Dress Rehearsal for Mars

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.

• Video: Life on Mars — The Search Continues
• Life Found Where You Least Expect It
• Unlocking Martian Rocks