Scientists sifting through decades-old spacecraft data have found clear signs of recent volcanic activity on Venus. The results, published in the journal Sciencenot only reveals that the planet’s surface is currently a turbulent place, but offers insight into its geological past and future.
By any measure, Venus is a hellscape: crushing pressure, a toxic atmosphere, and surface temperatures hot enough to melt lead. It’s like a scene lifted straight from Dante’s Hell.
It’s “my favorite planet,” says Robert Herrick, a planetary scientist at the University of Alaska Fairbanks.
For all its hostility, Venus – our nearest planetary neighbor – is actually quite similar to Earth. So much so that Herrick calls it our “true sibling” in the solar system. The similarity is “driven by what’s going on inside them,” he says.
“Other than Earth,” Herrick says, “it’s the only planet that has true mountain ranges and a wide variety of volcanic features.” These features include lava fields, channels carved out of molten rock, and hundreds, if not thousands, of volcanoes.
So it’s clear that Venus is volcanically active, giving it a youthful (in geological terms) appearance. But it is not clear exactly how active.
“It could still mean that the time between eruptions could be months, years or tens of thousands of years,” says Herrick.
So he set out to try to narrow that time window by searching for evidence of recent volcanic activity. He turned to radar surface images collected by the Magellan spacecraft in the early 1990s.
“Thirty years ago,” he says, “it just wasn’t possible to pan around and zoom in and out and flip back and forth between different global mosaics.” But computer hardware and software have greatly improved, so Herrick was able to see through the images.
“It’s a needle in a haystack search with no guarantee that there is a needle,” he acknowledges.
Herrick focused his search around the tallest volcano on Venus called Maat Mons, named after the ancient Egyptian goddess of truth and justice. And after a few months of looking over an area the size of Australia, he found something.
That’s evident in two side-by-side black-and-white photos taken eight months apart of the same spot on the north side of the volcano. Each one is about 15 or 20 miles across. Herrick points out toward the bottom. It’s a vent – the area where a volcano erupts and spews its lava, ash and rock. But the shape of that venting is different between the two images.
“The outline has changed and the thing has actually gotten bigger and also looks shallower,” he says. That is, within just eight months in 1991 (the same year that President George HW Bush declared victory over Iraq and Clarence Thomas was confirmed as a Supreme Court justice), Herrick speculates that the volcano erupted and formed a lava lake within the vent.
“Of course, I could have been very lucky and seen the only thing that happened in the last million years on Venus,” says Herrick. “But I think the reasonable interpretation suggests that Venus is relatively Earth-like in the frequency of volcanic eruptions,” similar to the likes of Hawaii and Iceland.
Unlike Earth, Venus does not have plate tectonics. So scientists have been trying to figure out how the planet has evolved geologically over the last four and a half billion years and where it might be going. Herrick and his colleague Scott Hensley hope their findings will help do just that.
“It’s nice to have visual confirmation of the volcanic activity on Venus,” said Clara Sousa-Silva, a quantum astrochemist at Bard College who was not involved in the research. “But given that it was something we had speculated about, it’s not shocking to have this paper published.”
Still, Sousa-Silva says this confirmation of activity on Venus’ surface helps us better understand what to expect in Venus’ atmosphere.
“A planet that has a lot of volcanic activity,” she says, “has access to these extreme pressures and temperatures below the surface that can produce molecules that are really unusual and otherwise really hard to make.”
Much of NASA’s (and the public’s) recent attention has been drawn to Mars; the space agency has landed five rovers on the Red Planet’s dusty surface since 1997.
But Herrick says Earth’s resemblance to Mars is somewhat superficial, largely limited to surface features like blowing sand, desert landscapes and evidence of what may once have been lakes and rivers.
However, the winds of interest have shifted. “Maybe it will cycle back like clockwork,” Herrick says with a laugh.
That’s because NASA currently has two missions to Venus in the works, which will now be informed by Herrick’s findings. “We don’t just think it’s an active planet,” he says. “We know it’s an active planet — right now.”
Herrick is working with NASA to develop an instrument for future missions to monitor volcanic activity on Venus. He’s pretty sure now that the seismometer will register something once it’s installed—as long as it can survive the infernal planet long enough to make its measurements.