Scientists have recently identified a mineral on Mars that may offer new insights into the planet’s complex thermal and chemical history.
A recent study published in Nature Communications discusses the detection of a mineral called ferric hydroxysulfate at two separate locations. This mineral is formed when common sulfate minerals are transformed by heat.
The discovery hints at localized volcanic and geothermal activity within the last three billion years, raising new questions about Mars’ evolution and its potential for past habitability.
An Unknown Signature
Scientists use spectral data to identify minerals on the planet’s surface, as each mineral reflects light in a unique pattern based on the structure of its atoms, ions, and molecules. For years, scientists studying Mars have detected an unusual spectral signature that does not match any known mineral from Mars or Earth.
“People had seen that signature in the data before, but hadn’t conducted detailed studies about how it formed and what caused it,” said Catherine Weitz, senior scientist at the Planetary Science Institute and a co-author on the study.
The investigation targeted two regions containing this mysterious signature: a high plateau above Juventae Chasma and the low-lying basin of Aram Chaos. Though separated by thousands of miles and differing in elevation and geology, both sites contain traces of ancient water activity.
Ancient Water and Sulfate Deposits
Sulfur is abundant on Mars and frequently combines with metals to create sulfates, which are highly stable in the planet’s cold and dry environment. In contrast to Earth, where rainfall can dissolve these minerals, Martian sulfates can last for billions of years. At both Juventae and Aram Chaos, ferric hydroxysulfate was found associated with hydrated sulfate deposits.
At Juventae, narrow channels suggest ancient water once flowed across the plateau. Sulfates here were limited to a single low-lying depression, likely the remains of a sulfate-rich pool that dried up, leaving polyhydrated sulfate deposits. However, at Aram Chaos, layers of polyhydrated sulfates overlay monohydrated forms, with ferric hydroxysulfate detected beneath both.
From Orbit to the Lab
To confirm the mineral’s identity, the team utilized data from NASA’s Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) aboard the Mars Reconnaissance Orbiter. Matching spectral data to laboratory results, they attempted to reproduce the material under controlled conditions; this experiment was the first of its kind for this compound.
The mineral was produced by heating polyhydrated sulfates between 50–100 °C (122–212 °F); lower temperatures yielded the more common monohydrated sulfates. The team concluded that at Juventae, volcanic activity likely heated sulfate deposits from above, whereas geothermal heat rose from below to trigger the transformation at Aram Chaos.
“Our experiments suggest that this ferric hydroxysulfate only forms when hydrated ferrous sulfates are heated in the presence of oxygen,” said postdoctoral researcher Johannes Meusburger at NASA Ames. “While the changes in the atomic structure are very small, this reaction drastically alters the way these minerals absorb infrared light, which allowed identification of this new mineral on Mars using CRISM.”
A Rare but Telling Signature
Ferric hydroxysulfate appears to be rare in orbital datasets, with confirmed detections limited to only a few regions. That scarcity makes its presence a key indicator for heat-related geological processes. Due to temperatures on Mars rarely exceeding freezing, this detection points to events, such as volcanism or geothermal activity, that occurred long after the terrains formed, possibly during the Amazonian period, less than three billion years ago.
“The material formed in these lab experiments is likely a new mineral due to its unique crystal structure and thermal stability,” said lead author Janice Bishop of the SETI Institute and NASA Ames Research Center. “However, scientists must also find it on Earth to officially recognize it as a new mineral.”
Looking Ahead
The discovery of ferric hydroxysulfate closes a decades-old gap in Mars’ mineral record, providing scientists with a new way to chart the planet’s thermal history. Detecting this mineral in other regions could reveal traces of past volcanic or geothermal activity, or areas where heat and water may have once combined beneath the surface, creating conditions that could have supported microbial life.
“There may be other places where we see this sulfate, and we want to look more closely at those locations,” Weitz said. “On the other hand, it could be exciting to find ferric hydroxysulfate signatures in places where we don’t expect it, because then we’d have to think about how those locations got warm enough to form it.”
These rare mineral deposits could be targeted in future studies to test hypotheses about Mars’ recent geological past. If confirmed in more locations, ferric hydroxysulfate may become a key tracer of the Red Planet’s most recent chapters. It could even be used to identify sites where basic conditions for life may have once been met.
Austin Burgess is a writer and researcher with a background in sales, marketing, and data analytics. He holds a Master of Business Administration and a Bachelor of Science in Business Administration, along with a certification in Data Analytics. His work combines analytical training with a focus on emerging science, aerospace, and astronomical research.