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TOPIC: 2004 MN4


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The first sign of the threat was no more than a speck on a star-streaked telescope image. Just after 9 p.m. on June 18, 2004, as twilight faded over Kitt Peak National Observatory in Arizona, David Tholen was scanning for asteroids in an astronomical blind spot: right inside Earths orbit, where the suns glare can overwhelm telescopes. Tholen, an astronomer from the University of Hawaii, knew that objects lurking there could sometimes veer toward Earth. He had enlisted Roy Tucker, an engineer and friend, and Fabrizio Bernardi, a young colleague at Hawaii, to help. As they stared at a computer, three shots of the same swath of sky, made a few minutes apart, cycled onto the screen.

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NASA STATEMENT ON STUDENT ASTEROID CALCULATIONS
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. Therefore, consideration of this satellite collision scenario does not  affect the current impact probability estimate for Apophis, which remains at 1 in 45,000.

Source NASA

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"We have not corresponded with this young man and this story is absurd, a hoax or both. During its 2029 Earth close approach, Apophis will approach the Earth to about 38,900 km, well inside the geosynchronous distance at 42,240 km. However, the asteroid will cross the equatorial belt at a distance of 51,000 km - well outside the geosynchronous distance. Since the uncertainty on Apophis' position during the Earth close approach is about 1500 km, Apophis cannot approach an Earth satellite. Apophis will not cross the moon's orbital plane at the Moon's orbital distance so it cannot approach the moon either" - Don Yeomans, NASA

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A German teenager has corrected Nasa's estimates of the likelihood that the Earth will be hit by a large asteroid in 2036.
The Apophis asteroid will make a close flyby on 13 April 2029, and Nasa had previously predicted that the chances of it hitting the planet on its return in 2036 were 45,000 to 1.
But 13 year-old Nico Marquardt from Potsdam used open source software to find that the probability actually rises to 450 to 1 because it may hit a manmade satellite.

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Apophis
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Researchers at NASA/JPL, Caltech, and Arecibo Observatory have released the results of radar observations of the potentially hazardous asteroid 99942 Apophis, along with an in-depth analysis of its motion. The research will affect how and when scientists measure, predict, or consider modifying the asteroid's motion. The paper has been accepted for publication in the science journal "Icarus" and was presented at the AAS/DPS conference in Orlando, Florida in October of 2007.
The analysis of Apophis previews situations likely to be encountered with NEAs yet to be discovered: a close approach that is not dangerous (like Apophis in 2029) nonetheless close enough to obscure the proximity and the danger of a later approach (like Apophis in 2036) by amplifying trajectory prediction uncertainties caused by difficult-to-observe physical characteristics interacting with solar radiation as well as other factors.

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By analysing sunlight reflected off its surface, scientists say the asteroid Apophis is a "good match" for a rare type of stony meteorite known as a type LL chondrite. This group of space rocks represents just 7 percent of the known meteorites that fall to Earth.

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Apophis
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Researchers at MIT say they know what the near-Earth asteroid Apophis is made of, information that could be vital if we need to divert or pulverise the space-rock in 2036.
By analysing its spectrum and comparing it with meteorites that have already landed on Earth, the team has "nailed" its composition, says Richard Binzel, professor of planetary sciences in MIT's Department of Earth, Atmospheric, and Planetary Sciences (EAPS).


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In research that could aid decisions about future asteroids on a collision course with Earth, MIT researchers have for the first time determined the composition of a near-Earth asteroid that has a very slight possibility of someday hitting our planet.
 That information could be useful in planning any future space mission to explore the asteroid, called Apophis. And if the time ever were to come when this object or another turned out to be on its way toward an impact on Earth, knowing what it's made of could be one important factor in deciding what to do about it.

 "Basic characterisation is the first line of defence. We've got to know the enemy" - Richard P. Binzel, Professor of Planetary Sciences in the Department of Earth, Atmospheric, and Planetary Sciences (EAPS).

