Although on Earth we are very used to volcanoes and, often, to their ferocity, the truth is that this phenomenon is not very common in the current Solar System. Yes, many worlds have structures that in the past expelled material from the depths; but few do right now. For example, on Io, one of Jupiter’s moons, giant columns of smoke from volcanic activity have been seen; either Tritonsatellite of Neptuneor Enceladus, moon of Saturnhave cryovolcanoes, which do not ‘vomit’ molten rock, but rather water and gases.
However, the ‘king’ of volcanoes is Venus: It has more than 1,600 main volcanoes, but it is estimated that it could have more than 100,000 or even more than a million smaller volcanoes. For years there has been a debate about whether any of them could still be active, since their surface is ‘young’: scientists believe that it underwent an almost complete renewal approximately 300 to 500 million years ago, which in cosmic terms is almost a ‘sigh’ -considering that our Solar System formed about 4.6 billion years ago.
Now, the researchers Robert Herrick y Scott Hensley, from the University of Alaska Fairbanks, claim to have evidence of active volcanism on the surface of Venus, providing images that would show an area with a ‘before’ and an ‘after’ of lava flowing across the surface of our neighbor. The findings are published in the journal ‘Science’.
‘Search’ through old photos
Observing the surface of Venus has been difficult: the high pressures and temperatures of its surface, in addition to its thick clouds of sulfuric acid, greatly limit its vision from space. That is why Herrick and Hensley “dusted off” old images taken by the Magellan spacecraft, a NASA probe that was active over our neighbor between 1990 and 1994.
“During his mission, Magellan used radar to image the surface of Venus from different orbits, observing some locations two to three times over the course of two years, including areas that were later identified as potential locations for volcanic activity,” the authors explain.
They first thought about using the technology to detect possible changes in the geomorphology of the soil between images of the same place at different moments in time. But, due to the type of data obtained by the probe, which did not always photograph all locations in the same way, it was impossible. So they had to manually search through the full-resolution images.
This is how they located a volcanic vent -a ‘hole’ through which material emanates-, which is part of the largest volcanic system on Venus, called Maat Mons -and which reaches eight kilometers at its highest point-. The authors noticed that between two images taken eight months apart, it seemed to grow and change shape, and they propose that the change was caused by a river of lava that emanated from the volcano’s vent.
Radar images of a vent that has changed shape. (A) images of Cycle 1 looking to the east and (B) of Cycle 2 looking to the west of the modified vent and its surroundings. In the Cycle 1 image, the vent appears nearly circular and deep with steep walls. In Cycle 2, the vent appears larger, irregular in outline, shallower, and almost full.
“In the images from the second image, additional volcanic flows are observed downslope from the vent, although we cannot rule out that they were present in the first image, although they would have been invisible due to differences in the geometry of the images,” say the researchers, who are realistic about the limitations of their observations and the implication that this volcano is indeed active.
Comparison between observations and simulated appearances of model vents. Radar images acquired in (A) Cycle 1 and (B) Cycle 2, indicating the changed vent (labeled V) and an unchanged vent (labeled U). A smaller vent (labeled S) and a ridge (labeled L) are also visible.
“With just one modified feature, we cannot determine how common active volcanism on Venus can become (…) The low detection rate indicates that Venus is less volcanically active than the Jupiter moon Io, for which they have photographed more than 100 active points (…) However, there are activity scenarios that are compatible with levels of high activity similar to those of Hawaii«.
Several missions to map Venus are currently being planned, including NASA’s Veritas orbiter and ESA’s EnVision probe. If Venus is volcanically active, these projects will be able to prove it in the coming years, resolving the long debate of whether our neighbor’s volcanoes are as active as ours.