In a first, scientists have seen direct evidence of active volcanism on Earth’s twin, setting the stage for the agency’s VERITAS mission to investigate.
Direct geological evidence of recent volcanic activity has been observed on the surface of Venus for the first time. Scientists made the discovery after examining 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 changed shape and grew significantly in size in less than a year.
Venus is sometimes called Earth’s “evil twin” because its surface, despite being similar in size and composition to Earth, is incredibly hostile, with a thick atmosphere of carbon dioxide and clouds of sulfuric acid acid. The extreme greenhouse effect on Venus has caused its surface temperature to rise to over 900 degrees Fahrenheit (475 degrees Celsius), hot enough to melt lead. In contrast, Earth has a much milder climate and is much more hospitable to life as we know it. Therefore, Venus is often seen as Earth’s “evil twin” because it presents a sharp contrast to our planet’s relatively benign conditions.
Scientists study active volcanoes to understand how a planet’s interior can shape its crust, drive its evolution, and affect its habitability. One of NASA’s new missions to Venus will do just that. Led by the agency’s Jet Propulsion Laboratory in Southern California, VERITAS — short for Venus Emissivity, Radio science, InSAR, Topography, And Spectroscopy — will launch within a decade. The orbiter will study Venus from surface to core to understand how a rocky planet the size of 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 member of the VERITAS science team who led the search of the archival data. “I didn’t really expect to be successful, but after about 200 hours of manually comparing the images of different Magellan orbits, I saw two images of the same region taken eight months apart that showed clear geological changes caused by an eruption.”
The search and its conclusions are described in a new study published in the journal Science. Herrick also presented the findings at the 54th Lunar and Planetary Science Conference in The Woodlands, Texas, on March 15.
Modeling a volcano
The geological changes Herrick found occurred in the Atla Regio, a large highland area near Venus’ equator that houses two of the planet’s largest volcanoes, Ozza Mons and Maat Mons. The region has long been thought to be volcanically active, but there was no direct evidence of recent activity. While examining Magellan radar images, Herrick identified a volcanic vent associated with Maat Mons that changed significantly between February and October 1991.
In the February image, the vent appeared almost circular, covering an area of less than 1 square kilometer (2.2 square miles). It had steep interior sides and showed evidence of drained lava down its outer slopes, factors that suggested activity. On radar images taken eight months later, the same vent had doubled in size and was misshapen. It also appeared to be filled to the brim with a lava lake.
However, because the two observations were from opposite viewpoints, they had different perspectives, making them difficult to compare. The low resolution of the three-decade-old data only made the work more complicated.
Herrick teamed up with JPL‘s Scott Hensley, project scientist for VERITAS and specialist in analyzing radar data like Magellan’s. The two researchers created computer models of the vent in different configurations to test different geological event scenarios, such as landslides. From these models, they concluded that only an eruption could have caused the change.
“Only a few 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,” Hensley said. “Although this is only one data point for an entire planet, it confirms that there is modern geologic activity.”
The researchers compare the size of the lava flow generated by the Maat Mons activity to the 2018 Kilauea eruption on the Big Island of Hawaii.
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 array of radar images, which transformed humanity’s knowledge of Venus.
“Venus is an enigmatic world, and Magellan teased out so many possibilities,” said Jennifer Whitten, associate deputy principal investigator for VERITAS at Tulane University in New Orleans. “Now that we are very certain that the planet experienced a volcanic eruption just 30 years ago, this is a small taste 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 spacecraft will also measure the planet’s gravitational field to determine the structure of Venus’ interior. Together, the instruments will provide clues about the planet’s past and present geological processes.
And while Magellan’s data was initially difficult to study — Herrick said in the 1990s they relied on boxes of Venus data CDs compiled by NASA and delivered by mail — VERITAS’ data will be available online to the scientific community . This will enable the researchers to use ground-breaking techniques, such as machine learningto analyze the planet and help uncover its innermost secrets.
These studies will be complemented by EnVision, an ESA (The European Space Agency) mission to Venus planned for launch in the early 2030s. The spacecraft will carry its own synthetic aperture radar (called VenSAR), which is under development at JPL, as well as a spectrometer similar to what VERITAS will carry. Both Hensley and Herrick are key members of the VenSAR science team.
Reference: “Surface changes observed on a Venusian volcano during the Magellan mission” by Robert R. Herrick and Scott Hensley, 15 March 2023, Science.
More about the mission
In 2021, NASA selected the VERITAS and DAVINCI missions as their next venture to Venus under the Discovery program. VERITAS has collaborated with several organizations, including Lockheed Martin Space, the Italian Space Agency, the German Aerospace Center and France’s Center National d’Études Spatiales. The Planetary Missions Program Office at NASA’s Marshall Space Flight Center in Huntsville, Alabama, manages the Discovery Program for NASA’s Science Mission Directorate’s Planetary Science Division in Washington.