Scientists report that new spectral data from Mars appears to reveal a previously unknown mineral, so far unique to the Red Planet, which is indicative of a dynamic past capable of supporting life.
The researchers suggest that the heat of Mars‘ ancient hydrothermal or volcanic activity may have produced the mineral, called ferric hydroxysulfate. Revealed in a new paper in Nature Communications, the work finally makes sense of orbital observations going back 15 years.
Spectroscopy Explores the Cosmos
One of the primary techniques that astronomers use to investigate our universe is spectroscopy, which allows researchers to break light down into its separate wavelengths. These wavelengths, in turn, correspond to specific elements and minerals present on celestial features, including planets. Using this technique, researchers can determine the atmospheric composition of extremely distant exoplanets by analyzing spectroscopic readings from observatories like the James Webb Space Telescope.
In this case, spectroscopy was employed much closer to home, studying Earth’s neighbor, Mars. From its orbital position, the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) keeps an eye on the Red Planet, collecting spectroscopic data from its ancient dusty surface. It was during such activity that CRISM detected a strange spectral band while viewing an impact crater called Aram Chaos, located on a plateau over the canyon-like Juventae Chasma.
The shape and location of the spectral signature did not match any known mineral, prompting researchers to collect more data in order to solve the mystery.
Making Sense of the Data
“The data that comes out of the spectrometer is not usable the way it is,” said co-author Mario Parente, associate professor of electrical and computer engineering at UMass Amherst. “We have to calibrate the data, correct the data, remove the effect of the atmosphere. There are scattering molecules and gases that absorb light in the atmosphere. For example, on Mars, there is an abundance of carbon dioxide, and that will distort the data.”
Parente’s team employed deep learning artificial intelligence in their study, utilizing the most advanced atmospheric correction algorithm specifically tailored to Martian conditions. Down to the scale of individual pixels, the algorithm identifies anomalies as it recognizes known and unknown minerals in the data. The algorithm enabled the researchers to identify additional locations on Mars that produce the same mysterious spectral signal, while also providing a better context of the surrounding features across those locations.
Recreating Mars’ Mysterious Mineral
Based on the work done by Parente’s team, scientists from the SETI Institute and NASA Ames Research Center were able to artificially produce in a lab a mineral that they believe corresponds to the usual spectroscopic readings.
While iron may provide the planet’s distinctive red color, an abundance of sulfur also leads to the creation of many sulfate minerals on Mars. It turned out that the unique mineral combined iron and sulfur into a compound called ferric hydroxysulfate, which is formed in acidic environments with high temperatures featuring both oxygen and water.
“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, senior research scientist at the SETI Institute and NASA Ames Research Center. “However, scientists must also find it on Earth to officially recognize it as a new mineral.”
Based on the real-world data and lab work, the team believes that geothermal heat produced the ferric hydroysulfate present at Aram Chaos, while that found at Juventae came from volcanic activity within the last 3 billion years. Perhaps most intriguingly, this evidence of past activity on Mars increases the likelihood that the Red Planet was once habitable.
“Temperature, pressure and conditions such as pH are all very important indications of what the paleoclimate was,” says Parente.“The presence of this mineral puts a lot more nuance on what was going on. Parts of Mars have been chemically and thermally active more recently than we once believed—offering new insight into the planet’s dynamic surface and its potential to have supported life.”
The paper, “Characterization of Ferric Hydroxysulfate on Mars and Implications of the Geochemical Environment Supporting Its Formation,” appeared in Nature Communications on August 5, 2025.
Ryan Whalen covers science and technology for The Debrief. He holds an MA in History and a Master of Library and Information Science with a certificate in Data Science. He can be contacted at ryan@thedebrief.org, and follow him on Twitter @mdntwvlf.