Venus, erupting?

Beneath its dreary shroud of clouds, Venus could be positively hopping: Planetary geologists have spotted a lava flow they say is just decades old. If confirmed, it would be the youngest evidence for volcanism on Venus.

“The flow we studied seems to be very young — it is still warm inside,” says Nataliya Bondarenko, a planetary scientist at the University of California, Santa Cruz. She and her colleagues describe their findings in an upcoming issue of Geophysical Research Letters.

Researchers have long thought that Venus must be geologically active, since more than 1,000 volcanoes dot its surface. But scientists have struggled to gather definitive evidence that the planet is active today, like Earth, and not long dead, like Mars.

The new study builds on recent work suggesting that Venusian volcanoes are indeed a thing of the present.

Bondarenko’s team analyzed microwave data collected by NASA’s Magellan mission, which orbited Venus in the early 1990s. Microwave radiation indicates heat coming from the planet, such as a lava flow in the process of cooling.  

In the Bereghinia Planitia region in Venus’ northern hemisphere, the team found a flow that appeared up to 85 degrees Celsius hotter than expected. Had the flow been more than a century old, Bondarenko says, it would have cooled down enough that Magellan wouldn’t have spotted any excess heat.

The flow must have been at least 15 years old when detected by Magellan, she says, because the Pioneer Venus orbiter photographed it in 1978.

But there’s little other evidence supporting Bereghinia Planitia as recently volcanically active, says Suzanne Smrekar, a planetary geologist at the Jet Propulsion Laboratory in Pasadena, Calif.

In April, Smrekar and colleagues published a paper in Science describing lava flows from three regions in Venus’ southern hemisphere. All three were places known to be hot spots of geological activity, similar to Hawaii. Using data from the European Space Agency’s Venus Express mission, currently orbiting the second planet, Smrekar’s team found several flows that looked fresh. The flows’ unweathered appearance, compared with the surrounding landscape, suggests that they formed no more than 2.5 million years ago and probably in the past 250,000 years, the team concluded.

Because the Venus Express data come only from the southern hemisphere, they can’t say anything about whether Bereghinia Planitia is also active, Smrekar says. But any claim of a decades-old flow in the north “sort of falls into the ‘extraordinary claims require extraordinary proof’ category,” she says.

For their part, Bondarenko and her colleagues want to expand their research to look for other fresh flows on Venus.