Hydrogen is the most abundant element in the universe, thanks to it being simply one proton paired with one electron. Here on Earth we usually see it bound to oxygen to form water, and very rarely hydrogen atoms pair up and exist as a gas in our atmosphere. But theoretically in the right conditions hydrogen alone can act as a liquid metal, and learning more about it could answer some mysteries about planets in our solar system. We know Jupiter and Saturn are mostly Hydrogen based on their densities, which is why they’re called the gas giants. But they’re not puffy clouds all the way down as the name might suggest. Only the thin outermost layer is gaseous. Under that, the pressure compresses the hydrogen into a liquid state, and further down still the hydrogen takes on metallic properties. Most elements in the periodic table are metals. Their defining characteristic is they pass electrons freely amongst each other, like a shared pool of electrons. This makes them good conductors of heat and electricity. Normally the Hydrogen we see on Earth doesn’t behave like a metal, but at about 13,000 km below Jupiter’s gaseous surface, things are different. Like a substitute teacher, with enough pressure those hydrogen molecules snap. In fact the hydrogen atoms dissociate entirely into free electrons and protons. The pressure inside Jupiter gives it the properties of a metal: those electrons can flow freely from proton to proton, making the hydrogen conductive. We think this metallic hydrogen could account for the magnetic fields surrounding Jupiter and Saturn, instead of a molten iron core like inside Earth. But to understand metallic hydrogen better we have to make it, and that’s no easy task. It’s not like we can scoop some up from deep inside Jupiter, instead we have to recreate those conditions somehow here on Earth. I am very happy to report that one leading method involves giant lasers. The lasers, all 168 of them, are used to send shock waves through a sample of ultracool liquid deuterium, an isotope of hydrogen with one neutron. The waves compress the deuterium to six million times earth’s atmospheric pressure while keeping the sample below 1,700 degrees celsius, or what physicists call “cool.” At least they think it’s that cool, because measuring the temperature inside the shock wave isn’t possible and instead is inferred through computer simulations. Still, the scientists concluded liquid deuterium becomes metallic at 2 million times the pressure of Earth’s atmosphere. That contradicts another lab’s findings that the transition happens at around 3 million atmospheres of pressure. Each lab politely and professionally says the other one must have incorrect temperature estimates, and that their own results are the true and correct ones. That’s about the closest scientists get to reality show drama and I for one am living for it! There’s been even more drama around a 2017 Harvard experiment’s attempt at making metallic hydrogen. Using the tips of two diamonds like a vise, scientists claimed they crushed a hydrogen sample to nearly 4.9 million atmospheres until it wasn’t just metallic, but solid as well, a world first. They were going to send it to another lab for study, but wouldn’t you know it, just before shipping it they decided to check the pressure with a laser one more time for good measure, and the diamonds shattered to dust. The sample was lost. This has lead other scientists to speculate that it didn’t actually… happen. Still, the Harvard scientists think the lost hydrogen could still be in a solid state, even with the pressure lifted. It might even be a room temperature superconductor, which would revolutionize materials science. But finding the 10 micrometer wide sample in a pile of diamond dust is next to impossible. Darn. Funny, we go through all this trouble to create a speck of metallic hydrogen, but thanks to Jupiter and Saturn’s vast sizes it’s the most common form of hydrogen among all of our planets. Sometimes there are drawbacks to living on Earth. Some scientists don’t believe the Harvard experiment made solid metallic hydrogen because at a high enough pressure the hydrogen can diffuse right through the diamond