Volcanoes on Venus? Radar images from more than 30 years ago show evidence of volcanic activity, scientists say

Scientists say data from more than 30 years ago shows the planet Venus is volcanic. NASA's Magellan spacecraft collected images of the planet's surface between 1990 and 1992, and researchers recently searched that data to study the possible activity of the volcanoes in the terrain. 

The researchers from the University of Alaska and the California Institute of Technology found two large volcanoes in the Atla Regio region of Venus – the highlands of the planet. Ozza and Maat Mons were previously believed to be volcanoes, but the researchers identified their volcanic vents, the hole where they would erupt, and confirmed they are two of the largest volcanoes on the planet, according to the study, published in Science.

"Ozza and Maat Mons are comparable in volume to Earth's largest volcanoes but have lower slopes and thus are more spread out," University of Alaska Fairbanks Geophysical Institute research professor Robert Herrick said in a news release.

The researchers spent about 200 hours comparing images taken throughout the Magellan mission, and found the volcanic vents had changed over time, suggesting volcanic activity. A change in a vent could mean one of two things: magma has filled and expanded it, or magma drained from it, making the vent partially collapse. 

While the vent of Maat Mons expanded, indicating volcanic activity, an earthquake could have caused the change, according to the news release. However, when the vents of Earth's volcanoes change this drastically, it coincides with nearby volcanic eruptions. 

While questions about the volcanoes on Venus remain, the researchers believe they are less active than the ones on Jupiter's moon, Io, which "is so active that multiple ongoing eruptions have been imaged every time we've observed it," Herrick said. 

 Herrick said there are "at least a few eruptions per year" on Venus. 

"We can expect that the upcoming Venus missions will observe new volcanic flows that have occurred since the Magellan mission ended three decades ago, and we should see some activity occurring while the two upcoming orbital missions are collecting images," he said. 

Mars may also have active volcanoes, but "most scientists would say that you'd probably need to watch the surface for a few million years to have a reasonable chance of seeing a new lava flow," he said.

CBS News has reached out to Herrick for more information and is awaiting response.