NASA had some disappointing news for all those looking forward to the 2012 cataclysm, especially if those same people were looking for the end of the world via killer asteroid impact. The space agency reported on Sept. 29 that the WISE spacecraft, which was originally tasked with locating, identifying, and gathering data to assist in cataloguing near-Earth Asteroids (planetoids coming within 120 million miles of Earth orbit), had completed its assignment and had identified more than 90 percent of all the asteroids and objects hurtling throughout the Solar System. The data also suggests that there are 44 percent fewer intra-solar objects that pass near the Earth. But, the optimistic end-of-the-worlder might interject, what about that 10 percent that has yet to be identified?
According to NASA, the gathered data included the tracking of several "killer" asteroids, objects as large or larger than the massive meteor theorized to have played a major role in exterminating the dinosaurs. Only a few appear to be on a collision course with Earth but not for a couple centuries. The downgraded estimate of the number of total objects, which was derived from the extensive census taken by WISE, put the total estimate of mid-size near-Earth Asteroids (large enough to destroy a city) at roughly 19,500, not 35,000 as was originally thought to exist.
Lead author of the study (published in the Astrophysical Journal), Amy Mainzer, who heads the NEOWISE project at California's Jet Propulsion Laboratory, noted, "NEOWISE allowed us to take a look at a more representative slice of the near-Earth asteroid numbers and make better estimates about the whole population. It's like a population census, where you poll a small group of people to draw conclusions about the entire country."
And just like a population census, part of the population remains unaccounted for. It is those estimates that allow for 10 percent of the near-Earth objects that just might contain a subsection of unidentified asteroids that could be potentially harmful to planet Earth.
WISE was able to obtain a more accurate count of asteroids throughout the solar system due to its ability to detect in both visible and non-visible light. Besides the downgraded number of near-Earth objects detected, the spacecraft also photographed over 100,000 asteroids in the Main Belt between Mars and Jupiter.
But Main Belt asteroids aren't a danger to the Earth...
Tim Spahr, the director of the Minor Planet Center at the Harvard Smithsonian Center for Astrophysics in Cambridge, Mass., has reassuring words for those worrying of a deep space impact that could end life as we know it. "The risk of a really large asteroid impacting the Earth before we could find and warn of it has been substantially reduced."
Reduced...
The new data produced by the NEOWISE project indicated that the number of killer asteroids, small rocky planetoids measuring from 1 kilometer (3,300 feet) and larger, was also downgraded -- from 1,000 to 981. At present, only 911 have been found, but NASA believes that all the asteroids measuring 6 miles across (and larger), like the extinction-initiating Chicxulub meteorite that impacted off the Yucatan peninsula and hastened the demise of the dinosaurs, have already been found.
And yet, admittedly it is but an educated guess as to the just how many there actually are.
The hurtling planetoids pass close by the Earth all the time. In fact, by the end of the day on Sept. 30, more than a dozen smaller asteroids will have slipped by the Earth just in the preceding six days (Sept. 25 - Oct. 30), according to the Near Earth Object Program. On October 30, the closest of those being tracked (asteroid 2011 SM173), passed within .0019 astronomical units of the Earth (less than 177,000 miles). It was traveling at nearly 8 miles per second and is estimated to be 24 to 56 feet across, or the size of a small bus or a small house.
But it isn't the medium-sized and larger killer asteroids that have been located and are being tracked that pose the most concern -- it is the 10 percent of all near-Earth asteroids that are still unaccounted for, undetected and barreling through space at devastating speeds...
(photo credit: Don Davis/NASA, Wikimedia Commons)
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