The original question was: Is it possible to actually create a substance such as Kurt Vonnegut’s “Ice-9 (Nine)“, which could, in theory, bond with water (especially seawater) and replicate like a virus, freezing the oceans (or all liquid water on Earth) solid?
Physicist: Nope. There actually is an ice-IX, but there’s nothing that special about it.
Crystals in general are self-propagating. That is, once a crystal is present the raw materials in the environment find that falling into place in the crystal’s lattice results in a net drop in energy, but weirdly enough it usually takes a little energy to start a crystal from scratch. You can see this in action with super-cooled water: the water is cold enough that it should freeze, but no collection of water molecules is able to start the ice crystal.
The first tiny crystal that gets the ball rolling is called a “seed crystal”. Often it’s unnecessary because when a bunch of atoms are ready to crystallize small flaws in the environment can “look” like pieces of crystal to them, and they’ll just grab on to them (these are called “nucleation sites“).
It may seem strange to talk about a different kind of water-ice other than just regular “ice”, but keep in mind that many substances are perfectly happy to crystallize in multiple ways. For example, sapphires and rubies are made of exactly the same stuff, aluminum oxide (“aluminium” for our not-American readers), just put together in different ways due to the different environments that they form in.
Water in particular crystallizes in a surprising number of ways. To date, 15 different forms of water ice have been found, however here on Earth only one kind (“ice-I”) can form naturally. Even at the bottom of the Mariana Trench the pressure isn’t nearly high enough for any other kind of ice.
A general rule of thumb is, if something wants to crystallize, and it’s in an environment where it can do so, eventually it does. Even if there’s no seed crystal already present, at some point a nucleation point is bound to show up (given enough time) and a crystal will form and grow.
The whole idea of Vonnegut’s ice-9 is that it’s a crystalline form of water, that grows rapidly at reasonable, Earth-like pressures and temperatures. If it could form at all, then at some time in the last several billion years, at some place in our gargantuan oceans, a tiny ice-9 crystal should have formed accidentally and encompassed the world.
We’ve already seen this on other, aptly named, ice-worlds. For example, Europa has lots of water, and is in an environment (pressure and temperature) conducive to the formation of ordinary ice-I. Not surprisingly, Europa long ago underwent a colossal “ice-9 type catastrophe”, in that all of its water (at least on the surface) quietly froze solid.
Long story short, if the Earth’s water could somehow be induced to crystallize at room-temperature, it almost certainly would have done so at its earliest convenience, a very long time ago.
The very cool super-cooled water gif is from here.