WOODLANDS,
Texas — Evidence is building that NASA's Phoenix Mars Lander plopped down on a
microbe-friendly location.
Descending
onto Mars on May 25, 2008, Phoenix was designed to study the history of water and
habitability potential in the Martian
arctic's ice-rich soil. It did not pack instruments designed to find life. To
date, there is no firm evidence that Mars ever hosted biology.
But
researchers say the landing site has or had the ingredients necessary to
support life as we know it.
Recently,
scientists revealed controversial evidence
of liquid water at the landing site. Water is a key to life.
Now four papers are
under review for scientific publication on four major discoveries from the
mission, said Peter Smith, the Phoenix mission's principal investigator at the
University of Arizona in Tucson.
Smith and other Phoenix
scientists provided a review of what the spacecraft uncovered on the red planet
at last week's 40th Lunar and Planetary Science Conference held here.
Microbial metabolism
Carol Stoker of NASA's
Ames Research Center — and a Phoenix science team co-investigator — noted that
one goal of the Phoenix sampling at its Northern Plains landing site was to
determine whether this environment may have been habitable for life at some
time in its history.
Stoker said given our
current understanding of life, the potential for habitability in a specific
time and space takes in three factors: the presence of liquid water; the
presence of a biologically available energy source; and the presence of the
chemical building blocks of life in a biologically available form. In addition
to these factors, temperature and water activity must be high enough to support
growth.
A major Phoenix find in
its digging into and gulping quantities of Martian soil was identifying perchlorate
salt at its landing locale. Perchlorate and chlorate are compounds used for
microbial metabolism — energy sources relied on by numerous species of microbes
here on Earth, Stoker said.
Stoker rolled out at the
meeting a "habitability index" — an approach akin to the Drake equation to
evaluate the probability of life in the universe.
As a general conclusion,
Stoker valued the Phoenix landing site as having a higher potential for life
detection than any site previously visited on Mars. Moreover, the icy material that
was sampled might periodically be capable of sustaining modern biological activity.
Delving into the Phoenix
data, while admittedly still a work in progress, Stoker said it provides key
information about the potential habitability of a red planet environment ...and
the data suggest that habitable conditions have occurred in modern times. That
belief, she said, cries out for rovers and the ability to drill down into Mars.
"What you
see is that Phoenix comes down as a clear winner — a much, much higher
habitability index than any of the other sites," Stoker told conference
attendees. "The Phoenix landing site is the most habitable zone of any location
we have ever visited on Mars."
Crucial
factors
Phoenix
results have shown that no chemicals detrimental to all microbe life were found
at its landing spot, said Tufts University researcher Suzanne Young, one on a team
scientist working with the output from Phoenix's
wet chemistry laboratory — part of the suite of tools called the
Microscopy, Electrochemistry and Conductivity Analyzer, or MECA for short.
Several,
but not all, of the crucial factors for bio-habitability were found by the Mars
lander's wet chemistry laboratory. Some factors could not be measured by the
Phoenix, Young explained. The data of the full Phoenix mission points to no
true negative, she said, so further missions would be necessary to complete the
picture of habitability, and possibly life, on Mars.
"We have
lots of microbes out there that can do things...eat rock and release from it stuff
that they need" — a process, Young added, that creates a viable energy system
for other microbes.
The environment
at the Phoenix site was pretty gentle, Young said. "We didn't find anything
excessively toxic that's going to do bad things."
In terms of
a habitability checklist, "we've got bunches of checkmarks in really good
places," Young explained. "I think Phoenix really did expand the possibility
for serious consideration of looking for past and maybe even present life on mars
...but it's still a work in progress," she said.
Need to
go back
For now,
the Mars
Lander mission is over.
As the
craft's available solar power declined with the approaching Martian winter, the
mission was declared finished — maybe, anyway — Nov. 2 when Earth controllers
were unable to re-contact the robot.
"We will
try to get it back in October but the chances are poor," Smith said. "However,
it is known as the Phoenix mission and we do have a chance. We may be back," he
added.
Young
agreed that a repeat landing by a spacecraft near the northern polar region is
warranted.
"There are
things we couldn't do. There are things we didn't do," she said.
"There are things that serendipity could have delivered to us and didn't.
But we have not found any impossibilities...we've not found anything that's a no.
And we have added a lot to the possibility — and so more missions are needed.
We need to go deeper...we need to go back."
Leonard
David has been reporting on the space industry for more than four decades. He
is past editor-in-chief of the National Space Society's Ad Astra and Space
World magazines and has written for SPACE.com since 1999.
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