A study published in the journal Science analyzes several rocks at the bottom of Jezero Crater on Mars, where the Perseverance rover landed in 2020, revealing a significant interaction between the rocks and liquid water. These rocks also contain evidence consistent with the presence of organic compounds.
The presence of organic compounds (chemical compounds with carbon-hydrogen bonds) is not direct evidence of life, as these compounds can be created through non-biological processes. A future mission returning the samples to Earth would be needed to determine this.
The study, which was led by researchers at the California Institute of Technology, was conducted by an international team that includes Imperial researchers.
Professor Mark Sifton, from Imperial’s Department of Earth Sciences and Engineering, is a member of the science team that has been involved with the rover’s operations on Mars and considered the implications of the findings. He said, “I hope these samples can be returned to Earth one day so we can look at evidence of water and potential organic matter, and explore whether conditions were suitable for life in the early history of Mars.”
Perseverance previously found organic compounds in the Jezero Delta. Deltas are fan-shaped geological formations created at the intersection of a river and a lake on the crater rim.
Expedition scientists were particularly interested in the Jezero Delta because such formations can sustain microorganisms. A delta is created when a river that transports fine-grained sediment enters a deeper, slower-moving body of water. As the river water spreads, it slows abruptly, depositing the sediment it carries and trapping and preserving any microorganisms that may be present in the water.
However, the floor of the crater, where the rover landed for safety reasons before traveling to the delta, was more of a mystery. At the bottoms of the lakes, the researchers expected to find sedimentary rocks, because the water deposited layer after layer of sediment. However, when the rover touched down there, some researchers were surprised to find igneous rocks (cooled magma) on the floor of the crater that contained minerals that had not only recorded igneous processes, but significant contact with water.
These minerals, such as carbonates and salts, require water to circulate in igneous rocks, carving out niches and depositing molten minerals in various areas such as voids and fissures. In some places, the data shows evidence of organic matter within these potentially habitable niches.
Sherlock discovered it
Potential metals and organic compounds found in one location have been detected using SHERLOC, or Surveying Habitable Environments using the Raman & Luminescence Instrument for Organic Matters and Chemicals.
Mounted on the rover’s robotic arm, SHERLOC is equipped with a number of instruments, including a Raman spectrometer that uses a specific type of fluorescence to search for organic compounds and also see how they are distributed in a material, providing insight into how they are preserved at that location.
“SHERLOC’s compositional microscopy imaging capabilities have really opened up our ability to decipher the chronological order of Mars’ past environments,” said Bethany Ellman, co-author of the paper, professor of planetary sciences, and co-director of the Keck Institute for Space Studies.
As the rover headed toward the delta, it took several samples of water-altered igneous rocks and cached them for a potential future sample return mission. Samples must be returned to Earth and examined in laboratories with advanced equipment in order to finally determine the presence and type of organic matter and whether it has anything to do with life.