For half a century, scientists have dreamed of watching Venus’ volcanoes erupt. This burning inferno is hidden from view under toxic clouds, but past space missions have shown that its surface is full of volcanic phenomena, and now, thanks to the documented memory of a long-dead spacecraft, scientists have mined scientific gold: they witnessed the transformation, expansion and filling a Venus fissure with molten rocks.
“I bet it was a lava lake explosion,” said Robert Herrick, a planetary scientist at the University of Alaska Fairbanks and one of the two authors of the latest study.
Herrick and his colleagues spotted a vent on one side of the giant Maat Mons volcano in radar images from NASA’s Magellan spacecraft in 1991.
“This is one of the most compelling lines of evidence I’ve seen,” said Stephen Kane, a planetary astrophysicist at the University of California, Riverside, who was not involved in the research.
The results have surprised the scientific community. Experts expected to detect volcanic eruptions on Mars, but not before two advanced spacecraft equipped with cloud-penetrating radar systems — NASA’s VERITAS and Europe’s EnVision — arrive at Venus in the early 2030s.
Evidence of contemporary volcanic activity on Venus has deep implications. The planet’s composition and size are very similar to Earth, but its significant and ancient water reserves—probably in the form of oceans—vaporized long ago, and the planet went up in flames in a mysterious cataclysm. Out-of-control climate change caused by volcanic eruptions is the main culprit. By understanding the current volcanic activity of Venus, scientists can learn more about the different fates of Earth and its burning sister.
“If you want to study the only Earth-sized planet we can get to in the entire universe, Venus is the only option,” said Paul Byrne, a planetary scientist at Washington University in St. Louis who was not part of the study. “
The murky atmosphere of Venus prevents its surface from being seen from Earth. Only a handful of spacecraft have seen its sights, either by plunging into the clouds and surviving only an hour or two on the hot, high-pressure surface, or by circling the planet and penetrating the clouds with technologies such as radar.
A fleet of Soviet spacecraft in the early 1980s revealed that Venus is almost entirely covered in volcanic structures—some like Earth, others very alien. NASA’s radar-equipped Magellan spacecraft reached it in 1990 with the aim of mapping Venus with unprecedented precision.
By orbiting the planet several times and checking the same places multiple times, scientists hoped to see signs of volcanic activity. But there were complications. The low resolution of the radar meant that physical changes had to be very large to be detected in the images, and early in the mission, Magellan’s orbit began to shrink, resulting in the spacecraft mapping a smaller area of the surface with each round trip.
Despite these challenges, 43% of the planet’s surface has been mapped at least twice. But comparing multiple images of a volcano in order to find changes also became problematic; Because the angle of each image had changed between the two orbits.
In the decades since the mission, no one has been able to find an active volcano.
A changing volcanic vent
Scientists have found indirect evidence of many volcanic activities on Venus; including jumps in atmospheric gases associated with volcanic emissions, very young mineral masses, and unusual phenomena on circular structures called coronae, which indicate the underflow of magma.
“This circumstantial evidence keeps us excited,” Kane says. But the Holy Grail—an erupting volcano or a river of molten rock—was still missing.
In 2021, EnVision and VERITAS were selected for launch and became the best chance to find live volcanic activity on Venus. But everyone was not patient.
Referring to the height of the pandemic, he says: “I had many Zoom meetings where full participation was not required. Whenever I had an hour here or there, I started looking [به دادههای قدیمی ماژلان] I would.” He manually adjusted images of Venus’ volcanoes in search of something odd.
During one of these searches, Henrik carefully examined Matt Moons. Named after the Egyptian goddess of truth and justice, the mountain is the planet’s tallest volcano—and something had changed on one flank between February and October 1991. During those eight months, material appeared to have flowed into an opening, which had grown from 1.3 km to 2.4 km, and a new flow of material was moving downward.
“This is really him,” Herrick remembers saying to himself at the time. He quickly showed it to his colleague Scott Hensely at NASA’s Jet Propulsion Laboratory, and he confirmed it: something volcanic was going on.
The material that filled the opening could have been rock debris from the landslide. It is also possible that river-like formations were also present in February, but due to the angle of the images, they could not be seen.
But the most likely scenario is that in 1991 a large eruption of lava filled the widening vent and some of it flowed over the rim or leaked out through a fissure. “We can safely say that it changed shape,” Herrick says. And when a volcano on Earth causes such drastic deformation, the main cause is always molten rock.
In search of the heartbeat of Venus
After so much environmental evidence, “this is the first time we’ve seen a change in something,” said Anna Gülcher, a planetary scientist at the California Institute of Technology who was not involved in the study.
“I think what they’ve seen is real,” says Byrne of the University of Washington. He suspects that the opening change was caused by subsurface movements, such as the rapid movement of magma below the surface; Not because of an eruption.
Byrne says scientists hope to answer a fundamental question: “What is the planet’s daily volcanic heartbeat doing?”
The volcanoes of Earth and Io, Jupiter’s moon, are always erupting. Mars erupts maybe once every few million years. Where is Venus in this spectrum?
The discovery suggests that Venus has something closer to Earth-like vigorous volcanic activity. VERITAS and EnVision want to answer that question, but until then, the research encourages scientists to follow Magellan’s documentaries in hopes of finding another volcanic eruption on Venus.