Some Mars rocks contain signs of life, scientists call to bring them back to Earth

Seven rock samples collected from the “fan front” of Mars’ Jezero Crater contain minerals typically formed in the presence of water. This finding suggests that these rocks were either deposited by water or formed within watery environments, shedding light on the past conditions of the crater.

The research was conducted by scientists from MIT and NASA. The seven samples were gathered by the Perseverance rover in 2022 during its exploration of the crater’s western slope, where scientists had hypothesized that some rocks might have originated from an ancient lake that has since dried up. 

Signs of water and maybe life in Mars rocks

The Perseverance science team, which includes researchers from MIT, analyzed the rover’s images and chemical data, confirming that the rocks indeed show signs of water. This strengthens the theory that the Jezero Crater was once a watery, potentially habitable environment.

However, whether the crater was actually inhabited remains an open question. The team has not yet confirmed the presence of organic matter – the fundamental building blocks of life – based on the rover’s measurements. 

Nevertheless, the mineral content of the rocks offers scientists their best opportunity yet to search for signs of ancient Martian life, especially once these samples are returned to Earth for more detailed analysis.

“These rocks confirm the presence, at least temporarily, of habitable environments on Mars,” said the study’s lead author, Tanja Bosak, a professor of geobiology in MIT’s Department of Earth, Atmospheric, and Planetary Sciences (EAPS).

“What we’ve found is that indeed there was a lot of water activity. For how long, we don’t know, but certainly for long enough to create these big sedimentary deposits.”

Mars rocks may contain signatures of life 

Moreover, some of these samples may have been deposited in the ancient lake more than 3.5 billion years ago – a time before the first signs of life appeared on Earth.

“These are the oldest rocks that may have been deposited by water that we’ve ever laid hands or rover arms on,” said co-author Benjamin Weiss, the Robert R. Shrock Professor of Earth and Planetary Sciences at MIT.

“That’s exciting, because it means these are the most promising rocks that may have preserved fossils and signatures of life.”

Exploring the western slope of Jezero Crater 

The study’s co-authors from MIT include postdoctoral fellow Eva Scheller and research scientist Elias Mansbach, along with other members of the Perseverance science team.

The rock samples were collected during the rover’s Fan Front Campaign in 2022, an exploratory mission in which Perseverance traversed Jezero Crater’s western slope.

This area, known as the “fan front,” contains sedimentary, layered rocks that scientists believe may represent an ancient delta. 

The delta was likely formed by sediment carried by a river that flowed into what is now a bone-dry lakebed. If life existed on Mars, scientists speculate that it could be preserved within rocks and these sediment layers.

Perseverance collected seven samples from various locations along the fan front. The rover obtained each sample by drilling into the Martian bedrock and extracting a pencil-sized core, which it then sealed in a tube for future retrieval and analysis on Earth.

Mineral composition of Mars rocks

Before drilling, the rover captured images of the surrounding sediments at each location. The scientists processed these images to estimate the average grain size and mineral composition of the sediments.

The analysis revealed that all seven samples likely contain signs of water, suggesting they were initially deposited by water.

Bosak and her colleagues identified specific minerals in the sediments that are known to precipitate out of water.

“We found lots of minerals like carbonates, which are what make reefs on Earth,” Bosak said. “And it’s really an ideal material that can preserve fossils of microbial life.”

The researchers also discovered sulfates in some samples collected at the base of the fan front. Sulfates are minerals that form in very salty water, further indicating that water was once present in the crater. 

Looking for signs of life in Mars rocks

However, Bosak noted that very salty water is not necessarily the best thing for life. If the entire crater was filled with highly saline water, it would have been challenging for life to thrive. 

On the other hand, if only the bottom of the lake was salty, it could have preserved any signs of life that may have existed in the less salty upper layers, which eventually settled at the bottom.

“However salty it was, if there were any organics present, it’s like pickling something in salt,” Bosak explained. “If there was life that fell into the salty layer, it would be very well-preserved.”

Despite these findings, the team has not definitively detected organic matter with the rover’s instruments. While organic matter can be a sign of life, it can also result from non-biological processes. 

Detecting organic matter 

Perseverance’s predecessor, the Curiosity rover, detected organic matter throughout Mars’ Gale Crater, which may have originated from asteroid impacts on Mars in the past.

During its exploration of Jezero Crater’s floor, Perseverance’s SHERLOC instrument (Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals) appeared to detect signs of organic molecules. 

SHERLOC uses ultraviolet light to scan the Martian surface, and organic materials can emit a glow under this light, providing a “fingerprint” of the types of organic molecules present.

However, a careful analysis led by MIT’s Eva Scheller found that the wavelengths observed by SHERLOC could also be signals from non-organic substances. 

“It turns out that cerium metals incorporated in minerals actually produce very similar signals as the organic matter,” she said. “When investigated, the potential organic signals were strongly correlated with phosphate minerals, which always contain some cerium.”

Scheller’s work suggests that the rover’s measurements cannot be definitively interpreted as organic matter.

“This is not bad news,” Bosak said. “It just tells us there is not very abundant organic matter. It’s still possible that it’s there. It’s just below the rover’s detection limit.”

Transformative insights from Mars rocks

When the collected samples are eventually brought back to Earth, Bosak believes that laboratory instruments with much higher sensitivity will be able to detect any organic matter that might be present. 

“On Earth, once we have microscopes with nanometer-scale resolution, and various types of instruments that we cannot staff on one rover, then we can actually attempt to look for life,” said Bosak.

Returned sample science analyses of sulfate, carbonate, clay, phosphate and igneous minerals as well as trace metals and volatiles that are present in the samples acquired at the fan front would provide transformative insights into past habitable environments on Mars, the evolution of its magnetic field, atmosphere and climate and the past and present cycling of atmospheric and crustal water, sulfur and carbon.

What happens next? How will humanity change if/when life is confirmed on an extraterrestrial planet? Stay tuned… Earth’s relationship with Mars is getting more interesting by the day.

The study is published in the journal AGU Advances.

—–

Like what you read? Subscribe to our newsletter for engaging articles, exclusive content, and the latest updates.

Check us out on EarthSnap, a free app brought to you by Eric Ralls and Earth.com.

—–