Active volcanoes on Venus?

Lava flows at Sif Mons

The red areas on the western flank of the Venus volcano Sif Mons show where the surface has changed between two overflights of the Magellan spacecraft.© IRSPS/ Università d’Annunzio

There are numerous volcanoes and lava flows on our neighboring planet Venus – however, these are millions of years old and were thought to be inactive today. But now planetary researchers have discovered fresh changes to the surface in two volcanic areas on Venus. These structures, identified by radar on the shield volcano Sif Mons and in the Niobe Planitia plain, were formed within two years and resemble lava flows in their shape and flow direction, the team reports. In their view, this is evidence that there are still active volcanoes on Venus today.

The conditions on our neighboring planet Venus are hellish today: the surface is more than 460 degrees hot and is subject to an enormous pressure of 92 bar – 92 times that of the Earth’s atmosphere. Its surface is hidden by a thick veil of clouds. But radar measurements from space probes such as NASA’s Magellan probe penetrated this veil in the 1990s and mapped the topography of Venus. These measurements revealed, among other things, numerous shield volcanoes, volcanic cones and solidified lava flows on the planet’s surface. However, volcanic activity on Venus was thought to have ceased millions of years ago – at least that was the common assumption until a few years ago.

Radar view of volcanic areas on Venus

Since then, however, space probes have repeatedly found possible evidence of still active volcanism on Venus. For example, infrared measurements from the European probe Venus Express showed striking heat hotspots in some volcanic areas, some of which seemed to change their temperature within days. Further telltale evidence was provided in 2023 by comparing old radar images from the Magellan probe: Scientists discovered an area on the Venus volcano Maat Mons where the radar signatures had changed between two overflights of the probe. They interpreted this as potentially fresh lava eruptions. This is where a new study by Davide Sulcanese from the University of d’Annunzio in Italy and his colleagues comes in. Their reasoning: If Venus is still volcanically active today, then such fresh lava flows could also be seen in other volcanic areas.

For their study, the researchers therefore compared radar images taken by the Magellan probe between 1990 and 1992 as part of three radar mappings of volcanic areas. By comparing the data, Sulcanese and his colleagues determined whether and where anything on the surface of Venus had changed between the images taken several months apart. “Our analyses revealed striking changes in the backscatter in two regions between overflight 3 and the previous cycles,” the team reports. The first region is an area characterized by old lava flows on the western flank of the large shield volcano Sif Mons. There, the radar backscatter increased between the first and third overflights, indicating a fresher, smoother surface. In an area of ​​around 30 square kilometers, lighter lava flows can be seen, which partially cover rougher, darker flows, as the scientists explain.

Fresh changes indicate lava eruptions

Sulcanese and his colleagues found something similar in the second region, the Niobe Planitia plain, which is characterized by many smaller shield volcanoes and their ejecta. “We observed bright, wavy lines and fan-shaped structures extending to the northeast,” the researchers describe their results. These structures, which cover an area of ​​around 45 square kilometers, were only visible in the images from the probe’s third flyover, but not in those from the first or second. Analyses of the topography also showed in both areas that the bright structures appear to follow the slope of the terrain. But were these really fresh lava flows? To be absolutely sure, the researchers used a model to check alternative explanations such as radar artifacts, atmospheric disturbances or microdunes piled up by the wind. However, none of these phenomena matched the observations, as the team reports. They also ruled out landslides because the slope of the terrain in both areas is too low for this.

“All evidence suggests that the features we observed are real changes in terrain morphology,” the scientists state. According to them, the radar images document fresh lava flows on Venus. “In our analysis, we identified compelling evidence of lava flows associated with ongoing volcanism in two different regions of Venus,” write Sulcanese and his team. According to the researchers, this – together with the 2023 findings on Maat Mons – provides further evidence that our neighboring planet Venus has continued volcanic activity to this day. “These results underscore the importance of further exploration of Venus,” the researchers emphasize. Future missions to Venus such as VERITAS37 and EnVision38 could help to corroborate the current findings.

Source: Davide Sulcanese (Università d’Annunzio, Pescara) et al.,/ Nature Astronomy, doi: 10.1038/s41550-024-02272-1

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