November 5, 2000Pasadena, California – Asteroids headed towards, or near, earth are in the news again. On Friday, NASA’s Near-Earth Object Program Office in Pasadena, California announced that a small object discovered on September 29th had a small chance of colliding with this planet in September 2030. In fact, this was the first asteroid-like object to be given a Number One on the Torino scale which measures space collision threats. The scale was developed in 1998 by Richard Binzel, Professor of Planetary Science at the Massachusetts Institute of Technology, to help categorize near-earth objects. It’s a sliding scale from zero to ten. Zero is no threat. A ten means definite impact that would cause a global catastrophe. A category one means scientists think this new object deserves careful monitoring. Paul Chodas, Principal Engineer for the NEAR Program Office at JPL, said “This is the highest probability of impact that we have ever calculated for an object.”
However, by Saturday, November 4, more tracking data and calculations had downgraded the impact threat for the year 2030 to zero, but left open a possible collision in 2071. The reason is that the still-unidentified object is orbiting around the sun right in the earth’s plane. This weekend I talked with Dr. Paul Chodas about what the object could be.
Paul Chodas, Ph.D., Principal Engineer, NASA’s Near-Earth Object Program Office, Pasadena, California: “This particular asteroid is in such an orbit that it is almost flying in formation with the earth. The asteroid is moving slightly faster so it will take 31 revolutions to catch up to the earth in 30 years.
ABOUT HOW BIG IS THIS OBJECT?
We believe this object is approximately 50 meters in size. That’s 150 feet. There’s uncertainty on that because we only have a few observations of it.
COULD YOU PLEASE COMMENT ON SOME OF THE SUGGESTIONS THIS WEEK THAT IT MIGHT BE AN APOLLO BOOSTER RELIC?
Yes, the orbit of the asteroid is very similar to that which some of the Apollo 3rd stage booster rockets are in when they go around the sun. Five of these 3rd stage boosters are in orbit around the sun: Apollos 8 through 12 had these boosters and they are in orbits that are much like the earth and probably like the orbit of this asteroid.
BUT YOU HAD AN OBJECTION IN ONE OF THE PRESS RELEASES SAYING THAT THE ORBIT DOES NOT EXACTLY MATCH UP TO ANY ONE PARTICULAR APOLLO LAUNCH?
Exactly. The shape and the tilt of the orbit matches up. But I attempted to match the motion of the asteroid and its velocity in time and then bring the object back to the earth by following the motion in the computer backwards in time and when I do this, it comes back to the earth several weeks off of any known Apollo mission. That is to say the timing on the orbit doesn’t quite match. The size of the orbit matches approximately the expected size of a booster, but the timing does not match precisely. It does come back within a few weeks of Apollo 14 or Apollo 15 in 1971. But we know both of those boosters impacted the moon. So there is no match with those particular Apollo missions that I know of and the timing doesn’t seem to match the orbits of the other five known boosters.
WHAT YOU’RE SAYING ALMOST NEGATES THE HYPOTHESIS THAT THIS COULD BE AN APOLLO ROCKET BOOSTER
It makes it difficult to associate it with one particular booster. We do not know all of the forces that would be acting on the booster. Some of them are unpredictable. If the booster has any left over propellant in it at the end of the mission for Apollo, it may have some slight leaks, may have had some venting of propellants or something like this. And this would make it more difficult, it would be unpredictable to follow the motion precisely. So, we have to do more analysis before we can be sure that we can associate it with a particular Apollo launch.
IT ALSO SOUNDS AS IF THIS OBJECT IS LARGER THAN ONE WOULD EXPECT IN AN APOLLO ROCKET BOOSTER TO BE
No, not really. Our assumption of 30 to 70 meters are on average around 150 feet. That is assumption is based on the brightness of an asteroid. All we know right now is that the brightness of this particular object seems approximately correct for a booster. And the size that we gave was based on the assumption that it is an asteroid (rocky). It could also be a booster. And if it is a booster, then our size estimate would change to around 15 to 20 meters or the correct size for a Saturn 4V.
THE MYSTERY IS THAT YOU CAN’T MATCH UP ANY APOLLO ORBIT EXACTLY WITH THIS IN TERMS OF RUNNING BACKWARDS ON THE COMPUTER; THERE MAY BE AN UNKNOWN FACTOR ABOUT WHAT WOULD HAPPEN TO A BOOSTER MOVING AROUND THE SUN; OR IT COULD BE SOMETHING ELSE.
Yes, indeed. It could be a natural asteroid. That’s right. We cannot be sure one way or the other right now. Of course, this is a small object and you can’t resolve it in a telescope. You can’t see the size of it or the shape of it or anything like that. We used the Arecibo Radio Telescope in Puerto Rico on Friday, I believe it was, to bounce radar signals off the object to try to find out its nature, its radar reflectivity and that sort of thing. It was simply too far. We didn’t get a return signal.
