Perseverance rover finds traces of ancient delta on Mars

NASA's Perseverance rover has detected, using ground-penetrating radar, the underground remains of an ancient delta on Mars, providing some of the earliest evidence of liquid water on the planet, according to Reuters. The discovery bolsters the hypothesis that Mars once had conditions favorable for water and possibly microbial life. Researchers identified geological structures at depths of up to 35 meters, based on data collected by the rover during its exploration of Jezero crater, where the vehicle traveled about 6.1 kilometers. This crater, located in the planet's northern hemisphere, is considered by scientists to be a former lake basin, fed by streams.

• Evidence of a deltaic environment over 4 billion years old

The data analysis revealed the presence of layered sediments and eroded surfaces, characteristic of a deltaic environment - formations created when a river flows into a lake. Researchers estimate that this buried delta formed about 3.7 to 4.2 billion years ago, early in the planet's history. By comparison, another similar formation nearby, known as the Western Delta, is more recent, being dated at about 3.5 to 3.7 billion years old.

• RIMFAX radar, key instrument of the discovery

The RIMFAX instrument, installed on the rover, emits radar waves into the subsurface and analyzes their reflections to build a three-dimensional map of underground structures. The data analyzed comes from September 2023 to February 2024, corresponding to approximately 250 Martian days, representing the deepest observations made to date by this instrument.

• Implications for the search for life on Mars

Water is considered an essential element for the emergence of life, and the discovery of such structures increases scientific interest in the planet's past. "Based on the characteristics mapped by RIMFAX, we believe that this Jezero crater hosted an ancient water-rich environment - capable of preserving biosignatures," said Emily Cardarelli, lead author of the study published in Science Advances. On Earth, deltas are favorable environments for the development of microbial life, due to the accumulation of sediments and nutrients. Although it is currently a cold and arid planet, Mars had a thicker atmosphere and higher temperatures in the past, which allowed the existence of liquid water on the surface.

Recent discoveries, including those made by the Perseverance rover, increasingly indicate the existence of lakes, rivers and deltas in the distant past of the planet.

• Additional confirmations from other missions

The research is also supported by other space missions. The Chinese rover Zhurong has previously identified subsurface structures interpreted as possible beaches of an ancient ocean in the northern regions of the planet. In addition, analyses of samples collected by Perseverance have previously indicated possible biosignatures, although these may also have non-biological origins.

According to the researchers, each new mission contributes to reconstructing the geological history of Mars. "We have observed more and more evidence of the presence of liquid water on the Martian surface (...), and now also in the form of buried remains," stressed Emily Cardarelli. In turn, David Paige highlighted the role of ground-penetrating radar, considered an extremely valuable tool for the study of planetary geology.