For example, at least three types of rocks are evident, marked with red, white and blue arrows. The red arrows point to smooth rocks, which Pathfinder scientists hypothesize have been eroded by tumbling through ancient channels of water which evaporated long ago. The blue arrows indicate a different type of rock, ragged ones with sharp edges, hypothesized to have been ejected when nearby craters formed or volcanoes erupted. The white areas are more mysterious, and might be some sort of composite material. Sojourner was recently diverted to study these white areas to gather more clues so continued detective work can yield better insight into the Martian past.
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