The
western end of the Ganges Chasma in the Valles Marineris - a vast Martian canyon
some 3000 miles wide - appears as a large blemish in a 1977 photograph by the
Viking spacecraft. The snapshots shown here of a 28.2 mile stretch of the chasm
were taken from a height of some 400 miles during the Mars Global Surveryor's
twenty-eighth orbit of the planet on October 26.
They show details up to 50 times better than
the Viking images. "We now clearly know what is on the ground as opposed
to surmising what is there," says Michael Malin of Malin Space Science
Systems, the San Diego-based company that built the Surveyor's camera. The bottom
image is a close-up of the area within the lower part of the white rectangle
drawn on the Viking photo.
The
top image details the area inside the upper part of the rectangle. The rippled
Martian terrain resembles features pushed up by tectonic forces on the eastern
side of the Colorado rockies. Scientists don't yet know what processes rippled
Mars. More clues will come with more photos. "It's tough to tell,"
Malin says. "I'm revising judgement until I see other areas."
Postcard from Mars
