The question of whether Mars ever supported life has fascinated scientists and the public for decades.
To uncover this mystery, it’s crucial to understand Mars’ past climate.
Was the Red Planet warm and wet with seas and rivers like Earth, or was it cold and icy, making it less hospitable to life as we know it?
A new study provides evidence for the latter, finding similarities between Martian soils and those in Canada’s Newfoundland, which has a cold subarctic climate.
This study, published in Communications Earth and Environment, focused on soils from Mars’ Gale Crater.
Scientists use soil to reveal environmental history because the minerals present can tell the story of landscape changes over time.
By understanding how these materials formed, researchers can answer long-standing questions about Mars’ historical conditions. Gale Crater’s soils and rocks record Mars’ climate from 3 to 4 billion years ago, a time when water was more abundant on the planet—the same period when life first appeared on Earth.
“Gale Crater is a paleo lakebed—there was obviously water present. But what were the environmental conditions when the water was there?” says Anthony Feldman, a soil scientist and geomorphologist at the Desert Research Institute (DRI). “We can’t find an exact match to the Martian surface because conditions are so different between Mars and Earth. But we can study Earth soils to infer Martian conditions.”
NASA’s Curiosity Rover has been exploring Gale Crater since 2011, finding many soil materials known as “X-ray amorphous material.” These components lack the typical atomic structure of minerals, making them hard to analyze with traditional techniques like X-ray diffraction. This method, used by the Curiosity Rover, showed that X-ray amorphous material made up between 15 and 73% of the soil and rock samples tested in Gale Crater.
“You can think of X-ray amorphous materials like Jello,” Feldman says. “It’s a mix of different elements and chemicals that slide past each other.”
Chemical analyses of the soil and rock samples revealed that the amorphous material was rich in iron and silica but low in aluminum. Scientists still don’t fully understand what this material is or what its presence indicates about Mars’ past environment. Learning more about how these materials form and persist on Earth could help answer these questions.
Feldman and his colleagues visited three locations to find similar X-ray amorphous material: the Tablelands of Gros Morne National Park in Newfoundland, Northern California’s Klamath Mountains, and western Nevada. These sites had serpentine soils expected to be chemically similar to those in Gale Crater: rich in iron and silicon but low in aluminum. The varied climates of these locations helped the researchers understand the conditions that produce and preserve amorphous material.
Using X-ray diffraction analysis and transmission electron microscopy, the team studied the soils in detail. They found that the subarctic conditions of Newfoundland produced materials chemically similar to those in Gale Crater, which also lacked a crystalline structure. In contrast, soils from warmer climates like California and Nevada did not match.
“This shows that you need water to form these materials,” Feldman explains. “But it must be cold, near-freezing conditions to preserve the amorphous material in the soils.”
Amorphous material is often unstable, meaning its atoms haven’t yet organized into a crystalline form. “There’s something in the reaction rate that slows down in very cold conditions, allowing these materials to form and be preserved,” Feldman says. “Our study suggests that near-freezing temperatures are key for this process.”
“This research improves our understanding of Mars’ climate,” Feldman adds. “The results suggest that the abundance of amorphous material in Gale Crater aligns with subarctic conditions, similar to those in places like Iceland.”
In summary, this study provides new insights into Mars’ icy past, showing that the planet’s climate was likely cold and icy, similar to subarctic regions on Earth. This discovery is a significant step in understanding the history and potential habitability of the Red Planet.
