The rover’s latest findings suggest that for the past few months, it has been driving over rocks that once formed from magma or lava. The research team also concluded that the rocks in the crater have been in contact with water multiple times in their geological history — and some contain organic molecules.
Perseverance has been on Mars for less than a year, but it’s already taking important steps in helping us understand the Red Planet. Among its suite of instruments is also a robotic arm that can abrade or grind rock surfaces, allowing other instruments to study them in detail. The PIXL instrument, or Planetary Instrument for X-ray Lithochemistry, enables the rover to rapidly measure elemental chemistry at sub-millimeter scales by focusing an X-ray beam on a surface and analyzing the induced X-ray fluorescence.
The area that researchers are eager to investigate in detail is Jezero Crater, which is thought to contain a delta — a fan-shaped area at the mouth, or lower end, of a river, as it enters another body of water such as a lake or sea. But some believed the area wasn’t a delta shaped by rivers at all, but rather a geological structure shaped by a different flowing body: lava.
The mystery of what this structure actually is was haunting researchers for quite some time.
“I was beginning to despair we would never find the answer,” said Perseverance Project Scientist Ken Farley of Caltech in Pasadena. “But then our PIXL instrument got a good look at the abraded patch of a rock from the area nicknamed ‘South Séítah,’ and it all became clear: The crystals within the rock provided the smoking gun.”
Perseverance’s PIXL analysis showed that the rock contains an abundance of large olivine crystals engulfed in pyroxene crystals — two types of minerals that are clear indicators of magma. Furthermore, researchers can now know that this was magma that cooled down slowly.
Both olivine and pyroxene are “at home” at high temperatures and pressures, and are unstable on the surface. If magma containing the right chemistry to form these crystals cools down quickly, only small crystals will form — or if it cools really quickly, no crystals at all will form. In order for large crystals (such as the ones observed by Perseverance) to take shape, the magma needs to cool down slowly.
“A good geology student will tell you that such a texture indicates the rock formed when crystals grew and settled in a slowly cooling magma – for example a thick lava flow, lava lake, or magma chamber,” said Farley. “The rock was then altered by water several times, making it a treasure trove that will allow future scientists to date events in Jezero, better understand the period in which water was more common on its surface, and reveal the early history of the planet. Mars Sample Return is going to have great stuff to choose from!”
However, the rover didn’t survey rocks from the delta itself, but rather baseline rocks from the surrounding terrain, and there are still questions regarding how the area formed. For instance, the rocks may have not formed at the surface, but rather in a subterranean chamber that was later exposed by erosion. Overall, although this new evidence is tantalizing, it’s still not clear what it all means.
“This was completely unexpected, and we are struggling to understand what it means,” Farley said. “But I will speculate that this is not likely the original crater floor. From the diameter of this crater, we expect the original crater floor is significantly deeper than where we are right now.”
NASA also released the first radargram obtained from Mars. Perseverance is equipped with a radar that can help researchers study the subsurface of the planet. RIMFAX (Radar Imager for Mars’ Subsurface Experiment) creates a “radargram” of subsurface features up to about 33 feet (10 meters) deep.
NASA also released results obtained with its SHERLOC (Scanning Habitable Environments with Raman & Luminescence for Organics & Chemicals) instrument. Essentially, SHERLOC looks for carbon-containing organic molecules — and it found some. This doesn’t mean that these are signs of life (biosignatures), as there are both biological and non-biological organic molecules, but it shows that the Martian environment had, at least at some point, water and potentially life-breeding conditions.
While not necessarily a new idea, Perseverance allows us to understand the conditions on Mars better than ever before.
“Curiosity also discovered organics at its landing site within Gale Crater,” said Luther Beegle, SHERLOC principal investigator at NASA’s Jet Propulsion Laboratory in Southern California. “What SHERLOC adds to the story is its capability to map the spatial distribution of organics inside rocks and relate those organics to minerals found there. This helps us understand the environment in which the organics formed. More analysis needs to be done to determine the method of production for the identified organics.”
The question of whether or not life existed (or exists) on Mars is still not clear, but finding organic molecules is still extremely exciting, Beegle concludes.
“This is a question that may not be solved until the samples are returned to Earth, but the preservation of organics is very exciting. When these samples are returned to Earth, they will be a source of scientific inquiry and discovery for many years,” Beegle said.