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Vast Collapsed Terrains on Mercury Might Be Windows Into Ancient Habitability

fig 1 alexis 

Fig. 1 Extent of a vast chaotic terrain (white outline) at the antipode of the Caloris basin (~5 x 105 km2).

fig 2 alexis

Fig. 2 Zoom in showing variable magnitudes of collapse, which includes a relatively unmodified rim section that is smooth but not broken into knobs (arrow 1). This area adjoins another part of the rim that has been almost entirely removed (arrow 2). The adjacent intercrater regions also exhibit deep and abrupt relief losses (arrows 3 & 4).


New research raises the possibility that some parts of Mercury’s subsurface, and those of similar planets in the galaxy, once could have been capable of fostering prebiotic chemistry, and perhaps even simple life forms, according to a paper by a team led by Planetary Science Institute Research Scientist Alexis Rodriguez. 

Chaotic terrains on Mercury opposite the large Caloris impact basin are landscapes produced by the removal of vast volumes of upper crustal volatiles, the paper says. 

“The findings mean that Mercury had a thick volatile-rich – possibly but not necessarily water-rich – crust in this location,” said Rodriguez, lead author of “The Chaotic Terrains of Mercury Reveal a History of Planetary Volatile Retention and Loss in the Innermost Solar System” which appears in Nature Scientific Reports (www.nature.com/articles/s41598-020-59885-5). PSI scientists Jeff Kargel, Deborah Domingue, Daniel Berman, Maria Banks, Kevin Webster, and Mark Sykes are coauthors on the paper, written in collaboration with the University of Arizona, NASA Goddard, and the Southwestern Research Institute. 

“Mercury’s surface temperature reaches a scorching 430 degrees Celsius during the daytime, and in the absence of an atmosphere, it plummets to -180 degrees Celsius at night. So, its surface environments have rightfully been out of scientific consideration as a possible host of life. However, the paper raises the prospect that some subsurface regions of Mercury have shown capacity for hosting life,” Rodriguez said. 

“The deep valleys and enormous mountains that now characterize the chaotic terrains were once part of volatile-rich geologic deposits a few kilometers deep, and do not consist of ancient cratered surfaces that were seismically disturbed due to the formation of Mercury’s Caloris impact basin on the opposite side of the planet, as some scientists had speculated,” said coauthor Berman. “A key to the discovery was the finding that the development of the chaotic terrains persisted until approximately 1.8 billion years ago, 2 billion years after the Caloris basin formed.” 

fig 3 alexis

Fig. 3 Context view showing the location and extent of the chaotic terrain antipodal to the Caloris basin (outlined in white) relative to the ray systems of the Kuiper and Debussy impact craters. (B) Close-up view of panel A that provides the context and locations for panels C and D. The numbers 1-9 identify individual rays within the region’s view. (C, D) Close-up view showing crater rays that extend over the chaotic terrain (green lines 6, 8, 9) and other crater rays that appear truncated over the chaotic terrain (red lines 1-5, 7). We provide the location of the hollow hosting crater Dario in panel C. 

 

 

May 24, 2020
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