Curiosity rover finds opal on Mars - a possible source of water for astronauts

Old images collected by the Curiosity rover have revealed light-colored rocks surrounding the "halos" of faults on the Red Planet. Samples of these rocks have previously been collected with rover instruments. In the new research scientists from the University of Arizona analyzed this archival data using new methods. They were able to confirm that these light stones contain opal.

Opal is formed when water weathers silica-rich rocks. The resulting solution settles in the cracks and crevices of the rock. Over time, it hardens into a hard mineral that can be cloudy and dull or blindingly bright. Today, opal is mostly sourced either from Australia or Ethiopia.

In fact, this is not the first time opal material has been found on Mars. Back in 2008, the Mars Reconnaissance Orbiter noticed large pale spots in several regions of the Red Planet that were attributed to hydrated silica deposits. Now it seems that this material is more common than previously thought.

The discovery of an opal is a big event. After all, this suggests that water appeared on Mars a very long time ago. Even after the surface dried up and became unsuitable for any microbes that could live there, conditions below the surface remained potentially habitable for a long time to come.

This is good news for Curiosity and its successor, the Perseverance rover, which is currently searching for signs of life in Lake Jezero Crater, a site rich in opal material.

Another value of opal is that it could be a useful source of water for future astronaut missions. Theoretically, water can be released from the crystal structure if the stone is crushed and heated. The team calculated that a 1 meter long halo could hold up to 5.7 liters of water at a depth of 0.3 meters.