Volcanoes on Venus erupt every few months like Hawaii, study suggests
The findings, while not definitive, challenge long-held assumptions of Venus being a dormant planet
Robert Herrick made the biggest discovery of his career while tuning out during Zoom meetings.
The planetary scientist from the University of Alaska Fairbanks has found evidence of active volcanoes on Venus, and he did it by using new technology to painstakingly re-examine old images of the planet.
It's the kind of finding that challenges the longstanding assumptions about the geological state of Venus, and it will likely shape the research that comes out of NASA's planned robotic missions to the planet over the next decade.
Herrick called the research "a needle in a haystack search, without any guarantee that that needle existed."
"I have to say, it was pandemic aided," he told As It Happens host Nil Köksal with a laugh. "A fair fraction of the search was occurring on endless Zoom calls that I was, you know, obligated to be on, but [did] not necessarily have to be fully engaged while I was on them."
The findings were published this week in the journal Science.
Back to the '90s
Venus, Earth's next-door neighbour, is covered in craters, volcanoes, mountains and lava plains. But it lacks the plate tectonics that gradually reshape Earth's surface. Because of that, scientists long believed it to be geologically dormant.
But research in recent years — including Herrick's — challenges that assumption.
Venus is often called our "twin" or "sister" planet because of its proximity and similar size and composition to Earth. Despite this, it's extremely difficult to study because it's surrounded by a thick atmosphere of carbon dioxide and clouds made from sulphuric acid, making it the hottest planet in the solar system.
Much of the visual data we currently have on Venus comes from radar pictures taken by NASA's Magellan spacecraft, which orbited the planet for 24 months from 1990 to 1992.
"In order to kind of make this discovery, you really need computer hardware and software that's kind of like Google Maps or Google Earth, where you can zoom in and out and pan around at least a few hundred gigabytes of data," Herrick said.
That technology didn't exist when Magellan was in orbit. But it does now.
What did they find?
When Herrick and his colleague examined those old images closely, they discovered a volcanic vent about 1.6 kilometres wide on the planet's surface had expanded and changed shape over an eight-month period.
The vent is on Maat Mons, which, at nine kilometres tall, is Venus's highest volcano and second-highest mountain.
A February 1991 image showed it as a circular formation covering about 2.6 square kilometres. But an October 1991 image showed the vent with an irregular shape covering about 3.9 square kilometres.
The researchers suspect this change in size and shape was caused by an influx of magma beneath the vent.
"Although it is possible the vent collapse was not associated with active volcanism, on Earth this large a collapse is usually associated with some sort of magmatic movement, and hence we think it likely to be the case here," co-author Scott Hensley, a senior research scientist specializing in radar remote sensing at NASA's Jet Propulsion Laboratory in California, told Reuters.
The findings suggest there are eruptions on Venus about every few months, similar to some Earth volcanoes in places like Hawaii, the Canary Islands and Iceland, Herrick said.
'Venus is a tough planet to study'
Gordon (Oz) Osinski, an earth sciences professor from Ontario's Western University who wasn't involved in the study, says the findings are significant, but not definitive.
"The main challenge is that this study used radar, which is difficult to interpret and can result in spurious results. Venus is a tough planet to study," Osinski, who heads up Canada's Lunar Rover Mission, said in an email.
"If these findings do stand up to subsequent studies, it is definitely a major finding as it is the first clear evidence that Venus is still volcanically active. This is important for our understanding of how rocky planets like Earth from and evolve."
I think that's as close to a smoking gun as you're going to get.- Laurent Montési, geophysicist
This isn't the only study to suggest volcanic activity on Venus.
In 2020, scientists used Magellan images to identify dozens of ring-like structures called coronae, which are caused by an upwelling of hot rock from deep within the planet's interior. Of 133 coronae examined, 37 appeared to have been active in the past two to three million years.
Laurent Montési, a University of Maryland geophysicist and co-author of the 2020 study, said this new research provides a much more recent — and precise — timeline for volcanic activity.
Montési was there on Wednesday when Herrick presented his findings at the Lunar and Planetary Science Conference in Houston, and says he was "quite impressed" by the evidence.
"You had a very nice circular hole. Now you have something which is more shaped like a kidney bean and is bigger," he said. "I think that's as close to a smoking gun as you're going to get."
Within the next decade or so, researchers will get their hands on new data that could help verify these findings.
NASA is planning two missions to Venus, with orbiters scheduled to visit the planet in 2029 and 2031, while the European Space Agency is planning one for 2032.
"We will be getting, you know, images of volcanoes that are erupting," Herrick said. "It'll be in radar, but it'll sort of be like you're looking down on Hawaii and seeing something going on."
With files from Reuters. Interview with Robert Herrick produced by Morgan Passi.
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