14-07-2025
The Structure of Ice in Space Is Neither Order nor Chaos—It's Both
Jul 14, 2025 5:00 AM Long thought to be completely disordered, space ice appears to have some crystallized regions, new research suggests. Illustration: AllIce 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.
An illustration of the ordered molecular structure of water ice on Earth. GETTY IMAGES
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.
A simulation of space ice. The white fragments are ordered molecules in crystalline structures while the blue parts are disordered molecules. Illustration: Courtesy of the ICE Group, University of Cambridge
To reach this conclusion, the team first ran computer models of water molecules subjected to temperature changes at different rates, simulating the creation of ice in space. They then compared this with the results of lab experiments to produce actual amorphous ice. Water vapor was passed over an extremely cold slab to become ice, with no liquid state occurring in between, a process similar to what happens in a planetary system at birth. A partially amorphous material was produced, whose structure most closely matched a simulation from the models that comprised 20 percent crystalline material and 80 percent amorphous ice.
'We now have a good idea of what the most common form of ice in the universe looks like at the atomic level,' said Michael B. Davies, part of the ICE Group at the University of Cambridge and a coauthor of the study, in a statement.
Knowing the structure of space ice is important for interrogating the speculative idea of panspermia, a hypothesis that life on Earth originated through compounds or 'seeds' of life arriving on our planet from space. If space ice is amorphous and of low density, then building blocks for life could potentially have been carried inside. If, instead, there are lots of crystalline parts, then there is less likelihood (because of less space) of this having occurred.
This story originally appeared on WIRED en Español and has been translated from Spanish.
