April 17, 2008
Though they're not attached to creatures of the deep, fins made of rock poke up above the surface and suggest past water on Mars. NASA's Opportunity rover took images of a thin fin on the edge of a rock in "Victoria Crater." The fin was rich in hematite, a mineral that often forms in the presence of water. Long ago, water circulating through a crack in the sandstone may have dissolved some of the surrounding material and filled the crack with mineral deposits. The filling resisted weathering while the surrounding rock eroded away. Today, the fin marks a place that used to be empty, and the space around it used to be rock! Scientists nicknamed the blade "Dorsal Fin" because it resembles the fin on the back of a fish.
Image courtesy:
Navigation camera/Panoramic camera/Microscopic imager
Robotic arm image credits: NASA/JPL-Caltech
False-color image credits: NASA/JPL-Caltech/Cornell
Microscopic image mosaic credits: NASA/JPL-Caltech/Cornell/USGS
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More evidense of past water history.