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 about the same size as Earth took a very different path, developing 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 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 exhibiting telltale 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 Atla Regio, a vast highland region near Venus' equator that hosts 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 scrutinizing 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 nearly circular, covering an area of less than 1 square mile (2.2 square kilometers). It had steep interior sides and showed signs of drained lava down its exterior slopes, factors that hinted at activity. In radar images captured eight months later, the same vent had doubled in size and become misshapen. It also appeared to be filled to the rim with a lava lake.

But because the two observations were from opposite viewing angles, they had different perspectives, which made 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, the project scientist for VERITAS and a specialist in analyzing radar data like Magellan's. The two researchers created computer models of the vent in various configurations to test different geological-event scenarios, such as landslides. From those models, they concluded that only an eruption could have caused the change.

"Only a couple of the simulations matched the imagery, and the most likely scenario is that volcanic activity occurred on Venus' surface during Magellan's mission," said Hensley. "While this is just one data point for an entire planet, it confirms there is modern geological activity."

The scientists liken the size of the lava flow generated by the Maat Mons activity to the 2018 Kilauea eruption 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 trove of radar imagery, which transformed humanity's knowledge of Venus.

"Venus is an enigmatic world, and Magellan teased so many possibilities," said Jennifer Whitten, associate deputy principal investigator of VERITAS at Tulane University in New Orleans. "Now that we're very sure the planet experienced a volcanic eruption only 30 years ago, this is a small preview for 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 figure 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 offer clues about the planet's past and present geologic processes.

And whereas Magellan's data was originally cumbersome to study - Herrick said that in the 1990s they relied on boxes of CDs of Venus data that were compiled by NASA and delivered in the mail - VERITAS' data will be available online to the science community. That will enable researchers to apply cutting-edge techniques, such as machine learning, to analyze the planet and help reveal its innermost secrets.

Those studies will be complemented by EnVision, an ESA (European Space Agency) mission to Venus slated for 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 the one VERITAS will carry. Both Hensley and Herrick are key members of the VenSAR science team.

VERITAS and NASA's Deep Atmosphere Venus Investigation of Noble gases, Chemistry, and Imaging (DAVINCI) mission were selected in 2021 under NASA's Discovery Program as the agency's next missions to Venus. VERITAS partners include Lockheed Martin Space, the Italian Space Agency, the German Aerospace Center, and Centre National d'Etudes Spatiales in France. The Discovery Program is managed by the Planetary Missions Program Office at NASA's Marshall Space Flight Center in Huntsville, Alabama, for the Planetary Science Division of NASA's Science Mission Directorate in Washington.

Full Image Caption: Maat Mons is displayed in this computer generated three-dimensional perspective of the surface of Venus. The viewpoint is located 634 kilometers (393 miles) north of Maat Mons at an elevation of 3 kilometers (2 miles) above the terrain. Lava flows extend for hundreds of kilometers across the fractured plains shown in the foreground, to the base of Maat Mons.

The view is to the south with the volcano Maat Mons appearing at the center of the image on the horizon and rising to almost 5 kilometers (3 miles) above the surrounding terrain. Maat Mons is located at approximately 0.9 degrees north latitude, 194.5 degrees east longitude with a peak that ascends to 8 kilometers (5 miles) above the mean surface.

Maat Mons is named for an Egyptian Goddess of truth and justice. Magellan synthetic aperture radar data is combined with radar altimetry to develop a three-dimensional map of the surface. The vertical scale in this perspective has been exaggerated 10 times. Rays cast in a computer intersect the surface to crate a three-dimensional perspective view. Simulated color and a digital elevation map developed by the U.S. Geological Survey are used to enhance small-scale structure.

The simulated hues are based on color images recorded by the Soviet Venera 13 and 14 spacecraft. The image was produced by the Solar System Visualization project and the Magellan Science team at the JPL Multimission Image Processing Laboratory and is a single frame from a video released at the April 22, 1992 news conference.

Related Links
Venus Emissivity, Radio science, InSAR, Topography, And Spectroscopy VERITAS
Magellan mission
Venus Express News and Venusian Science