New research reveals Mars' cold, icy past

A new study has found important clues hidden in the soil of the Red Planet.

Recent research compares soil from the Earth and Mars The study suggests that the historical climate of Mars was cold and subarctic, similar to Newfoundland. The study focused on amorphous materials in the soil of Gale Crater, which may have been preserved under sub-freezing conditions, providing new insights into the environmental conditions of Mars and the potential for life on it.

Exploring the past climate of Mars through Earth's soil

The question of whether Mars once supported life has captivated scientists and the public for decades. The gist of the discovery is that it provides insight into the past climate of our neighboring planet: Was the planet warm and wet, with seas and rivers much like our own? Or was it very cold and icy, and thus perhaps less likely to support life as we know it?

A new study has found evidence to support this view by identifying similarities between soils on Mars and those found in Newfoundland, Canada, a region with a cold, subarctic climate.

The rim and floor of Gale Crater as seen from NASA's Curiosity rover. Image credit: NASA/JPL-Caltech

Insights from Gale Crater Soil Analysis

The study, published in the journal Earth and Environment Communications On July 7, Scientists have been searching for soil on Earth that contains materials similar to those found in Gale Crater on Mars. Scientists often use soil to map environmental history, as the minerals present can tell the story of how landscapes evolved over time. Understanding more about how these materials formed could help answer long-standing questions about historical conditions on the Red Planet. The soil and rocks in Gale Crater provide a record of the climate of Mars between 3 and 4 billion years ago, during a period when the planet had relatively abundant water — the same time period when life first appeared on Earth.

“Gale Crater is an ancient lake bed—and it was clear that there was water there,” says Anthony Feldman, a soil scientist and geomorphologist now at DRI. “But what were the environmental conditions like when the water was there? We’ll never find a direct analog of the Martian surface, because the conditions are so different on Mars and Earth. But we can look at trends under terrestrial conditions and use them to try to extrapolate questions about Mars.”

Study site in the Newfoundland Highlands. Photo credit: Anthony Feldman/DRI

Challenges in the analysis of Martian materials

NASA’s Curiosity rover has been examining Gale Crater since 2011 and has found an abundance of soil materials known as “amorphous X-ray material.” These soil components lack the typical repeating atomic structure that defines minerals, and therefore cannot be easily characterized using traditional techniques such as X-ray diffraction. When X-rays are fired at crystalline materials such as diamond, for example, the X-rays scatter at characteristic angles based on the internal structure of the mineral. However, X-ray amorphous material does not produce these distinctive “fingerprints.” Curiosity has used this X-ray diffraction method to show that X-ray amorphous material makes up between 15 and 73 percent of soil and rock samples tested at Gale Crater.

“You can think of the amorphous materials that you get from X-rays as jelly,” Feldman says. “They’re a mixture of different elements and chemicals that slide over each other.”

Curiosity also conducted chemical analyses on soil and rock samples, finding that the amorphous material is rich in iron and silica but lacks aluminum. Beyond the limited chemical information, scientists don’t yet understand what the amorphous material is, or what its presence means for the historical Martian environment. Discovering more about how these mysterious materials formed and persisted on Earth could help answer persistent questions about the Red Planet.

Field studies simulating Martian conditions

Feldman and his colleagues visited three sites in search of similar X-ray amorphous material: the plateaus of Gros Morne National Park in Newfoundland, the Klamath Mountains in northern California, and western Nevada. All three sites had weathered soils that the researchers expected to be chemically similar to the X-ray amorphous material in Gale Crater: rich in iron and silicon but lacking in aluminum. The three sites also offered a range of rainfall, snowfall, and temperatures that could help provide insight into the type of environmental conditions that produce amorphous material and encourage its preservation.

At each site, the research team examined the soil using X-ray diffraction analysis and transmission electron microscopy, which allowed them to see soil materials at a much more detailed level. The subarctic conditions in Newfoundland produced materials that were chemically similar to those found at Gale Crater and also lacked a crystalline structure. Soils produced in warmer climates such as California and Nevada did not.

“This shows that you need water there to form these materials,” Feldman says. “But conditions have to be cold, with the average annual temperature close to freezing, to keep the amorphous material in the soil.”

Amorphous materials are often thought of as relatively unstable, meaning that at the atomic level, the atoms have not yet organized into their final, more crystalline forms. “Something is happening in the kinetics — or reaction rate — that is slowing it down so that these materials can be maintained over geological timescales,” Feldman says. “What we’re suggesting is that very cold, near-freezing conditions are a limiting factor in the kinetics that allows these materials to form and be maintained.”

“This study improves our understanding of the Martian climate,” Feldman says. “The results suggest that the abundance of this material in Gale Crater is consistent with subarctic conditions, similar to what we might see in Iceland, for example.”

Reference: “Iron-Rich Amorphous X-ray Material Records of Past Climate and Persistent Water on Mars” by Anthony D. Feldman, Elizabeth M. Hausrath, Elizabeth B. Rampe, Valerie Tu, Tanya S. Peretiazko, Christopher DeFelice, and Thomas Sharp, July 7, 2024. Earth and Environment Communications.
DOI: 10.1038/s43247-024-01495-4