September 22nd, 2011
03:13 PM ET

NASA not sure where space junk will come down

Miami (CNN) - A satellite whose orbit is degrading will fall back to Earth Friday afternoon, but only some of its pieces will survive the fiery ride through the atmosphere, NASA scientists said Thursday.

The pieces are not expected to come down over North America, scientists said, but where they'll likely land is something NASA expects to narrow down over the next 24 hours.

Most of the Upper Atmosphere Research Satellite (UARS) is made of aluminum and will burn up on re-entry, NASA said. Of the satellite's 6 tons, only about half a ton of it will make it back to Earth. The components that won't burn are made of stainless steel, titanium and beryllium. NASA has identified 26 pieces they expect to survive, ranging in size from around 10 pounds to hundreds of pounds.

Mark Matney of NASA's Orbital Debris team in Houston told CNN there's no way to know exactly where those pieces will come down.

"Keep in mind, they won't be traveling at those high orbital velocities. As they hit the air they tend to slow down and travel, they're still traveling fast a few tens to hundreds of miles per hour but no longer those tremendous orbital velocities," he explained.

Because the satellite travels thousands of miles in a matter of minutes as it orbits - even just before it hits the Earth's atmosphere - it will be impossible to pinpoint the exact location the pieces will come down. On top of that, Matney said, the satellite is not stable.

"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."

Because water covers 70% of the Earth's surface, NASA believes that most, if not all of the surviving debris will land in water. Even if pieces strike dry land, there's very little risk any of it will hit people.

NASA says space debris the size of the UARS components re-enters the atmosphere about once year. Harvard University astrophysicist Jonathan McDowell noted that UARS is far from being the biggest space junk to come back.

"This is nothing like the old Skylab scare of the '70s when you had a 70-ton space station crashing out of the sky. So, I agree with the folks in Houston. It's nothing to be worried about," McDowell said.

Pieces of Skylab came down in western Australia in 1979.

The only wild card McDowell sees is if somehow a chunk hits a populated area.

"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 says once the debris hits the atmosphere at 50 miles up, it will take only a matter of minutes before the surviving pieces hit the Earth.

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Filed under: In Space
soundoff (14 Responses)
  1. Paul

    I'm going to jinx us here but is this the first time we don't see any creationist commentary in one of these forum. Doh! I mean, this has go to correspond with some scripture somewhere, right? Isn't this satellite entry kind of like the flaming sword of 'X', striking down to punish the infidels as foretold in 'Y'?😛

    September 23, 2011 at 2:26 pm |
  2. ivanir ribeiro

    deveria filmar a reentrada na terra seria um feito importante e ainda ao vivo.mundo muito louco.

    September 23, 2011 at 12:34 pm |
  3. Josh

    The odds of being hit by one of the pieces of this satellite are about equal to winning the Power Ball lottery. But as we all know, someone does indeed win the lottery.

    September 23, 2011 at 12:11 pm |
  4. Rooscow

    Everyone is so worried about this thing coming down that the website advertised for tracking it is overwhelmed preventing access to it.

    September 23, 2011 at 11:41 am |
  5. conoclast

    Wouldn't it be providential if a big chunk hit the House chamber - in-session, preferably!

    September 23, 2011 at 11:02 am |
    • petercha

      The White House would be much better, being that it has a liberal in it.

      September 23, 2011 at 11:27 am |
  6. Cult of Personality

    If we're lucky, maybe it will fall on Michele Bachmann's head!! That would wake her up!!

    September 23, 2011 at 10:42 am |
    • meglet44

      Aim lower. Think Sarah Palin's head. 'Course it'd prolly just bounce off...

      September 23, 2011 at 10:53 am |
      • Sana

        I read NASA's 5 Key Indidators of Climate Change. What are your thoughts on the pole shift,that is tknaig place, on climate change. Everything can't be blamed on global warming.

        September 13, 2012 at 12:58 am |
    • Rich

      Maybe we can get the entire Tea Party to go on a cruise.

      September 23, 2011 at 11:08 am |
    • petercha

      How about Obama's head? Maybe it would wake him up!

      September 23, 2011 at 11:28 am |
  7. helenecha

    Of course, NASA is not sure where space junk will come down. Because there's no NASA trash basket are getting ready for them here on Earth even if they're the well-refined materials.

    September 22, 2011 at 11:12 pm |
  8. Abdelwahab elSadek Salem

    I think that by following the path of this space junk moment by moment the people can be warned to empty the area before it reached the ground. Is this is difficult? It deserve to register that this made some vision in the Revelation to John Come true.

    September 22, 2011 at 5:21 pm |
    • fimeilleur

      Considering that the objects will be falling at an incredible speed, and the debris field will stretch about 500 miles... you should have started heading somewhere else yesterday. And no, John's hallucinations are not coming true... 80% of the earth's surface is water... the probability of the space junk hitting water are that much greater than hitting land.

      September 22, 2011 at 8:57 pm |

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