January 13th, 2013 by James Ayre
The asteroid Apophis is extremely unlikely to impact the Earth in 2036, according to researchers at NASA. The newly refined projections of the asteroid’s fly-by in 2036 were possible thanks to new data that was just obtained during the fly-by that occurred on January 9, 2013.
Only very recently discovered, in 2004, the asteroid Apophis, which is roughly the size of 3.5 football fields, has been of great interest to researchers and to the general public. This has largely been due to the fact that “initial calculations of its orbit indicated a 2.7% possibility of an Earth impact during a close flyby in 2029. Data discovered during a search of old astronomical images provided the additional information required to rule out the 2029 impact scenario, but a remote possibility of one in 2036 remained — until Wednesday.”
“With the new data provided by the Magdalena Ridge (New Mexico Institute of Mining and Technology) and the Pan-STARRS (Univ. of Hawai)] optical observatories, along with very recent data provided by the Goldstone Solar System Radar, we have effectively ruled out the possibility of an Earth impact by Apophis in 2036,” according to Don Yeomans, the manager of NASA’s Near-Earth Object Program Office at JPL. “The impact odds as they stand now are less than one in a million, which makes us comfortable saying we can effectively rule out an Earth impact in 2036. Our interest in asteroid Apophis will essentially be for its scientific interest for the foreseeable future.”
The flu-by on April 13, 2029, is still expected to be extremely close though. The asteroid Apophis is expected to become the closest-ever known flyby of such a large asteroid that year, coming as 19,400 miles to the Earth.
“But much sooner, a closer approach by a lesser-known asteroid is going to occur in the middle of next month when a 40-meter-sized asteroid, 2012 DA14, flies safely past Earth’s surface at about 17,200 miles,” said Yeomans. “With new telescopes coming online, the upgrade of existing telescopes and the continued refinement of our orbital determination process, there’s never a dull moment working on near-Earth objects.”
“NASA detects and tracks asteroids and comets passing close to Earth using both ground and space-based telescopes. The Near-Earth Object Observations Program, commonly called ‘Spaceguard,’ discovers these objects, characterizes a subset of them and plots their orbits to determine if any could be potentially hazardous to our planet.”
Some background on what a near-Earth object, such as Apophis, is:
“A near-Earth object (NEO) is a Solar System object whose orbit brings it into proximity with the Earth. They include a few thousand near-Earth asteroids (NEAs), near-Earth comets, a number of solar-orbiting spacecraft, and meteoroids large enough to be tracked in space before striking the Earth. It is now widely accepted that collisions in the past have had a significant role in shaping the geological and biological history of the planet. NEOs have become of increased interest since the 1980s because of increased awareness of the potential danger some of the asteroids or comets pose to the Earth, and active mitigations are being researched.”
“While orbiting the Sun, most potential impactors can be classified as meteoroids, asteroids, or comets depending on size and composition. Asteroids can also be members of an asteroid family, and comets can leave debris in their orbits.” This includes the debris that causes meteor showers.
“Objects with diameters of 5-10 m impact the Earth’s atmosphere approximately once per year, with as much energy as the atomic bomb dropped on Hiroshima, approximately 15 kilotonnes of TNT. These ordinarily explode in the upper atmosphere, and most or all of the solids are vaporized. Every 2000–3000 years NEAs produce explosions comparable to the one observed at Tunguska in 1908. Objects with a diameter of one kilometer hit the Earth an average of twice every million year interval. Large collisions with five kilometer objects happen approximately once every ten million years.”
“Assuming that these rates will continue for the next billion years, there exist at least 2,000 objects of diameter greater than 1 km that will eventually hit Earth. However, most of these are not yet considered potentially hazardous objects because they are currently orbiting between Mars and Jupiter. Eventually they will change orbits and become NEOs. Objects spend on average a few million years as NEOs before hitting the Sun, being ejected from the Solar System, or hitting a planet.”
“On 6 June 2002 an object with an estimated diameter of 10 meters collided with Earth. The collision occurred over the Mediterranean Sea, between Greece and Libya, at approximately 34°N 21°E and the object exploded in mid-air. The energy released was estimated (from infrasound measurements) to be equivalent to 26 kilotons of TNT, comparable to a small nuclear weapon.”
There are a number of asteroids being tracked currently that have a notable chance of hitting the Earth in the next thousand or so years. The most well known being the asteroid 1950DA, which is estimated to have a 1 in 300 chance of impacting the Earth in 2880.
Image Credits: UH-IA; Impact Event via Wikimedia Commons
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