An analysis of data from the Magellan radar finds two volcanoes that erupted in the early 1990s. This adds to the 2023 discovery of a new active volcano in the Magellan data.

Who is NASA’s Magellan?

It was the first unmanned remotely piloted spacecraft launched by NASA after the success of the Voyager space program in 1977, specifically after the successful mission of Voyager 1 and Voyager 2 to the outer planets of the solar system.

Direct geological evidence of recent volcanic activity on Venus has been observed for the second time. Scientists in Italy analyzed archival data from NASA’s Magellan mission and discovered surface changes that indicate the formation of new rock from lava flows linked to volcanoes that erupted while the spacecraft orbited the planet. Managed by NASA’s Jet Propulsion Laboratory in Southern California, Magellan mapped 98% of the planet’s surface from 1990 to 1992, and the images it produced remain the most detailed of Venus to date.

Volcanic activity on Venus could be comparable to Earth’s

“Using these maps as a guide, our results show that Venus may be much more volcanically active than previously thought,” said Davide Sulcanese of the University d’Annunzio in Pescara, Italy, who led the study. “By analyzing lava flows we observed at two locations on the planet, we discovered that volcanic activity on Venus could be comparable to that on Earth.”

This latest data builds on the historic 2023 discovery of images from the Magellan radar that revealed changes in a vent associated with the Maat Mons volcano near Venus’ equator. The radar images are the first direct evidence of a recent volcanic eruption on the planet. By comparing radar images of Magellan over time, the authors of the 2023 study detected changes caused by the outflow of molten rock from Venus’ subsurface filling the vent crater and spilling onto its slopes.

Scientists study active volcanoes to understand how a planet’s interior can shape its crust, direct its evolution and affect its habitability. The discovery of the recent volcano on Venus provides valuable insight into the planet’s history and why it took a different evolutionary path than Earth.

NASA’s Magellan spacecraft

Radar Backscatter

For the new study, published in the journal Nature Astronomy, the researchers also focused on archival data from the Magellan radar. The radio waves sent by the radar traveled through Venus’ thick cloud cover, then bounced off the planet’s surface and back to the spacecraft. These reflected radar signals, called backscatter, carried information about the rock surface material they encountered.

The two sites studied were the Sif Mons volcano in Eistla Regio and the western part of Niobe Planitia, which hosts many volcanic features. Analyzing backscatter data taken from both sites in 1990 and again in 1992, the researchers found that the radar signal strength increased along certain paths during later orbits. These changes indicate the formation of new rock, likely solidified lava from volcanic activity that occurred during this biennial. But they also looked at other possibilities, such as the presence of small dunes (formed by wind-blown sand) or atmospheric phenomena that could affect the radar signal.

To confirm the existence of new rock, the researchers analyzed Magellan’s altimetry (surface height) data to determine the slope of the topography and identify obstacles around which the lava would flow.

“We interpret these signals as flows along slopes or volcanic plains that can deviate around obstacles such as fluid-like shield volcanoes,” said one of the study’s authors, Marco Mastrogiuseppe of Sapienza University of Rome. “After ruling out other possibilities, we confirmed that our best interpretation is that these are new lava flows.”

Using Earth flows as a comparison, the researchers estimate that the new rock placed at both sites averages between 10 and 66 feet (3 and 20 meters) deep. They also estimate that the Sif Mons eruption produced about 12 square miles (30 square kilometers) of rock—enough to fill at least 36,000 Olympic-sized swimming pools. The Niobe Planitia eruption produced about 17 square miles (45 square kilometers) of rock, which would fill 54,000 Olympic-size swimming pools. By comparison, the 2022 eruption of Mauna Loa in Hawaii, Earth’s largest active volcano, produced a lava flow with enough material to fill 100,000 Olympic-size swimming pools.

Scott Hensley, a senior researcher at JPL and one of the authors of the 2023 study said, “This result, combined with the previous discovery of present-day geological activity, increases excitement in the planetary science community for future missions to Venus.”

VERITAS mission in the footsteps of Magellan

NASA’s VERITAS mission was selected in 2021 as part of NASA’s Discovery program. Hensley is the project scientist for NASA’s upcoming VERITAS mission, and Mastrogiuseppe is a member of its science team. VERITAS is due to launch early next decade, using a state-of-the-art radar to create 3D global maps and a near-infrared spectrometer to understand what Venus’ surface is made of while also monitoring volcanic activity. In addition, the spacecraft will measure the planet’s gravitational field to determine its internal structure.

“These new discoveries of recent volcanic activity on Venus by our international colleagues provide compelling evidence for the kinds of areas to target with VERITAS when it arrives at Venus,” said Suzanne Smrekar, JPL senior scientist and principal investigator for the VERITAS. “Our spacecraft will have a series of approaches to detect surface changes that are much more comprehensive and of higher resolution than the Magellan images. Evidence of activity, even in the lower-resolution Magellan data, raises the possibility of revolutionizing our understanding of this enigmatic world.”