Seeing the blood-red fires caused by a volcanic eruption on Earth is unforgettable. But seeing molten rock bleeding from a volcano on a different planet would be unusual. This is close to what scientists discovered on Venus: two vast, sinuous lava flows flowing from two different corners of Earth’s planetary neighbor.

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

Earth and Venus were formed at the same time. They are both made of the same primordial material, and both are of the same age and size. So why is Earth a paradise overflowing with water and life, while Venus is a scorching hellscape and acidic sky?

Volcanic eruptions manipulate planetary atmospheres. One theory is that many eons ago, several apocalyptic eruptions created a runaway greenhouse effect on Venus, turning it from a temperate, waterlogged world into a barren desert of scorched glass.

In order to better understand its volcanic activity, scientists hoped to detect an eruption of Venus while it was happening. But although the planet is known to be choked with volcanoes, the opaque atmosphere prevented anyone from seeing the eruption the way spacecraft observed it on Io, Jupiter’s hypervolcanic moon.

In the 1990s, NASA’s Magellan spacecraft used cloud-penetrating radar to scan much of the planet. But at the time, relatively low-resolution images made detecting new molten rock a troublesome task.

Using modern software to look at Magellanic data, scientists have now discovered two unambiguous lava flows: one tumbling down the side of Mons Sword, a broad shield volcano, and the other meandering its way across the western part of Niobi Planitia, a flat, cratered plain. Many volcanic mountains.

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

Venus lacks the tectonic plates found on Earth. But its similar rocky composition and similar size suggest that something is still cooking inside the Sun’s second planet, and it must be volcanically active.

There is indirect supporting evidence: volcanic gases linger in Venus’ skies, and the way parts of the planet glow suggest they may have been coated with lava in the recent geologic past.

Finally, direct evidence of volcanic fury emerged, surprisingly, in 2023, when researchers observed a volcanic vent doubling in size and possibly filling with lava in old Magellanic data. Still other scientists yearn for signs of an unmistakable lava flow, almost definitive proof.

Mr. Solcanesi agreed to their wish. He found bright, river-like spots on the Sword of Mons and Niobe Planitia in later Magellanic Survey images, which were not present in the earlier data. After carefully ruling out other possibilities, including landslides, his team concluded that lava was the only plausible 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 Kilauea volcano in Hawaii during its three-month bout of eruption in 2018. Using these two eruptions, the study authors estimate that there is much more eruptive activity than previously assumed, and that it is actually occurring in place Another of the planet in the present day.

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

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

This result also complicates the initial detection of phosphine in Venus’ atmosphere; Phosphine is a substance commonly associated on Earth with living organisms. But other explanations for its possible presence on Venus cannot be ruled out. Volcanic activity could also produce phosphine, but refutations of this idea suggest that Venus simply does not have enough volcanoes to make it.

“Well, it seems there is,” said Dr. Kane.

The only way to find better answers — regarding phosphine, Venus’ volcanic rhythm, and its cataclysmic transformation — is to reexamine the planet. Fortunately, a fleet of new spacecraft is scheduled to do just that in the 2030s.

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

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