Before
testing for life on other planets, it's useful to practice on barren areas of
the Earth. One such place is Rio Tinto in Spain, where conditions are analogous
to Mars.
The
water of that Spanish river is very acidic, similar to water scientists think
may have once flowed on the martian surface. Also, chemical studies hint that
rocks on Mars' Meridiana Planum plain have been moved by Rio Tinto-type water.
Using
life-searching drilling techniques along the Rio
Tinto river, scientists were surprised to find microscopic life where they
thought conditions were too harsh for anything to survive.
Practice makes perfect
Fernando Rull Pérez from the Centro de
Astrobiologia in Madrid is an expert in hunting for signs of life using
spectroscopic techniques, and he has been conducting studies in the Rio Tinto
region.
"We
are developing instrument prototypes looking for minerals and organics in Rio
Tinto and other places," he says. "We are also trying to prepare a
scientific model with which we can learn about the possibility [of life] and
how we can extrapolate these models to Mars."
Why
is Rull Pérez looking for organic
materials? They contain carbon, which is present in all known forms of
life. If organics are found it may indicate a type of organism that we would
recognize. In other words, life as we know it.
Areas
on Earth like Rio Tinto provide opportunities for scientists to "train"
their instruments in the search for organics, and prepare them for similar searches
on Mars. The challenging conditions make for a useful proving ground.
Seeing what results from such conditions on Earth may indicate what sort of
unusual minerals we can expect to find on the martian surface.
Rull
Pérez and his colleagues are testing what are
known as "in
situ" techniques. That means samples are examined at the site
there and then, instead of being removed and taken to a lab for analysis.
Results are gathered much faster, and it also avoids the problem of
contamination that can occur during a return journey.
The
specter of such contamination will likely haunt samples from Mars that are
brought back to Earth for study. But while in situ experiments solve one
problem, they add another: experiments on Mars must be performed by rovers,
millions of miles away from controllers on Earth.
Ready for Mars
Rull
Pérez is working in Rio Tinto on a special in
situ tool that will form part of the European Space Agency's ExoMars mission to the Red
Planet, due to launch in 2013. The instrument is known as Raman/LIBS, after the
scientist Sir Chandrasekhara Raman, and LIBS for Laser Induced Breakdown
Spectroscopy. This tool is a spectrometer that uses a laser to "excite"
atoms and molecules. These agitated atoms exhibit more movement than normal,
and this atomic dancing can indicate what kinds of molecules are present. It's
a cutting edge system which to date has been almost exclusively
laboratory-based, so using it in situ is an experiment in itself.
The
instrument has two optical heads. One located outside the rover will identify
minerals and potential organics on the surface. Another inside the rover will
be used for identification and analysis of core samples excavated by the rover's
drill. Current plans are to dig down to 2 meters (6.5 feet) beneath the martian
surface. Delving this deep will allow scientists to investigate the possibility
of past or present water — and even life — on the red planet.
The
Raman/LIBS spectrometer has an advantage over other spectrometers because it's
non-destructive: The laser used to probe the matter doesn't cause any harm.
This means that it will be deployed before any other instruments on ExoMars.
As Rull Pérez says, this instrument will be "on
the front line of identification and analysis." If any organic material is
found, then ExoMars's other gadgets will swing into action and probe the
samples to gather as much data as possible.
Even
as Rull Pérez's Raman/LIBS spectrometer is
being tested for use on ExoMars, work is underway inside his group on the next
generation of the instrument which could probe samples up to 65 feet (20 meters)
away. Unlike Rull Pérez's contact spectrometer,
this updated version won't be ready for ExoMars — although it may feature on
future missions. It's an exciting time for astrobiologists searching for life,
and in situ instruments tested in Rio
Tinto are at the forefront of their endeavors.
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