Researchers have long suspected that volcanoes are still simmering on Venus today – but until now there has been no clear evidence of this. Two scientists have now discovered an active volcanic vent on old radar images from the planetary probe Magellan. The images show that the volcanic vent has changed significantly in eight months. The only explanation for this is that the volcano ejected magma during this time, according to the scientists in the journal Science.
NASA’s Magellan spacecraft was launched in May 1989 and scanned Venus with radar beams from 1990 to 1992. For the first time, a complete image of the planet’s surface, which lies hidden under a dense cloud cover, was obtained. The radar images also show numerous volcanic regions – but “it was previously unknown whether there is still active volcanism on the planet,” write Robert Herrick of the University of Alaska and Scott Hensley of the California Institute of Technology.
Observations – such as fluctuating amounts of sulfur dioxide in Venus’ atmosphere – already indicated that there are indeed active volcanoes on the planet. Because volcanoes emit large amounts of this gas, which is quickly decomposed by sunlight. The Pioneer Venus probe had already observed that in the years from 1978 to 1992 the amount of sulfur dioxide fell sharply. In 2006, however, the European space probe Venus Express found a value ten times higher – which then fell again in the years that followed. So there had to be a process that transported sulfur dioxide back into the atmosphere between 1992 and 2006.
To solve this mystery, Herrick and Hensley revisited the old data from the Magellan probe—specifically, all those images of known volcanic regions that Magellan had repeatedly observed. Comparing the recordings was not easy, as the regions had been scanned from different perspectives. A comparison was not possible with automatic methods, so the two researchers laboriously inspected the images with their own eyes.
And indeed they found what they were looking for: They came across a 2.2 square kilometer volcanic vent in the Maat Mons region. They found clear differences between two recordings that were eight months apart. During this time, the chimney had not only changed its shape, but had also become considerably larger. Herrick and Hensley conclude that the volcano must have erupted in the time between the two recordings. In addition, changes can be seen in the vicinity of the volcanic vent, which indicate lava flows.
However, it is not possible to say how frequently active volcanoes occur on Venus. However, the researchers assume that there are other active regions on Venus – after all, they have only examined a very small part of the surface of the planet, about 1.5 percent. So the volcanic activity as a whole could possibly be comparable to that on Earth.
