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It is possible that Mars in the past experienced a cyclical pattern in its climate.

Photo of the red Martian surface

Mars is a dry, dusty planet, but evidence is mounting that water once flowed freely at its surface. Now, researchers have found patterns in Martian sediments that suggest the planet once had a cyclical climate similar to Earth’s. The study, which furthers our understanding of Mars’s history and its suitability for life, was published in Nature.

Mars has preserved ancient rivers and lakes, unlike Earth which constantly changes its landscapes through plate tectonics. NASA’s Curiosity rover has been investigating these remnants since 2012 and has found evidence of basic organic molecules. The development of early life depends on certain environmental factors that allow water-soluble molecules to form more intricate organic compounds.

It is essential to comprehend the previous conditions on Mars in order to evaluate its potential to support life and determine if life ever thrived there.

According to William Rapin, a planetary scientist from the French National Center for Scientific Research and lead author of the study, comprehending Mars’ previous environments is essential in determining its potential for supporting life and the possibility of past existence. While it is known that ancient Mars had areas with water, there is limited knowledge on its behavior and impact on the planet’s habitability and life evolution.

Rapin and his team utilized information collected by the Curiosity rover to examine Gale crater, a desiccated lake named after an amateur Australian astronomer who studied Mars in the 1800s. By analyzing data from Curiosity’s Mastcam and ChemCam, which capture images and analyze rock samples on the planet’s surface, the researchers identified sulfate formations in sediment layers dating back approximately 3.8-3.6 billion years. This time period coincided with a shift in weathering patterns and environmental conditions on Mars.

A photo of hexagonal patterns in the red Martian surface

NASA’s Curiosity rover has observed honeycomb-like patterns in sediment samples taken from Gale crater. These formations may indicate the occurrence of alternating wet and dry periods on Mars. Photo credit: NASA/JPL-Caltech/MSSS/IRAP

Reworded: According to Rapin, certain deposits contained cracks that were most likely created during the drying process, while others had a hexagonal form. These hexagonal patterns are similar to those found in landscapes on Earth that go through cycles of drying and wetting.

“These salt formations serve as the initial fossil proof of a recurring climate on Mars, characterized by alternating periods of dryness and moisture,” stated Rapin. Previous laboratory simulations of this cyclical climate on Earth have demonstrated its potential to foster repeated interactions between molecules, a critical factor in the formation of vital components of life such as RNA.

A Scenery for Existence

During the Noachian-Hesperian transition period, approximately 3.6-3.8 billion years ago, the alternating wet and dry conditions may have provided a conducive environment for the development of life on Mars. According to Rapin, this period may have been more suitable for habitation compared to the earlier Noachian eon, which had consistently wet conditions.

The difficulty in connecting surface data from Mars to both climate and origin of life theories is the requirement for multiple sources of data.

The theory, derived from previous understandings of Mars, and the approach utilized in the research, are strong, according to Harvard University planetary scientist Robin Wordsworth. He stated, “The results align with the concept of intermittent cycles of wet and dry periods on Mars, rather than a consistently warm and wet environment.”

But, since there is not enough information about the previous conditions of Gale Crater, Wordsworth suggests that more research must be conducted to strengthen the findings of this study. According to him, the difficulty in connecting surface observations on Mars with climate and origin of life scenarios is that multiple sources of information are needed. He also emphasized the importance of comprehending the chemical composition of ancient Martian fluids in determining if organic compounds could have been created and remained preserved.

—Vijay Shankar Balakrishnan (@VijaySciWri), Science Writer

Reference: Balakrishnan, V. S. (2023), Evidence suggests Mars may have had a repeating climate pattern, Eos, 104, Published on September 29, 2023.

Text published in 2023 by the authors under the CC BY-NC-ND 3.0 license.

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