When volcanoes turn metal

What would a volcano – and its lava flows – look like on a planetary body made mostly of metal? A pilot study from North Carolina State University provides insights into ferro-volcanism that could help scientists interpret landscape features on other worlds.

Volcanoes form when magma, which consists of the partially molten solids beneath a planet’s surface, erupts. On Earth, that magma is mostly molten rock, largely composed of silica. But not every planetary body is made of rock – some can be mainly ice-like or even metal.

“Cryovolcanism is volcanic activity on icy worlds, and we’ve seen it happen on Saturn’s moon Enceladus,” said Arianna Soldati, assistant professor of marine, terrestrial and atmospheric sciences at NC State and lead author of an article describing the work. “But ferrovolcanism, volcanic activity on metal worlds, has not yet been observed.”

Enter 16 Psyche, a 140-mile diameter asteroid in the asteroid belt between Mars and Jupiter. According to infrared and radar observations, the surface consists mainly of iron and nickel. Psyche is the subject of an upcoming NASA mission, and the asteroid inspired Soldati to think about what volcanic activity might look like on a metallic world.

“When we look at images of worlds that are different from ours, we still use what is happening on Earth – such as evidence of volcanic eruptions – to interpret them,” Soldati says. “However, we don’t have widespread metallic volcanism on Earth, so we have to imagine what those volcanic processes might look like on other worlds so we can interpret images correctly.”

Soldati defines two possible types of ferro-volcanism: Type 1, or pure ferro-volcanism, which occurs on all-metal bodies; and Type 2, spurious ferrovulcanism, occurring on hybrid rocky metal bodies.

In a pilot study, Soldati and colleagues from the Syracuse Lava Project produced Type 2 ferrovolcanism, in which metal separates from rock as magma forms.

“The Lava Project furnace is configured for rock melting, so we worked with the metals (mainly iron) that naturally occur in it,” Soldati said. “When you melt rock under the extreme conditions of the furnace, some of the iron will separate out and sink to the bottom because it is heavier. with the stone. “

The metal lava flows traveled 10 times faster and spread thinner than the rock flows, breaking into a large number of braided channels. The metal also largely traveled under the rock stream and emerged from the leading edge of the rocky lava.

The smooth, thin, braided, widespread layers of metallic lava would leave a very different impression on a planet’s surface than the often thick, rough, rocky streams we find on Earth, according to Soldati.

“While this is a pilot project, there are still some things we can say,” Soldati says. “If there were volcanoes on Psyche 16 – or on any other metal body – they certainly wouldn’t look like craggy Mount Fuji, an iconic terrestrial volcano. Instead, they would likely have gentle slopes and wide cones. volcano – thin streams that extend over greater distances. “

The work appears in Nature Communications