Matter does strange things under extreme pressure. It can collapse atoms down to neutrons and squeeze quarks together into strange matter. And if any of that strange matter should reach Earth... Yeah, we'd be screwed.
The universe is filled with strange things. But perhaps nothing stranger than the stuff at the core of neutron stars.
Gravity and pressure are responsible for everything we see around us. Because it's the pressure that fused together atoms in the core of stars that eventually produced the carbon, oxygen, and other elements that keep us and everything alive.
Much bigger stars went supernova, collapsing down under gravity and creating even heavier elements. Even bigger stars collapse down so far, they create a singularity, ripping a black hole into the fabric of the universe.
But there's a slightly smaller size of star that doesn't manage to go black hole, but does crush down the atoms of its core into neutrons, creating a neutron star, the densest objects in the universe.
But it doesn't stop there, because at the core of neutron stars, the up and down quarks that make up neutrons can fuse with each other to create a much heavier type of quark, a strange quark.
The strange matter that is made up of strange quarks has the ability to turn any other type of matter into strange matter. This means that if quark stars collide and explode, they could scatter bits of strange matter, or strangelets, across space. And if any of those strangelets were to collide with Earth, it could spell the end of our entire planet.