Mars’ Jezero Crater: Ancient Water and Potential Life – What Did the Rover Find?
NASA’s Perseverance rover has revealed that ancient rocks in Jezero Crater were formed in the presence of water. These sedimentary rocks, over 3.5 billion years old, may predate life on Earth. Scientists are hopeful that once these samples are returned to Earth, they might provide evidence of ancient Martian life.
In 2022, Perseverance sampled rocks from a region known as the ‘fan front’ on Jezero Crater’s western slope. It was hypothesized that these rocks formed in the lakebed when the crater was once filled with water. Perseverance analyzed the rocks’ chemistry and took images of their surroundings. The findings have been published in the journal AGU Advances, led by Tanja Bosak, a geobiology professor at MIT.
“These rocks confirm the presence, at least temporarily, of habitable environments on Mars,” said Bosak. “We’ve found significant water activity, although the duration remains uncertain, but it was enough to create these substantial sedimentary deposits.”
Perseverance collected seven samples from the fan front, including sulphate- and clay-bearing mudstone, sandstone, and carbonate-bearing sandstone. Sulphates, clays, and carbonates typically form in water, revealing insights into the ancient water’s chemistry, temperature, and acidity. The carbonate-bearing sandstones also provide clues about Mars’ atmospheric conditions at the time.
“The hydrated, sulphate-bearing mudstone has the highest potential to preserve organic matter and biosignatures,” the authors explain. “Carbonate-bearing sandstones help determine when and for how long Jezero Crater contained liquid water.”
While the samples are sealed for future return to Earth, Perseverance also abraded rock surfaces at each sample location to analyze mineral content. These ancient Martian rocks are the oldest sedimentary rocks studied to date and likely formed when Jezero Crater was a habitable lake. They could potentially contain ancient organic matter, but this will only be confirmed once the samples reach Earth.
“These are the oldest rocks deposited by water that we’ve ever encountered,” said co-author Benjamin Weiss, a professor at MIT. “This makes them the most promising for preserving fossils and signs of life.”
Sedimentary rocks consist of grains and cement. The grains are the building blocks, while the cement, which fills rock pores, solidifies the rock. The researchers believe that both components in the fan front sedimentary rocks likely formed in water. During lithification, organic matter from ancient life could have been trapped in the rock.
The fan front is an ideal location for searching for evidence of ancient life. “We found many minerals like carbonates, which are similar to those forming reefs on Earth,” Bosak notes. “This material is well-suited to preserve microbial life fossils.”
Though sulphates form in salty water, which isn’t ideal for life, the salt’s preservative effect could be beneficial. If the brine was confined to the lake bottom, life could have survived in the upper layers. Dead organisms might have sunk to the bottom, where the brine could have preserved their remains.
“Even if the water was salty, any organic material could be well-preserved, like pickling in salt,” Bosak adds.
Mars is known to have been warm and wet in the past. The next step is to determine if life ever existed there. Finding organic matter is crucial, but distinguishing between life-related and geologically produced organic matter is challenging. The Curiosity Rover previously found organic carbon in Gale Crater, but it was determined to be the result of UV fractionation.
Perseverance also detected organic matter on Jezero Crater’s floor, but subsequent analysis suggested it might not be linked to life. This highlights the limitations of rovers compared to Earth-based labs.
The Mars Sample Return mission is essential for a comprehensive analysis. Only by bringing Martian samples to Earth can scientists thoroughly investigate the evidence collected by Perseverance.
“On Earth, advanced microscopes and instruments that we can’t deploy on a rover will allow us to search for life in greater detail,” Bosak concludes.
Source: Mars’ Jezero Crater: Ancient Water and Potential Life – What Did the Rover Find?
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Mars’ Jezero Crater: Ancient Water and Potential Life – What Did the Rover Find?