In this illustration, NASA's Perseverance rover uses its Planetary Instrument for X-ray Lithochemistry (PIXL) instrument to analyze a rock on the surface of Mars.

PIXL uses a focused X-ray beam to analyze the chemistry of features as small as a grain of sand. The tiny but powerful beam causes rocks to fluoresce, or produce a glow. While the glow is invisible to the human eye, it is detectable by the instrument and varies according to the rock's elemental chemistry. PIXL scan the beam across the surface of the rock to produce a postage-stamp-sized map of the rock's chemistry at the end of an overnight scan.

PIXL also has an optical fiducial system (OFS) that includes white "flood lights" — seen on the rock in this artist's concept — that is used together with a pattern of red lasers to illuminate the rock while its camera captures images of the mapped area.

The pictures are used for multiple purposes: PIXL analyzes them on board to work out where the target is — in 3D — and move itself into the right position for science collection and the safety of the instrument. The pictures are also downlinked to Earth so scientists can see exactly where each measurement was taken. This allows scientists to tie chemistry accurately to rock texture, which helps them to determine how these features formed and whether they were biological in nature.

For more information about the mission, go to https://mars.nasa.gov/mars2020/.