Evidence of volcanic activity on Venus confirmed for first time

By Stephen Beech

Evidence of volcanic activity on Venus has been confirmed for the first time.

An empty lava tube beneath the planet’s surface has been identified by analyzing radar data collected by NASA’s Magellan mission over 30 years ago.

It was known that volcanic activity is not unique to Earth as traces - such as lava tubes - have previously been found on Mars and the Moon.

Now a study by Italian scientists, published in the journal Nature Communications, has demonstrated the existence of an empty lava tube in the depths of Venus.

Research co-ordinator Professor Lorenzo Bruzzone said: "Our knowledge of Venus is still limited, and until now we have never had the opportunity to directly observe processes occurring beneath the surface of Earth’s twin planet.

"The identification of a volcanic cavity is therefore of particular importance, as it allows us to validate theories that for many years have only hypothesized their existence.

"This discovery contributes to a deeper understanding of the processes that have shaped Venus’s evolution and opens new perspectives for the study of the planet."

He explained that finding lava tubes outside the Earth is not easy as they form underground, and the caves usually remain hidden.

They can only be spotted when part of their roof collapses, creating a pit visible on the planet’s surface.

Bruzzone, of the University of Trento, says the collapses may reveal both the presence of a lava tube and a possible entrance to it.

But the search on Venus is even more challenging as the planet is covered by thick clouds that block direct views of the surface with standard cameras, forcing scientists to rely on radar images.

Between 1990 and 1992, a Synthetic Aperture Radar, an instrument aboard NASA's Magellan spacecraft, mapped the surface of Venus.

Bruzzone said: "We analyzed Magellan's radar images where there are signs of localized surface collapses using an imaging technique that we have developed to detect and characterize underground conduits near skylights.

"Our analysis revealed the existence of a large subsurface conduit in the region of Nyx Mons, the area named after the Greek goddess of the night.

"We interpret the structure as a possible lava tube, with an estimated diameter of approximately one kilometre, a roof thickness of at least 150 metres and an empty void deep of no less than 375 metres."

He says the physical and atmospheric parameters of Venus could favor the formation of lava tubes as the planet has a lower gravity and a denser atmosphere than Earth, which would favor the rapid creation of a thick insulating crust immediately after the lava flow leaves the vent.

Bruzzone said the lava tube that has been identified appears to be wider and taller than those seen on Earth or predicted for Mars.

It falls at the upper end of what scientists have suggested - and in one case actually observed - on the Moon.

Bruzzone says that is not surprising, since Venus has lava channels that are larger and longer than those observed on other planets.

He said: "The available data allow us to confirm and measure only the portion of the cavity close to the skylight.

"However, analysis of the morphology and elevation of the surrounding terrain, together with the presence of other pits similar with the one studied, supports the hypothesis that the subsurface conduits may extend for at least 45 kilometres.

"To test this hypothesis and identify additional lava tubes, new higher-resolution images and data acquired by radar systems capable of penetrating the surface will be required.

"The results of this study are therefore very important for future missions to Venus, such as the European Space Agency’s Envision and NASA’s Veritas.

"Both spacecraft will carry advanced radar systems capable of capturing higher-resolution images, allowing scientists to study small surface pits in greater detail.

"In addition, Envision will carry an orbital ground penetrating radar capable of probing Venus’s subsurface to depths of several hundred metres and potentially detecting conduits even in the absence of surface openings."

Bruzzone added: "Our discovery therefore represents only the beginning of a long and fascinating research activity."