This graphic depicts Perseverance’s entry into “Séítah” from both an orbital and subterranean perspective. The bottom image is an underground “radar diagram” from the rover’s RIMFAX instrument; the red lines indicate features below the surface for erosion-resistant rock outcrops that are visible above the surface. Credit: NASA / JPL-Caltech / University of Arizona / USGS / FFI
Scientists with NASA’s Perseverance Mars rover mission have discovered that the bedrock that their six-wheeled explorers have run on since landing in February is likely formed by red-hot magma. The discovery has implications for understanding and accurately dating critical events in the history of the Jezero crater – as well as the rest of the planet.
The team has also concluded that rocks in the crater have interacted with water several times during the eons, and that some contain organic molecules.
These and other findings were presented today during a news briefing at the American Geophysical Union’s Fall Science Meeting in New Orleans.
Even before Perseverance landed on Mars, the mission’s science team had wondered about the origin of the rocks in the area. Were they sedimentary – the compressed accumulation of mineral particles that may have been carried to the site by an ancient river system? Or where they are magmatic, possibly born in lava flows rising to the surface from a now long-extinct Mars volcano?
“I was starting to despair that 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 worn part of a rock from the area nicknamed ‘South Séítah’, and it all became clear: the crystals in the rock delivered the smoking gun.”
The drill at the end of Perseverance’s robotic arm can grind or grind rock surfaces to allow other instruments such as PIXL to study them. Map for Planetary Instrument for X-ray Lithochemistry, PIXL uses X-ray fluorescence to map the elemental composition of rocks. On November 12, PIXL analyzed a stone from the South Séítah that the science team had chosen to take a core sample using the rover’s drill. The PIXL data showed that the rock, nicknamed “Brac”, consists of an unusual abundance of large olivine crystals engulfed by pyroxene crystals.
“A good geology student will tell you that such a texture indicates the rock that was formed when crystals grew and settled in a slowly cooling magma – for example, a thick lava flow, lava lake or magma chamber,” Farley said. “The rock was then modified by water several times, making it a treasure trove that will allow future scientists to date events in Jezero, better understand the period when water was more common on the surface, and reveal the planet’s early history. Mars Sample Return will have great things to choose from. “
The multi-mission Mars Sample Return campaign began with Perseverance, which collects rock samples from Mars in search of ancient microscopic life. Of Perseverance’s 43 test tubes, six have been sealed to date – four with rock cores, one with a Mars atmosphere and one containing “witness” material to observe any contamination that the rover may have brought from Earth. The Mars Sample Return seeks to bring selected tubes back to Earth, where generations of scientists will be able to study them with powerful laboratory equipment that is far too large to send to Mars.
It remains to be seen whether the olivine-rich rock is formed in a thick lava lake that cools on the surface or in an underground chamber that was later exposed by erosion.
Organic molecules
Also good news for Mars Sample Return is the discovery of organic compounds with the SHERLOC instrument (Scanning Habitable Environments with Raman & Luminescence for Organics & Chemicals). The carbonaceous molecules are not only in the interior of worn stones, SHERLOC analyzed, but in the dust of non-ground stones.
Confirmation of organic matter is not a confirmation that life once existed in Jezero and left revealing signs (biosignatures). There are both biological and non-biological mechanisms that create organic matter.
“Curiosity also discovered organic matter at its landing site in Gale Crater,” said Luther Beegle, SHERLOC’s chief investigator at NASA’s Jet Propulsion Laboratory in Southern California. “What SHERLOC adds to history is its ability to map the spatial distribution of organic matter inside rocks and relate these organic matter to the minerals found there. This helps us understand the environment in which the organic matter is formed. Several analyzes must be carried out to determine the method of production of the identified organic substances. “
The preservation of organic matter inside ancient rocks – regardless of origin – at both the Gale and Jezero craters means that potential biosignatures (signs of life, whether past or present) can also be preserved. “This is a question that may not be resolved until the samples are returned to Earth, but the conservation of organic matter is very exciting. When these samples are returned to Earth, they will be a source of scientific study and discovery for many years. , “said Beegle.
Six facsimile test tubes hang on the test tube plate. Credit: NASA / JPL-Caltech
‘Radargram’
Along with its rock-core sampling capabilities, Perseverance has brought the first ground-penetrating radar to the surface of Mars. RIMFAX (Radar Imager for Mars’ Subsurface Experiment) creates a “radar chart” of underground functions up to about 33 feet (10 meters) deep. Data for this first released radar diagram were collected as the rover drove over a ridge from the “Crater Floor Fractured Rough” geological unit into the Séítah geological unit.
The ridge has several rock formations with a visible downward slope. With RIMFAX data, Perseverance researchers now know that these angled rock layers continue at the same angle well below the surface. The radar chart also shows the project of the Séítah rock layer below those of Crater Floor Fractured Rough. The results further confirm the science team’s belief that the creation of Séítah preceded Crater Floor Fractured Rough. The ability to observe geological features even below the surface adds a new dimension to the team’s geological mapping capabilities on Mars.
Rocks on the floor of the Jezero crater on Mars show signs of sustained interactions with water
More information:
For more on Perseverance: mars.nasa.gov/mars2020/ and nasa.gov/perseverance
Provided by Jet Propulsion Laboratory
Citation: Perseverance Mars rover makes surprising discoveries (2021, December 15) retrieved December 15, 2021 from https://ift.tt/3GKcR26
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