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マート モンス ビーナス火山

マート モンスは、金星の表面のこのコンピュータ生成された 3 次元遠近法で表示されます。 視点は、マート モンスの北 634 キロメートル (393 マイル)、地上 3 キロメートル (2 マイル) の高さにあります。 溶岩流は、前景に示されている破砕された平野を横切って、マート モンスのふもとまで数百キロメートルにわたって伸びています。 NASA マゼラン ミッションの合成開口レーダー データをレーダー高度計と組み合わせて、表面の 3 次元マップを作成します。 このパースペクティブの垂直スケールは 10 倍に誇張されています。 クレジット: NASA/JPL


新しい研究は、火山活動の強力な証拠を提供します[{” attribute=””>Venus. The study identified a nearly 1-square-mile volcanic vent that changed shape and grew over eight months in 1991. Such changes on Earth are associated with volcanic activity, either through eruptions or magma movement causing vent walls to collapse and expand. This discovery offers insights into the geology of Venus, Earth’s sister planet, which, despite being similar in size and mass, lacks plate tectonics.

Venus appears to have volcanic activity, according to a new research paper that offers strong evidence to answer the lingering question about whether Earth’s sister planet currently has eruptions and lava flows. Although planets are not considered “alive” in the biological sense, scientists refer to a planet as “alive” when it is geologically active. A geologically active planet may have a dynamic core, volcanic activity, or tectonic movement. Scientists used to think Venus was geologically dead, but this new research is strong evidence that it is still geologically active.

Venus, although similar to Earth in size and mass, differs markedly in that it does not have plate tectonics. The boundaries of Earth’s moving surface plates are the primary locations of volcanic activity.

New research by University of Alaska Fairbanks Geophysical Institute research professor Robert Herrick revealed a nearly 1-square-mile volcanic vent that changed in shape and grew over eight months in 1991. Changes on such a scale on Earth are associated with volcanic activity, whether through an eruption at the vent or movement of magma beneath the vent that causes the vent walls to collapse and the vent to expand.

The research was published recently in the journal Science.

Venus Global View Magellan Mapping Annotated

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. Credit: NASA/JPL-Caltech

Herrick studied images taken in the early 1990s during the first two imaging cycles of NASA’s Magellan space probe. Until recently, comparing digital images to find new lava flows took too much time, the paper notes. As a result, few scientists have searched Magellan data for feature formation.

“It is really only in the last decade or so that the Magellan data has been available at full resolution, mosaicked and easily manipulable by an investigator with a typical personal workstation,” Herrick said.

The new research focused on an area containing two of Venus’ largest volcanoes, Ozza and Maat Mons. 

“Ozza and Maat Mons are comparable in volume to Earth’s largest volcanoes but have lower slopes and thus are more spread out,” Herrick said.

Maat Mons contains the expanded vent that indicates volcanic activity.

Venus Maat Mons 3D Perspective View

This image is a colored 3D perspective view of Venus’ Maat Mons. Credit: David P. Anderson, SMU/NASA science photo library

Herrick compared a Magellan image from mid-February 1991 with a mid-October 1991 image and noticed a change to a vent on the north side of a domed shield volcano that is part of the Maat Mons volcano.

The vent had grown from a circular formation of just under 1 square mile to an irregular shape of about 1.5 square miles.

The later image indicates that the vent’s walls became shorter, perhaps only a few hundred feet high, and that the vent was nearly filled to its rim. The researchers speculate that a lava lake formed in the vent during the eight months between the images, though whether the contents were liquid or cooled and solidified isn’t known.

Evidence That Venus Is Volcanically Active

The panels show the east-looking first (A) and west-looking second (B) images of the vent. Credit: Science, DOI: 10.1126/science.abm7735

The researchers offer one caveat: a nonvolcanic, earthquake-triggered collapse of the vent’s walls might have caused the expansion. They note, however, that vent collapses of this scale on Earth’s volcanoes have always been accompanied by nearby volcanic eruptions; magma withdraws from beneath the vent because it is going somewhere else.  

The surface of Venus is geologically young, especially compared to all the other rocky bodies except Earth and Jupiter’s moon Io, Herrick said.

“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.

Robert Herrick

Research professor Robert Herrick. Credit: UAF/GI photo by JR Ancheta

Herrick contrasts the lack of information about Venusian volcanism with what is known about Jupiter’s moon Io and about Mars.

“Io is so active that multiple ongoing eruptions have been imaged every time we’ve observed it,” he said.

On a geological time scale, relatively young lava flows indicate Mars remains volcanically active, Herrick said.

 “However, nothing has occurred in the 45 years that we have been observing Mars, and most scientists would say that you’d probably need to watch the surface for a few million years to have a reasonable chance of seeing a new lava flow,” he said.

Herrick’s research adds Venus to the small pool of volcanically active bodies in our solar system.

“We can now say that Venus is presently volcanically active in the sense that there are at least a few eruptions per year,” he said. “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.”

For more on this research:

Reference: “Surface changes observed on a Venusian volcano during the Magellan mission” by Robert R. Herrick and Scott Hensley, 15 March 2023, Science.
DOI: 10.1126/science.abm7735

Co-author Scott Hensley of NASA’s Jet Propulsion Laboratory performed the modeling for the research.

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