Short answer: Bad news for space travel. And this isn't just idle speculation for boozy astrophysicist parties. Space junk—spent rockets, lost astro-screwdrivers, satellite parts—could form rings around our planet as surely as water, ice and dust encircle Saturn. Scientists have been especially concerned about satellite collisions, where debris from one wreck could trigger a futuristic 12-car pileup.
On 10 February 2009 it started to happen. In the first collision between two intact satellites, the defunct Russian craft Kosmos-2251 struck communications satellite Iridium 33 at a speed of 42,100 kilometres per hour. The impact shattered one of Iridium 33's solar panels and sent the satellite into a helpless tumble. Kosmos-2251 was utterly destroyed. The two orbits are now home to clouds of debris that, according to the US military's Space Surveillance Network (SSN), contain more than 2000 fragments larger than 10 centimetres. The collision may also have produced hundreds of thousands of smaller fragments, which cannot currently be tracked from Earth.
Such debris is a serious worry. With satellites travelling at tens of thousands of kilometres per hour, any encounter with debris could be lethal. "Being hit by a 1-centimetre object at orbital velocity is the equivalent of exploding a hand grenade next to a satellite," says Heiner Klinkrad, head of the space debris office at the European Space Agency in Darmstadt, Germany.
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