Near Earth Objects: Closest Approaches Through the Year 2020
The NEOs in the table below are mainly the Apollo, Aten and Amors
asteroids (Earth Orbit Crossing Asteroids).
To see the behavior of the Apollo and Aten asteroids, launch the
Voyager II program (Carina Software) and select the appropriate
file from the DEMOS folder. More data are accessible from the
web site at JPL and NASA.
From the JPL technical reports server, the following abstract
should pique your curiosity:
Thomas J. Ahrens and Alan W. Harris , Deflection and Fragmentation of Near-Earth Asteroids , Nature , December 1992.
Abstract:
Collisions by near-earth asteroids or the nuclei of comets pose
varying levels of threat to man. A relatively small object, approximately
100 m diameter, which might be found on an impact trajectory with
a populated region of the Earth, could potentially be diverted
with a velocity of approximately1 cm/sec from an Earth impacting
trajectory by impact (at 12 km/sec) by a rocket launched, 10^2
to 10^3 Kg impactor. For larger bodies, the use of kinetic energy
impactors appear impractical because of the larger mass requirement.
For any size object, nuclear explosions appear to be more efficient,
using either the prompt blow-off from neutron radiation, the impulse
from ejecta of a near-surface explosion for deflection, or, least
efficiently, as a fragmenting charge.
More academic publications concerning hazards from asteroids, for fascinating reading.
1 AU = one Astronomical Unit = Earth-sun distance = 9.3 x 10^6
miles or 1.5 x 10^8 km
Average distance of the Moon = 0.00256 AU or 2.4 x 10^5 miles or 3.84 x 10^5 km
|