Ice is a key component in the universe. There are frozen water molecules on comets, moons, exoplanets, and in your drink as you cool off from the summer heat. However, under the microscope, not all ice is the same, even though it is made of the same components.
The internal structure of Earth’s ice is a cosmological oddity. Its molecules are arranged in geometric structures, usually hexagons that repeat each other. Ice on Earth forms this way due to the temperature and pressure of the our planet: water here freezes slowly, and this allows its molecules to arrange themselves into crystals.
But ice that forms in space is different because of the conditions—the water exists in a vacuum and is subject to extreme temperatures. Space ice, as a result, is believed to be amorphous, lacking a distinct organizational structure like on Earth.
This presents a challenge for scientists trying to understand the formation of planets and the generation of life. Not fully understanding the dynamics of amorphous ice in space has knock-on effects. For instance, not knowing exactly how space water freezes makes it difficult to estimate the proportion of water in other solar systems.
Researchers are therefore studying space ice to gain a better understanding of how frozen water behaves away from Earth. Ice samples from comets, asteroids, and other solar system debris would be helpful, but until these can be captured, scientists are trying to understand space ice with computer models and simulations of ice on Earth. The more they study it, the more surprises it reveals.
A recent report, published in the journal Physical Review B, posits that the amorphous ice that abounds in the universe does have some kind of order. The paper theorizes it is likely made up of structured fragments—crystallized regions, as on Earth, but only about 3 nanometers wide—surrounded by chaos.