Explanation:
What is this bright soil on Mars?
Several times while rolling across Mars, the treads of the
robotic rover Spirit have serendipitously uncovered
unusually bright soil.
Spirit uncovered another batch unexpectedly last month while
rolling toward its winter hibernation location on
McCool Hill.
The physics and chemistry
instruments on Spirit have determined the soil,
shown above, contains a high content of
salts
including iron-bearing
sulfates.
A leading hypothesis holds that these salts record the presence of past
water,
with the salts becoming concentrated as the water
evaporated.
Lecture: APOD editor to give public talk in Princeton on April 11
