Stone sample that could preserve traces of ancient Martian life

NASA's Perseverance robot, which has been circulating on the surface of Mars since it arrived on the planet in 2021, has been extracting stone cores (samples from the interior of rocks that it accesses by drilling) inside the immense Jezero crater and one of those samples It has aroused great expectation because, due to its characteristics, it could preserve vestiges of ancient Martian life.

Although the origin of the rock from which this sample comes is still under investigation and the Perseverance team of scientists continues to analyze different hypotheses, the sample is particularly promising because it appears to be composed mainly of two minerals: carbonate and silica. Both carbonate and silica are excellent minerals for preserving ancient biosignatures (signs of past life). These minerals also have the potential to record the environmental conditions under which they formed, making them important minerals for finding out how habitable the Jezero Crater area was a few billion years ago.

The rock has been given the name Comet Geyser.

The presence of carbonate within the sample extracted from Comet Geyser suggests that water, carbon dioxide and chemical elements derived from rocks or sediments in and around Jezero Crater once reacted chemically to form carbonate.

Carbonate minerals from the Earth's rock record are often used to reconstruct ancient climate (including temperature, precipitation, and degree of aridity) and the history of fauna and flora.

Silica phases that form when water interacts with rocks or sediments can provide information, through the composition and crystallinity of the material, that reveals the degree of interaction with water, as well as the intensity or duration of weathering and the pressure and temperature prevailing during formation.

On Earth, biosignatures can be preserved in carbonate and silica for millions of years, or even billions of years in the case of silica. Some of the oldest evidence we have for life on Earth comes from rocks containing fragments of microbial cells that underwent permineralization by silica. This is a fossilization process that buries the remains of ancient life and protects them from degradation. Therefore, Martian rocks containing these materials are considered priority targets for analysis to determine whether Jezero Crater hosted microbial life in the past.

The intriguing sample collected by Perseverance, shortly after its extraction. (Photo: NASA JPL/Caltech/ASU)

With this valuable sample already stored on board in an isolated capsule, Perseverance advances towards its next target to investigate: a place called Bright Angel, which is a light-colored rocky outcrop. Challenges are likely to arise on this journey, as the terrain before Perseverance is littered with sharp boulders and accumulations of sand that are proving difficult obstacles for the robot's automatic navigation system. (Fountain: NCYT by Amazings)