Cold and icy past of Mars revealed in new research

A new study finds critical clues lurking in the Red Planet’s soil.

Recent research comparing soils from Earth and Mars 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, potentially preserved in near-freezing conditions, and offers new insights into Martian environmental conditions and its potential for life.

Exploring Mars’ past climate through Earth’s soil

The question of whether Mars ever supported life has captured the imagination of scientists and the public for decades. Central to the discovery is gaining insight into the past climate of Earth’s neighbor: was the planet warm and wet, with seas and rivers similar to those found on our planet? Or was it frigid and icy, and therefore potentially less susceptible to supporting life as we know it?

A new study finds evidence to support the latter by identifying similarities between soils on Mars and soils in Canada’s Newfoundland, a cold subarctic climate.

Insights from Gale Crater soil analysis

Study published in journal Earth and environment communication on July 7, they looked for soils on Earth with materials comparable to Mars’ Gale Crater. Scientists often use soil to depict environmental history because the minerals present can tell the story of how a landscape has evolved over time. Understanding more about how these materials formed could help answer long-standing questions about historical conditions on the Red Planet. The soils and rocks of Gale Crater provide a record of the Martian climate 3 to 4 billion years ago, a time when water was relatively abundant on the planet — and the same time period when life first appeared on Earth.

“Gale Crater is a paleo lake – there was obviously water there. But what were the environmental conditions when the water was there?” says Anthony Feldman, a soil scientist and geomorphologist now at DRI. “We will never find a direct analogy to the surface of Mars because the conditions on Mars and on Earth are so different.” But we can look at trends in Earth conditions and use that to try to extrapolate to Martian questions.”

Challenges in the Analysis of Martian Materials

NASA’s Curiosity Rover has been exploring Gale Crater since 2011 and found an abundance of soil material known as “X-ray amorphous 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, the X-rays scatter at characteristic angles based on the mineral’s internal structure. However, X-ray amorphous material does not produce these characteristic “fingerprints”. This X-ray diffraction method was used in the Curiosity Rover to demonstrate that X-ray amorphous material comprised 15 to 73% of the soil and rock samples tested in Gale Crater.

“You can think of X-ray amorphous materials like Jello,” says Feldman. “It’s a soup of different elements and chemicals just shifting around.”

The Curiosity Rover also performed chemical analyzes of soil and rock samples and found that the amorphous material was rich in iron and silica but deficient in aluminum. Beyond limited chemical information, scientists do not yet understand what the amorphous material is, or what its presence means about the historical environment of Mars. Uncovering more information about how these mysterious materials form and persist on Earth could help answer lingering questions about the Red Planet.

A field study simulating conditions on Mars

Feldman and his colleagues visited three locations in search of similar X-ray amorphous material: the Tablelands of Gros Morne National Park in Newfoundland, the Klamath Mountains in northern California, and western Nevada. The three sites had serpentine soil that scientists 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 provided a range of rainfall, snowfall and temperatures that could help provide insight into the type of environmental conditions that produce the amorphous material and support its preservation.

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

“This shows that you need water to make these materials,” Feldman says. “But there must be cool, average annual temperature conditions near freezing to preserve the amorphous material in the soil.”

Amorphous material is often considered relatively unstable, meaning that at the atomic level the atoms have not yet organized into their final, more crystalline forms. “There’s something going on in the kinetics—or the rate of the reaction—that slows it down, so these materials can be preserved on a geologic time scale,” Feldman says. “What we’re suggesting is that very cold, near freezing, is one particular kinetic limiting factor that allows these materials to form and be preserved.”

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

Reference: “X-ray iron-rich amorphous material records past climate and persistence of water on Mars” by Anthony D. Feldman, Elisabeth M. Hausrath, Elizabeth B. Rampe, Valerie Tu, Tanya S. Peretyazhko, Christopher DeFelice, and Thomas Sharp, 7 July 2024, Earth and environment communication.
DOI: 10.1038/s43247-024-01495-4