The red planet may not have been as warm and wet as scientists suspect, according to new research into geological formations.
A study in the journal Nature Geoscience suggests that ancient clay minerals on Mars may have originated from cooling lava, rather than being formed from liquid water as scientists have speculated.
Orbiting satellites have observed an abundance of mineral-rich clay deposits on Mars, formed during the planet's early Noachian period, about 4 to 4.5 billion years ago. According to conventional thinking, these clays are the product of aqueous weathering – a chemical process between rocks and surface water – over long periods of time.
These deposits are among the strongest pieces of evidence that Mars, which today has an arid and acidic landscape, once had a warmer climate and large bodies of water that could have sustained life.
But a team of researchers studying similar rocks at Moruroa Atoll, a former nuclear testing site in French Polynesia in the southern Pacific Ocean, has proposed an alternative explanation for how they formed.
Researchers found that the clays at Moruroa were produced from cooling volcanic magma in a process that doesn't require large volumes of water. Based on infrared testing on both Martian and Moruroan rocks, they believe that both clays have similar origins.
The findings mean that the red planet could have been drier and colder than what scientists have theorized.
"We are speaking of clays formed in the oldest rocks of Mars' crust…Their detection on large areas was classically interpreted as an effect of weathering processes," Professor Alain Meunier, the study's lead author, told CBC News.
"This led the scientific community to consider that the early climate on Mars was warm and wet. Of course, if these clays originate from a magmatic process, they cannot be used to reconstitute climatic conditions."
Nevertheless, the findings don't rule out the possibility of life on Mars.
"Water in a liquid state has undoubtedly existed on Mars: river valleys, sedimentary deposits, presence of sulfates," said Meunier. "However, these features witness a more recent period in the history of Mars."