Scientists analyzing two soil samples their Phoenix spacecraft dug from the surface of Mars announced they have discovered what may be the highly oxidizing chemical called perchlorate, a common component of rocket fuels, explosives and some medicines, they reported Monday, according to San Fransisco Chronicle.

The surprising discovery in the Martian soil seems contradictory, because if it really is confirmed as a perchlorate compound it suggests that the planet`s soil may be very much like Earth`s, said Peter Smith, the University of Arizona scientist who heads the Phoenix mission.

However, Smith said in his announcement, "further analysis has revealed un-Earthlike aspects of the soil chemistry."

And whether the chemical actually is perchlorate - or in which of its many compounds it exists in the Martian soil - has not yet been determined, Smith said.

The Phoenix science team would not speculate on whether the chemical is naturally part of the Martian soil or whether it might have contaminated the soil directly around the spacecraft when Phoenix landed gently on the arctic plains of Mars on May 25, slowed by its 12 hydrazine retro-rockets in a blast of gas for its safe upright landing. Hydrazine is not a perchlorate, however.

NASA officials and the scientists will hold a teleconference today to discuss steps the Phoenix team has taken over the past month to pin down the identity of the perchlorate and why an experiment Sunday by one of its instruments found no evidence of the chemical directly above an ice layer that was scraped from soil near the spacecraft.

Two samples of the chemical have now been analyzed and detected on Mars by the spacecraft`s miniaturized Wet Chemistry Lab, which is part of a more elaborate series of Phoenix instruments called MECA -for Microscopy, Electrochemistry and Conductivity Analyzer, Smith said.

An earlier measurement of surface soil by another Phoenix instrument called TEGA - for the Thermal and Evolved Gas Analyzer - "was consistent with but not conclusive of the presence of perchlorate," Smith said.

On Earth, perchlorates are used in many types of explosives - including the rockets that blast astronauts into orbit aboard the space shuttles. They are also commonly used in fireworks, in blasting caps and even in medicine as part of a combination treatment for hyperthyroidism.

It is also a serious and toxic environmental contaminant left over from many American chemical plants, and Congress is now in a battle with the Environmental Protection Agency over the EPA`s refusal to set safety standards for perchlorates in drinking water and milk.

San Francisco Chronicle