This is a gigantic hole that's been melted into the South Pole. It's one of the 100 or so such vertical caves that have been punched into the Antarctic surface as part of the IceCube Neutrino Observatory, which is searching for tiny, almost massless particles known as neutrinos. This remarkable image reveals the incredible lengths scientists have to go in order to detect these ultra small particles.

A NASA astronomer explains:

Astronomers with the IceCube Neutrino Observatory lowered into each vertical lake a long string knotted with basketball-sized light detectors. The water in each hole soon refreezes. The detectors attached to the strings are sensitive to blue light emitted in the surrounding clear ice. Such light is expected from ice collisions with high-energy neutrinos emitted by objects or explosions out in the universe.

Late last year, the last of IceCube's 86 strings was lowered into the frezzing abyss, pictured above, making IceCube the largest neutrino detector yet created. Data from a preliminary experiment, AMANDA, has already been used to create the first detailed map of the high-energy neutrino sky. Experimental goals of the newer IceCube include a search for cosmic sources of neutrinos, a search for neutrinos coincident with nearby supernova and distant gamma-ray bursts, and, if lucky, a probe of exotic physical concepts such as unseen spatial dimensions and faster-than-light travel.