A study published in Science analyzes multiple rocks found at the bottom of Mars’ Jezero crater, where the Perseverance rover landed in 2020, and revealed significant interaction between the rocks and liquid water. Those rocks also contain evidence consistent with the presence of organic compounds.
The existence 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, led by Caltech researchers, was conducted by an international team that included Imperial researchers.
Professor Mark Sephton, from Imperial’s Department of Earth Science & Engineering, is a member of the science team that took part in rover operations on Mars and considered the implications of the results. He said: “I hope that one day these samples can be returned to Earth so that we can look at the evidence of water and possibly organic matter, and investigate whether conditions were good for life in the early history of Mars. “
Perseverance previously found organic compounds in the Jezero delta. Deltas are fan-shaped geological formations formed at the junction of a river and lake at the crater rim.
Mission scientists were particularly interested in the Jezero Delta because such formations can sustain microorganisms. Deltas form when a river carrying fine-grained sediments enters deeper, slower-moving water. As the river water spreads, it slows down abruptly, depositing the sediments it carries and trapping and sustaining all the microorganisms that exist in the water.
However, the crater floor, where the rover landed for safety reasons before traveling to the delta, was more of a mystery. The researchers expected to find sedimentary rocks in lake bottoms, because the water deposits sediment layer after layer. However, when the rover landed there, some researchers were surprised to find igneous rocks (cooled magma) at the bottom of the crater containing minerals that not only recorded igneous processes, but also significant contact with water.
These minerals, such as carbonates and salts, require water to circulate in the igneous rocks, carve out niches and deposit dissolved minerals in various areas such as voids and cracks. In some places, the data shows evidence of organic matter within these potentially habitable niches.
Discovered by SHERLOC
The minerals and co-localized possible organic compounds were discovered using SHERLOCor the Scanning Habitable Environments with Raman & Luminescence for Organics & Chemicals instrument.
Mounted on the rover’s robotic arm, SHERLOC is equipped with a number of tools, including a Raman spectrometer that uses a specific type of fluorescence to look for organic compounds and also see how they are distributed in a material, providing insight into how they were kept in that location.
Bethany Ehlmann, co-author of the paper, professor of planetary science and associate director of the Keck Institute for Space Studies, said: “SHERLOC’s microscopic compositional imaging capabilities have really blown open our ability to decipher the time sequence of Mars. environments.”
As the rover rolled toward the delta, it took several samples of the water-altered igneous rocks and cached them for a possible future sample return mission. The samples would have to be returned to Earth and examined in laboratories with advanced instruments to definitively determine the presence and type of organics and whether they have anything to do with life.