Miller had filled the vial in 1972 with a mixture of ammonia and cyanide, chemicals that scientists believe existed on early Earth and may have contributed to the rise of life.

He had then cooled the mix to the temperature of Jupiter’s icy moon Europa—too cold, most scientists had assumed, for much of anything to happen. Miller disagreed. Examining the vial in his laboratory at the University of California at San Diego, he was about to see who was right. As Miller and his former student Jeffrey Bada brushed the frost from the vial that morning, they could see that something had happened. The mixture of ammonia and cyanide, normally colorless, had deepened to amber, highlighting a web of cracks in the ice. Miller nodded calmly, but Bada exclaimed in shock. It was a color that both men knew well—the color of complex polymers made up of organic molecules. 

Tests later confirmed Miller’s and Bada’s hunch. Over a quarter-century, the frozen ammonia-cyanide blend had coalesced into the molecules of life: nucleobases, the building blocks of RNA and DNA, and amino acids, the building blocks of proteins…

Although life requires liquid water, small amounts of liquid can persist even at –60°F. Microscopic pockets of water within the ice may have gathered simple molecules like the ones Miller synthesized, assembling them into longer and longer chains. A single cubic yard of sea ice contains a million or more liquid compartments, microscopic test tubes that could have created unique mixtures of RNA that eventually formed the first life.

If life on Earth arose from ice, then our chances of finding life elsewhere in the solar system—not to mention elsewhere in the galaxy—may be better than we ever imagined…

Cyanide is a good candidate as a precursor molecule in the life-in-a-freezer model for several reasons. First, planetary scientists suspect that cyanide was abundant on early Earth, deposited here by comets or created in the atmosphere by ultraviolet light or by lightning (once the atmosphere became oxygen rich, 2.5 billion years ago, the process would have stopped). Second, although cyanide is lethal to modern animals, it has a convenient tendency to self-assemble into larger molecules. Third, and perhaps most important, no matter how much cyanide rained down, it could become concentrated only in a cold environment—not in warm coastal lagoons—because it evaporates more quickly than water…

According to some solar evolution models, the sun was some 30 percent dimmer at that time, providing less heat to Earth. So as soon as the hail of asteroids stopped, Earth may have cooled to an average surface temperature of –40°F and a crust of ice as much as 1,000 feet thick may have covered the oceans. Many scientists have puzzled over how life could have arisen on a planet that was essentially a giant snowball…

Biebricher sealed small amounts of RNA nucleobases—adenine, cytosine, guanine—with artificial seawater into thumb-size plastic tubes and froze them. After a year, he thawed the tubes and analyzed them for chains of RNA. For decades researchers had tried to coax RNA chains to form under all sorts of conditions without using enzymes; the longest chain formed, which Orgel accomplished in 1982, consisted of about 40 nucleobases. So when Biebricher analyzed his own samples, he was amazed to see RNA molecules up to 400 bases long. In newer, unpublished experiments he says he has observed RNA molecules 700 bases long…

Vlassov and his coworkers, Sergei Kazakov and Brian Johnston, realized that the ice was driving both enzymes to work in reverse. Normally when an enzyme cuts an RNA chain in two, a water molecule is consumed in the process, and when two RNA chains are joined, a water molecule is expelled. By removing most of the liquid water, the ice creates conditions that allow the RNA enzyme to work in just one direction, joining RNA chains. The SomaGenics scientists wondered whether an icy spot on early Earth could have driven a primitive enzyme to do the same.

To investigate this, they introduced random mutations into the hairpin RNA, shortened it from its normal length of 58 bases, and even cut it into pieces—all in an effort to produce RNA enzymes that were as dodgy and imperfect as early Earth’s first enzymes likely were.

These pseudoprimitive RNA enzymes do nothing at room temperature. But freeze them and they become active, joining other RNA molecules at a slow but measurable rate. These findings inspired a theory that the first, extremely inefficient RNA enzymes got help from ice, which created an environment that encouraged short segments of RNA to stick together and behave as a single, larger RNA molecule.

“Freezing stabilizes the complexes formed from multiple pieces of RNA,” concludes Kazakov. “So small pieces of RNA could be enzymes, not just large 50-base molecules.”

… On the young Earth, pockets of liquid could have expanded into a network of channels that mixed their contents during freeze-thaw cycles, like day-night temperature changes in summer. In winter, the liquid pores would have contracted and become isolated again, returning to their separate experiments. With all the mixing, something special might eventually have formed: an RNA molecule that made rough copies of itself. And as Earth warmed, these molecules might have found a home in newly thawed seas or ponds, where something even more complex might have emerged—such as a cell-like membrane…

Those speculations are more relevant than ever, with recent discoveries of geysers on Saturn’s icy moon Enceladus and elaborate organic molecules on Titan, another Saturnian moon. Recent studies show that Mars too has vast quantities of buried ice, especially at its poles.