Squeezed between two pieces of man-made diamond in the laboratory, hydrogen has finally been transformed into a metallic form that is believed to exist inside planets such as Jupiter, scientists revealed last Thursday.

Metallic hydrogen, deemed the rarest and potentially among the most valuable on Earth, was theorized almost a century ago. If certain theoretical predictions hold true, the hydrogen could turn into a solid metal that can remain solid once crushing pressure is removed. It could also serve as a room-temperature superconductor, conducting electricity sans resistance.

“This is the holy grail of high-pressure physics,” said Harvard physics professor Isaac Silvera, who created the material along with postdoctoral fellow Ranga Dias.

How They Did It

The physicists squeezed a tiny sample of hydrogen at 495 gigapascal, which is equivalent to over 71.7 million pounds-per-square inch or higher than the pressure at Earth’s center. At the extreme pressures, according to Silvera, solid molecular hydrogen breaks down, and the tightly bound molecules break away to transform into atomic hydrogen, meaning a metal.

The hydrogen was positioned between two small man-made diamonds, which were cooled to -433 degrees Fahrenheit and about one 850th of an inch in diameter. The diamonds were coated with alumina to block the hydrogen from diffusing into their structure and making them weak and brittle.

The researchers predict that their material will stay metallic even with taking the pressure off, similar to how diamonds form from graphite under extreme heat and pressure, and remain in their diamond form once heat and pressure are taken out.

They believe their work opens a window of opportunities in creating revolutionary materials. As a potential superconductor, for instance, metallic hydrogen could benefit transportation systems: make electric cars more efficient, make high-speed trains’ magnetic levitation possible, and improve today’s electronic devices.

Metallic hydrogen is also considered promising in humans’ space exploration as “the most powerful rocket propellant yet discovered.” Its so-called specific impulse, the measure of how fast a propellant is fired from the back of a rocket, is 1,700 seconds in theory, which Silvera believes could assist in easy exploration of outer planets.

The findings were discussed in the journal Science.

Contentious Research?

Some scientists, however, have performed similar experiments and think it’s not a cause for celebration yet.

It’s “the product of [Isaac’s] imagination from the title to the end,” said University of Edinburgh physicist Eugene Gregoryanz in a New York Times report.

Paul Loubeyre, a physicist at Atomic Energy Commission in France, hit “some flaws” in the journal’s reviewing process given the publication of the new paper.

In a statement, Science editor-in-chief Jeremy Berg emphasized that all submissions needed to pass strict expert reviews, with only around 7 percent of them getting published.

Silvera, however, is confident they would get the same results in another round of experiment.

Hydrogen is the lightest among elements, with each atom consisting only of a single proton and electron. Over eight decades ago, physicists Eugene Wigner and Hillard Bell Huntington thought that high enough pressures could turn hydrogen metallic.

Via turbulent shock wave experiments, scientists have transformed the element momentarily into liquid metal. For planetary researchers, however, the metallic form must actually exist inside Jupiter, generating its potent magnetic fields.

At present, no one has, without a shred of doubt, demonstrated the said solid metallic hydrogen form.