Active Volcanoes on Venus?

I remember back in the early days of science fiction, writers thought that our sister planet Venus might be a swamp world filled with life. If you’re a Heinlein fan, for example, you might have read “Between Planets”, which took place on a very watery planet populated with aliens, including a Venerian dragon. That was the state of public views of the planet until the Space Age. The public didn’t expect to find anything different, much less surface features such as alien-looking volcanoes on Venus.

That watery depiction of the planet went away when the first spacecraft actually got to Venus in the 1960s. They showed us what scientists had long suspected: that the planet is a cloud-covered desert and a not-very-hospitable place. It’s so hot there that probably nothing can live on the surface. Even if life existed there, the sulfuric acid rain and incredible atmospheric pressure would play havoc with it.

In the 1990s, Magellan gave us high-resolution radar views of the surface. They provided tantalizing visual evidence of volcanoes and other features on the Venerian landscape. But, were those volcanoes still active? Or dormant?

Venus Volcanoes: The Debate vs. Data

These and other questions are still being debated. Scientists continue to sift through data from Magellan and other missions to figure out if Venus has live volcanoes. Recent studies show that the volcanoes could still be active. Some flows may only be a few years old. If so, that means Venus is the only other planet in the solar system with active volcanoes. The bigger news is that Venerian activity could give scientists insight into the interiors of the terrestrial planets. We already know something about our own world’s interior and are learning about Mars. But, Venus has remained quite mysterious.

How to figure out if Venus’s volcanoes are still active? Study the flows. In particular, look at their appearance. On Earth, that’s easy. but, Venus is a different proposition. So, a group of scientists from the Universities Space Research Association (USRA), led by Dr. Justin Filiberto of the Lunar and Planetary Institute (LPI), focused on something called the “alteration rate” of fresh lava. That is what happens to lava flows when they get to a planet’s surface.

What Changes Lava

Here on Earth, when lava emerges, it immediately cools. It can get rained on (or flow into ocean), which changes it. The minerals in the lava also can be altered by interactions with the atmosphere. In the field, geologists can tell roughly how old a flow is by how it has been altered after it cools. For example, a fresh pahoehoe flow has a somewhat shiny, crinkly surface. That thin crystalline “overlay” can be shattered by a rainstorm or when someone walks over it (after cooling).

Other changes can “weather” the lava, too, and there’s a distinct difference in appearance between new and older flows. If you study it with various instruments, you can also find other changes. The big question facing the research team was how the flows on Venus would be altered. And, how long would it take for them to change?

Venus and the Altered Flows

Dr. Filiberto’s team used data from the Magellan mission as well as the European Space Agency’s Venus Express orbiter to study Venus lava flows. They looked at infrared light emitted from the surface at night. The resulting data showed them what “fresh” flows looked like on Venus versus older, weathered flows.

The team also constructed an experiment in the lab that mimicked Venus’s corrosive and hot atmosphere, to see what happens to lava flows when they come into contact with it. At least one mineral, called olivine, reacts with such an atmosphere pretty quickly. After a relatively short period of time (a few weeks at most), the olivine gets coated with oxides such as magnetite and hematite. On Venus, such a change would take just a few years.

So, flows on Venus that are rich in olivine that is coated with oxides may to answer the question: when did volcanoes on Venus erupt last? If they’re pretty recent, then it means that Venus has activity volcanoes spewing lava on to its surface. Judging by the visual evidence given by Magellan and other spacecraft, I’d say that’s a foregone conclusion. BUT, in science, we have to nail down everything with facts and data. That’s the value of the USRA study, and it gives new insight into the interior of our “sister” planet Venus.

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