Geoscience Reference
In-Depth Information
cementing by a fluid containing minerals. There was evidence of clouds and maybe
fog. Sojourner rover studied rocks using an Alpha Proton X-ray Spectrometer.
8.3.9.7
Mars Odyssey
The 2001 Mars Odyssey found much evidence for water on Mars in the form of
images, and with its spectrometer, it proved that much of the ground is loaded with
water ice. Mars has enough ice just beneath the surface to fill Lake Michigan twice.
In both hemispheres, from 55 ı latitude to the poles, Mars has a high density of ice
just under the surface; one kilogram of soil contains about 500 g of water ice. But
close to the equator, there is only 2-10 % of water in the soil.
Scientists think that much of this water is also locked up in the chemical structure
of minerals, such as clay and sulfates. Although the upper surface contains a few
percent of chemically bound water, ice lies just a few meters deeper, as it has
been shown in Arabia Terra, Amazonis quadrangle, and Elysium quadrangle that
contain large amounts of water ice. Analysis of the data suggests that the southern
hemisphere may have a layered structure, suggestive of stratified deposits beneath,
now extinct large water mass.
The instruments aboard the Mars Odyssey are only able to study the top meter
of soil, while the radar aboard the Mars Reconnaissance Orbiter can measure a few
kilometers deep. In 2002, available data were used to calculate that if all soil surfaces
were covered by an even layer of water, this would correspond to a global layer of
water (GLW) 0.5-1.5 km deep.
Thousands of images returned from Odyssey orbiter also support the idea that
Mars once had great amounts of water flowing across its surface. Some images
show patterns of branching valleys; others show layers that may have been formed
under lakes; even river and lake deltas have been identified.
For many years, researchers thought that glaciers existed under a layer of
insulating rocks. Lineated valley fill is one example of these rock-covered glaciers.
They are found on the floors of some channels. Their surfaces have ridged and
grooved materials that deflect around obstacles. Lineated floor deposits may be
related to lobate debris aprons, which have been shown by orbiting radar to contain
large amounts of ice.
8.3.9.8
Phoenix Lander
The Phoenix mission landed a robotic spacecraft in the polar region of Mars on
May 25, 2008, and it operated until November 10, 2008. One of the mission's two
primary objectives was to search for a “habitable zone” in the Martian regolith where
microbial life could exist, the other main goal being to study the geologic history
of water on Mars. The lander has a 2.5-m robotic arm that was capable of digging
shallow trenches in the regolith. There was an electrochemistry experiment which
analyzed the ions in the regolith and the amount and type of antioxidants on Mars.
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