In Focus

Published: Tuesday 30 September 1997

The Pathfinder mission sprung a surprise towards end August when the roving vehicle revealed at least two different kinds of rocks on the planet. Neither resembles the Earth's volcanic rocks or meteorites presumed to originate in Mars. These findings have confused scientists, waiting for moredata on the rocks. They are curious about the formation of these rocks and the information they may have in store with respect to the planet's geologic history. Of the four rocks studied in detail so far, two contain higher amounts of the element silicon found in Martian meteorites, while the other two have more sulphur than is commonly found in the Earth's volcanic rocks.

Thanasis Economou, a member of the Pathfinder team also pointed out that there were extraordinary differences between the composition of the soil and the rocks at the site. The soil was found to contain chromium, not present in the rocks and much higher concentrations of sulphur and chlorine. While the rocks contained abundant quantities of aluminium and silicon.

Possible explanations as to the differences have come pouring in from other geologists. It has been suggested that the rover's spectrometre used for determining surface chemistry is perhaps detecting only the dust covering the rocks and is not able to penetrate any further. The dust -- an amalgamation of material from far and near -- could actually exhibit amazing chemical traces. Others claim that the sulphur traces could be remnants of past water reactions.

What these findings do assert is that Martian geology is more complex than was earlier believed. A year ago, scientists believed they had found possible evidence of life on that planet. Such claims would now have to wait for more concrete evidence. The remote-controlled rover is expected to complete its analysis of several other rocks in a region of the planet which has been nicknamed the "rock garden".

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