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Threatening asteroid Apophis a possible target for NASA’s Orion Asteroid Mission.
Threatening asteroid Apophis a possible target for NASA’s Orion Asteroid Mission.
Apophis is a large asteroid which is expected to make unusually close approaches to Earth. It is a potential target for NASA’s Orion Asteroid Mission, in which a modified Altair lunar lander will land crewmembers on a near-Earth asteroid.
At the moment, the mission is expected to not take place until long after Orion 15/Altair 2 has landed on the Moon. I am coming to the conclusion that, notwithstanding the possibility of mining helium 3 from the Moon for use in fusion reactors as a source of cheap and clean energy, more attention must be paid to dealing with the potential asteroid threat - not only from Apophis in 2036, but also from other fast moving asteroids, many of which are not detected until they have nearly arrived. In the last few weeks, two asteroids have approached Earth within 1.3 lunar distances, and recently one arrived not much further from us than the altitude of a geostationary satellite. In October 2008, an asteroid exploded over a desert in Africa.
Of the four asteroids in our neighborhood today, 2009 HS44 is the closest, approaching us at closest distance of 0.0118 AU or ~1.76 million miles. It's between 42 and 95 across and is travelling at about 40,332 mph, so it's faster than usual, although the estimated speed of asteroid 2009 HE21 is 63,372 mph - it's nearly three times larger in diameter, but will be further away, making its close approach on April 30. Today's 2009 HS44 asteroid is the closest known in the next 5 months, and the 2009 HE21 asteroid of April 30 the fastest.Whether Apophis will be a threat to us in 2036 is not fully known. There is a gravitational keyhole near Earth about 600 metres across. If Apophis passes through this in 2029, it is more likely that it will collide with Earth in 2036.
“An equivalent way of describing the problem of computing an impact probability for Apophis is that the true 2029 “keyhole” leading to a 2036 impact - as distinct from the theoretical keyhole derived from the Standard Dynamical Model - is not known in the absence of knowledge of the complete dynamics. The problem is acute enough for Apophis that, IF impact hasn’t been previously excluded, AND there hasn’t been a through physical characterization, it can’t be known for certain it will impact until during or after the 2029 encounter, even if a spacecraft is accompanying Apophis and providing position measurements good to 2 meters. That is, the keyhole could be determined only retrospectively, after passage through it.” - http://neo.jpl.nasa.gov/apophis/
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