NASA scientists announced Monday that they discovered what seems to be a highly oxidizing chemical called perchlorate after analyzing two soil samples the Phoenix spacecraft dug from the surface of Mars. The chemically reactive salt in the Martian soil is a common component of rocket fuels, explosives and some medicines.

The unexpected discovery appears to be incompatible, because if further analysis really confirms it as a perchlorate compound it indicates that the soil of the planet may be very similar to that on Earth, said Peter Smith, scientist with the University of Arizona, in Tucson, who is leading the Phoenix mission.

Nevertheless, Smith said in his announcement that "further analysis has revealed un-Earthlike aspects of the soil chemistry," as quoted by the San Francisco Chronicle.

And whether the element really is perchlorate or in which of its many compounds it exists in the Martian soil has not yet been concluded, said Smith.

The Phoenix science team would not hypothesize on whether the salt is naturally part of the Martian soil or whether it might have contaminated the soil exactly around the module when Phoenix landed smoothly on the arctic plains of Mars on May 25, slowed by its 12 hydrazine retro-rockets in a blast of gas for a safe upright touch down. Yet, hydrazine is not linked to perchlorate.

A teleconference will be held today by NASA officials and the scientists to discuss steps the Phoenix team has taken over the past month to pin down the identity of the perchlorate and why an experiment conducted on Sunday by one of its mechanisms revealed no evidence of the chemical straight above an ice blanket that was scrubbed from soil near the spacecraft.

According to Smith, two samples of the chemical have now been analyzed and detected on Mars by Wet Chemistry Lab, the spacecraft's miniaturized part of a more elaborate series of Phoenix instruments called MECA — Microscopy, Electrochemistry and Conductivity Analyzer.

A previous measurement of surface soil by another Phoenix instrument called TEGA — 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 propel astronauts into orbit aboard the space shuttles. They are also regularly used in fireworks making, in blowing caps and even in medicine as part of a combination treatment for hyperthyroidism.

In addition, it is a dangerous toxic left over from many American chemical plants contributing to the serious pollution of the environment. Because the Environmental Protection Agency refuses to fix safety standards for perchlorates present in drinking water and milk, the Congress is now in a conflict with the EPA.