Direct geological evidence of recent volcanic activity has been observed on the surface of Venus for the first time. Scientists made the discovery after poring over archival radar images of Venus taken more than 30 years ago, in the 1990s, by NASA’s Magellan mission. The images revealed a volcanic vent that had changed shape and grown significantly in less than a year.
Scientists study active volcanoes to understand how a planet’s interior can shape its crust, control its evolution, and affect its habitability. One of NASA’s new missions to Venus will do just that. VERITAS short for Venus Emissivity, Radio science, InSAR, Topography, And Spectroscopy — led by the agency’s Jet Propulsion Laboratory in Southern California will launch within a decade.
The orbiter will study Venus from the surface to the core to understand how a rocky planet the same size as Earth took a very different path and evolved into a world covered in volcanic plains and deformed terrain hidden beneath a thick, hot, toxic atmosphere.
“NASA’s selection of the VERITAS mission inspired me to look for recent volcanic activity in the Magellan data,” said Robert Herrick, a research professor at the University of Alaska Fairbanks and a member of the VERITAS science team that led the archival data search. “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 area taken eight months apart that showed the telltale geological changes caused by the eruption.”
Modeling a volcano
The geological changes Herrick found took place in the Atla Regio, a vast highland region near the equator of Venus that hosts the planet’s two largest volcanoes, Ozza Mons and Maat Mons. The area has long been thought to be volcanically active, but there is no direct evidence of recent activity. Examining Magellan radar images, Herrick identified a volcanic vent associated with Maat Mons that had changed significantly between February and October 1991.
In the February image, the vent appeared to be nearly circular and covered an area of ​​less than 1 square mile (2.2 square kilometers). It had steep inner sides and showed signs of lava flow down its outer slopes, factors that indicated activity. In radar images taken eight months later, the same vent was doubled and disfigured. It also appeared to be filled to the brim with a lava lake.
But since the two observations were from opposite viewing angles, they had different perspectives, making it difficult to compare them. The low resolution of the three-decade-old data only made the job more difficult.
Herrick teamed up with JPL’s Scott Hensley, a project scientist at VERITAS and a specialist in analyzing radar data like Magellan’s. The two researchers created computer models of the vents in different configurations to test different scenarios of geological events such as landslides. From these models, they concluded that only an eruption could have caused the change.
“Only a few simulations matched the images, and the most likely scenario is that volcanic activity occurred on the surface of Venus during the Magellan mission,” Hensley said. “Even though this is just one data point for the entire planet, it confirms that there is modern geologic activity.”
Scientists compare the size of the lava flow generated by Maat Mons activity to the 2018 eruption of Kilauea on the Big Island of Hawaii.
Magellan’s legacy
Herrick, Hensley and the rest of the VERITAS team are eager to see how the mission’s suite of advanced science instruments and high-resolution data will complement Magellan’s remarkable treasure trove of radar images that have transformed human knowledge of Venus.
“Venus is a mysterious world, and Magellan teased out so many possibilities,” said Jennifer Whitten, VERITAS deputy principal investigator at Tulane University in New Orleans. “Now that we know for sure that the planet experienced a volcanic eruption only 30 years ago, this is a small sample of the incredible discoveries VERITAS will make.”
VERITAS will use state-of-the-art synthetic aperture radar to create 3D global maps and a near-infrared spectrometer to find out what the surface is made of. The probe 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.
And while studying the Magellan data was initially cumbersome — Herrick said in the 1990s they relied on boxes of Venus data CDs compiled by NASA and delivered by mail — the VERITAS data will be available online to the scientific community. This will allow researchers to use cutting-edge techniques such as machine learning to analyze the planet and help uncover its innermost secrets.
These studies will complement EnVision, the ESA (European Space Agency) mission to Venus, which is scheduled to launch in the early 2030s. The spacecraft will carry its own synthetic aperture radar (called VenSAR), which is being developed at JPL, as well as a spectrometer similar to that carried by VERITAS. Both Hensley and Herrick are key members of the VenSAR science team.
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