Earlier NASA said Phoenix analyzers detected water in the soil, which suggested that Mars could have the conditions for life. However, if the presence of perchlorate were confirmed, the probability of detecting living organisms there would be reduced.
"The Phoenix team has been waiting for complementary results from the Thermal and Evolved-Gas Analyzer, or TEGA, which also is capable of detecting perchlorate. TEGA is a series of ovens and analyzers that "sniff" vapors released from substances in a sample," NASA said on its website.
NASA scheduled a media teleconference for later Tuesday to discuss the research team's findings.
NASA said it was important to confirm the presence of perchlorate, particularly as analysis of a sample 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," said Peter Smith, Phoenix's principal investigator at the University of Arizona, Tucson.
TEGA and the Microscopy, Electrochemistry, and Conductivity Analyzer (MECA) are specifically designed to gather data 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," Smith said.
"Initial MECA analyses suggested Earth-like soil. Further analysis has revealed un-Earthlike aspects of the soil chemistry," he said.
NASA said the researchers were working to exclude any chance that the perchlorate detected came from a terrestrial source and migrated from the spacecraft to contaminate either the soil samples or the instrument.
Perchlorates are used to produce explosives, including solid rocket fuel.
The Phoenix probe, built by the Lockheed Martin Corporation at a cost of $420 million, was launched in August 2007 and made a textbook landing in May after its 680 million km (423 million mile) journey from Earth before opening its solar arrays and sending data back to NASA's Jet Propulsion Laboratory in Pasadena, California.