Binzel presented the new findings this week at the annual meeting of the Division for Planetary Sciences of the American Astronomical Society.
Studying the composition of Apophis has been a useful "practice case," Binzel says, because "you never know when the real one will come along" that is on a collision with the Earth. For determining the composition of a threatening asteroid.

 "We don't know when the real test will come, but we're ready" - Richard P. Binzel.

On April 13, 2029, Apophis will come relatively close to Earth (it will miss us by about 22,000 miles). But when it comes by again in 2036, there is a very small possibility - about one chance in 45,000 - that it could be on a collision course.
 So Binzel, working with EAPS graduate students Cristina Thomas and Francesca DeMeo and others, has been using telescopes on Earth to find out as much as possible about the nature of Apophis and other asteroids. Short of putting together a space mission that would take years and cost hundreds of millions of dollars, such observations are the best way to find out as much as possible about any space rock that might someday be coming our way.
Using the MIT Magellan telescope in Chile and NASA's Infrared Telescope Facility in Hawaii, they have now been able to figure out exactly what Apophis is made of.

"The composition, I think, is really nailed".

The key to understanding the mineral makeup of an asteroid is to compare it with samples of asteroidal material that have been delivered, free of charge, to the Earth, in the form of the many thousands of meteorites that have been collected over the years.
Spectral analysis - measuring how the meteorites reflect light of different wavelengths - can be used to determine their exact mineral constituents. Similarly, a spectral analysis of the light reflected from a distant asteroid shows the same telltale lines that reveal its composition. By comparing the two kinds of spectra, an asteroid that is just a faraway pinprick of light can be correlated with a piece of a space rock in the laboratory.
Binzel and his students were able to use both visible-light and infrared spectroscopy to show that Apophis is "a good match" for a rare type of meteorite, known as a type LL chondrite. These represent just 7 percent of the known meteorite falls on Earth, and are rich in the minerals pyroxene and olivine, which are also common on Earth.

"The beauty of having found a meteorite match for Apophis is that because we have laboratory measurements for the density and strength of these meteorites, we can infer many of the same properties for the asteroid Apophis itself" - Richard P. Binzel.

An object the size of Apophis (about 270 metres across) could devastate a region as large as France, or produce tsunamis over a wide area if it struck at sea. Many ideas have been proposed for how to deal with such a threat, ranging from using bombs, lasers or spacecraft to nudge it out of the way to blowing it to pieces while it is still far away. The selection of the best course of action may depend of the physical characteristics of the object, including its mineral composition.

Source: MIT

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99942 Apophis
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Engineering services and concept development firm SpaceWorks Engineering, Inc. (SEI) and small satellite developer SpaceDev, Inc. announce the submission of a joint proposal, the Foresight spacecraft, to the Planetary Society's Apophis mission design competition. Foresight is a low-cost, low-risk, minimal science approach to achieve the specific goal of obtaining accurate tracking to reduce the uncertainty in the orbit of potentially hazardous asteroid (PHA) Apophis.
Apophis, a 260 meter near-Earth asteroid, will pass within the range of geostationary satellites during its close approach to the Earth in April 2029. The 2029 close approach will significantly alter Apophis' orbit. There is a small possibility that the asteroid will pass through an area of space called a "keyhole", which would cause Apophis to impact the Earth in 2036. More precise measurements of the orbit of Apophis can confirm or deny this possibility.

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Celestial objects hold great interest for this scribbler. Which is why I was miffed to miss out on last Tuesday night's show as a blazing meteorite or suchlike streaked across the skies lighting them up in extraordinary fashion. That's how the precious few lucky enough to witness the event described it.
No explanation of just what the mysterious object was has been forthcoming but after the recent Peru meteorite phenomenon, which saw 600 people fall ill after it belted a crater in the ground _ and talk we've raised also of potentially-dangerous microbes attached to space junk _ it set me to thinking about a colossal piece of space rock called 99942 Apophis hurtling our way.

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