The history of Mars and the possibility that it supported life has long fascinated scientists. The key to understanding this history is uncovering the climatic conditions that prevailed on Mars: was Mars warm and wet with oceans and rivers or cold and icy, which would mean a lower probability of supporting life? A recent study provides evidence supporting the idea of a colder and icier Mars, comparing soils from Mars with those from Newfoundland in Canada, known for its cold subarctic climate.

This study, published on July 7 in the journal Communications Earth and Environment, sought soils on Earth similar to those in Gale Crater on Mars. Soil is important for reconstructing environmental history because the minerals present in it can reveal the evolution of landscapes over time. Understanding how these materials formed can help answer long-standing questions about historical conditions on Mars. Soils and rocks in Gale Crater record Mars' climatic conditions between 3 and 4 billion years ago, a period when there was relatively much water on the planet, and life appeared on Earth.

Gale Crater as a paleo lake
Anthony Feldman, a pedologist and geomorphologist from DRI, explains: "Gale Crater was once a lake with water. But what were the environmental conditions then?" Feldman emphasizes that a direct analog of Mars' surface won't be found on Earth due to different conditions. However, by analyzing trends on Earth, we can try to understand Mars' conditions.

NASA's Curiosity rover has been exploring Gale Crater since 2011 and has found many materials in the soil known as "X-ray amorphous material." These materials do not have the typical atomic structure that defines minerals, so they cannot be easily characterized by traditional techniques such as X-ray diffraction. When X-rays are directed at crystalline materials, they scatter at characteristic angles based on the mineral's internal structure. However, X-ray amorphous material does not produce these characteristic patterns. The X-ray diffraction method used by the Curiosity rover has shown that amorphous material makes up between 15 and 73% of the soil and rock samples examined in Gale Crater.

Feldman describes amorphous material as "jelly," where elements and chemicals move freely next to each other. The Curiosity rover has also conducted chemical analyses of soil and rock samples, revealing that the amorphous material is rich in iron and silica but poor in aluminum. Scientists still do not fully understand what amorphous material is or what its presence means for historical conditions on Mars. Discovering more information about how these materials form and persist on Earth could help address these questions.

Feldman and his colleagues investigated three locations in search of similar X-ray amorphous material: Tablelands in Gros Morne National Park in Newfoundland, the Klamath Mountains in Northern California, and western Nevada. These locations have serpentine soils that are chemically similar to those in Gale Crater: rich in iron and silica but poor in aluminum. The three locations provided different levels of precipitation, snow, and temperature, which helped understand the environmental conditions that create amorphous material and allow its preservation.

At each location, the research team used X-ray diffraction analysis and transmission electron microscopy to study soil materials in more detail. Subarctic conditions in Newfoundland produced materials chemically similar to those in Gale Crater, lacking a crystalline structure. Soils in warmer climates such as California and Nevada did not show such results.

"This shows that water is needed to form these materials," says Feldman. "But cold, almost frozen annual temperature conditions are required to preserve amorphous material in the soil."

Amorphous material is often considered relatively unstable because the atoms have not yet organized into their final crystalline forms. "There is something in the kinetics – the rate of reaction – that slows down the organization of atoms and allows these materials to be preserved over geological time scales," says Feldman. "Very cold, almost frozen conditions are one of the factors that enable the formation and preservation of these materials."

The study improves understanding of Mars' climate. The results suggest that the abundance of this material in Gale Crater is consistent with subarctic conditions similar to those in Iceland. Feldman and his team plan further research to more precisely determine the conditions that allowed these materials to be preserved on Mars.

According to research published in the journal Nature Communications, it has been discovered that Mars has seasonal changes that affect climate and surface conditions. This includes changes in temperature and pressure that can affect the preservation of amorphous material. A team of scientists is analyzing data from the Mars Reconnaissance Orbiter (MRO) to better understand these changes. This data helps predict where other key soil samples might be found on Mars, which could aid in future Mars exploration missions.

Additional research
Scientists have also analyzed data collected by the InSight lander, which has been exploring the interior of Mars. This data allows for a better understanding of seismic activities that affect surface conditions. Findings show that Mars has active tectonic plates that influence the formation and preservation of amorphous material. A 2023 study published in Science Advances indicates that certain regions of Mars are geologically active, further supporting the theory of preserving amorphous material in cold conditions.

These results not only improve understanding of Mars' past but also help in planning future missions. NASA and ESA are planning new missions focused on collecting soil samples and returning them to Earth. These samples could provide key information about the chemical composition of Mars' soil and historical climatic conditions.

Researchers at MIT are working on developing new technologies for analyzing soil samples on Mars. Their goal is to develop portable laboratories that can analyze samples in real-time on Mars, without the need to return them to Earth. These laboratories will use advanced techniques such as mass spectrometry and X-ray fluorescence to provide detailed analyses of the chemical composition of Mars' soil.

The results of these studies could significantly impact our ability to understand Mars' history and its potential to support life. As scientists continue to explore Mars, each new discovery brings us closer to answering the question of whether Mars ever supported life and what conditions prevailed on the planet in the past.

Source: Desert Research Institute