Radar Probes Beneath Mars' Surface
Mars photograph courtesy of NASA
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An international research team now reports the first radar soundings
of Mars' subsurface, revealing the layered deposits reaching more than
1 kilometer deep at the planet's poles and a shallow, buried structure
that may be an impact basin, Science reports.
The European Space Agency's Mars Express spacecraft is carrying the Mars
Advanced Radar for Subsurface and Ionospheric Sounding, or "MARSIS,"
and Giovanni Picardi and colleagues have analyzed the first radar echoes
from the deep subsurface (hundreds to thousands of meters deep) obtained
by MARSIS during the early phase of its investigation. The planet's north
polar layered deposits consist mainly of an upper unit thought to be dominated
by water ice and a lower unit with a large amount of sand that is probably
cemented together with ice. The MARSIS data seem to have penetrated all
the way to the base of these deposits, the researchers report.
Additional data from the northern lowlands of Chryse Planitia, in Mars'
northern equatorial region, reveal a quasi-circular structure about 250
kilometers across that the authors propose is a buried impact basin.
MARSIS radar can also be used to probe other parts of the environment,
and a second study details the results that came from using MARSIS soundings
to explore the martian ionosphere, the part of the atmosphere that is
ionized by solar radiation. D. A. Gurnett and colleagues describe several
types of ionospheric echoes that were observed. The oblique echoes, for
example, are believed to arise, at least in part, from interactions with
Mars' complex crustal magnetic fields.
30 November 2005
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