On Venus there are active volcanoes: this is indicated by some morphological changes of the largest volcanic relief on the planet, Mount Maat, detected eight months later in the radar images collected almost 30 years ago by NASA's Magellan probe and re-examined with a laborious manual method by Robert R. Herrick of the University of Alaska at Fairbanks and Scott Hensley of the California Institute of Technology.
The results are published in the journal Science.
The study focused on a region of the surface of Venus that has been flown over several times by the probe and which includes two of the largest volcanic systems on the planet: Mounts Maat and Ozza.
"By volume, they are comparable to the largest volcanoes on Earth, but have lower slopes and are therefore more extensive," Herrick explains.
In Mount Maat, in particular, a volcanic vent was identified which in the space of eight months (between February and October 1991) changed from a circular shape of about 2.2 square kilometers to an irregular shape of about 4 square kilometers.
In this transformation the walls of the volcanic vent have become lower and have been filled inside by what appears to be a lake of lava (we do not know if liquid or solidified).
The researchers acknowledge that this phenomenon could also be explained by a phenomenon not related to volcanism: the walls of the volcanic vent could in fact have collapsed as a result of an earthquake.
Usually, however, this kind of collapse on Earth is always accompanied by volcanic eruptions in the vicinity.
“We can now say that Venus is volcanically active in the sense that there are at least a few eruptions a year,” Herrick adds. “We can expect that future missions to Venus will observe new volcanic flows that have occurred since the Magellan mission ended three decades ago, and we should see some activity occurring just as the next orbital missions collect images."
