Rover’s Findings Mystify and Please Mars Team

The Spirit rover’s first look at the soil of Mars has left earthbound researchers pleased and a little puzzled -- pleased because the instruments are working exceptionally well and puzzled because some initial results were not quite what they expected.

The findings “have posed some new questions for us to pursue in the weeks and months ahead,” said principal investigator Steven Squyres of Cornell University.

Researchers chose the Gusev Crater landing site because its appearance suggests that it is the bed of an ancient lake, but some of the first results from the rover’s sophisticated instruments suggest otherwise.

The elemental composition of the soil “is very similar to what was seen in the Viking and Pathfinder missions,” Squyres said. So it is quite possible that the fine particulates that coat the surface were brought in from somewhere else by the large dust storms common on Mars.

“It’s going to be very interesting to dig holes” and see what is underneath it, he said.

The most significant finding is the presence of significant amounts of olivine in the soil, he said. Olivine is an iron magnesium silicate generally found in volcanic rocks. If the dust consists of large amounts of olivine, “one possibility is that the Martian soil is simply ground-up lava,” Squyres said. “That would be a surprise to me.”

But some members of the scientific team, he noted, are arguing that the alpha particle X-ray spectrometer that discovered the olivine is actually looking all the way through the powdery layer to the rock underneath, which may well have been formed by a volcanic eruption.

Another puzzle is what is holding the powdery layer together. Squyres initially thought it was electrostatic forces -- “static cling.” But when the face of the Mossbauer spectrometer was pressed lightly into the soil, the soil did not collapse as it would have if static electricity were holding it together.

“We don’t know what’s holding it together,” he added, but the X-ray spectrometer gives some hints, showing the presence of sulfates and chlorides. They could form a “chemical glue” holding the soil together, he noted. Significantly, such a glue would have been formed by the action of water.

Squyres concluded that it is going to take a lot of hard work to answer these and other questions. “Mars is not going to give up its secrets easily, but the key is, we’ve got the tools” to pry them out, he said.