Lava rivers on Venus reveal a more volcanically active planet

Witnessing the blood-red fires of a volcanic eruption on Earth is unforgettable. But it would be incredible to see molten rock bleeding from a volcano on another planet. That’s close to what scientists have observed on Venus: two huge, winding lava flows oozing from two different corners of Earth’s planetary neighbor.

“After you see something like this, the first reaction is ‘wow,'” said Davide Sulcanese, a doctoral student at the University d’Annunzio in Pescara, Italy, and author of a study reporting the discovery in the journal Nature Astronomy, published Monday.

Earth and Venus were minted at the same time. Both are made of the same primal matter, and both are of the same age and size. So why is Earth a paradise full of water and life, while Venus is a scorched hellscape with acidic skies?

Volcanic eruptions play with the planetary atmosphere. One theory is that, eons ago, several apocalyptic eruptions triggered a greenhouse effect on Venus, turning it from a temperate, water-soaked world into a dry desert of scorched glass.

To better understand its volcanism, scientists hoped to capture Venus’ eruption in action. But even though the planet is known to be choked with volcanoes, the opaque atmosphere prevented anyone from seeing the eruption the way spacecraft spotted it on Io, Jupiter’s hypervolcanic moon.

In the 1990s, NASA’s Magellan spacecraft used cloud-penetrating radar to survey most of the planets. But then relatively low-resolution images made spotting fresh molten rock a problematic task.

Using modern software to study Magellan’s data, scientists have now found two unequivocal lava flows: one flowing down the slopes of Sif Mons, a broad shield volcano, and the other winding across the western part of Niobe Planitia, a flat plain speckled with numerous volcanic mountains.

Many planetary scientists believe that Venus is teeming with eruptions. “But it’s one thing to strongly suspect it, and quite another to know,” said Paul Byrne, a planetary scientist at Washington University in St. Louis who was not part of the new study.

Venus lacks Earth’s plate tectonics. But its similar rocky composition and comparable size suggest that something is still cooking inside the Sun’s second planet – and it should be volcanically active.

There is circumstantial evidence: volcanic gases linger in Venus’ sky, and the way parts of the planet glow suggests they were covered by lava in the recent geologic past.

Direct evidence of volcanic fury finally emerged, surprisingly, in 2023, when researchers saw a volcanic vent that doubled in size and likely filled with lava according to old Magellan data. Other scientists still longed for signs of an unequivocal lava flow, an almost literal smoking gun.

Mr. Sulcanese fulfilled their wish. He found bright river-like spots on Sif Mons and Niobe Planitia in the images of the later Magellan surveys that were not present in the earlier data. After carefully ruling out other possibilities, including landslides, his team concluded that lava was the only reasonable explanation.

“Magellan is the gift that keeps on giving,” said Stephen Kane, a planetary astrophysicist at the University of California, Riverside, who was not involved in the new study.

Both lava flows are comparable in size to the output of Hawaii’s Kilauea volcano during its three-month paroxysm in 2018. Using these two eruptions, the study authors estimate that there is significantly more eruptive activity than previously thought — and that it is happening elsewhere on the planet today .

“Venus is active,” said Giuseppe Mitri, an astronomer also at the University d’Annunzio and author of the study.

More importantly, volcanically speaking, Venus is “Earth-like,” said Anna Gülcher, a planetary scientist at the California Institute of Technology who was not involved in the work.

The result also complicates the tentative detection of phosphine in Venus’ atmosphere; phosphine is a substance that is usually associated with living things on Earth. But other explanations for its possible presence on Venus could not be ruled out. Volcanic activity can also produce phosphine, but rebuttals to the idea suggest that Venus simply doesn’t have enough volcanism to create it.

“Well, apparently there is,” said Dr. Kane.

The only way to find better answers—about phosphine, Venus’s volcanic cadence, its cataclysmic transformation—is to revisit the planet. Fortunately, a fleet of new spacecraft should do just that in the 2030s.

While we wait, Magellan’s memories will continue to offer unexpected gifts.

“We can start to think of Venus as a living, breathing world,” Dr Byrne said.