Dirty Ice on Mars
Planetary Science Research Discoveries
June 5, 2002

--- Instruments on the Odyssey spacecraft show that a lot of
dirty ice sits within a meter of the surface in the south
polar latitudes of Mars.

Written by G. Jeffrey Taylor
Hawai'i Institute of Geophysics and Planetology

The gamma-ray and neutron spectrometers onboard the orbiting 2001 Mars
Odyssey spacecraft have detected strong signals from hydrogen quite close to
the Martian surface. The concentration of hydrogen is so large that it must
be in the form of ice. The amount of ice in the upper meter or so begins to
rise at about -60o latitude and continues to increase toward the South Pole.
Detailed analysis of the data indicates that the ice-rich layer resides
beneath a hydrogen-poor upper layer. The thickness of the upper layer
decreases from about 75 cm at -42o to about 20 cm at -77o. The amount of ice
in the lower layer is between 20 and 50 wt% (weight percent), with a best
estimate of 35 wt%. Because ice is much less dense than mineral grains, this
translates to more ice than rock by volume. It's dirty ice. The results were
reported in papers by William Boynton (University of Arizona) and the
gamma-ray team, by William Feldman (Los Alamos National Laboratory) and
others, and Igor Mitrofanov (Russian Space Research Institute) and others.

References:

Boynton, W. V. and others (2002) Distribution of hydrogen in the
near-surface of Mars: Evidence for subsurface ice deposits. Published
online May 30 2002; 10.1126/science.1073722 (Science Express Reports.)

Feldman, W. C. and others (2002) Global distribution of neutrons from
Mars: Results from Mars Odyssey. Published online May 30 2002;
10.1126/science.1073541 (Science Express Reports.)

Mitrofanov, I. and others (2002) Maps of subsurface hydrogen from the
high-energy neutron detector, Mars Odyssey. Published online May 30
2002; 10.1126/science.1073616 (Science Express Reports.)

Full story here.

Alex R. Blackwell
University of Hawaii