For the first time, direct geological evidence of recent volcanic activity has been observed on the surface of Venus. The discovery was made by two American researchers after analyzing radar images of Venus taken more than 30 years ago, in the 1990s, by NASA’s Magellan mission.
The results showed a volcanic chimney that changed shape and considerably increased in size in less than a year, as published in Science and reported this week on 54th Lunar and Planetary Science Conference.
“I really didn’t expect to be successful, but after about 200 hours of manually comparing images from different Magellanic orbits, I saw two images of the same region taken eight months apart that showed telltale geological changes caused by an eruption,” he says. One of the authors, Robert Herrick, a professor at the University of Alaska Fairbanks, who led the search for archival data.
Two images of the same region (Maat Mons volcano on Venus) taken eight months apart in 1991 showed telltale geological changes caused by an eruption.
Robert Herrick (University of Alaska Fairbanks)
The geological changes discovered took place in Atla Regio, a vast mountainous region near Venus’ equator that is home to two of the planet’s largest volcanoes, Ozza Mons and Maat Mons. This area was long thought to be volcanically active, but there was no direct evidence of recent activity.
Examining the data, Herrick identified a volcanic vent associated with Maat Mons that changed significantly between February and October 1991. In February, the vent appeared nearly circular, covering an area of less than 2.2 km2. It had steep inner sides and showed signs of lava running down the outer slopes, factors that indicated activity.
Computer-simulated global map of the surface of Venus made using data from NASA’s Magellan and Pioneer Venus Orbiter missions. Maat Mons, the volcano that showed signs of a recent eruption, lies within the black square near the planet’s equator. / NASA/JPL-Caltech
Radar images taken eight months later showed that the same chimney had doubled in size and deformed. It also appeared to be filled to the brim with a lava lake.
A volcanic vent was observed to double in size and deform
But because the two observations were made from opposite viewing angles, they had different perspectives, making comparison difficult. In addition, the low resolution of data from three decades ago further complicated the work.
Modeling of a volcano
Herrick then collaborated with fellow author Scott Hensley of NASA’s JPL laboratory. The two created computer models of the opening in different settings to test different geological scenarios, such as landslides. From these models, they concluded that only an eruption could have caused the change.
Scientists compare the size of the lava flow generated by Maat Mons activity to the 2018 Kilauea volcano eruption on the Big Island of Hawaii
“Only some of the simulations matched the images, and the most likely scenario is that volcanic activity occurred on the surface of Venus during the Magellan mission,” explains Hensley, “even if it’s just a point relative to an entire planet, it confirms that there is modern geological activity”.
Scientists compare the size of the lava flow generated by Maat Mons activity to the 2018 Kilauea volcano eruption on the Big Island of Hawaii.
VERITAS’ future mission
The two authors are part of the mission team TRUE from NASA, which will launch within a decade to precisely study Venus’ active volcanoes and understand how their interiors can shape its crust, drive its evolution, and affect habitability.
An orbiter will study it from surface to core to see how a rocky planet the same size as Earth took a very different path, becoming a world covered in volcanic plains and warped terrain hidden under a thick, hot and toxic atmosphere.
“Venus is an enigmatic world and Magellan has offered us many possibilities,” says Jennifer Whitten, a VERITAS researcher at Tulane University in New Orleans, who adds, “We are now pretty sure that the planet experienced a volcanic eruption just 30 years ago, a little preview of the incredible discoveries that VERITAS will make.”
Within a decade, NASA’s VERITAS and ESA’s EnVision missions are scheduled to study Venus up close.
This mission will use state-of-the-art synthetic aperture radar to create 3D global maps and a near-infrared spectrometer to discover what the surface is made of. The spacecraft will also measure the planet’s gravitational field to determine the structure of Venus’ interior. Together, the instruments will offer clues about the planet’s past and present geological processes.
While the Magellan data was initially tricky to study (in the 1990s it relied on CD boxes of Venus data collected by NASA and sent in the mail), the VERITAS data will be available online to the scientific community. This will allow researchers to apply modern techniques like machine learning to analyze them.
These studies will be complemented by those of the mission InVision of the European Space Agency (ESA), scheduled to launch to Venus in the early 2030s. The spacecraft will carry its own synthetic aperture radar, which is also being developed at JPL, in addition to a spectrometer similar to that of VERITAS. The two missions will help unlock the innermost secrets of Earth’s volcanic twin.
Robert Herrick and Scott Hensley. “Surface changes observed on a Venusian volcano during the Magellan mission”. Science2023.