Using satellites around Mars, scientists examined the morphological and mineralogical structure of the mountainous and plain regions of the Red Planet’s southern hemisphere (Eridania, Cimmeria and Sirenum regions of Mars). The discoveries were quite unexpected.

Tectonic plates in constant motion on Earth appeared about three billion years ago, but this does not mean that the surface of our planet remained unchanged until that moment. It was actively “reworked” during the first forms of volcanism and tectonics. Since tectonic processes have changed so much since then, we do not have the opportunity to study this early stage of the evolution of the earth’s crust. But we have Mars and other rocky planets where ancient crust is preserved.

To better understand this early period in the evolution of the crust of rocky planets, an international group of scientists led by geologist and planetary scientist Joseph Michalski from the University of Hong Kong (China) focused on an area with very diverse topography in the southern hemisphere. Mars: Erie Basin, ancient sea, as well as the adjacent highlands of Cimmeria and the rugged region of Cyrenum.

Researchers examined the morphological and mineralogical structure of these areas based on data collected by various orbiters, including Mars Global Surveyor, Mars Odyssey and Mars Reconnaissance Orbiter. About 3.5 billion years ago volcanoes raged there: both on land and at a depth of 400-1200 meters in a giant sea three times larger than the modern Caspian Sea.

According to the authors of the study published in the journal Nature AstronomyThere were hundreds of volcanoes in the Eridania region. In this study, scientists identified 63 volcanoes and divided them into four categories: volcanic domes, stratovolcanoes, pyroclastic shields and caldera complexes.

The domes are small in size, with an average diameter of about 14 kilometers and a height of about 0.8 kilometers. Stratovolcanoes are similar to them in structure, but much larger: 40-80 kilometers in diameter and up to two to three kilometers in height. They often have upper and lateral craters connected by faults.

Pyroclastic shields are lower than stratovolcanoes, but their diameters are much larger – up to 100 kilometers at an altitude of about 1.1 kilometers. A distinctive feature of shields and stratovolcanoes is dense networks of valleys on the slopes. They testify to the active erosion of the constituent rocks.

After all, they are caldera complexes. Its defining features are a network of depressions and plains that do not resemble traces of meteorite impacts in structure. The authors of the study found complexes of up to 14 such depressions in the mountainous regions of Cimmeria and the rugged region of Sirenium.

In general, they all resemble similar volcanic structures on Earth, but their diameters are different. This is a smaller gravitational force (38% of Earth). In such cases, volcanism is more “explosive” and pyroclasts, fragmented rocks formed during such activities, fly much greater distances. Therefore the height is not that big.

According to the authors of the study, the diversity in the structure and composition of volcanic structures (numerous felsic minerals) in these regions indicates possible “crustal remelting” and vertical tectonics at this early stage of crust formation. It turns out that Mars is not a stable “basalt world” as previously believed.

The discovered underwater and coastal volcanoes are of particular interest. The chemical composition and physical conditions of the Eridania sea on young Mars were similar to the hydrothermal conditions in which life on young Earth emerged, scientists hypothesize. Therefore, the new study opens interesting prospects for studying not only volcanic activity on the entire Red Planet, but also the special conditions of Eridania.