A new study finds that Mars likely had a cold and icy past

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 our own? 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.

The study, published in Earth and Environment Communication, they looked for soils on Earth with comparable materials to those in Gale Crater on Mars. 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 clearly 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’ll never find a direct analogy to the surface of Mars because conditions are so different on Mars and on Earth. But we can look at trends in Earth conditions and use that to try to extrapolate to Martian questions.”

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 with different elements and chemicals pushing each other.”

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.

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 the very cold, near-freezing conditions are one particular kinetic limiting factor that allows these materials to form and be preserved.”

“This study improves our understanding of the Martian climate,” adds 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.”