April 13, 2009 -- About 20 years from today, an asteroid about the size of a 25-story building will come closer to Earth than the networks of communications satellites orbiting the planet. NASA says there's no chance of an impact -- at least not in 2029 -- but the asteroid, named Apophis, will be back. Analysis of the asteroid's orbit show it will return to Earth seven years later. Astronomers don't yet know if Apophis' second visit will be a rendezvous or a collision, as its orbit will be bent by Earth's gravity during the 2029 flyby. Most of the rocks whizzing around Earth are too small to do damage even if they were on collision paths. "Things much below 30 meters in size don't pose much of a threat at all since the atmosphere protects us," said Nick Kaiser, lead scientist of a new University of Hawaii asteroid-hunting project known as the Panoramic Survey Telescope and Rapid Response System, or Pan-STARRS. Related Content:
The telescope array, funded by the Air Force Research Laboratories, combines small mirrors with massive digital cameras to image the entire sky several times a month. Pan-STARRS supplements ongoing NASA-funded efforts to survey 90 percent of near-Earth objects bigger than 140 meters, or 459 feet. "As things get bigger, the amount of devastation goes up dramatically," Kaiser said, but so too does the length of time between occurrences. A half-mile diameter object impacting Earth likely would cause a global catastrophe, but these events happen every couple of million years or so, Kaiser said. The asteroid that is believed to be responsible for wiping out the dinosaurs 65 million years ago was about 10 kilometers, or 6.2 miles, in size. More recently, a rock about 50 meters, or 164 feet, exploded over an unpopulated region of Russia known as Tunguska, devastating an area tens of miles across. As of March 31, NASA's list of so-called near-Earth objects numbers 6,191. The catalog includes 773 objects one kilometer in diameter or larger and 1,042 objects -- including Apophis -- classified as "potentially hazardous" to Earth, according to the agency's Near-Earth Object Program web site. Get More NewsSpiders, Scorpions Among World's Oldest CreaturesMany creepy crawlies have been on Earth much longer than previously believed.Blood-Sucking Vampire Bats Sing DuetsWhite-winged vampire bats "harmonize" with separated roost mates.Oldest Hebrew Writing Possibly FoundAncient inscriptions on a 3,000-year-old pottery shard could make history.Rare, Prehistoric-Age Reptile Found in N.Z.A tuatara has been spotted on the New Zealand mainland for the first time in 200 years.Iceman Has No Living RelativesOetzi, the 5,300 year-old frozen mummy, left no living genetic legacy.SLIDE SHOW: Landscapes of TerrorWhat makes a place feel scary? There are scientific explanations.It's Official: People Are Warming the PolesHumans are conclusively to blame for polar warming, say scientists.Eight-Armed Animal Preceded DinosaursWhat may be one of Earth's first animals was no bigger than a coaster and had eight arms.Phoenicians Live on in People's GenesOne in 17 Mediterranean men may be descended from ancient Phoenicians.Pesticides, Fertilizers Linked to Frog DeclineA pesticide is found to promote parasites among amphibians.Hubble Telescope Taking Photos AgainThe Hubble Space Telescope is once again snapping stunning photos of the universe.Andean Mummy Hairs Show Hallucinogen UseScientists find direct evidence of hallucinogenic drug use among ancient Andeans.Opals on Mars Reveal Planet's Long Wet PastOpals found on Mars suggest the planet has been wet for much longer. |
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