MIT scientists have developed a technique to help the 2020 NASA Mars rover quickly and non-invasively identify rocks which are more likely than others to hold signs of ancient life on the red planet.

In 2020, NASA plans to launch a new Mars rover that will be tasked with probing a region of the planet scientists believe could hold remnants of ancient microbial life.

The rover will collect samples of rocks and soil, and store them on the Martian surface; the samples would be returned to Earth sometime in the distant future so that scientists can meticulously analyse them for signs of present or former extraterrestrial life.

Now, scientists at Massachusetts Institute of Technology (MIT) in the US have developed a technique that will help the rover quickly and non-invasively identify sediments that are relatively unaltered, and that maintain much of their original composition.

Such "pristine" samples give scientists the best chance for identifying signs of former life, if they exist, as opposed to rocks whose histories have been wiped clean by geological processes such as excessive heating or radiation damage.

The team’s technique centres on a new way to interpret the results of Raman spectroscopy, a common, non-destructive process that geologists use to identify the chemical composition of ancient rocks.

Among its suite of scientific tools, the 2020 Mars rover includes SHERLOC or Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals, an instrument that will acquire Raman spectra from samples on or just below the Martian surface. SHERLOC will be pivotal in determining whether life ever existed on Mars.

Raman spectroscopy measures the minute vibrations of atoms within the molecules of a given material.

As atoms and molecules vibrate at various frequencies depending on what they are bound to, Raman spectroscopy enables scientists to identify key aspects of a sample’s chemical composition.

More importantly, the technique can determine whether a sample contains carbonaceous matter – a first clue that the sample may also harbour signs of life.

Nicola Ferralis, a research scientist in MIT’s Department of Materials Science and Engineering, discovered hidden features in Raman spectra that can give a more informed picture of a sample’s chemical makeup.

The researchers were able to estimate the ratio of hydrogen to carbon atoms from the substructure of the peaks in Raman spectra.

This is important because the more heating any rock has experienced, the more the organic matter becomes altered, specifically through the loss of hydrogen in the form of methane, researchers said.

The study was published in the journal Carbon.