The U.S. space agency NASA says two communications satellites have collided some 800 kilometers over Siberia, in the first-ever crash of two intact spacecraft in orbit.
The collision on February 10 of an American commercial satellite and a disused Russian military satellite produced a spectacular shower of debris, which will now add to the existing dangers for other spacecraft.
It's thought the disused Russian craft, one of the Cosmos series launched in 1993, was spinning out of control and entered the orbit of the Iridium company's commercial communications satellite, which had been aloft since 1997.
NASA space debris expert Nicholas Johnson told the Associated Press that about 17,000 pieces of man-made debris are already orbiting Earth, not counting the latest junk.
By NASA's reckoning, this orbiting debris is now 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.
In view of this, the space agency coordinates its shuttle flights with the military-run U.S. Space Surveillance Network, which tracks the enormous volume of space junk to ensure that the shuttles do not get too close to dangerous objects.
Another debris expert at the Houston space center in Texas, Mark Matney, is quoted as saying that collisions of space objects are likely to become an ever greater risk in the decades to come.
In Moscow, Russian space agency spokesman Aleksandr Vorobyov told local television that there is no danger to the orbiting International Space Station, currently home to three spacemen. The ISS orbits more than 400 kilometers below the site of the accident.
An estimated 6,600 satellites have been launched into space since Russia's Sputnik satellite in 1957. Nearly 1,000 are currently in operation.