Yang
Chen1, Yang Liu1, Yunbin Guan2,
John M. Eiler2,
Chi Ma2, George R. Rossman2,
Lawrence A. Taylor3.
1
Jet
Propulsion Laboratory, California Institute
of Technology, Pasadena, CA 91109, USA
2
Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125
3
Planetary Geosciences Institute, Department of Earth and Planetary Sciences, University of Tennessee, Knoxville, TN 37996, USA
Abstract
Abstract:
We report unambiguous chemical evidences for subsurface water activity
in martian crust at <600 Ma based on the data from Tissint, a fresh
martian meteorite fall with minimal terrestrial weathering. The impact
melt pockets in Tissint contain abundant volatiles (H2O, CO2, F, and Cl) and their concentrations are positively correlated with each other. Higher H2O
concentrations also accompany higher deuterium contents. These
correlations suggest mixing between two volatile sources. The first
source is H2O in the precursor basalt inherited from martian magma. Magmatic H2O
in the basalt had low deuterium concentration and was likely stored in
the nominally anhydrous minerals. This source contributed little CO2
or halogens to the impact melts. The second source is inferred to be
aqueous alteration products introduced to the basalt by water
activities after the basalt erupted. These alteration materials
contributed more volatiles to the impact melts than the magmatic
source, and had high deuterium abundance, reflecting isotope
equilibrium with recent martian atmosphere. The water activities
occurred beneath the martian surface after ~600 Ma (crystallization
age) but before ~1 Ma (ejection age). The chemical and isotopic
signatures of the alteration products in Tissint resemble previously
known martian samples associated with old water activities on Mars,
which can be traced back to ~4.2 billion years ago (e.g., the mudstone
at Gale Crater). This similarity in chemistry and the wide age span
indicate that such water activities were common on Mars throughout its
history, which had the potential to form habitable environment.
However, the rarity of the volatilerich zone in Tissint may suggest
that recent subsurface water activities on Mars were limited.