July 29, 1997
Galaxies were colliding long before you were born, and they will keep colliding long after us all.
Strange Rocks on Mars
Birthday · July 29, 1997
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APOD published July 29, 1997. Full image credits are on the original APOD entry below. A publication-date match, not a photo taken on your date. Independent of NASA.
The rocks on Mars tell us stories about their past. To decipher these stories, a scientist must become a detective, searching for clues and fitting them with theories. The above photograph of the rocky Martian surface to the northeast of Pathfinder's landing site provides many such clues. 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.