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January 16, 2012

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Space probe on collision course

A FAILED Russian probe designed to travel to a moon of Mars but stuck in Earth orbit was expected to come crashing down early today, likely in a shower of fragments that survive the fiery re-entry.

The unmanned Phobos Ground is one of the heaviest and most toxic space derelicts ever to crash to Earth, but space officials and experts say the risks are minimal as its orbit is mostly over water and most of the probe's structure will burn up in the atmosphere anyway.

Russia's space agency Roscosmos said the Phobos-Ground will crash between 1730 and 1912 GMT. It said the probe could come down anywhere along its orbit that includes South America, Australia, southeast Asia, China, Central Asia and southern Europe. The rest of the world are outside the risk zone.

"The resulting risk isn't significant," said Professor Heiner Klinkrad, head of the European Space Agency's Space Debris Office.

He wouldn't say where exactly the probe may enter the atmosphere, but said that "most of Europe is excluded from an impact risk."

Roscosmos predicts that only between 20 and 30 fragments of the Phobos probe with a total weight of up to 200 kilograms will survive the re-entry and plummet to Earth.

Klinkrad agreed with that assessment, adding that about 100 metric tons of space junk fall on Earth every year. "This is 200 kilograms out of these 100 tons," he said.

Thousands of pieces of derelict space vehicles orbit Earth, occasionally posing danger to astronauts and satellites in orbit, but so far no one has ever been hurt by falling space debris.

The Phobos-Ground weighs 13.5 metric tons, and that includes a load of 11 metric tons of highly toxic rocket fuel intended for the long journey to the Martian moon of Phobos. It has been left unused as the probe got stuck in orbit around Earth after its November 9 launch.

Roscosmos says all of the fuel will burn up on re-entry, a forecast Klinkrad said was supported by calculations done by NASA and the ESA. He said the craft's tanks are made of aluminum alloy that has a very low melting temperature, and they will burst at an altitude of over 100 kilometers.




 

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