Strange signals on Venus may be coming from an erupting volcano


Venus, Earth’s hellish doppleganger. NASA/JPL-Caltech


A new study adds to a growing pile of evidence that Venus may be volcanically active — a finding that, if true, would help explain how volcanoes impact planetary evolution and habitability across the cosmos. The research, which focuses on strange signals coming from a Venusian volcano called Idunn Mons, is fueling excitement about future missions to Earth’s nearest neighbor that will settle the matter once and for all.

It’s long been known that Venus is covered in some seriously surreal volcanoes. But it is impossible to tell from Earth whether they are still oozing lava today, because Venus’s thick and hazy atmosphere obscures whatever may be happening on the ground.

Now, using archival observations from old orbiter missions and the results of experimental work conducted on Earth, a team of scientists is making the case that the 1.5-mile high, 125-mile wide Idunn Mons has been active within the past few thousand years, and is likely still erupting today. They won’t have to wait long to confirm their hunch: Within the next decade, a small squadron of missions capable of detecting volcanic activity on the surface will begin their journeys to Venus.

Justin Filiberto, the branch chief in Astromaterials Research and Exploration Science (ARES) Research Office at NASA Johnson Space Center and co-author of the study published last month in The Planetary Science Journal, says that at this point he doesn’t think “anyone would be surprised that, when we got to Venus, we’d find evidence of volcanic activity.”

Still, confirming that suspicion would have major implications. Like Earth, Venus once had an ocean’s worth of water, but today it’s an arid wasteland with a dense, acid-laden atmosphere and a surface hot enough to melt lead. A leading explanation for Venus’s hellish transformation is epic volcanic eruptions that kickstarted irreversible climate change. Studying Venus’s volcanoes up close, then, will help us better understand why Earth has not (yet) undergone a similar eruptive apocalypse. And while dead volcanoes would offer some clues, volcanoes are a lot easier to comprehend if you can observe them in action.

“THE LIKELIHOOD OF THERE BEING NO ACTIVE VOLCANISM ON VENUS MUST BE FUNCTIONALLY ZERO”

While there’s no direct evidence of active volcanism on Venus, there are several indirect clues. The high concentration of sulfur dioxide, a common volcanic gas, in Venus’s atmosphere makes much more sense if volcanoes are still belching it out today. Venus’s surface features tectonic rift zones – hotspots of volcanic activity on Earth – as well as cauldron-like volcanic features which are sometimes shaped in a way that suggests they are being transformed by underlying heat. More straightforwardly, it would be bizarre if Venus was volcanically dead because of its size. “Venus is basically the same size as Earth. Earth isn’t volcanically dead, so why would we expect Venus to be?” says Lauren Jozwiak, a planetary volcanologist at the Johns Hopkins University Applied Physical Laboratory.

The new study brings an array of evidence together to suggest that the magmatic heart of Idunn Mons is still beating today.

Europe’s Venus Express orbiter, which circled the planet from 2006 to 2014, found lava flow deposits all over —including at Idunn Mons — that were glowing in infrared. Venus’s corrosive atmosphere quickly chews up volcanic minerals, dimming their infrared glow. So these intense thermal emissions were thought to represent lavas that had erupted as recently as 250,000 years ago. But recent experimental work, in which volcanic minerals were baked under Venusian atmospheric conditions and degraded faster than previously thought, implies the lavas may have erupted within the last 1,000 years. And at Idunn Mons specifically, winds are being disrupted more than would be expected based on the volcano’s topography. The authors suggest heat from molten rocks may be adding to the turbulence above the volcano.

Jozwiak, who wasn’t involved with the study, says it represents “really compelling case work.” But ultimately, future spacecraft missions to Venus, including NASA’s VERITAS and DAVINCI+ missions, and Europe’s EnVision probe, which are slated to launch toward the end of this decade, will be the ones to confirm its suspicions.

VERITAS (the Venus Emissivity, Radio Science, InSAR, Topography, and Spectroscopy mission) is kitted out with a state-of-the-art radar system that will be able to identify fresh lava unambiguously. It will make multiple passes of the same areas mapped by an earlier radar-equipped orbiter known as Magellan. If a lava flow pops up that wasn’t there when Magellan visited Venus in the early 1990s, VERITAS will find it. NASA’s intrepid orbiter may even spot new lava flows that pop up during its tenure around the planet. VERITAS’s infrared camera will also make youthful lava flows that are still emitting heat easy to spot.

THESE THREE FUTURE MISSIONS WILL SOON UNEARTH THE ANSWER

While VERITAS will study giant patches of the planet, Europe’s EnVision orbiter will conduct surgical scientific strikes. Its radar system will examine the ground for recent signs of volcanic or tectonic terraforming, and its infrared and ultraviolet spectrometers will look for curious chemical concoctions on the land and in the sky. If the spacecraft focuses on a volcano that’s spewing lava or noxious gases, or or a quiet one whose magma is radiating heat from beneath the surface, it will know.

DAVINCI+ (Deep Atmosphere Venus Investigation of Noble Gases, Chemistry, and Imaging Plus) is going to drop a probe through Venus’s atmosphere that will document its chemistry as it plunges to its death on the surface. With DAVINCI+ providing a profile of the volcanic gases present at that moment in time, scientists working with VERITAS and EnVision will be able to more easily identify spikes in the concentrations of those gases—indications than a recent eruption has topped them up.

To many planetary scientists, confirming that Venus is volcanically active is a mere formality at this point. “It would be truly astonishing if it wasn’t,” says Richard Ghail, a planetary geologist at the Royal Holloway University of London and EnVision’s lead scientist. Paul Byrne, a planetary scientist at Washington University in St. Louis, agrees. “The likelihood of there being no active volcanism on Venus must be functionally zero,” says Byrne.

For Ghail and others, the exciting thing about future missions to Venus is what they will be able to tell us about how active it is. Is it more like Earth, where dozens of eruptions occur every day, or like Mars, a volcanically comatose world where giant cascades of molten rock might flood the surface every few million years? Some suspect Venus will erupt to its own beat; others believe its rhythm will hew closer to our planet’s own. These three future missions will soon unearth the answer, putting decades of volcanic speculation to rest.

“I think we’re going to be writing brand new textbooks about Venus once all of these missions get there,” says Filiberto. “It’s going to change how we think about planetary evolution.”