NASA's Phoenix Mars Lander found evidence of mineral
nutrients essential to life in Martian dirt, mission scientists announced Thursday.
After performing the first
wet chemistry experiment ever done on another planet, Phoenix
discovered that a sample it dug of Martian dirt contained several soluble
minerals, including potassium, magnesium and chloride. Though the data is
preliminary, the results are very exciting, scientists said.
"We basically have found what appears to be the
requirements for nutrients to support life," said Phoenix's wet chemistry
lab lead, Sam Kounaves of Tufts University. "This is the type of soil
you'd probably have in your backyard. You might be able to grow asparagus
pretty well, but probably not strawberries."
Asparagus, which thrives in alkaline soil, would like the
Martian dirt, which Phoenix measured to have a very alkaline pH of between
eight to nine. Strawberries, meanwhile, like acidic soil, he said.
The finding comes a week after the lander discovered water
ice in the same dirt.
On June 25, the probe placed a cubic centimeter sample of
Martian dirt in its onboard wet chemistry laboratory for the first time. The
lab, part of Phoenix's
suite of instruments called the Microscopy, Electrochemistry and
Conductivity Analyzer, or MECA, was designed to test Mars' dirt for salts,
acidity, minerals and conductivity.
After mixing the dirt with water Phoenix brought from Earth
in one of MECA's teacup-sized beakers, the instrument measured various
characteristics of the solution to learn about the properties of the dirt.
MECA includes four beakers, each of which can be used only
once. The inside of each beaker contains 26 sensors designed to study red
planet material, NASA officials have said.
"We're making mud, we're stirring it up, we're
measuring it with sensors," said Jet Propulsion Laboratory scientist
Michael Hecht, lead of the MECA instrument.
Habitable world
The new findings help fulfill Phoenix's main purpose: to
search for signs that the red planet's northern polar regions could have been
habitable to life. The probe landed in the arctic plains of Mars May 25 to
begin what is now a planned four-month mission. It is not equipped to find life
itself.
The soluble mineral nutrients it found, and the dirt's hospitable
pH level, are both promising signs. However the MECA instrument is not able to
test for organic compounds, such as carbon, oxygen and nitrogen, which are also
necessary for life as we know it.
"We did find basically that there's nothing about [the
dirt] that would preclude life," Kounaves said. "In fact it seems
very friendly."
Though the dirt itself seems to be hospitable, Kounaves
pointed out that the very top layer at the surface is exposed to high levels of
harsh UV light that is damaging to organic compounds, so may not be able to
support life.
"There could be microbes living meters and meters
underground," he said. "They would be very happy."
Water ice
Phoenix also recently found another promising sign that this
Mars environment could be habitable to life. In a major success last week, the
probe photographed what scientists say must
be water ice: a few bright crumbs that evaporated over four days from a
trench in the ground. The scientists think it's water, and not some other
material such as carbon dioxide, because of the time frame over which it
vaporized. The local temperatures are too warm for carbon dioxide to remain
frozen for even one day, scientists said.
Launched in August 2007, Phoenix includes cameras, a
scoop-tipped robotic arm, weather station and ovens in addition to its wet
chemistry lab.
The probe's oven instrument, the Thermal and Evolved Gas
Analyzer (TEGA), also recently completed an experiment in which it heated up a
sample of Martian dirt to 1,000 degrees Celsius (1,832 degrees Fahrenheit).
When the sample was heated, the instrument measured signs of water, which
researchers think was probably emitted when minerals melted that contained chemically-bound
water. This water would have been bonded to other molecules in the minerals,
rather than existing on its own in the dirt.
"This is the first time anybody's ever heated up part
of a planet to such high temperatures," said William Boynton of the
University of Arizona, lead scientist for TEGA. "When we heated up the
sample we got some modest amounts of water vapor. This is what we were hoping
to see."
Though further analysis is needed to determine the source of
the water vapor for sure, "what we can say now is that the soil clearly
has interacted with water in the past," he said.
The results of both the TEGA and MECA tests are showing
scientists that it's possible Mars may indeed have hosted, or be hosting, some
form of life.
"Over time I've come to the conclusion that the amazing
thing about Mars is not that it's an alien world but that it's actually very Earth-like,"
Kounaves said.
http://www.space.com/scienceastronomy/080626-phoenix-update.html
