『Abstract
Low albedo sediments cover ＞107 km2 in
the northern lowlands of Mars, but the composition and origin
of these widespread deposits have remained ambiguous despite many
previous investigations. Here we use near-infrared spectra acquired
by the Mars Express OMEGA (Observatoire pour la Mineralogie（最初のeの頭に´）, l'Eau, les Glaces, et l'Activite（eの頭に´）) imaging spectrometer to show that these
sediments exhibit spectral characteristics that are consistent
with both high abundances of iron-bearing glass and silica-enriched
leached rinds on glass. This interpretation is supported by observations
of low-albedo soil grains with possible rinds at the Phoenix Mars
Lander landing site in the northern lowlands. By comparison with
the extensive glass-rich dune fields and sand sheets of Iceland,
we propose an explosive volcanic origin for these glass-rich sediments.
We also propose that the glassy remnant rinds on the sediment
are the result of postdepositional alteration, as these rinds
are commonly formed in arid terrestrial volcanic environments
during water-limited, moderately acidic leaching. These weathered,
glass-rich deposits in the northern lowlands are also collocated
with the strongest concentrations of a major global compositional
surface type previously identified in mid-infrared spectra, suggesting
that they may be representative of global processes. Our results
provide potential confirmation of models suggesting that explosive
volcanism has been widespread on Mars, and also raise the possibilities
that glass-rich volcaniclastics are a major source of eolian sand
on Mars and that widespread surficial aqueous alteration has occurred
under Amazonian climatic conditions.』
Introduction
Methods
Results
Discussion
Acknowledgments
References cited