Scientists have argued for years about what ancient Mars was actually like. Was it warm and wet, or cold and dry? And where did the sulfur on Mars come from?

Today, the planet is freezing and dry, with an average temperature of about -80°F. But three to four billion years ago, it could have been very different - thanks to volcanoes.

A new study indicates that Martian volcanoes may have done more than simply sculpt the planet's surface.

They could have emitted gases that trapped heat, creating an environment where water - and perhaps even life - could flourish.

When we think of greenhouse gases, we usually picture carbon dioxide or methane. But this research points to something else: sulfur.

Researchers ran over 40 computer simulations based on the chemical makeup of Martian meteorites. They were looking to see what types of gases early volcanoes on Mars might have released into the atmosphere.

Instead of just finding high levels of sulfur dioxide (SO₂), which past models predicted, the experts saw something more complex.

They found "reduced" sulfur gases such as hydrogen sulfide (H₂S), disulfur (S₂), and possibly sulfur hexafluoride (SF₆). These forms of sulfur are highly reactive, and SF₆ is especially effective at trapping heat.

"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 lead author Lucia Bellino, a doctoral student at the UT Jackson School of Geosciences.

These sulfur gases may have created conditions suitable for microbes - similar to what's seen in certain environments on Earth.

"The degassed sulfur species and redox conditions are also found in hydrothermal systems on Earth that sustain diverse microbial life," Bellino explained.

But the team didn't stop at just figuring out what gases were released.

They also looked at how sulfur moved through the planet over time, including how it separated from other minerals deep underground and eventually reached the surface.

This is significant because it shows how much of the sulfur existed in a form that could affect the atmosphere and climate.

One key discovery is that sulfur didn't stay the same. While meteorites from Mars contain high levels of reduced sulfur, the planet's surface is full of sulfur bonded with oxygen. That means something kept changing its chemical form.

"This indicates that sulfur cycling - the transition of sulfur to different forms - may have been a dominant process on early Mars," said Bellino.

That kind of chemical cycling isn't just interesting - it's important. On Earth, cycles like this one play a big role in supporting ecosystems. If Mars had something similar, it would raise big questions about its potential to support life in the past.

During the research, the team got a lucky break. NASA's Curiosity rover cracked open a rock and found something rare: elemental sulfur. This was the first time anyone had seen sulfur on Mars in its pure form, not bonded with oxygen.

"We were very excited to see the news from NASA and a large outcrop of elemental sulfur," said Chenguang Sun, Bellino's advisor.

"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."

This surprise finding helped support the team's theory that volcanic gases released S₂, which then turned into elemental sulfur - exactly what Curiosity found.

The research team isn't done yet. Their next step is to dig deeper into how volcanic activity could have shaped other parts of early Mars's environment.

That includes figuring out whether volcanoes might have released enough water to form rivers or lakes, and if the reduced sulfur gases could have been used as food by tiny microbes.

Bellino hopes the results will help other scientists better model early Mars's climate. If it was warm enough for water to remain liquid, perhaps it was warm enough for life.

And if microbes existed there, the question then becomes: how long did they live? There's plenty more to learn about.

But for now, this research adds a valuable piece to the puzzle - one that makes the early Mars look a little more vibrant.

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