Researchers at Washington University in St. Louis have been playing the role of super villain, by slowly vaporizing the Earth. In a simulator, that is.
"We want to understand exactly what it would be like if it happened," says Bruce Fegley, professor of earth and planetary sciences.
It's not just for fun, though. The team wants to find out what astronomers should see when they look at the atmospheres of ultra-hot super-Earths, so they can know the exact composition of the exoplanet.
You see, planet-hunting techniques allow astronomers to measure the average density of an exoplanet but, for rocky planets at least, that density could be the result of a whole variety of different materials. That's not specific enough for Fegley and crew.
Because most of the detected super-Earths orbit very close to their stars, they're within rock-melting distance. So the team decided to simulate what would happen to an exoplanet's atmosphere when its underlying rocky body was cooked up by a star.
The researchers ran calculations on two types of pseudo-Earth. One was very much like Earth, with its continental crust. A second, bulk silicate Earth, had a composition like the Earth's before our continental crust formed.
They cooked the planets up to have surface temperatures ranging from about 270 to 1700 degrees Celsius. Compare that to the Earth's nippy 15°C average temperature.
The simulations showed that the atmospheres of both model Earths would be dominated over a wide temperature range by steam, from vaporizing water and hydrated minerals, and carbon dioxide, from vaporizing carbonate rocks.
The continental crust melted at about 940°C, while the bulk silicate Earth was vaporised at roughly 1,730°C. The atmosphere of the latter changed dramatically at different heats. Below 730°C, and it contained methane and ammonia. Above that temperature, and the atmosphere became like that of Venus—but with steam.
Once you reach temperatures of 1,430°C, both planets would feature silicon monoxide in their atmosphere. As frontal systems moved through these balmy atmospheres, the silicon monoxide and other rock-forming elements might condense and rain out as pebbles.
Fegley admits that his team went ahead and completely vaporised the entire planet. "You're left with a big ball of steaming gas that's knocking you on the head with pebbles and droplets of liquid iron," he said.