Do we have to worry about an as­teroid strike?

Tehran Times - - SCIENCE -

The as­teroid Apophis seems like a friendly rock speeding through the space near Earth for now, but later on in its re­la­tion­ship with our planet, it might strike down to the sur­face with dev­as­tat­ing re­sults.

It may never hap­pen, but it’s not out of the realm of pos­si­bil­ity, ac­cord­ing to a re­port on

After all, sci­en­tists were briefly wor­ried in 2004 about that as­teroid strik­ing Earth, be­fore fur­ther cal­cu­la­tions showed there was noth­ing to be alarmed about. It has passed through our space neigh­bor­hood since then with­out in­ci­dent, but Apophis has fu­ture fly­bys sched­uled and while the next cou­ple are go­ing to go pretty smoothly, oth­ers may not be as pleas­ant.

NASA pro­jects that Apophis will come by in 2029 and will re­turn again in 2036. In the for­mer jour­ney, the clos­est the as­teroid may get to Earth a lit­tle less than 20,000 miles, which is closer than some of our satel­lites. That’s a pretty close pass to the planet, and will put it into the record books as the clos­est one of its size. It will ap­pear “to the naked eye as a mod­er­ately bright point of light mov­ing rapidly across the sky” over the mid-At­lantic area.

The lat­ter flyby, in 2036, will be from much farther out, sev­eral mil­lion miles away. NASA sci­en­tists fi­nal­ized cal­cu­la­tions a few years ago that showed there was no dan­ger dur­ing that pass.

Im­pact odds

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,” Don Yeo­mans, man­ager of NASA’s Near-Earth Ob­ject Pro­gram Of­fice at the Jet Propul­sion Lab­o­ra­tory, said at the time. “Our in­ter­est in as­teroid Apophis will essen­tially be for its sci­en­tific in­ter­est for the fore­see­able fu­ture.”

“We can rule out a col­li­sion at the next clos­est ap­proach with the Earth, but then the or­bit will change in a way that is not fully pre­dictable just now, so we can­not pre­dict the be­hav­ior on a longer timescale,” Al­berto Cellino, of the Ob­ser­va­tory of Turin in Italy, told Astrowatch. net.

Apophis is be­tween 700 and 1,100 feet long, more than large enough to do sub­stan­tial da­m­age if it were to crash down onto the Earth. But even with­out Apophis, our planet is still vul­ner­a­ble to a deadly as­teroid. They pass by Earth all the time, some­times more than one in a day. Usu­ally they are rel­a­tively small and far out, but there are ex­cep­tions. For ex­am­ple, NASA is pre­dict­ing an as­teroid be­tween 800 and 1,800 feet across fly­ing by on June 27, from a dis­tance that is equiv­a­lent to about a tenth of the dis­tance be­tween the Earth and the sun.

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