It was spring in Mars's northern hemisphere when the HST took this view
of the, Red Planet on February 25, 1995. At the time, Mars was 103 million
kilmeters (65 million miles) away from Earth. The north polar ice cap visible
here is several hundred kilometers across and made of solid water-ice.
In winter, carbon dioxide frost settles and enlarges the polar cap but,
at this time, the frost has gone.
On the western edge of the planet, where it is dawn, the surface is
shrouded in clouds that have formed over night. When the temperature falls
sharply at night, water in the atmosphere freezes to create clouds of ice
crystals.
The summit of the extinct volcano, Ascraeus Mons, pokes through the cloud, appearing as a small oval shape near the left edge of the planet. It rises 25 kilometers (16 miles) above the surrounding plains and is 400 kilometers (250 m iles) across. The dark feature running east-west towards the lower left is the Valles Marineris, a vast system of canyons extending for more than 5,000 kilometers (3, 100 miles).
The dark areas were misinterpreted by early Mars watchers as region of vegetation. In reality, they are areas of coarse sand that is less reflective than the finer orange dust. Seasonal changes in the appearance of the surface are the result of winds moving dust and sand around.
Camera: WFPC2 in PC mode.
Technical Information: Exposures through three color filters
combined to create a true color image. Pictures map-projected onto a sphere
for accurate registration and perspective.
Credit: P. James (University of Toledo), S. Lee (University
of Colorado, Boulder), and NASA
