Scientists said today they have "found proof" of
water ice on Mars away from the polar ice caps, a discovery made by NASA's
Phoenix Mars Lander.
The finding is a crucial first step toward learning
whether the ground on Mars is hospitable, because all life as we know it requires
water. Now scientists can get on with the business of studying the chemistry of
Mars dirt in more detail.
When the probe took photos of a ditch it had dug four days
before, scientists noticed that about eight small crumbs of a bright material
had disappeared. They concluded those crumbs had been water ice buried under a
thin layer of dirt that vaporized when Phoenix exposed them to the air.
"It's with great pride and a lot of joy I announce
today we have found proof that this hard material really is water ice and not
some other substance," Phoenix principal investigator Peter Smith of the
University of Arizona, Tucson said at a briefing Friday.
The finding had been discussed tentatively yesterday, but in
a press conference today, researchers left no doubts.
Phoenix's robotic arm first revealed the crumbs about 5 cm
deep in the trench called "Dodo-Goldilocks" on June 15. By June 19,
they had vanished. If the crumbs had been salt, they wouldn't have disappeared,
scientists said, and if the ice had been made of carbon dioxide, they wouldn't
have vaporized.
"What this tells us is we found what we're looking
for," said Mark Lemmon, a Phoenix co-investigator from Texas A&M
University. "This tells us that we've got water ice within reach of the [robotic]
arms, which means that we can continue the investigation."
The $420
million mission landed on the arctic plains of Mars May 25,
embarking on a quest of at least four months to search for signs that the
environment was once habitable to life.
A "significant result"
Finding ice on Mars isn't completely shocking, since
observations from past satellites sent to orbit the planet, such as the 2001
Mars Odyssey spacecraft, have indicated that ice is likely to lie beneath the planet's
surface. Still, if confirmed, this would be the first direct finding of that
ice by a probe on the ground.
"We certainly expected to find ice there," said Bruce
Jakosky, a geologist at the University of Colorado who has been involved with
past missions to the red planet. "It was the [previous] evidence for ice
that sent us to that location. But there's a difference between expecting it
and finding."
Jakosky called the discovery a "significant result" that
allows the Phoenix mission to go forward with its wet chemistry experiments,
analyzing the soil for the history and composition of the ice.
"If they had found no ice, which was a real possibility, that
would make this much harder," he told SPACE.com. "I'm anxious to see the
results of the chemical analysis."
And although the 2001 Mars Odyssey satellite could measure
the average water ice content in roughly the top meter of
ground over areas of several hundred kilometers, these data didn't
reveal how that ice was spread out, said Maria Zuber, a geophysicist at MIT who
worked on past Mars missions, including the Spirit rover.
"We don't know the form of the water, beyond the fact
that there is too much there to be explained solely by water bound in
minerals," Zuber said. "So chunks, a layer, etc. are all
possibilities. The [Phoenix] observation is an important advance in our
understanding of water on Mars, and continued sampling will
undoubtedly add to the story."
Next steps
The next questions to answer are what chemicals, minerals
and organic compounds might be mixed in with the water.
"Just the fact that there's ice there doesn't tell you
if it's habitable," Smith said. "With ice and no food it's not a
habitable zone. We don't eat rocks — we have to have carbon chain materials
that we ingest into our bodies to create new cells and give us energy. That's
what we eat and that's what has to be there if you're going to have a habitable
zone on Mars."
To find this out, mission scientists plan to eventually put
samples of ice into Phoenix's oven instrument, the Thermal and Evolved-Gas
Analyzer (TEGA), which is designed to bake Martian dirt and analyze the vapors
it emits to detect
its composition. They also plan to use the onboard Microscopy,
Electrochemistry and Conductivity Analyzer (MECA) instrument, a wet chemistry
lab that measures levels of acidity, minerals, and conductivity in dirt
samples.
"Now we know for sure that we are on an icy surface and
we can really meet the science goals of our mission at the highest level,"
Lemmon said. "I am just sitting at the edge of my chair waiting to find
out what the TEGA and MECA can tell us about these soils."
Expect the unexpected
Although the ice finding was expected, until Phoenix
actually found it, many scientists were still holding their breath.
"As for the ice, we were expecting to find it, but
science is full of the unexpected, so until they actually found the ice and can
begin to study it there are real questions about whether or not the hypothesis
was correct," said Phil Christensen, a geophysicist at Arizona State
University who worked on 2001 Mars Odyssey, Mars Global Surveyor, and the Mars
Exploration Rover missions. "The real excitement will come when they start
to study the ice in detail and attempt to learn how it formed and how old it
is."
Additional reporting for this article was contributed by
Jeremy Hsu, SPACE.com staff writer.
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