Using radar images taken by the Magellan spacecraft in the early 1990s, scientists discovered a volcanic vent that changed shape in 1991 and grew in eight months. This is one of the most convincing clues that the volcanism that shaped the planet’s surface and atmosphere is still active on Venus. This has implications for how we interpret observations of our neighboring planet, including the discovery of phosphine gas, which was originally attributed to potential life but may also be the result of volcanic activity.

“We’re investigating volcanic sites on Venus that have been imaged two or three times by Magellan and we identify a volcanic vent with an area of ​​~2.2 km2, ^{Which one} “The shape changed in the eight months between the two radar images,” said geophysicist Robert Herrick of the University of Alaska Fairbanks and engineer Scott Hensley of NASA’s Jet Propulsion Laboratory in California.

“We interpret these results as consistent volcanic activity on Venus.”

Venus and Earth have a lot in common; their sizes, masses, densities and compositions are very similar to each other. But for two similar pieces of stone, they definitely went their separate ways. The land is moist, temperate and full of life. Venus is dry, blisteringly hot, and shrouded in a poisonous, suffocating, turbulent atmosphere. Another difference between the two planets is the lithosphere, which is the rocky outer crust containing the sticky molten interior. Earth’s lithosphere is like a broken eggshell, made up of several pieces, tectonic plates, whose edges rub against each other. Most of Earth’s volcanic activity occurs along these boundaries.

Venus’s lithosphere is a single, integrated crust without tectonic plates. This raised the question of the planet’s volcanic activity. Its young surface indicates recent volcanic recovery, but whether and how volcanically active it is still remain open questions.

Venus’s surface is not easy to see because of its atmosphere; this requires imaging techniques that can cut through intense carbon dioxide. Additionally, probes reserved for Venus are few. The Japan Aerospace Exploration Agency’s Akatsuki probe is the only one so far and is studying the atmosphere, not the surface, of the planet. Other probes have passed by Venus and taken images, but to understand any potential volcanism you need something that can track the surface over time.

Magellan comes to the rescue here.

Between 1990 and 1992, it spent a little less than 4.5 years orbiting Venus, using radar to image the surface. However, the probe’s orbit was elliptical, meaning the different angles it photographed the surface of Venus made the data unsuitable for automatic comparative analysis. This meant that one had to do it manually, which was time consuming and difficult.

“Only in the last decade, Magellan data has become full resolution, mosaiced, and easily manipulated by a researcher with a typical personal workstation,” Herrick explains.

First, it narrowed down the data it needed to scan by selecting places that were previously identified as volcanically active. He then manually reviewed Magellan’s images and looked for changes in the landscape around these locations.

And he found something near the two largest volcanoes on Venus, Ozza and Maat Mons. These volcanoes are comparable in volume to volcanoes on Earth, but are flatter and more diffuse. Between February and October 1991, the vent on the north side of the shield volcano, which is part of Maat Mons, changed shape significantly.