Volcanic activity on Venus revealed by Magellan images

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When scientists recently took a closer look at archival images of the surface of Venus, they discovered something new: evidence of volcanic activity on Earth’s “twin.”

NASA’s Magellan spacecraft captured the images in the early 1990s as it orbited our nearest planetary neighbor, which is similar in size and composition to Earth.

A new analysis of the orbital perspective in a region near Venus’ equator reveals a volcanic vent that changed shape and greatly increased in size over eight months.

The images of the opening represent the first direct geological evidence of recent volcanic activity on the surface of Venus, according to the researchers. A study detailing the findings was published Wednesday in the journal Science and presented at the 54th Lunar and Planetary Science Conference in The Woodlands, Texas.

The Magellan mission became the first to image the entire surface of Venus before the spacecraft deliberately plunged into the planet’s hot, toxic atmosphere in 1994 to collect a final data set. However, a fleet of new missions will be headed to Venus within a decade, including the VERITAS, Venus Emissivity, Radio Science, InSAR, Topography, And Spectroscopy missions.

The orbiter will use its instruments to uncover the secrets behind why a planet similar in size to Earth was covered in volcanic plains and topped with an inhospitable atmosphere.

“NASA’s selection of the VERITAS mission inspired me to look for recent volcanic activity in the Magellan data,” study lead author Robert Herrick, a research professor at the University of Alaska Fairbanks and a member of the VERITAS science team, said in a statement.

“I didn’t really expect to be successful, but after about 200 hours of manually comparing images of different Magellan orbits, I saw two images of the same area eight months apart, showing telltale geological changes caused by an eruption.”

Herrick spotted the changes in images of the Atla Regio, a vast mountainous region that is home to two of Venus’ largest volcanoes, called Ozza Mons and Maat Mons. Both are similar to Earth’s largest volcanoes, but because they have lower slopes, Venus’ two volcanoes are more spread out, Herrick said.

A map shows the area examined for volcanic activity that occurred over an eight-month period during the Magellan mission.

He observed that a vent on the north side of a dome volcano that was part of Maat Mons changed between February and October 1991.

Magellan’s image of the vent from February showed a circular hole spanning less than 1 square mile (2.2 square kilometers) with steep interior sides and areas of drained lava on the slopes.

Eight months later, the spacecraft captured another image showing a drastically different hole that appeared misshapen, had nearly doubled in size, and was filled almost to the brim with a lava lake.

Although the differences sound obvious, both images were taken from opposite angles and perspectives and at a much lower resolution than images taken by cameras on the spacecraft today.

Altitude data (left) and images taken by Magellan of the crater (right) depict volcanic activity on Venus.

Herrick worked with Scott Hensley, a project scientist for VERITAS at NASA’s Jet Propulsion Laboratory in Pasadena, California, to create computer models of the venting to determine what might have caused the changes.

“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,” Hensley said. “Although this is only one data point for an entire planet, it confirms that there is modern geologic activity.”

Researchers believe the lava flow seen by Magellan in 1991 was similar to that released by the 2018 Kilauea eruption in Hawaii.

“This was a needle in a haystack investigation with no guarantee that the needle is there,” Herrick said. “Finding a change that could clearly be confirmed as real was absolutely a surprise. We were pretty sure that Venus is volcanically active, but we didn’t know if eruptions happen every few months, years, once every 10,000 years or more. All options could match the existing data. Unless we’ve been incredibly lucky, we now know that the frequency is every few months or so, similar to Earth’s family of large basaltic intraplate volcanoes such as Hawaii, the Galapagos Islands, the Canary Islands, etc.”

A 3D computer-generated image of Maat Mons shows how the volcano and lava flows stretch for hundreds of kilometers across the fractured plains.

While it is possible that an earthquake could have caused the walls of the volcanic vent to collapse, researchers believe that such activity would also have caused a volcanic eruption.

Volcanoes act as windows into a planet’s interior, allowing scientists to understand more about the factors that affect its ability to be a habitable world. Missions like VERITAS will help scientists better understand Venus, just as Magellan did decades ago.

The new mission will be equipped with radar to create global 3D maps of Venus and record details about its surface composition, gravitational field and what unfolded in the planet’s past.

“Venus is an enigmatic world, and Magellan teased out so many possibilities,” Jennifer Whitten, VERITAS deputy principal investigator and assistant professor of Earth and environmental sciences at Tulane University in New Orleans, said in a statement. “Now that we’re pretty sure the planet experienced a volcanic eruption just 30 years ago, this is just a small preview of the incredible discoveries VERITAS will make.”

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