The habitability of ancient Mars has long been a topic of intense scientific interest and debate. While it is widely accepted that water once flowed on the Red Planet and that it had a denser atmosphere, the question of how long Mars remained habitable has been the subject of ongoing research. A recent study led by scientists at New York University Abu Dhabi (NYUAD) suggests that Mars may have experienced periods of habitability that lasted for eons, significantly longer than previously thought.
The research, published in the Journal of Geophysical Research – Planets, focused on analyzing data from NASA's Curiosity rover, which has been exploring the Gale Crater on Mars. The team, led by Dimitra Atri, the Principal Investigator of NYUAD's Center for Astrophysics and Space Science (CASS), found evidence that billions of years ago, ancient sand dunes within the crater gradually turned into rock through interaction with underground water.
"Our findings indicate that Mars may have been habitable much longer than expected, challenging the notion that it ceased being habitable billions of years ago," said Atri. "This has significant implications for the search for past life on Mars."
Examining the Stimson Formation
The team examined dunes in the Stimson Formation (SF), a system of wind-blown sand and sedimentary rock in the Gale Crater. Curiosity has observed evidence of these "lithified" formations, sediments that hardened into stone, at this location on several occasions. Given the pervasive dry conditions in the Gale Crater, these formations likely formed during the Noachian Period (ca. 4.1 to 3.7 billion years ago) when extensive flooding, including rivers that flowed into the Gale Crater, is believed to have taken place.
The researchers accessed data through the Mars Science Laboratory's (MSL) Curiosity Notebook, which provides information gathered by Curiosity's instruments. They then compared this data to field studies of rock formations in the desert environment of the United Arab Emirates (UAE), which are also known to have formed in the presence of water.
Evidence of Late-Stage Aqueous Activity
The team determined that the SF was the product of late-stage aqueous activity, meaning the formations developed from interaction with groundwater from the nearby mountain. They further found that this interaction left behind minerals such as gypsum, a soft sulfate mineral composed of calcium sulfate dihydrate (CaSO4) that is also found in Earth's deserts.
This latest research echoes similar findings presented by Krishnamoorthi and Atri last year at the Tenth International Conference on Mars, where they examined data collected on the Greenheugh Pediments (GP), a nearby dune formation with similarly lithified rock deposits.
Implications for the Search for Life on Mars
The researchers believe that these dunes and their systems of underground water led to the creation of these curious formations, which could have significant implications in the search for past and present life on Mars. On Earth, sandstone deposits contain some of the oldest evidence of life, including communities of microorganisms that bind sediment and cause minerals to precipitate. Based on these terrestrial analogues, the team believes that lithified deposits in the Gale Crater could contain the preserved remains of ancient bacteria.
This latest research not only provides new insight into how Mars evolved and transitioned to the extremely cold and dry environment we see today but also suggests that these sites would be good candidates for future missions that will continue the search for life on Mars.
Future Exploration and Research
As our understanding of Mars' geological history continues to evolve, the findings from this study will help guide future exploration efforts. Upcoming missions, such as NASA's Perseverance rover and ESA's ExoMars programme, will build upon this research, targeting sites with the potential to harbor evidence of past life.
By studying the complex interactions between water, sediment, and the Martian atmosphere over time, scientists can piece together a more comprehensive picture of the planet's habitability. This research not only reshapes our understanding of Mars' past but also informs the search for life beyond Earth, as we continue to explore the potential for habitable environments throughout the solar system and beyond.
