Volcanoes Were Erupting on Venus in the 1990s

Start talking about Venus and immediately my mind goes to those images from the Venera space probes that visited Venus in the 1970’s. They revealed a world that had been scarred by millennia of volcanic activity yet as far as we could tell those volcanoes were dormant. That is, until just now.  Magellan has been mapping the surface of Venus and between 1990 and 1992 had mapped 98% of the surface. Researchers compared two scans of the same area and discovered that there were fresh outflows of molten rock filling a vent crater! There was active volcanism on Venus. 

Venus is the second planet from the Sun and similar in size to Earth, the similarities end there though. It has a thick atmosphere that is toxic to life as we know it, there is sulphuric acid rain high in the atmosphere and a surface temperature of almost 500 degrees. When the Venera probes visited they measured an atmospheric pressure of around 90 times that at the Earth’s surface. Combined with the other hostile properties of the atmosphere, a human visitor would not survive long. 

The dense atmosphere of Venus is largely the result of volcanic activity. Over the millennia, there have been extensive volcanic eruptions that pumped carbon dioxide into the atmosphere. The lack of bodies of water on Venus meant the built up carbon dioxide in the atmosphere didn’t get absorbed. In addition to this, the lack of a magnetic field meant the solar wind – the pressure from the Sun – drove away the lighter elements leaving behind the thick, carbon dioxide rich atmosphere we see today. But the volcanoes that drove the atmospheric changes are thought to have been extinct for a long time. 

It’s not just the Venera probes that have been exploring Venus. In 1980, the Magellan spacecraft was launched by NASA to map the surface of the hottest planet in the Solar System. On arrival, it was put into a polar orbit and used radar to penetrate the thick clouds. Back in 2023, a study of some of the Magellan images from the synthetic aperture radar showed changes to a vent near the summit of Maat Mons. It was the first direct evidence of an eruption on the surface of Venus and changes in the lava flows. 

In the latest study that was published in Nature Astronomy, more data from the synthetic aperture radar was studied. The team focussed on Sif Mons and Niobe Planitia and the data that had been collected from both areas in 1990 and again in 1992. The data revealed stronger radar returns in the later set of data suggesting new rock formations from volcanic activity. The team did consider it may have been caused by some other phenomena such as sand dunes or atmospheric effects but altimeter data confirmed the presence of new solidified lava. 

The team were able to use lava flows on Earth as a comparison to help understand the new flows on Venus. They estimated that the new flows are between 3 and 20 metres deep. They could go a step further though and estimated that the eruption at Sif Mons produced about 30 square kilometres of rock which would be enough to fill over 36,000 swimming pools.  The eruption at Niobe Planitia produced even more with an estimated 45 square kilometres of rock..

Studying volcanic activity on Venus helps to understand not just the geological processes but also helps to understand the structure of the interior too. This can help inform the likelihood of habitability for future explorers. None of which would have been possible without the recent volcanic activity to help us probe further the secrets of Venus.

Source: Ongoing Venus Volcanic Activity Discovered With NASA’s Magellan Data