astroengine writes: "New results from the MESSENGER spacecraft not only confirm that the planet closest to the sun has ice inside shaded craters near the north pole, but that a thin layer of very dark organic material seems to be covering a good part of the frozen water. Both likely arrived via comets or asteroids millions — or hundreds of millions — of years ago. "It could easily have been delivered by comets and asteroids, along with water ice, and may even have darkened in the Mercury environment in response to the intense radiation and space weathering," lead MESSENGER scientist Sean Solomon, with Columbia University, told Discovery News. "Certainly the darkness of the covering material was a surprise and the explanation that seems to fit all the data is that it’s organic material. It's quite interesting.""
egrep patterns are full regular expressions; it uses a fast deterministic
algorithm that sometimes needs exponential space.
-- unix manuals