Recent studies comparing soils from Earth and Mars suggest that the historical climate of Mars was cold and subarctic, similar to that of Newfoundland. The study focused on amorphous materials that have the potential to be preserved in near-freezing conditions in the Gale Crater soils, providing new insights into the Martian environment and potential for life.

Investigating Mars’ past climate through Earth soil

The question of whether life once existed on Mars has captured the imagination of scientists and the public for decades. Central to the exploration is understanding the past climate of Earth’s neighbor: Was the planet warm and wet, with seas and rivers similar to our own? Or was it cold and icy, and therefore less likely to support life as we know it?

A new study finds evidence supporting the latter by identifying similarities between soils found on Mars and those of Newfoundland, Canada, which has a cold subarctic climate.

Information from Gale Crater soil analysis

A study published in the journal Contact World and Environment 7 July , He searched for soils on Earth that contained materials comparable to those in Gale Crater on Mars. Scientists often use soil to describe the history of the environment because the minerals present can tell the story of how the landscape evolved over time. Learning more about how these materials formed could help answer long-standing questions about historical conditions on the Red Planet. The soil and rocks of Gale Crater contain evidence of the Martian climate 3 to 4 billion years ago, when the planet had relatively abundant water, a period when life first appeared on Earth.

“Gale Crater is paleo-grained soil; there was obviously water there. So what were the environmental conditions like when the water was there?” says Anthony Feldman, a soil scientist and geomorphologist at DRI. “We’re never going to find a direct analogue of the Martian surface because conditions on Mars and Earth are so different. But we can observe trends in Earth conditions and use those to make predictions about the Mars question.”

Problems in analyzing Martian materials

NASA’s Curiosity rover has been exploring Gale Crater since 2011 and has found a variety of ground materials known as “X-ray amorphous material.” These ground 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 hit crystalline materials, such as diamond, they scatter at characteristic angles depending on the mineral’s internal structure. But X-ray amorphous material does not produce these characteristic “fingerprints.” This X-ray diffraction technique was used by the Curiosity rover to show that X-ray amorphous material made up 15 to 73 percent of the soil and rock samples examined in Gale Crater.

“You can think of X-ray amorphous materials like Jello,” Feldman says. “It’s a soup of different elements and chemicals sliding past each other.”

The Curiosity rover also conducted chemical analysis of soil and rock samples, finding that the amorphous material is rich in iron and silica but deficient in aluminum. Beyond the limited chemical information, scientists do not yet understand what the amorphous material is or what its existence means for the historical environment of Mars. Uncovering more about how these mysterious materials were formed and stored on Earth could help answer persistent questions about the Red Planet.

Field studies simulating Martian conditions

Feldman and his colleagues visited three sites to find similar X-ray amorphous material: the Gros Morne National Park plateau in Newfoundland, the Klamath Mountains in northern California, and western Nevada. The three sites contained serpentine soils that the researchers expected to be chemically similar to the X-ray amorphous material from Gale Crater: rich in iron and silicon but lacking in aluminum. The three locations also provided a range of precipitation, snowfall, and temperatures that could help understand the environmental conditions that created the amorphous material and encourage its preservation.

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

“This suggests that you need water to form these materials,” Feldman says. “But for amorphous material in the soil to be preserved, there needs to be cold conditions where the annual average temperatures are near freezing.”

Amorphous material is generally considered relatively unstable, meaning that at the atomic level, the atoms are not yet organized into their final, more crystalline form. “Something happens in the kinetics (or rate of reaction) that slows down the reaction, and so these materials persist on geological timescales,” Feldman says. “We hypothesize that the very cold conditions near freezing are one of the kinetic limiting factors that allow these materials to form and persist.”

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