Characterization of the martian surface by Pathfinder Mission

Matijevic et al (30 authors at 2 installations, US) report that Sojourner, the Mars Pathfinder rover, discovered pebbles on the surface and in rocks that may be sedimentary and not volcanic in origin. The authors suggest the surface pebbles may have been rounded by Ares flood waters or liberated by weathering of sedi- mentary rocks called conglomerates. These conglomerates imply that water existed elsewhere and earlier than the Ares flood. The data also indicate that most Martian soil-like deposits are similar to moderately dense soils on Earth, and that small amounts of dust are currently settling from the atmosphere.

QY: H. J. Moore
Science5 Dec 97

Related Background:
The first photographs from the Mars Pathfinder mission to the Ares Vallis region of Mars have been interpreted as evidence for a huge flood hundreds of miles wide, hundreds of feet deep, and thousands of miles in extent, that occurred 1 to 3 billion years ago. Meanwhile, Sojourner, the minuscule ambulatory robot has begun exploring a succession of rocks with its main instrument, an alpha proton x-ray spectrometer, which bombards a rock with radiation and records the radiation backscatter. From this information, the chemical composition of a rock can be determined. The first rock examined showed a preponderance of silicon, which suggests quartz, which in turn suggests a likely origin in a volcanic eruption. This first rock appears to be similar to the common terrestrial volcanic rock called andesite.

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