Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2006 April 6
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Unusual Bright Soil on Mars
Credit: Mars Exploration Rover Mission, Cornell, JPL, NASA

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.

Tomorrow's picture: The Crown of the Sun

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Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (USRA)
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& Michigan Tech. U.