Small volcanoes are a big deal on Mars

Life may be at the center of exploration of Mars today, but our planetary neighbor is home to the largest volcanoes in the solar system. Olympus Mons towers 23 kilometers (75,000 feet) above the surrounding landscape, and its neighbors, the Tharsis Montes (Arsia Mons, Pavonis Mons and Ascraeus Mons), stand out as a lineage of volcanic giants. These are the most important volcanic features on the planet, but a new study suggests that the thousands of small volcanoes that dot the landscape are equally important to Mars’ volcanic history.

Small volcanoes are surprisingly important in understanding the volcanic history of a planet. On Earth, ash cones and fissure vents are found everywhere on volcanic terranes, and in many places can be volumetrically as large as shield volcanoes or larger stratovolcanoes. The contribution of these small volcanic features has piqued the interest of Jacob richardson, an assistant researcher at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and lead author of the new study.

“We know a lot about the big volcanoes in Tharsis province, but what about all the small vents?” Richardson said when asked what study, published in the Journal of Geophysical Research: Planets. “What is the extent of all these small volcanoes and what is the nature of their relationship to all the large volcanoes?”

Track down volcanic vents

Richardson and his colleagues have identified more than 1,000 small volcanic vents in the Volcanic Province of Tharsis, an area roughly the size of Africa. Most vents were less than 100 meters high, which is not much different from the height of these vents on Earth. Many of these ancient vents could be analogous to the cracks and small cones formed during the basaltic eruptions of 2020-2021 on the Reykjanes Peninsula in Iceland.

Richardson and his colleagues used high-resolution camera images along with infrared and laser altimetry data from various orbiters on Mars to compile a database of these small volcanic features. The features vary in age from 3 billion years to less than 250 million years, some probably only tens of millions of years old, and imply that a new volcanic vent is forming somewhere in the province all of them. the 3 million years.

While resolving the datasets made it possible to identify these features, trying to decide what constituted a “volcanic vent” was a challenge, according to Richardson. Several times erosion and faults have destroyed potential vents in the millions to billions of years since their formation. On top of that, Martian dust and sand buried many vents. Even identifying crack vents (which can extend long distances with low elevation) versus cones (which are more compact but have higher elevation) is difficult. This challenge makes the catalog only a minimal estimate of potential small volcanic vents in the volcanic province of Tharsis.

Independent ventilation

The census of researchers shows the importance of small volcanoes in the volcanic province of Tharsis, where previously only Tharsis Montes and Olympus Mons were valued. The existence of these small volcanoes suggests spatially large and long-lasting magmatism in the region. Taken together, these clusters of hundreds of vents may have provided the same volume of lava as the large Tharsis Montes volcanoes, albeit over longer periods of time.

These small vents are probably not directly related to the larger volcanoes. On Earth, large shield volcanoes that are declining in activity, like Hawaii’s Mauna Kea, have small vents littering their slopes. On Mars, however, the abundant small volcanic vents are not found on the flanks of Tharsis Montes and Olympus Mons. Instead, they lie east of the line of volcanoes, suggesting that they may have had their own magma source that fueled eruptions for the past 500 million years.

Why this difference in volcanism? Richardson and others believe that the magma beneath the Tharsis Montes could more efficiently reach the surface by following pre-existing fractures in the crust. However, the crust to the east does not appear to be so fractured, so the magma cannot follow these same efficient routes. Instead of forming a big volcano like Arsia Mons, you get smaller and distributed volcanoes.

Better understand the Martian mantle

Mariek schmidt, an associate professor of earth sciences at Brock University in Ontario who was not involved in this study, said the new study supports our understanding of the Martian mantle. “The strong tectonic control over the vent distributions, rather than focusing on large shield volcanoes, is consistent with our understanding of the prolonged igneous history of Mars involving thickening of the lithosphere and decreased mantle melt inputs. over time.

Lionel wilson, professor emeritus at Lancaster University in the UK who also did not participate in this study, calls the new research an extremely valuable systematic catalog of volcanic activity in the volcanic province of Tharsis. These large data sets allow for analyzes that were not possible before, he said.

“It helps us think about the contribution of volcanic gases to the atmosphere over geological time,” Wilson said. “More generally, it adds information on the long-term evolution of the crust and mantle on a planet devoid of tectonics.” It gives us an end member to understand our own planet. “Mars is by far the best candidate to try to understand why Earth was the only one among Venus, Mars and Earth to have developed plate tectonics. The data from this study make a major contribution to this question. “

—Erik Klemetti (@eruptionsblog), Scientific editor

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