Abstract
The general scientific objectives of an in situ experiment employing
a Mossbauer spectrometer on a Martian lander are, for both rock and
soil samples, identification and relative abundance of iron-bearing
minerals (including carbonates, phyllosilicates (clays), hydroxyoxides,
phosphates, oxides, silicates, sulfides, sulfates), measurement of
the ferric (Fe3+) to ferrous (Fe2+) ratio, determination of the properties
of magnetic phases including the size distribution of magnetic particles
(nanophase versus larger particles) in the Martian soil. These data
provide information about the nature and extent of atmosphere-surface
chemical and physical weathering processes involving Fe-bearing phases.
These objectives are directly relevant to studying the evolution
of volatiles and climate over time on Mars because surface materials
are major volatile sinks. In fact one of the major problems associated
with understanding the evolution of volatiles on Mars is understanding
the processes in the past and/or present that are responsible for
oxidizing the red planet. A miniaturized backscattering Mossbauer
spectrometer, developed at the Technical University of Darmstadt,
is reported on which is a flight prototype of an instrument that
could be used for in situ analysis as part of a payload of a Martian
lander. Its critical instrument parameters are < 300 g mass, 250
cm(3) volume, about 0.4 W power, and about 300 mCi (at launch) Co-57
radiation source. Results of test measurements on Mars sample analogues
will be presented. As an example for laboratory weathering studies
on Fe-bearing phases, which are important for analysis and interpretation
of returned data from Mars, first results of the study of weathering
of basalt under CO2 and CO2-O-2 atmospheres will be presented and
discussed. Copyright (C) 1996 Elsevier Science Ltd
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