Venus Is Erupting
If new indirect observations are correct, Venus is an active planet today with huge volcanoes.
The number of “active bodies” in our solar system is an exclusive club. Earth, of course, has volcanoes. So does Io, Jupiter’s innermost large moon. Enceladus, a small moon of Saturn, pours out icy eruptions from large cracks at its south pole. And Triton, Neptune’s large moon, was seen erupting geysers of dirty nitrogen at Voyager 2’s flyby in 1989. More evidence will be needed to establish whether Europa (at Jupiter), Titan (at Saturn), and a few other candidates, are currently active. Earth’s moon, also, has hints of ongoing activity from time to time; at the very least, some of its volcanism is considered recent (14 July 2020).
It’s noteworthy that Earth is the only active planet; all the others are moons of other planets. Clearly some planets have been active in the past: Mercury has lava-filled craters, and Mars has dead volcanoes, including Olympus Mons, the largest volcano in the solar system. Pluto may have current or recent eruptive activity. But why Enceladus, Triton, or Io? It should be an article of deduction for those who believe the solar system formed 4.5 billion years ago that all small bodies should be dead – and yet Io is more volcanically active than the Earth. Be that as it may, another planet is joining the active body club: our sister planet Venus.
Global radar map of Venus (JPL) from Magellan mission. The spacecraft mapped the surface in radar between 1989 and 1994.
Scientists Discover Volcanoes on Venus Are Still Active (University of Maryland). Since the Magellan spacecraft mapped the surface of Venus with radar, it was known that Venus possessed volcanic terrains. Some of its “coronae” (the name given to large, circular features) are much larger than the Earth’s volcanoes. What was not known is whether they are still erupting today. It’s been hard to tell due to the thick, cloudy atmosphere. Now, scientists think they have the smoking gun evidence.
“This is the first time we are able to point to specific structures and say ‘Look, this is not an ancient volcano but one that is active today, dormant perhaps, but not dead,’” said Laurent Montési, a professor of geology at UMD and co-author of the research paper. “This study significantly changes the view of Venus from a mostly inactive planet to one whose interior is still churning and can feed many active volcanoes.”
The evidence is indirect; it comes from models associating corona features to theories of thermal evolution of the planet. New Scientist explains the reasoning process:
The simulations allowed the researchers to identify what features a currently active volcanic site would possess. Most notably, they looked for a trench around a site’s outer ring and a bulge on the trench’s edge.
Looking at the Magellan images, they found that at least 37 volcanic sites had these features, suggesting they are active. The volcanic sites, called coronae, are much larger than Earth’s volcanoes. The average corona that the researchers looked at had a diameter of 300 kilometres. Mauna Loa in Hawaii, the largest active volcano on Earth, is only 120 kilometres wide.
The scientists admit that this should not be happening on a planet without plate tectonics. The press release says,
But it was thought that the coronae on Venus were probably signs of ancient activity, and that Venus had cooled enough to slow geological activity in the planet’s interior and harden the crust so much that any warm material from deep inside would not be able to puncture through. In addition, the exact processes by which mantle plumes formed coronae on Venus and the reasons for variation among coronae have been matters for debate.
You can see one of the coronae that the team concludes is active or recently active by enlarging the photo. A rotating globe in the press release indicates the 37 spots where active vent candidates have been mapped.
In the New Scientist article, writer Jason Arunn Murugesu cannot resist thinking of habitable planets and life:
“Based on size, chemistry and position in the solar system, Venus is the most Earth-like planet ever observed,” says Sami Mikhail at the University of St Andrews, UK. “Understanding whether or not the planet is volcanically active today is an integral piece of the puzzle to revealing why Earth is the definition of habitable, and Venus is a barren, hot and hellish wasteland.”
Certainly nothing could live today on Venus, where surface temperatures are hot enough to melt lead. Astrobiologists will need to remember the lesson of Venus. Just because a rocky planet orbits a star at or near the habitable zone, that does not imply that it is suitable for life.
The paper in Nature Geoscience by Gülcher et al., “Corona structures driven by plume–lithosphere interactions and evidence for ongoing plume activity on Venus” (20 July 2020), points out why Venus should not be active after billions of Darwin Years:
In the absence of global plate tectonics, mantle convection and plume–lithosphere interaction are the main drivers of surface deformation on Venus. Among documented tectonic structures, circular volcano-tectonic features known as coronae may be the clearest surface manifestations of mantle plumes and hold clues to the global Venusian tectonic regime. Yet, the exact processes underlying coronae formation and the reasons for their diverse morphologies remain controversial.
Controversial to whom? To the scientists who expected that “Venus had cooled enough to slow geological activity in the planet’s interior and harden the crust so much that any warm material from deep inside would not be able to puncture through.”
Scientists love to write with passive voice verbs. Such verbs conceal who is talking or thinking. They say that processes making Venus active today “remain controversial” instead of coming right out and saying, with active voice verbs, ‘We don’t agree how Venus could be active today.’ Scientists should be accountable for their mistakes. Since there are people who are not surprised that Venus is still active (e.g., those who deny the moyboy article of faith that the solar system is billions of years old), these scientists should admit that they find it controversial, and not assume that every human being on Earth suffers from their worldview-based delusion.
Globe of Venus at JPL showing its largest mountain, Maxwell Montes, named for James Clerk Maxwell.