‘Space junk’ expected to land on Earth

(NECN/CNN: John Zarrella) – A dead satellite is barreling toward Earth from space in pieces. NASA expects more than two-dozen chunks of the space junk to survive re-entry into the atmosphere.

Sometime after midnight Friday, if NASA's calculations are right - an old, dead satellite will re-enter the earth's atmosphere and burn up... most of it... but not all of it. About half of a ton will make it through.

"There are some pieces that are made of stainless steel and titanium and beryllium that have very high melting temperatures and those pieces will survive.” Jonathan McDowell, of Harvard-Smithsonian Center for Astrophysics, said.

“We have a list of about 26 pieces and they range from a few tens of pounds to a few hundred pounds in size."

Some of the chunks of junk could be hundreds of pounds. There is no need for people to run out and buy a hard hat. NASA scientists in Houston say there is very little risk that any of the debris from the six ton UARS, upper atmosphere research satellite, will hit humans.

McDowell believes the space agency is probably right, because much of the earth is water.

"This is nothing like the old Skylab scare of the 70s when you had a 70 ton space station crashing out of the sky. This thing's only six or seven tons. So, I agree with folks in Houston. It's really nothing to be terribly concerned about." McDowell said.

Parts of Skylab did hit western Australia in 1979. So, where will this one come down? Well, no one knows.

Even minutes before re-entering the atmosphere, NASA won't be able to pinpoint the exact location. The satellite is traveling so fast, it covers thousands of miles of space in just minutes. Right now, the impact swath covers portions of six continents.

"Part of the problem is the spacecraft is tumbling in unpredictable ways and it is very difficult to very precisely pinpoint where it's coming down, even right before the re-entry." McDowell said.

"If the thing happens to come down in a city that would be bad. The chances of it causing extensive damage or injuring someone are much higher." NASA Orbital Debris Scientist Mark Matney said.

One thing is certain: once it hits the atmosphere, 50 miles up, it will take only a few minutes before the surviving pieces hit the earth.