Phoenix Mars Team Opens Window on Scientific Process
Phoenix Mars mission scientists spoke today on research in progress
concerning an ongoing investigation of perchlorate salts detected
in soil analyzed by the wet chemistry laboratory aboard NASA's
"Finding perchlorates is neither good nor bad for life, but it
does make us reassess how we think about life on Mars," said Michael
Hecht of NASA's Jet Propulsion Laboratory, Pasadena, Calif., lead
scientist for the Microscopy, Electrochemistry and Conductivity
Analyzer (MECA), the instrument that includes the wet chemistry laboratory.
If confirmed, the result is exciting, Hecht said, "because different
types of perchlorate salts have interesting properties that may bear
on the way things work on Mars if -- and that's a big 'if ' -- the
results from our two teaspoons of soil are representative of all of
Mars, or at least a significant portion of the planet."
The Phoenix team had wanted to check the finding with another lander
instrument, the Thermal and Evolved-Gas Analyzer (TEGA), which heats
soil and analyzes gases driven off. But as that TEGA experiment was
underway last week, speculative news reports surfaced claiming the team
was holding back a major finding regarding habitability on Mars.
"The Phoenix project has decided to take an unusual step" in talking
about the research when its scientists are only about half-way through
the data collection phase and have not yet had time to complete data
analysis or perform needed laboratory work, said Phoenix principal
investigator Peter Smith of the University of Arizona, Tucson. Scientists
are still at the stage where they are examining multiple hypotheses,
given evidence that the soil contains perchlorate.
"We decided to show the public science in action because of the extreme
interest in the Phoenix mission, which is searching for a habitable
environment on the northern plains of Mars," Smith added. "Right now,
we don't know whether finding perchlorate is good news or bad news for
possible life on Mars."
Perchlorate is an ion, or charged particle, that consists of an atom of
chlorine surrounded by four oxygen atoms. It is an oxidant, that is, it
can release oxygen, but it is not a powerful one. Perchlorates are found
naturally on Earth at such places as Chile's hyper-arid Atacama Desert.
The compounds are quite stable and do not destroy organic material under
normal circumstances. Some microorganisms on Earth are fueled by processes
that involve perchlorates, and some plants concentrate the substance.
Perchlorates are also used in rocket fuel and fireworks.
Perchlorate was discovered with a multi-use sensor that detects perchlorate,
nitrate and other ions. The MECA team saw the perchlorate signal in a sample
taken from the Dodo-Goldilocks trench on June 25, or Sol 30, or the 30th Martian
day of the mission after landing, and again in another sample taken from
the Snow White trench on July 6, or Sol 41.
When TEGA heated a sample of soil dug from the Dodo-Goldilocks trench on Sol
25 to high temperature, it detected an oxygen release, said TEGA lead scientist
William Boynton of the University of Arizona. Perchlorate could be one of
several possible sources of this oxygen, he said.
Late last week, when TEGA analyzed another sample, this one from the Snow
White trench, the TEGA team looked for chlorine gas. The instrument detected none.
"Had we seen it, the identification of perchlorate would be absolutely clear,
but in this run we did not see any chlorine gas. We may have been analyzing a
perchlorate salt that doesn't release chlorine gas upon heating," Boynton said.
"There's nothing in the TEGA data that contradicts MECA's finding of perchlorates."
As the Phoenix team continues its investigation of the artic soil, the TEGA
instrument will attempt to validate the perchlorate discovery and determine
its concentration and properties.
More information on Phoenix is at http://www.nasa.gov/phoenix
The Phoenix mission is led by Smith with project management at JPL, and development
partnership at Lockheed Martin, located in Denver. International contributions come
from the Canadian Space Agency; the University of Neuchatel, Switzerland; the universities
of Copenhagen and Aarhus in Denmark; the Max Planck Institute in Germany; and the
Finnish Meteorological Institute. The California Institute of Technology in
Pasadena manages JPL for NASA.
Media contacts: Veronica McGregor/Guy Webster 818-354-5011
Jet Propulsion Laboratory, Pasadena, Calif.
Dwayne Brown 202-358-1726