis-quadrangle","tag-cold-trap","tag-comet","tag-cryosphere","tag-habitability","tag-impact-event","tag-mercury","tag-new-zealand","tag-newzealand","tag-nz","tag-permanently-shadowed-regions","tag-polar","tag-science","tag-water"],"_links":{"self":[{"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/posts\/462784","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/comments?post=462784"}],"version-history":[{"count":0,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/posts\/462784\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/media\/462785"}],"wp:attachment":[{"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/media?parent=462784"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/categories?post=462784"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/tags?post=462784"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}
Cite as: arXiv:2606.05024 [astro-ph.EP] (or arXiv:2606.05024v1 [astro-ph.EP] for this version)
https:\/\/doi.org\/10.48550\/arXiv.2606.05024<\/a>
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Related DOI:
https:\/\/doi.org\/10.1029\/2025JE009436<\/a>
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Submission history
From: Jordan Steckloff
[v1] Wed, 3 Jun 2026 15:47:54 UTC (23,834 KB)
https:\/\/arxiv.org\/abs\/2606.05024<\/a><\/p>\n