Leonard David's INSIDE OUTER SPACE

Schematic illustration of sulfur cycling from an evolving crustal magmatic system on early Mars.
Image credit: Lucia G. Bellino/Chenguang Sun

Volcanic emissions of reactive sulfur gases on early Mars may have made for a unique Martian environment. If so, that environment on the Red Planet could have been hospitable to certain forms of life.

That is one output from new research led by geoscientists at the University of Texas (UT) at Austin. This finding comes from a study published in Science Advances.

Hazy environment

“The presence of reduced sulfur may have induced a hazy environment which led to the formation of greenhouse gases, such as SF6, that trap heat and liquid water,” said Lucia Bellino, a doctoral student at the UT Jackson School of Geosciences.

“The degassed sulfur species and redox conditions are also found in hydrothermal systems on Earth that sustain diverse microbial life,” Bellino added in a university statement.

Making use of data from the composition of Martian meteorites, Bellino and colleagues ran more than 40 computer simulations to estimate how much carbon, nitrogen, and sulfide gases may have been emitted on early Mars.

The Red Planet as seen by Europe’s Mars Express.
Image credit: ESA/D. O’Donnell – CC BY-SA IGO

Sulfur cycling

Instead of the high concentrations of sulfur dioxide (SO₂) that previous Mars climate models predicted, their research shows volcanic activity on Mars around 3-4 billion years ago may have led to high concentrations of a range of chemically “reduced” forms of sulfur – which are highly reactive.

This includes sodium sulfide (H₂S), disulfur (S₂) and possibly sulfur hexafluoride (SF6) – an extremely potent greenhouse gas, the university statement on the research points out.

“Sulfur cycling” – the transition of sulfur to different forms – may have been a dominant process occurring on early Mars, Bellino explains.

Cracked rock

As Bellino and team members were deep into their research, NASA’s Curiosity Mars rover exploring Gale Crater wheeled over and cracked open a rock last year. That was fortuitous for the researchers, seemingly backing their findings.

That fractured rock revealed elemental sulfur – it was the first time the mineral had been found in pure form, unbound to oxygen.

Sulfur crystals found inside a rock after NASA’s Curiosity Mars rover happened to drive over it and crush it on May 30, 2024. This discovery supports new research led by scientists at The University of Texas at Austin on what types of sulfur would be present on Mars billions of years ago.
Image credit: NASA

The rover discovering a large outcrop of elemental sulfur was a plus, added Chenguang Sun, an assistant professor at the Jackson School’s Department of Earth and Planetary Sciences, also a Bellino advisor and co-author of the research paper in Science Advances.

“One of the key takeaways from our research is that as S₂ was emitted, it would precipitate as elemental sulfur. When we started working on this project, there were no such known observations.”

Food source for microbes?

As for what next, the researchers will use their computer simulations to investigate other processes that would have been essential to sustain life on Mars. That includes the source of water on early Mars, and whether volcanic activity could have provided a large reservoir of water on the Red Planet’s surface.

In addition, the team will also seek to understand whether the reduced forms of sulfur may have served as a food source for microbes in an early climate that resembled Earth’s hydrothermal systems.

Bellino hopes her team’s research can be used by climate modeling experts to predict how warm the early Mars climate might have been.

Mars beckons. Human explorers can maximize the science output for unraveling the complex nature of the Red Planet.
Image credit: NASA/Pat Rawlings

If indeed microbes were present, how long could they have existed in a warmer atmosphere?

Important implications

Bellino and Sun conclude in their research paper, “our findings may also have important implications for understanding the habitability potential of martian hydrothermal systems.”

Furthermore, results of their modeling “indicate that the magmatic gases in the martian surface environment share similar reducing capacities as those from the hydrothermal systems in terrestrial submarine environments.”

To read the research paper – “Volcanic emission of reduced sulfur species shaped the climate of early Mars” – go to:

https://www.science.org/doi/10.1126/sciadv.adr9635