Late Hesperian aqueous alteration at Majuro crater, Mars

Research areas:
Year:
2012
Keywords:
Mars
Authors:
Journal:
PLANETARY AND SPACE SCIENCE
Volume:
72
Number:
1, SI
Pages:
18-30
Month:
November
ISSN:
0032-0633
Abstract:
Impact craters cover a large portion of the surface of Mars and could
constitute a significant exobiology research target as their formation
provided heat sources for aqueous processes. To date, only rare examples
of hydrothermal alteration in craters have been reported on Mars while
many studies have focused on modeling their effect. Using data from the
Mars Reconnaissance Orbiter and Mars Express probes, we report the
presence of hydrated minerals, mainly Fe/Mg phyllosilicates, with
vermiculite as best-fit, that are found in an alluvial fan. This fan is
located inside a crater located in NE Hellas region and dated to the
Late Hesperian by crater counts and crosscutting relationships. The
stratigraphic position of the hydrated minerals and presence of small
domes interpreted as hydrothermal vents indicate that the alteration
occurred in the lower level of the alluvial fan and was triggered by
bottom-up alteration. These observations are best explained by a
combination of snow deposition and subsequent melting eroding crater
rims and forming the fan, with impact warming, which triggered the
alteration at the base of the fan. This example shows that
phyllosilicates are able to form late in the Martian history, especially
in local niches of strong exobiological interest. It also suggests that
a similar process was possible in alluvial fans of other large impact
craters including those at Gale crater. (C) 2012 Elsevier Ltd. All
rights reserved.