By Andrew Bridges Pasadena Bureau Chief Space.Com
PASADENA,
Calif. -- NASA has released a quartet of Martian images that show
several of the Red Planet’s numerous craters patched with
snow-white frost.
The American
space agency’s Mars Global Surveyor orbiter captured the
images as part of its ongoing monitoring of the seasonal advance
and retreat of polar frosts on the planet’ s surface.
The four images
render wide-angle views of four distinct craters -- two each in
Mars' northern and southern hemispheres. They are located the
middle polar latitudes of each hemisphere.
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Lomonosov
Crater
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Unnamed
Crater
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Barnard
Crater
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Lowell
Crater
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The images
(upper left and right) show Lomonosov and an unnamed crater 10
degrees north of it as they appeared in August and October during
the northern spring. Frost that had accumulated during the hemisphere’s
six-month winter has been shrinking since May. In the case of
the unknown crater, just 30 miles (48 kilometers) across, portions
of the frost may well persist through the summer on its cool,
shady floor -- much as it was seen to do in Viking orbiter images
acquired in the 1970s.
In the southern
hemisphere, it is now autumn on Mars, with frost appearing as
early as August in Barnard Crater (lower left). By mid October,
the frost line had moved farther north, and the white stuff appeared
in images of Lowell Crater (lower right) as well.
In each of
the four images, north is toward the top. In the two northern
hemisphere images, the Sun illuminates the scene from the lower
left. In the southern hemisphere, the sun does so from the upper
left.
NASA’s
Global Surveyor has been orbiting Mars since September 1997. It
will be joined late next year by another NASA satellite, the 2001
Mars Odyssey, scheduled for launch on April 7, 2001.
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