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You're probably used to the idea of a few states of matter. You've got solids, liquids, gases.

At least, that's what you see in everyday life. But scientists keep finding that elements can exist in other states in extreme environments. Earlier this week, research published in the Proceedings of the National Academy of Sciences described a whole new one called the chain-melted state where some elements are basically liquids and solids at the same time.

If you ask any chemistry teacher, the state of a substance depends on its temperature and the pressure that it's under. As you heat things up or lessen the pressure, molecules begin to move more and spread out, causing solids to melt into liquids, and liquids to evaporate into gases. You can even go from a solid to a gas sometimes, or create a plasma by zapping a hot gas with an electric current.

And while exact conditions where these phase changes occur are different for each element, in general, this is how matter behaves. But that all kind of flies out the window under, like, extreme conditions. Like, when you cool things way, way down, you can get groups of atoms that act like they're all one atom.

And scientists have seen some bizarre solids at the opposite extreme. We're talking at over 2 gigapascals of pressure, that's 20,000 times the atmospheric pressure at sea level, and temperatures of more than 400 Kelvin. When pure potassium gets heated and pressed that much, the atoms arrange themselves into two interlocked lattices.

This looks like a weird X-shaped structure that's made out of five “tubes” with four “chains” running through the gaps. Then, as the temperature and pressure increases, something weird happens. Exactly what happens wasn't clear, and scientists have been arguing about it for years, so researchers from the University of Edinburgh taught a neural network quantum mechanics to try and figure that out.

The computer simulation found that as you continue to dial things up, those chains actually melt, hence the name “chain-melted state”. The molecules from the chains act like a liquid. They diffuse within the solid, and even leak out.

Meanwhile, the X-shaped crystal part stays as solid as ever. One of the researchers described the whole thing as, like, a wet sponge, if the sponge itself was also made of water. This leaky solid state explains the results from observational experiments.

And the simulation suggests it's stable enough to be considered its own state of matter rather than an awkward transition phase. It also might not be unique to potassium. The researchers speculate that under the right conditions, several other elements like bismuth and sodium could also exist in a chain-melted state.

But that's not actually the most exciting part of this. You see, it's hard to heat and press things enough to see how they behave in such extreme conditions, and it's even harder to see what's happening at the atomic level when you do. And that means it's really hard to figure out what's going on in places like the Earth's mantle.

The fact that this simulation was able to explain what scientists were seeing by other methods means it could be applied to all sorts of elements or mixtures of elements. So it could help us understand the parts of the universe we can't easily recreate in a lab or sample directly. And physicists aren't the only one with big announcements this week.

Archeologists also uncovered something new: a new species of human. Way back in 2007, archaeologists found a human-looking foot bone in a cave on the northern side of. Luzon Island in the Philippines.

Researchers dated the bone to about 67,000 years old, which made it the earliest evidence of humans in the Philippines. But it wasn't clear what species of human this bone belonged to. So, they kept digging.

From 2011 to 2018, excavations uncovered more human remains from the same cave. The study summarizing their findings, published in Nature earlier this week, described teeth, hand and foot bones, and part of a femur. The scientists concluded that the bones belonged to at least three individuals of a new human species: Homo luzonensis, named after the island they were found on.

But before they could confidently say that they'd found anything new, they had to compare their evidence with bones of already known human species. So they used precise digital measurement tools to analyze the remains, and they found some key differences. For example, they noticed that the premolars were large when compared to the molars, something not seen in other human species.

Now, that kind of tooth proportion has been seen in Paranthropus, a genus of primates closely related to the early offshoots of our lineage like Lucy. But other teeth from the site were more similar to Homo erectus than teeth from any Paranthropus species. The same kind of logic was applied to the other bones, ultimately leading to the conclusion that the remains were from a species in our genus Homo.

We also know that at least one specimen from the cave was a child or adolescent because a cross-section of the femur fragment revealed a lot of Haversian canals: little passageways for blood vessels and nerves found in young primate bones. Exactly how long luzonensis was present in the Philippines is unclear. From this study, we know that they were there over 50,000 years ago.

But evidence from other recent studies suggests that humans of some variety have been on Luzon for almost 700,000 years. All this goes to how just how complex human evolution has been, not just on the mainland, but on islands as well. And while scientists were able to infer some things about luzonensis, the remains are incomplete and efforts to extract DNA have been unsuccessful.

So there's a lot left to learn about this distant cousin of ours. If you like learning new things, and you know, you're watching SciShow News right now, so, like, probably you do, you might like the courses offered by Skillshare. Skillshare has more than 25,000 classes that cover all sorts of new skills that you could pick up, from small business management to photography.

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