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Posted by Peter Munn on April 18, 2008, 11:38 am
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Leafing through sci.space.news, I read Ron's message of Wed, 16 Apr
2008:
>WASHINGTON -- The Near-Earth Object Program Office at NASA's Jet
>Propulsion Laboratory in Pasadena, Calif., has not changed its
>current estimates for the very low probability (1 in 45,000) of an
>Earth impact by the asteroid Apophis in 2036.
>
>Contrary to recent press reports, NASA offices involved in near-Earth
>object research were not contacted and have had no correspondence
>with a young German student, who claims the Apophis impact
>probability is far higher than the current estimate.
>
>This student's conclusion reportedly is based on the possibility of a
>collision with an artificial satellite during the asteroid's close
>approach in April 2029. However, the asteroid will not pass near the
>main belt of geosynchronous satellites in 2029, and the chance of a
>collision with a satellite is exceedingly remote.
The relevant previous post to read is this one:-
From: baalke@earthlink.net
Newsgroups: sci.astro, alt.sci.planetary
Subject: Predicting Apophis' Earth Encounters in 2029 and 2036
Date: Tue, 20 Nov 2007 14:04:18 -0800 (PST)
Message-ID:
which not only explains in detail why the asteroid is not likely to hit
a satellite but lists several much more significant unquantified effects
that deserve attention. Most notably, it mentions solar-energy-related
momentum effects might be responsible for as much as 30 _million_ km
position variation by 2036.
>Therefore, consideration of this satellite collision scenario does
>not
>affect the current impact probability estimate for Apophis, which
>remains at 1 in 45,000.
The post I just referenced does a much better job at throwing the 1 in
45,000 odds into doubt. In fact, its authors effectively say that the
current models and knowledge of Apophis aren't good enough for
calculating such moderately precise odds for 2036, basically because the
potential impact follows a previous close encounter.
But with unknowns as big as 30,000,000 km thrown into the mix, there's
no way the odds can be much shorter than 1 in 45,000.
So it's not something for anyone to get worked up about. Unless, that
is, we stop watching the big mound and trying to improve the
predictions. The authors reckon that provided we know where it's
heading early enough (2018 is a date they mention as an example) then
deflecting it will easy.
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