"Wow: two satellites have collided in orbit, destroying both," said Phil Plait in Discover magazine. It was the first crash between two intact spacecraft, ever. The satellites—an old Russian Cosmos satellite and an Iridium satellite, one of a fleet of communication satellites launched by Motorola in the late 90s and early 2000s—slammed into each other over Siberia at 17,500 miles per hour, "which is pretty dang fast." The result was a "total wipeout."
As you might expect, this made space a bit messier, said Paul Rincon in BBC News. The crash created thousands of new pieces of debris, adding to the 17,000 man-made objects now orbiting the planet. The satellites were flying nearly 500 miles up. That's more than twice as high as the International Space Station, so the threat to the space station is low.
But by NASA’s reckoning, said Radio Free Europe/Radio Liberty, orbiting debris is already "the most serious threat to flights by manned U.S. space flights—greater even than the take-off and re-entry phases of a mission.” So with each new smattering of space junk the danger to all spacecraft only grows.
The crash has no immediate ramifications for space science, said Emily Lakdawalla in The Planetary Society’s blog. But this is “still a big deal.” With no clear way to safely handle all the junk orbiting the planet, this crash—though a rare and low-probability event—“is in all likelihood a harbinger of more orbital disasters to come.”