For the
first time, satellite imagery reveals thick Martian salt deposits scattered
across the planet's southern surface, which one planetary scientist claims could
be sites of ancient life.
The mats of
sodium chloride — the same taste-enhancing mineral found on your kitchen table
— serve as more evidence of Mars' watery past, and researchers
think the briney pools that made them could have been hospitable
to life.
"If
you're trying to find life on Mars, the more and different places that exist,
the better the chances are that one of them is going to have the right conditions,"
said Phil Christensen, a planetary geologist at Arizona State University.
"It takes a lot of water to form salt, so this is another place to
look."
Christensen,
who co-authored a March 21st study in the journal Science detailing the
findings, said the salt deposits are a clear sign of water's past presence, adding
that they could be the most welcoming environment for life on Mars yet discovered.
Take a
chance
Christensen
said the salt deposits probably formed from dried-up brine pools,
which would not have been as acidic as other places on Mars where water is
thought to have existed, such as clay and hydrated mineral deposits.
Sites such
as those found by the Mars Exploration Rovers show sulfur in high levels, which
means any water there may have been too harsh to support life.
"That's
not the case with salt deposits, because they tend to not be acidic,"
Christensen said.
He added
that some of the oldest organisms ever discovered on Earth have been found
locked away in salt crystals, and that there may be Martian life forms entombed in the new crumbly flats that are about 3 to 10 feet (1 to 3 meters) thick.
"Salt
is a fantastically good preserver, so maybe there's not only life but also organic
compounds preserved there," Christensen told SPACE.com. "We
need to send a rover to these places. I hope some day we will explore these
salt sites on the ground."
Transparent
treasure
Christensen
said the route to identifying the salt deposits, thought to be more than 3.5
billion Earth years old, wasn't easy.
"Salt,
it turns out, is pretty hard to detect," Christensen said, explaining that
light analysis, or spectroscopy, of the mineral doesn't often show clear-cut
signatures in satellite data. "They're actually very transparent, so
there's generally a lot of difficulty in identifying them."
Using the Mars
Odyssey orbiter's Thermal Emission Imaging System (THEMIS),
the research team found dozens of strange sites in a belt just south of Mars'
equator. Christensen said it took them a couple of years to figure out what,
exactly, they were.
"Once
we realized we were looking at a transparent mineral, the light bulbs in our
heads went off," he said. "When you look at the sites with visual satellite
images, they look all the world like dried-up salt flats."
Salty
skepticism?
Christensen
said a handful of planetary scientists are likely to be skeptical of his team's
conclusion, but noted that a large majority should be on board.
"The spectroscopy
of these salt sites is complicated, so I don't expect everyone will agree with
us," he said. "Salts do this bizarre thing to spectrographs, so we have
to do more singing and dancing to make the case."
In any
event, Christensen said the sites he and his team have pinpointed are worthy of
future investigation, especially if other ancient Martian
water sites don't pan out to support life.
"I
always worry that someone will say that's the end of the story for life on Mars
if that happens," Christensen said. "I think these salt sites are
really exciting. They may give us the best chance yet of finding something."
NASA funded
the work by Christensen and his team.
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