Possible Earth impact in 2030 by asteroid 2000 SG344 No Longer a Concern

By Keith Cowing
November 3, 2000
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UPDATE: According to the IAU: “On the afternoon of November 3, Carl Hergenrother of the Catalina Sky Survey (CSS) near Tucson, Arizona, obtained and made available additional observations of object 2000 SG344 from the CSS image archives. These pre-discovery observations significantly improved the certainty of the object’s position in 2030 and effectively ruled out the chance of an Earth impact in that year.”

° Additional Information on Asteroid 2000 SG344, IAU

° New Results for Object 2000 SG344, NASA JPL

Earlier Information from the NASA ARC NEO Newsletter

NEO News (11/3/00) Possible impact prediction

Dear Friends and Students of NEOs:

Information is being released this morning from NASA and the
International Astronomical Union (IAU) concerning a possible impact
in 2030 by asteroid 2000 SG344. This is the first verified impact
prediction at a level of probability (1 in 500) to put it above
hazard level 0 on the Torino hazard scale. While this prediction is
no cause for alarm, it certainly focuses attention on the long-term
impact hazard. Since the asteroid has a very small space velocity
with respect to the Earth, it would be rather likely to survive down
to the surface in the unlikely event of an impact in 2030. The
energy is such a case would be about 1/10 of the Tunguska impact and
about 100 times the Hiroshima bomb. Additional observations this
winter may significantly improve the orbit, but unfortunately it
already seems to be out of the range of even the powerful Arecibo
radar. Definitive information on the orbit might therefore not be
obtained until 2028, as it again approaches the Earth.

David Morrison

Following is a statement prepared by Don Yeomans of JPL:

Recent computations by a group of international experts suggest a
very small asteroid-like object, designated 2000 SG344, has a remote
1 in 500 chance of impacting the Earth in 2030. These results have
been verified by a Technical Review Team of the International
Astronomical Union. The greatest likelihood is that future
observations of the object will yield higher precision orbit
computations that will show with certainty that it will miss the
Earth entirely. The unusual nature of the orbit of 2000 SG344
suggests the possibility that it is simply a man-made rocket booster
from the Apollo era.

Object 2000 SG344 was discovered on September 29, 2000 by David J.
Tholen and Robert J. Whiteley using the Canada-France-Hawaii
3.6-meter aperture telescope on the island of Hawaii. Shortly
thereafter, pre-discovery observations taken in May 1999 by MIT’s
LINEAR observatory team were also identified. Given the observed
brightness of the object and its assumed reflectivity, an estimate
can be made for its diameter. While the reflectivity of this object
is not known, values typical for near-Earth asteroids imply this
object’s extent is about 30-70 meters. Paul Chodas of the
Near-Earth Object Program Office at NASA’s
Jet Propulsion Laboratory estimates a one in 500 chance of it hitting
the Earth on September 21, 2030. The possibility of an Earth
impacting orbit was confirmed by Steven Chesley (NASA/JPL), Giovanni
Valsecchi (Italian National Research Center in Rome Italy), Andrea
Milani (University of Pisa, Italy) and Karri Muinonen (University of
Helsinki). If the object is near the large end of the estimated size
range for an asteroid, it would be classified as category 1 within
the 10 point Torino Scale,meaning the object is one that merits
careful monitoring. If the object’s size is closer to the lower
limit of 30 meters, it would be classified as Torino Scale 0 and
hence not of immediate concern.

Because the orbital period of this object about the sun is 354 days,
it moves a bit faster than the Earth about the Sun so it is drifting
slowly away and will not return to the Earth’s neighborhood until
nearly three decades. It was last in the Earth’s neighborhood in
1971. As yet undiscovered pre-discovery observations made in 1971
and additional observations made in the coming months would provide
the data for further refining this object’s orbit and the
circumstances of its close Earth approach in 2030. During the 2030
close approach, the perturbative effects of the Earth upon the object
could change its orbital period so that numerous encounters might be
possible after 2030. The likelihood of this situation is also under

Because of its Earth-like orbit, this object is an obvious candidate
for being a left-over space probe or rocket stage. For example, the
S-IVB stages of the five Apollo rockets (Apollo 8-12) entered into
heliocentric orbits that are similar to the orbit of object 2000
SG344. If this objectis a man-made rocket booster, it would have a
higher reflectivity than a natural asteroid and hence it would have
to be smaller (about 15 meters)to reflect as much light as a much
darker asteroid. While object 2000SG344 seems too bright to be an
Apollo rocket booster, the possibility of its being man-made has not
been ruled out.

While object 2000 SG344 will likely pass close to the Earth in 2030,
it should be made clear that the probability of the object missing
the Earth is at least 500 to 1. If the ongoing studies determine
that this object is likely to be a relatively small man-made booster
then such a lightweight object would pose no hazard. It is
interesting to note the chance of object 2000 SG344 striking the
Earth in 2030 is actually less than the chance of an undiscovered
object of the same size striking the Earth in any given year. Thus
object 2000 SG344 is more interesting than threatening but the
international efforts to characterize the nature and future motion of
this object will continue.

Added note: The International Astronomical Union (IAU)was closely
involved in the verification of the orbit predictions. The IAU has
noted that this is the first time the new IAU procedures for
technical review have resulted in the verification of a significant
impact risk (Torino scale hazard index 1). The IAU system worked
very well an stands as an example of international collaboration.
The IAU statement concerning the technical review of the orbital
calculations is posted on the IAU webpage

Web page addresses for:

  • Torino Scale: http://impact.arc.nasa.gov/torino/index.html

  • NASA Near-Earth Object web site at JPL: http://neo.jpl.nasa.gov

  • NEODyS web site at University of Pisa:

  • NASA/Ames NEO Impact Hazard page: http://impact.arc.nasa.gov


  • NASA’s Near-Earth Object Program Office at the Jet Propulsion Laboratory

    Steve Chesley

    Paul Chodas

    Don Yeomans, Manager

  • Chair, International Astronomical Union Working Group for Near-Earth Objects

    David Morrison, NASA/Ames

  • University of Pisa, Italy

    Andrea Milani

  • University of Helsinki

    Karri Muinonen

  • Italian Space Research Center

    Giovanni Valsecchi

  • Torino Scale

    Richard Binzel, MIT

  • SpaceRef co-founder, Explorers Club Fellow, ex-NASA, Away Teams, Journalist, Space & Astrobiology, Lapsed climber.