Mars was once cold and icy—this intriguing question has captivated scientists and the public alike for decades. Central to this discovery is the investigation into Mars’s past climate: Was the planet once warm and wet, featuring seas and rivers similar to those on Earth?
Or was Mars once cold and icy, potentially making it less hospitable to life as we know it? A new study provides compelling evidence that supports the latter hypothesis, showing that Mars was once cold and icy by comparing Martian soils with those found in Newfoundland, Canada—a region with a frigid, subarctic climate.
Published in Communications Earth and Environment, this study examined Earth soils that share similarities with the materials found in Gale Crater on Mars. By analyzing these soils, scientists aim to reconstruct the environmental history of the Red Planet, as minerals present in the soils can reveal the evolution of Martian landscapes over time.
The study enhances our understanding of Mars’s ancient conditions. Gale Crater, which dates back 3 to 4 billion years, offers a record of Mars when it had relatively abundant water—around the same time that life began on Earth. This period has led researchers to question whether Mars was hospitable or if Mars was once cold and icy, thereby posing challenges to potential life.
“Gale Crater is a paleo lakebed, indicating that water was present,” explains Anthony Feldman, a soil scientist and geomorphologist at DRI. “While we cannot find a direct analogy for the Martian surface due to the stark differences between Mars and Earth, we can study trends in terrestrial conditions to infer Martian climates.”
NASA’s Curiosity Rover, operational since 2011, has been exploring Gale Crater and discovered various soil materials known as “X-ray amorphous materials.” These materials lack the typical repeating atomic structures found in minerals, making them challenging to analyze with conventional methods like X-ray diffraction.
When X-rays interact with crystalline materials, such as diamonds, they scatter at specific angles depending on the material’s internal structure. However, X-ray amorphous materials do not produce these distinct “fingerprints.” The Curiosity Rover’s findings revealed that X-ray amorphous materials constituted between 15% and 73% of the soil and rock samples from Gale Crater, suggesting that Mars was once cold and icy to allow such materials to form.
“You can think of X-ray amorphous materials like Jello,” Feldman describes. “It’s a mix of different elements and chemicals that slide past each other without a fixed structure.”
Further chemical analyses by the Curiosity Rover showed that these amorphous materials were rich in iron and silica but low in aluminum. Despite these findings, scientists are still uncertain about the exact nature of these materials and what their presence signifies about Mars’s historical environment. Investigating how these materials form and persist on Earth could shed light on the ancient conditions of Mars.
To gain further insights, Feldman and his team examined soils from three locations: the Tablelands of Gros Morne National Park in Newfoundland, Northern California’s Klamath Mountains, and western Nevada. These sites feature serpentinite soils, which were expected to be chemically similar to the X-ray amorphous materials in Gale Crater, demonstrating that Mars was once cold and icy.
The diverse climatic conditions at these locations, including varying rainfall, snowfall, and temperatures, provided valuable insights into how amorphous materials form and are preserved. The subarctic conditions in Newfoundland produced materials with chemical characteristics similar to those in Gale Crater, while warmer climates in California and Nevada did not.
“This indicates that the presence of water is essential for forming these materials,” Feldman says. “However, preserving these materials requires very cold, near-freezing average temperatures.”
Amorphous materials are often seen as unstable because their atomic structure has not yet organized into more stable crystalline forms.
“There is a particular kinetic factor—related to the rate of reaction—that slows down the formation and preservation of these materials,” Feldman explains. “Very cold, near-freezing conditions are one key factor that enables these materials to form and be preserved over geological timescales.”
“This research enhances our understanding of Mars’s climate,” Feldman concludes. “The findings suggest that the abundance of these materials in Gale Crater aligns with conditions similar to subarctic climates, such as those found in Iceland.”
