NASA's Juno spacecraft blasted off on a 5-year voyage to a freakish world: planet Jupiter. Jupiter has a long list of oddities. For one thing, it's enormous, containing 70% of our solar system's planetary material, yet it is not like the rocky world beneath our feet. Jupiter is so gassy, it seems more like a star.
Jupiter's atmosphere brews hurricanes twice as wide as Earth itself, monsters that generate 400 mph winds and lightning 100 times brighter than terrestrial bolts. The giant planet also emits a brand of radiation lethal to unprotected humans.
Jupiter's strangest feature, however, may be a 25,000 mile deep soup of exotic fluid sloshing around its interior. It's called liquid metallic hydrogen.
"Here on Earth, hydrogen is a colorless, transparent gas," says Juno principal investigator Scott Bolton. "But in the core of Jupiter, hydrogen transforms into something bizarre."
Jupiter is 90% hydrogen1, with 10% helium and a sprinkle of all the other elements. In the gas giant's outer layers, hydrogen is a gas just like on Earth.
As you go deeper, intense atmospheric pressure gradually turns the gas into a dense fluid.2 Eventually the pressure becomes so great that it squeezes the electrons out of the hydrogen atoms and the fluid starts to conduct like a metal.
What's this fluid like?
"Liquid metallic hydrogen has low viscosity, like water, and it's a good electrical and thermal conductor," says Caltech's David Stevenson, an expert in planet formation, evolution, and structure.
"Like a mirror, it reflects light, so if you were immersed in it [here's hoping you never are], you wouldn't be able to see anything."
Here on Earth, liquid metallic hydrogen has been made in shock wave experiments, but since it doesn't stay in that form it has only been made in tiny quantities for very short periods of time. If researchers are right, Jupiter's core may be filled with oceans of the stuff.