Hot water on ancient Mars may have been habitable

A 4.45-billion-year-old grain from a famous Martian meteorite shows that there was hot water on ancient Mars which had the potential to be habitable.

It is the oldest direct evidence of hot water on Mars as scientists continue to look for signs that the Red Planet once hosted (or could host) life.

The study, led by researchers at Western Australia’s Curtin University, is published in the journal Science Advances.

NWA 7034, also known as “Black Beauty”, is a 320-gram Martian meteorite found in 2011 in the western Sahara Desert. It contains the most water of any Martian meteorite found on Earth. A 2022 study suggests that the rock was ejected from Mars’s surface in an impact 1.5 billion years ago, making its way to Earth 5–10 million years ago.

The new study analysed a zircon grain from Black Beauty and found the geochemical “fingerprints” of water-rich fluids. The study suggested a history on Mars of hydrothermal systems associated with magmatism.

Elements including iron, aluminium, yttrium and sodium were found in the zircon, suggesting water was present during a time when there was magmatism on early Mars.

“Hydrothermal systems were essential for the development of life on Earth and our findings suggest Mars also had water, a key ingredient for habitable environments, during the earliest history of crust formation,” says co-author Aaron Cavosie, a planetary scientist from the Space Science and Technology Centre at Curtin University.

Evidence now abounds that ancient Mars had liquid water. But much of this research also points to the Red Planet being too cold to sustain that liquid water long enough for life to emerge.

The presence of hydrothermal systems on Mars may have made it habitable.

“It’s hard to say for sure how long hot water was present on Mars, but it was probably present for tens of millions of years or longer,” Cavosie tells Cosmos.

“The zircon we analysed crystallized in magma at 4.45 billion years ago. This age places it in a previously recognized time of igneous magmatic activity related to the growth of the Martian crust from 4.48 to 4.43 billion years ago. It’s possible that hydrothermal systems driven by magmatism were prevalent during this entire ~50-million-year span. This is now a testable hypothesis that can be addressed by collecting more data from Martian zircons.”

Cavosie says hydrothermal systems, like those still found deep in Earth’s oceans, can reach 100–600°C. Cavosie’s earlier research suggests that Earth also had water about 4.3 billion years ago.

“Another interesting question is what drove the early magmatism that made these zircons?” Cavosie says. “Most evidence from the study of meteorites indicates that Mars experienced a high level of meteorite impact events at this time. So it’s possible that the magmatism and the hydrothermal systems were in part driven by meteorite impacts.”

The researcher says that about 20 meteorites have been found that may have come from Mars, but Black Beauty is different.

“What makes Black Beauty so special is that it’s a sample of regolith from the surface, similar to soil, so it contains hundreds of rock and mineral fragments sourced from all over Mars,” Cavosie explains. “The Black Beauty meteorites are an extraordinary buffet of pieces to the Martian geological puzzle.”

Cavosie is excited by the prospect that future missions to Mars might return samples to Earth for further study.

“Orbiters and landers and rovers have revolutionised our understanding of Mars. However, detailed nano-scale geochemical studies, as was done in our work on a meteorite, can only take place in laboratories on Earth.

“The ability to analyse materials collected directly from the surface of Mars and returned to Earth represents an unprecedented science opportunity. In such a case, the regional setting of the samples is known, and laboratories on Earth can provide the best age and geochemical analysis possible. Return of samples from Mars will undoubtedly trigger a new generation in understanding Martian history, surface conditions, habitability, climate, and other processes.

“In the meantime, we’re going to keep squeezing everything we can out of the bit of Mars lucky enough to have landed on Earth.”