Barnacle Bill is a 40-centimetre (16 in) rock on Mars in Ares Vallis. It was the first rock on Mars analyzed by the Sojourner rover using its Alpha Proton X-ray Spectrometer. The encounter occurred during Sol 3 of the Mars Pathfinder mission on the surface of Mars and took ten hours to complete.
"Barnacle Bill" rock - close-up
Early analysis of data sent from Sojourner led scientists to speculate that the rock was andesite.
The name was inspired in mission scientists by barnacle-like structures on the rock that appeared in transmitted photos.
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