The instant the sprightly vapor molecules enter the chamber they are literally frozen in their tracks. Still pointing every which way, the molecules are transformed immediately from their gaseous state into the disorderly solid called amorphous ice. Amorphous ice is exactly the opposite of the typical ice on Earth, which forms perfect crystals like those that make up snowflakes or frost needles. These crystals are so orderly and predictable that this ice is considered a mineral, complete with a rating of 2.5 on the Mohs scale of hardnessthe same rating as a fingernail.
Though almost unheard of on Earth, amorphous ice is so widespread in interstellar space that it could be the most common form of water in the universe. Left over from the age when the solar system was born, it is scattered across vast distances, often as particles no bigger than grains of dust. It's also been spotted in comets and icy moons.
The secret to making amorphous ice in the lab, Gerakines finds, is to limit the layer to a depth of about half a micrometerthinner than a strand of spider's silk.
"Water is such a good insulator that if the ice gets too thick, only the bottom of the sample, closer to the cooling source, will stay sufficiently cold," says Gerakines. "The ice on top will get warm enough to crystallize."
The superthin ice can be spiked with all kinds of interesting chemicals found in space. One set of chemicals that Gerakines works with is amino acids, which are key players in the chemistry of life on Earth. Researchers have spent decades identifying a whole smorgasbord of amino acids in meteorites (including some involved in life), as well as one found in a sample taken from a comet.
"And because water is the dominant form of frozen material in the interstellar medium and outer solar system," says Gerakines, "any amino acids out there are probably in contact with water at some point."
For his current set of
|Contact: Liz Zubritsky|
NASA/Goddard Space Flight Center