A Colorful Mars

1. Hellas Basin, an ancient impact crater, has the lowest elevation on the surface of Mars. At the bottom of the basin are complex folded features that planetary scientists do not understand. They might have formed billions of years ago when perhaps water filled the basin. “It could be these are underwater features,” said Alfred S. McEwen, principal investigator for this camera on the orbiter.

2. Mars is not really blue. But if they looked at realistically colored images, scientists would be trying to distinguish between red rocks and soil and not-quite-so-red rocks and soil. The false-color images, like this one of Ius Chasma in the western part of the Valles Marineris canyon system, stretch the color palette to accentuate details.

3. These valleys in the Melas Chasma section of Mars appear to have been carved by rain rather than ground water flowing out of the ground. “It’s quite a dense network of channels,” Dr. McEwen said. The area near the equator also appears relatively young, perhaps about two billion years old, which makes it even more interesting to scientists. 

4. “Slope streaks,” here on the rim of Henry Crater, a 103-mile impact crater, are one of the few geological features known still to be active today. Scientists do not know how these patterns form, but hypotheses include “dry avalanches” and geochemical weathering.

5. A section of the Aureum Chaos region of Mars in false color reveals layers of light-toned rocks. Other instruments on Mars Reconnaissance Orbiter have detected sulfate salts and the mineral hematite in these light-toned rocks — similar composition to the rocks that the rover Opportunity detected in its trek across Meridiani Planum. These indicate the possibility of a wet but acidic environment early in Mars’ history.