Scientists at The University of Texas at Austin have discovered that volcanic activity on Mars between 3 and 4 billion years ago likely released unusual forms of sulphur gases that could have trapped heat and maintained liquid water on the planet's surface. This finding, published in Science Advances, offers a fresh perspective on how Mars might have supported early life.
Unlike previous studies that focused on sulphur dioxide, this research reveals that Martian volcanoes probably emitted "reduced" sulphur compounds, highly reactive chemicals including hydrogen sulphide, disulphur, and possibly sulphur hexafluoride, an extremely potent greenhouse gas.
Lead author Lucia Bellino, a doctoral student at the Jackson School of Geosciences at the University of Texas explains that these reduced sulphur compounds could have created a unique Martian environment. Importantly, these chemical conditions mirror those found in Earth's hydrothermal systems, which today support diverse microbial communities at the bottom of the oceans. This suggests that if life existed on early Mars, it might have thrived in similar sulphur-rich environments.
The research team used data from Martian meteorites to run over 40 computer simulations, modelling how sulphur behaved as it moved through Mars' geological processes. Rather than just examining surface emissions, they traced sulphur's journey from deep within the planet's crust to its release into the atmosphere, providing a more complete picture of early Martian chemistry.
Their simulations revealed that sulphur was constantly changing forms on early Mars, cycling between different chemical states in ways that could have significantly influenced the planet's climate. The timing couldn't have been better for validating their research. Last year, while the team was conducting their study, NASA's Curiosity rover accidentally crushed a rock and revealed pure elemental sulphur crystals, the first time this mineral had been found in pure form on Mars.
"We were very excited to see the news from NASA. One of the key takeaways from our research is that as disulphur was emitted, it would precipitate as elemental sulphur."— Chenguang Sun, Bellino's advisor and assistant professor at the Jackson School.
This research opens exciting new avenues for understanding Mars' potential for ancient life. The team plans to investigate whether volcanic activity could have provided large water reservoirs on early Mars and whether reduced sulphur compounds might have served as food sources for microbes.
Today, with average surface temperatures a frigid -62 degrees Celsius. But these results suggest its early atmosphere might have been dramatically warmer. As climate modelling experts use this new data, we may finally understand whether ancient Mars was truly warm enough, for how long, and whether it could have supported life as we know it.