“There is a real possibility that the team will find itself attempting to evaluate a potential biosignature on Mars in the next five years,” Allwood said. “When that happens, we need to already have a pretty detailed, solid understanding of the processes that formed the rocks we find that potential biosignature in. Otherwise we might get a false positive.”

Before getting into the working of PIXL, a little background:

Microbes change the texture and chemistry of their environment. An example that NASA likes to give is the plaque your dentist scrapes off your teeth. That hard stuff is minerals left behind by millions of bacteria. It’s an example of a “biofilm.”

Biofilms form when a group of microbes stick together to form a surface. You can find biofilms on surfaces everywhere in nature. PIXL can detect signs of biofilms made by microbes in the Martian environment long ago because rocks can and sometimes do preserve their texture and chemistry.

This relates directly to the stromatolite issue in Greenland, because stromatolites are mounds of sediment that once had biofilms between their layers of non-biological material. Sediments in the water would stick to the gluey biofilms, form a layer, and then result in more biofilms growing on top of the layer to get the life-supporting material it needed.

What is new about PIXL is the level of detail it provides. PIXL uses a very tiny (about 0.3mm diameter), powerful x-ray beam to rapidly measure the elemental chemistry of rocks. In about 10 seconds, it can accurately measure the elemental chemistry of an individual grain of sand. Scanning the beam across the surface of the rock, PIXL can acquire a postage stamp-sized chemical map overnight, while the rover is “sleeping”.

PIXL can detect some of the kinds of miniscule or faint changes that life brings to the chemistry of rocks or minerals. It can, for instance, detect unusual and meaningful concentrations of a particular element or compound, it can find other anomalies known to be produced by biology, it can potentially detect changes in the textures and forms of rock details down to the rock grain to tell if perhaps a biofilm was once present.

“Interpreting the geological past, unravelling the details of ancient environments – that is the bread and butter of any geological or astrobiological investigation,” Allwood said.