Confirmation of the presence of perchlorate and supporting data is important prior to scientific peer review and subsequent public announcements. 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," said Peter Smith, Phoenix's principal investigator at the University of Arizona, Tucson.
Scientists at the Phoenix Science Operations Center at the University of Arizona, Tucson, are specifically 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, "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.
"When surprising results are found, we want to review and assure our extensive pre-launch contamination control processes covered this potential," said Barry Goldstein, Phoenix project manager at NASA's Jet Propulsion Laboratory in Pasadena, Calif.