Venus is erupting - these radar images over 30 years old may prove it

A new study adds Venus to the small pool of volcanically-active bodies in our solar system.
Sade Agard

Scientists have discovered evidence they interpret as ongoing volcanism on the surface of Venus, according to a new analysis of radar images from the Magellan spacecraft published in Science on March 15.

The findings showed that over eight months in 1991, a volcanic vent of over one square mile changed shape and grew. Significantly, the research adds Venus to the small pool of volcanically-active bodies in our solar system.

What are Venus' active volcanoes?

Similar changes occur on Earth due to volcanic activity, whether it be an eruption at the vent or magma migration that expands the vent and causes its walls to collapse.

The University of Alaska's Robert Herrick and colleagues examined images obtained by NASA's Magellan space probe during its first two imaging cycles in the early 1990s.

The paper emphasizes that until recently, it took too much time to compare digital images to discover new lava flows. Therefore, scientists had yet to look for feature formation in Magellan data.

In this most recent investigation, the scientists concentrated on a region that includes the two largest volcanoes on Venus: Ozza and Maat Mons. Herrick noted a change to a vent on the north side of a domed shield volcano that is a component of the Maat Mons volcano when he compared a Magellan image from mid-February 1991 with one from mid-October 1991.

Venus is erupting - these radar images over 30 years old may prove it
Maat Mons: Magellan synthetic aperture radar data is combined with radar altimetry to develop this 3D image

The vent had expanded from about 1 square mile circular configuration to a roughly 1.5 square miles irregular shape. The later photograph revealed that the vent was almost filled and that its walls had shrunk to barely a few hundred feet high.

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While it is unknown if the contents were liquid or cooled, and solidified during the eight months between the photographs, the researchers hypothesize that a lava lake formed in the vent.

Though, one alternative explanation is proposed by the researchers: it's possible that the enlargement was brought on by a nonvolcanic, earthquake-triggered collapse of the vent's walls.

That said, the team also reasons that nearby volcanic eruptions have always accompanied such large-scale vent collapses that have occurred on Earth. This happens as magma retreats from beneath the vent and moves to another location.

Venus' surface is geologically young, particularly compared to all other rocky bodies aside from Earth and Jupiter's moon Io, Herrick highlighted.

"However, the estimates of how often eruptions might occur on Venus have been speculative, ranging from several large eruptions per year to one such eruption every several or even tens of years," he said in a press release.

"We can expect that the upcoming Venus missions will observe new volcanic flows that have occurred since the Magellan mission ended three decades ago, and we should see some activity occurring while the two upcoming orbital missions are collecting images."

The full study was published in Science on March 15 and can be found here.

Study abstract:

Venus has a geologically young surface, but it is unknown whether it has ongoing active volcanism. From 1990 to 1992, the Magellan spacecraft imaged the planet’s surface using synthetic aperture radar. We examined volcanic areas on Venus that were imaged two or three times by Magellan. We identify a ~2.2 km2 volcanic vent that changed shape in the eight months between two radar images. Additional volcanic flows downhill from the vent are visible in the second epoch images, though we cannot rule out that they were present but invisible in the first epoch due to differences in imaging geometry. We interpret these results as ongoing volcanic activity on Venus.

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