LONDON The collision between a U.S. and a Russian satellite over Siberia may have been accidental and the first of its kind, but experts say more crashes will inevitably occur and could have geopolitical consequences.
"This is an event that really makes us realize that things are not so straightforward as we originally thought," said Francisco Diego, a senior research fellow in physics and astronomy at University College London.
"I couldn't put a number on the probability of this happening again, but now that it has happened, it changes things a lot and it becomes a concern."
The collision, between a spacecraft operated by U.S. communications group Iridium Satellite LLC and a Russian Cosmos-2251 military satellite, happened 485 miles above the Russian Arctic on Tuesday afternoon.
The crash sent at least 600 pieces of debris off into space, officials said, increasing the risk that other satellites, including the vast International Space Station, which orbits 220 miles up, could be struck and damaged.
There are about 18,000 identifiable, man-made objects in space, including operational and defunct satellites, spent rocket boosters and debris. Experts said that while the risk of satellite collisions like Tuesday's was exceptionally small, now one had occurred it made another more likely.
"The problem with collisions like this is that they don't destroy satellites, they just create smaller ones, like fast moving shotguns, that are potentially much more damaging," said Diego.
Andrew Brookes, an aerospace analyst at the International Institute for Strategic Studies, said the area where the collision occurred -- called low-Earth orbit -- was the most crowded portion of space and also one of the most important for sensitive communications, science and weather satellites.
Not only does the density of objects orbiting in that band increase the likelihood of collisions, it makes it all the more pressing that the world draw up a more detailed protocol regulating satellite movements, he said.
"More and more of this is going to happen because, basically, there's more and more stuff, satellites and space junk, up there in this low-Earth orbit," said Brookes.
"We're crying out for some sort of regulation, but people are not sharing because a lot of it is sensitive. The great powers are not willing to sit down and deal like grown-ups."
Two years ago China carried out an experiment to destroy a satellite, creating thousands of pieces of space debris. While some are tiny, they are traveling at speeds of thousands of kilometers an hour and can cause huge damage.
The risk that Chinese space junk could destroy a sensitive American satellite, for example, or that U.S. debris might hit an Iranian satellite, could have serious consequences.
"In the longer term, there are geopolitical implications to this because people are going to start wondering, 'was that crash deliberate?'" said Brookes.
"The international community needs to get a grip of space and become much more transparent about what's going on, otherwise we're going to end up in a situation where there are serious diplomatic incidents as a result."
The collision was confirmed by Russian and U.S. officials on Wednesday. The U.S. Strategic Command said it believed it was the first of its kind between orbiting satellites.
The European Union urged nations on Thursday to adopt a code of conduct for civil and military activities in space, part of an initiative to prevent environmental emergencies and the risk of space becoming another frontier for conflict.
There are already United Nations agreements on launched satellites, and protocols on "space debris mitigation measures," according to the European Space Agency, but not enough detail is provided to prevent potential collisions.
U.S. space authorities maintain a database on known man-made objects in space, but the details are scarce, according to the head of space debris office at the European Space Agency.
"The orbit is provided in two-line element format," said Heiner Klinkrad. "That format is good for many applications, but not reliable for conjunction event analysis -- collisions."
Klinkrad said the fact one collision had occurred increased the likelihood of more collisions, particularly as even more space debris had been created.
In the very long term, that raises the risk of something called Kessler's Syndrome, he said, in which one collision and the ensuing space debris cause another crash and more debris, expanding almost exponentially.
(Editing by Robert Woodward)