IT DISAPPEARS AND THEN WILL REAPPEAR SOME PLACE IN 2030. AND THE QUESTION IS: WILL IT BE ON AN IMPACT COURSE WITH THE EARTH?
Perhaps two or three years before then as it comes around and is approaching us from our behind, I guess, as we go around the sun. We’ll be able to see it a few years before then. It would be nice to settle the issue now before it disappears on the other side of the sun.
But realistically, you shouldn’t lose sleep over this and the odds are this thing will miss in 2030. I would point out, however, that its orbit is so similar to the earth’s that it will make repeated encounters with the earth in future years if it misses in 2030 which is the most likely scenario.
THIS IS AN OBJECT THAT WILL KEEP CROSSING THE EARTH’S POSITION IN THE EARTH’S PLANE ON SOME KIND OF PERIODIC CYCLE?
That is correct, yes
IN THE NEXT THREE DECADES, WHAT ARE WE DOING RIGHT NOW AS A NATION TO TRY TO ANTICIPATE THE POSSIBILITY OF AN OBJECT SUDDENLY HAVING AN IMPACT COARSE WITH THE EARTH AND WHAT WE COULD DO ABOUT IT?
We have several surveys that are funded by NASA. They are looking for near-earth objects. We have, for example, a telescope in New Mexico which is actually an Air Force telescope looking for debris in orbit around the earth. But when it’s not in use for that purpose, it’s looking for asteroids. And over the last few years, we have made dramatic increases in our ability to find asteroids out there. And we are finding them in large numbers. We don’t know exactly how many asteroids are in the near earth region. But estimates have been refined lately to indicate there are around a thousand or 900 of these asteroids in total that come within a certain distance of the earth, whose orbits bring them within a certain distance of the earth.
This particular asteroid 2000 SG 344 this asteroid is quite small. And it is well below the limits of size where it would cause a global catastrophe.
UNLESS IT HIT IN ONE OF THE OCEAN BODIES AND CAUSED A GIANT TSUNAMI, CORRECT?
Yes. It’s a small enough object that it would not even cause a giant tsunami. It would be a tsunami perhaps, but not very large. It’s a small object and it’s barely large enough to register any concern at all. If our estimates of its size were half as large, we wouldn’t worry about it at all. It would break up in the atmosphere and not reach the earth’s surface for certain.
BUT AT 150 FEET OR SO…
But at 150 feet, there is the possibility that it could reach the earth’s surface. But it just barely registers.
IF IT HIT THE WATER, THAT’S ONE CONSIDERATION. BUT IF IT HIT SAY A CITY LIKE NEW YORK OR LOS ANGELES, IT COULD DO CONSIDERABLE DAMAGE, RIGHT?
That is correct. There would certainly be some local damage. Mind you, we often forget the earth is mostly covered by unpopulated areas. And it’s in all likelihood even if it did hit which is not likely it would hit in an unpopulated area.
YOU HAVE MADE THE POINT THAT THERE ARE LITERALLY HUNDREDS IF NOT THOUSANDS OF THESE ASTEROID-LIKE OBJECTS OUT THERE AND THAT MEANS THAT THE ODDS THAT SOMETHING COULD COME ON THE RADAR AND IMPACT WITH THE EARTH IS ALSO OUT THERE. WHAT CAN WE DO ABOUT AN INCOMING ASTEROID?
We would have to first be sure that the asteroid, fairly sure that the asteroid was going to impact on the earth and did pose a threat, based on its size and probability of hitting us. If the warning was sufficiently long that is to say, many years, or a decade, hopefully then it would be possible to send a mission out and visit the asteroid and possibly deflect it lightly. Over time, a small deflection would be enough to make the asteroid miss the earth.
MEANING THAT WE GET SOMETHING OUT TO AN ASTEROID AND MAYBE WE USE SOME KIND OF GAS JET OPERATION, SORT OF PUSH IT IN A DIFFERENT ORBIT?
Yes. A very slightly different orbit.
AS OPPOSED TO BLOWING IT UP?
YOU SAID ON THIS CURRENT ONE WHEN IT COMES BACK AROUND THE SUN, THAT WE MIGHT SEE IT IN ADVANCE MAYBE THREE YEARS. THAT’S NOT A DECADE.
That’s correct. That’s one reason why we would like to get more observations of it right now. But, there are a couple of things. This asteroid would be fairly easy to get to if it were, if we were truly concerned about this impact chance. But a 1 in 500 chance of impact is quite small and furthermore, the asteroid has not been terribly well observed. We haven’t seen it for a long period of time and it’s too early, really, to consider a deflection mission for this asteroid. But it does provide an example of the sorts of scenarios that could possibly arise as we discover more asteroids and as we discover the larger asteroids.”