A "Livable Mars" Created by Volcanoes and Sulfur — The Foundation of Life was Volcanic Gas: The Story of Planets and Microorganisms Connected by Sulfur

Was the Early Martian Sky "Sulfur Yellow"?

Mars is now a cold, dry world with average temperatures between −60 to −70℃, but as the channels and lake remnants suggest, there was once a time when liquid water flowed on its surface. The long-favored source of this "lost warmth" has been the greenhouse effect of SO₂. However, the latest peer-reviewed research suggests a shift in the main player. Instead of SO₂, volcanic emissions may have been dominated by reducing sulfur gases like H₂S and S₂, which could have intensified aerosols and the greenhouse effect, possibly making Mars temporarily a "habitable planet." Phys.org

What's New — Viewing Chemistry from "Underground to Sky"

The research team ran over 40 models incorporating the evolution and separation processes of magma based on the chemical composition of Martian meteorites, evaluating which gases would be "realistically" released at crust-to-surface pressures. The results were clear, with H₂S and S₂ being dominant. The potential formation of SF₆ (sulfur hexafluoride) was also suggested under certain conditions. SF₆ is known as one of the most potent greenhouse gases on Earth, with high radiative forcing even in trace amounts. While the presence and concentration of SF₆ remain subjects for future investigation, the traditional view of "SO₂ dominance" is challenged. PMC

Field Evidence from an "Accidental Crack"

On May 30, 2024, NASA's Curiosity rover accidentally cracked a rock, revealing bright yellow elemental sulfur inside. While sulfur-containing minerals like sulfates are not uncommon on Mars, "raw sulfur" not bonded with oxygen was confirmed for the first time. This discovery naturally aligns with a new scenario where S₂ precipitates from the atmosphere to form elemental sulfur. It was a moment where observation and theory fit together like puzzle pieces. JPL

Proximity to Life — An Analogy with Hydrothermal Systems

Reducing sulfur and redox environments support diverse microbial communities in Earth's seafloor hydrothermal systems. A similar chemical energy gradient might have temporarily existed on Mars. However, this study does not claim the existence of life. It merely suggests conditions where "long-lasting liquid water and energy sources could have coexisted." The detection of life is left to future sample returns and precise analyses of minerals and isotopes. Phys.org

Remaining "Homework"

① The Wall of Photochemistry
H₂S is easily decomposed by solar ultraviolet radiation, and its persistence is not high. Detailed atmospheric chemistry models are needed to determine how much aerosol formation and interactions with other components can extend its lifespan.

② How Much SF₆ is Produced?
SF₆ is powerful, but its formation pathways and budget in the Martian environment are uncertain. While effective even in trace amounts, if production falls below a threshold, its climate impact would be limited. PMC

③ Atmospheric Escape and Scale
With Mars' weak gravity, long-term atmospheric retention is challenging. Even if a greenhouse effect was established, its duration and timing (somewhere in the Noachian period) are separate issues. It is necessary to explore consistency with recent studies depicting a "cold but temporarily thawed" image. Science News

Scope of Discussion — "Cold and Wet Mars" vs "Warm and Wet Mars"

How much greenhouse effect was needed when the ancient sun was dimmer than it is now? Adding sulfur to CO₂ and H₂O broadens the range of solutions, but explaining the formation and duration of river and lake landforms remains a challenge. The significance of this achievement lies in breaking the SO₂-centric assumption and introducing a new knob (adjustment variable) of "sulfur cycle" into climate models. PMC

Future Verification Plans

The research team plans to use the same model to delve into the "origin of water sources," "volcanic water storage," and "chemical environments that could serve as 'food' for microorganisms." Simultaneously, the framework of H₂S and S₂ dominance has been reported at the LPSC (Lunar and Planetary Science Conference), rapidly increasing community interest. On the ground, JPL's follow-up observations and geological context elucidation of elemental sulfur outcrops are also expected to progress. hou.usra.edu

SNS Reaction Digest

• X (formerly Twitter): Curiosity's "yellow sulfur" photo is being reshared, with excitement over how this accidental discovery perfectly matched the theory. Posts from SETI Institute and science media followed, having a significant impact on the general public. X (formerly Twitter)

• Reddit/r/space & r/science: In the elemental sulfur thread, a top comment suggests "intentionally breaking more rocks." In the greenhouse effect discussion, there are notable calm remarks on the effectiveness of SF₆ and the challenges of atmospheric retention. RedditReddit

• Technical and Researcher Community (LinkedIn, etc.): Numerous shares of key point summaries based on university press releases have established the key messages of H₂S and S₂ dominance and "sulfur haze + greenhouse effect." jsg.utexas.edu

• Long-time Mars Fans: The classic debate on whether SF₆ could terraform Mars is reignited. However, counterarguments always highlight the high hurdles of production and retention in reality.  Reddit
  
  

Summary of Interview Notes

• The research was published in Science Advances on September 11, 2025. The key point is that it unraveled the "life of sulfur" from material origin to atmospheric release. PMC

• The 2024 elemental sulfur discovery aligns with model predictions, mutually reinforcing theory and observation. JPL

• "How much warming occurred" is a task for future climate models. It's time for a new generation of models incorporating the sulfur cycle. Phys.org

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