[meteorite-list] Asteroid 2003 QQ47's Potential Earth Impact in 2014 Ruled Out

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Apr 22 10:29:50 2004
Message-ID: <200309032214.PAA01687_at_zagami.jpl.nasa.gov>

http://neo.jpl.nasa.gov

Asteroid 2003 QQ47's Potential Earth Impact in 2014 Ruled Out

Paul W. Chodas and Steven R. Chesley
NASA's Near Earth Object Program Office
September 3, 2003

Newly discovered asteroid 2003 QQ47 has received considerable media
attention over the last few days because it had a small chance of
colliding with the Earth in the year 2014 and was rated a "1" on
the Torino impact hazard scale, which goes from 0 to 10. The odds
of collision in 2014, as estimated by JPL's Sentry impact
monitoring system, peaked at 1 chance in 250,000, a result which
was posted on our Impact Risk Page (http://neo.jpl.nasa.gov/risko) o
n Saturday, August 30. Impact events at the Torino Scale 1 level
certainly merit careful monitoring by astronomers, but these events
do not warrant public concern. In fact, each year several
newly discovered asteroids reach Torino Scale 1 for a brief period
after discovery; 2003 QQ47 is the fourth such case this year.

As astronomers continue to monitor an asteroid and measure its
position, more precise predictions can be made. On September 2,
new measurements of QQ47's position allowed us to narrow our
prediction of its path in 2014, and thus we could rule out any
Earth impact possibilities for 2014. In our Impact Risk Page for
2003 QQ47, the entry for the year 2014 has now disappeared,
although a number of potential impact events remain for later
years. We expect that these too will be ruled out in the coming
days as astronomers continue to track the object and we refine
our orbit predictions.

These seemingly large day-to-day changes in impact predictions for
newly discovered asteroids are just what we expect. In the few days
after an asteroid is first discovered, its orbit is known only very
approximately. The range of possible positions in future years is
wide and can easily encompass the Earth, but as the object continues
to be tracked, the range of possibilities shrinks quickly, allowing
us to rule out any possibility of impact. This process is ongoing
for 2003 QQ47, and could take days or even weeks before all potential
impacts are ruled out.
Received on Wed 03 Sep 2003 06:14:39 PM PDT