NASA will announce today that new data from the Phoenix Mars lander indicate that it is looking less conclusive that soil analyzed by the lander's soil chemistry experiment is Earth-like and can support life.

AviationWeek.com reported Aug. 1 and Aviation Week & Space Technology reports today that the new information involves the "potential for life" on Mars. That potential can either be positive or negative, and the new data indicate the new soil tests are at best inconclusive, according to the information being released on the soil chemistry experiment.

An initial soil test by the Microscopy, Electrochemistry, and Conductivity Analyzer (MECA) instrument indicated that the soil is highly Earth-like. The second test, however, is leading scientists to view the data as more inconclusive.

Other media outlets and websites around the world incorrectly reported that the "potential for life" meant that actual life on Mars had been detected. Coverage by Aviation Week states that the wet chemistry experiment can not detect life, nor can any other Phoenix instrument such as the Thermal and Evolved Gas Analyzer (TEGA) organics experiment.

NASA disputes that any of the information was provided to the White House in advance. But such data are routinely passed between NASA and White House science staff when briefings are planned, as is the case with the new MECA data. A briefing is set for Aug. 5.

Update:

Within the last month, two samples have been analyzed by MECA, suggesting one of the soil constituents may be perchlorate, a highly oxidizing substance, says NASA.

As Aviation Week has reported, the Phoenix team has been waiting for complementary results from the Thermal and Evolved-Gas Analyzer, or TEGA. NASA says TEGA is capable also of detecting perchlorate. TEGA is a series of ovens and analyzers that "sniff" vapors released from substances in a sample.

"Confirmation of the presence of perchlorate and supporting data is important prior to scientific peer review and subsequent public announcements, NASA says. "The results from Sunday's TEGA experiment, which analyzed a sample taken directly above the ice layer, found no evidence of this compound.

"This is surprising since an earlier TEGA measurement of surface materials was consistent with but not conclusive of the presence of perchlorate," says Peter Smith, Phoenix's principal investigator, in a NASA news release.

Scientists at the Phoenix Science Operations Center at the University of Arizona, Tucson, are looking at the data from these instruments to provide information on the composition of Martian soil.

"We are committed to following a rigorous scientific process. While we have not completed our process on these soil samples, we have very interesting intermediate results," said Smith in the release. "Initial MECA analyses suggested Earth-like soil. Further analysis has revealed un-Earthlike aspects of the soil chemistry.

"The team also is working to totally exonerate any possibility of the perchlorate readings being influenced by terrestrial sources which may have migrated from the spacecraft, either into samples or into the instrumentation," NASA says

"When surprising results are found, we want to review and assure our extensive pre-launch contamination control processes covered this potential," says Barry Goldstein, Phoenix project manager at NASA's Jet Propulsion Laboratory in Pasadena, Calif.

MECA's robotic wet-chemistry lab studies soluble chemicals in the soil by mixing a soil sample with a water-based solution with several reagents brought from Earth. The inner surface of each cell's beaker has 26 sensors that provide information about the acidity or alkalinity and concentrations of elements such as chloride or perchlorate. The beaker also can detect concentrations of magnesium, calcium and potassium, which form salts that are soluble in water.

With continuing results and the lander in good condition, the mission has been extended through Sept. 30. The original, prime mission of three months ends in late August. The mission extension adds five weeks to that.

Photo: NASA