posted 03-15-2023 06:29 PM               

NASA's Magellan Data Reveals Volcanic Activity on Venus

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 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 changing shape and increasing significantly in size in less than a year.

Above: This computer-generated 3D model of Venus' surface shows the summit of Maat Mons, the volcano that is exhibiting signs of activity. A new study found one of Maat Mons' vents became enlarged and changed shape over an eight-month period in 1991, indicating an eruptive event occurred. (NASA/JPL-Caltech)

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.

Above: Altitude data for the Maat and Ozza Mons region on the Venus surface is shown at left, with the area of study indicated by the black box. At right are the before (A) and after (B) Magellan observations of the expanded vent on Maat Mons, with possible new lava flows after an eruptive event. (Robert Herrick/UAF)

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.

Above: This annotated, computer-simulated global map of Venus' surface is assembled from data from NASA's Magellan and Pioneer Venus Orbiter missions. Maat Mons, the volcano that has exhibited signs of a recent eruption, is within the black square near the planet's equator. (NASA/JPL-Caltech)

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.