New Form of Ice Discovered with Implications for the Outer Solar System
The AO Editors
The configuration for making medium-density amorphous (MDA) ice, a never-before-seen kind of ice, which involves smashing ultra-cold crystalline ice with small steel balls.
Christoph Salzmann/SWNS
Chemists have discovered a new type of ice known as medium-density amorphous (MDA) ice, which could have significant implications for our understanding of the solar system's outermost regions. On Earth, solid ice primarily takes the form of water molecules arranged in an orderly and repeated crystalline structure. However, there are 19 other types of water-ice that could exist in the universe, including amorphous ice that does not rely on repeated structures. Scientists previously identified two types of amorphous ice, low-density and high-density, but a team of chemists recently discovered a new type of amorphous ice using a simple experimental setup.
To make the new ice, the researchers placed ice chilled to -340°F (-255°C) in a container with small steel balls and vigorously shook the container back and forth 20 times per second. The resulting MDA ice has remarkable properties and falls precisely within the previously thought-to-be-impossible density gap between low-density and high-density amorphous ice.
When the researchers warmed up MDA, it reverted to a regular crystal lattice, releasing a surprising amount of heat. Because MDA has nearly the same density as water, this could have significant implications for the nature of frozen moons such as Europa and Ganymede.
Europa and Ganymede are thought to have thick ice shells that surround vast oceans of liquid water, making them ideal candidates for searching for signs of past or present life. However, due to their distance from the Sun and cold temperatures, the chemistry of their ice and water differs from that of Earth. If the ice forms on those moons match those found on MDA, then more research will be needed to better understand the conditions and potential habitability of the moons in the outer solar system.
The research, which was published in the journal Nature, emphasizes the significance of amorphous ice, which may be the most common type of ice in the universe. Although most comets and outer moons in the solar system are packed with amorphous ice, their surfaces evaporate due to solar radiation, making them difficult to observe and study.
