An important discovery has been made beneath the Martian equator: a large honeycomb-shaped pattern, similar to formations found near Earth’s poles. Each is about 70 meters long, surrounded by mud and ice, and each is about 30 meters wide. Scientists estimate that the age of this material ranges between 2 billion and 3.5 billion years.
These patterns were identified through data sent by China’s Zhurong spacecraft, which is now no longer able to communicate. The rover traveled through an area known as the Utopia Plain, located north of the Martian equator. On its journey of just over a kilometer towards Mars’ southern region, the rover’s radar detected a continuous pattern of 15 buried polygons, indicating the possibility of more undiscovered patterns.
Comparison with Earth geology
On Earth, similar patterns have been observed in regions such as Greenland, Iceland and Antarctica. These formations occur due to drastic changes in temperature that lead to the soil shrinking and cracking. Ice and mud fill these cracks, preventing them from healing and causing the surface to crack even further.
A similar process on Mars, which occurred between 2 billion and 3.5 billion years ago, may have led to the formation of these Martian faults, which are much larger than any existing on Earth. The discovery provides new evidence suggesting that Mars once had water and a potentially habitable climate.
Furthermore, the presence of these patterns in the equatorial regions of Mars suggests that these regions were once cold enough to cause fractures similar to those seen near Earth’s ice poles. This could support the theory that Mars had a very different axial tilt in the past, perhaps as much as forty degrees or more, about 5 million years ago. This difference in tilt complicates the traditional understanding of polar regions as cold and low-latitude regions as warm.
Implications for the climate history of Mars
William Rabin, a scientist at the Institute for Astrophysical and Planetary Research in Paris who was not involved in the study, recognizes the importance of this discovery for understanding Mars’ past. Rabin, part of a team that discovered similar mud fissures near Gale Crater explored by NASA’s Curiosity rover, underscores the difficulties of accessing similar ancient periods on Earth due to the recycling of its surface. In contrast, Mars preserves its layers well, providing a unique opportunity to explore a period that may have been favorable for the origin of life.
Mars’ axial tilt, or skew, has changed over the past 3.5 billion years, affecting its climate. The planet’s equator would be hottest without its tilt due to direct sunlight, but computer models suggest that Mars experienced excessive tilt a few million years ago, changing the distribution of sunlight throughout the year.
This would have resulted in long periods of night reaching the equator. It is known that the tilt of Mars differs more than that of Earth, as it has shifted by more than ten degrees in 100 thousand years. This difference is thought to have contributed to drastic climate changes, transforming Mars from a potentially habitable world into the barren region we see today.
The detection of a pattern of polygons at a depth of 35 meters below the surface indicates that these formations developed over time but suddenly stopped. This indicates that Martian soil in the recent past did not experience similar temperature fluctuations, which led to the accumulation of layers above the cracks. The cessation of polygon formation could represent a period of significant climate change on Mars, perhaps a transition from a colder to a more temperate climate.
NASA’s Curiosity rover, which recently celebrated its 4,000th day on Mars, is expected to explore terrain with large fractures visible from orbit next year. Rabin hopes to compare these with new polygons found on the Utopia Plain, hypothesizing that they may indicate an ancient severe drought.
Research on this discovery was published in the journal Nature astronomy.
