Asteroid buzzes Earth, will be back

In September, a large asteroid passed close by our planet
The asteroid, 2013 TV135, was discovered this month
NASA says there is very little chance of it posing a threat to Earth
Someday a massive asteroid will wreak havoc on Earth, but that is likely millions of years away







(CNN) -- One of the most dangerous asteroids on record zipped close by Earth last month.
It made headlines on Thursday, when reports said that there's a chance it could strike our planet in less than 20 years. Such aollision could unleash a force as powerful as a couple of thousand atomic bombs.
But NASA was quick to calm nerves and point out some very good news. The most dangerous known asteroids don't really pose much of a threat. And there are very few of them.
Also, the chances that this one, which the Ukrainian astronomers who discovered it named 2013 TV135, will collide with Earth are extremely slim, NASA said in a statement it called "a reality check."
The space agency is 99.998% certain that when it whooshes back around the planet in 2032, it will simply sail past us again.

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A diagram shows the orbit of an asteroid named 2013 TV135 (in blue), which made headlines in September 2013 when it passed closely by Earth. The probability of it striking Earth currently stands at 1 in 63,000, and even those odds are fading fast as scientists find out more about the asteroid. It will most likely swing past our planet again in 2032, according to NASA.
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Asteroid 1998 QE2 about 3.75 million miles from Earth. The white dot is the moon, or satellite, orbiting the asteroid.
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Asteroid 2012 DA14 made a record-close pass -- 17,100 miles -- by Earth on February 15. Most asteroids are made of rocks, but some are metal. They orbit mostly between Jupiter and Mars in the main asteroid belt. Scientists estimate there are tens of thousands of asteroids and when they get close to our planet, they are called near-Earth objects.
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Another asteroid, Apophis, got a lot of attention from space scientists and the media when initial calculations indicated a small chance it could hit Earth in 2029 or 2036. NASA scientists have since ruled out an impact, but on April 13, 2029, Apophis, which is about the size of 3½ football fields, will make a close visit -- flying about 19,400 miles (31,300 kilometers) above Earth's surface. The images above were taken by the European Space Agency's Herschel Space Observatory in January 2013.
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If you really want to know about asteroids, you need to see one up close. NASA did just that. A spacecraft called NEAR-Shoemaker, named in honor of planetary scientist Gene Shoemaker, was the first probe to touch down on an asteroid, landing on the asteroid Eros on February 12, 2001. This image was taken on February 14, 2000, just after the probe began orbiting Eros.
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The first asteroid to be identified, 1 Ceres, was discovered January 1, 1801, by Giuseppe Piazzi in Palermo, Sicily. But is Ceres just another asteroid? Observations by NASA's Hubble Space Telescope show that Ceres has a lot in common with planets like Earth. It's almost round and it may have a lot of pure water ice beneath its surface. Ceres is about 606 by 565 miles (975 by 909 kilometers) in size and scientists say it may be more accurate to call it a mini-planet. NASA's Dawn spacecraft is on its way to Ceres to investigate. The spacecraft is 35 million miles (57 million kilometers) from Ceres and 179 million miles (288 million kilometers) from Earth. The photo on the left was taken by Keck Observatory, Mauna Kea, Hawaii. The image on the right was taken by the Hubble Space Telescope.
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One big space rock got upgraded recently. This image of Vesta was taken by the Dawn spacecraft, which is on its way to Ceres. In 2012, scientists said data from the spacecraft show Vesta is more like a planet than an asteroid and so Vesta is now considered a protoplanet.
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The three-mile long (4.8-kilometer) asteroid Toutatis flew about 4.3 million miles (6.9 million kilometers) from Earth on December 12, 2012. NASA scientists used radar images to make a short movie.
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Asteroids have hit Earth many times. It's hard to get an exact count because erosion has wiped away much of the evidence. The mile-wide Meteor Crater in Arizona, seen above, was created by a small asteroid that hit about 50,000 years ago, NASA says. Other famous impact craters on Earth include Manicouagan in Quebec, Canada; Sudbury in Ontario, Canada; Ries Crater in Germany, and Chicxulub on the Yucatan coast in Mexico.
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NASA scientists say the impact of an asteroid or comet several hundred million years ago created the Aorounga crater in the Sahara Desert of northern Chad. The crater has a diameter of about 10.5 miles (17 kilometers). This image was taken by the Space Shuttle Endeavour in 1994.
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In 1908 in Tunguska, Siberia, scientists theorize an asteroid flattened about 750 square miles (1,200 square kilometers) of forest in and around the Podkamennaya Tunguska River in what is now Krasnoyarsk Krai, Russia.
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What else is up there? Is anyone watching? NASA's Near-Earth Object Program is trying to track down all asteroids and comets that could threaten Earth. NASA says 9,672 near-Earth objects have been discovered as of February 5, 2013. Of these, 1,374 have been classified as Potentially Hazardous Asteroids, or objects that could one day threaten Earth.
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One of the top asteroid-tracking scientists is Don Yeomans at the Jet Propulsion Laboratory, which is managed by the California Institute of Technology. Yeomans says every day, "Earth is pummeled by more than 100 tons of material that spewed off asteroids and comets." Fortunately, most of the asteroid trash is tiny and it burns up when it hits the atmosphere, creating meteors, or shooting stars. Yeomans says it's very rare for big chunks of space litter to hit Earth's surface. Those chunks are called meteorites.
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Asteroids and comets are popular fodder for Earth-ending science fiction movies. Two of the biggest blockbusters came out in 1998: "Deep Impact" and "Armageddon." (Walt Disney Studios) Others include "Meteorites!" (1998), "Doomsday Rock" (1997), "Asteroid" (1997), "Meteor" (1979), and "A Fire in the Sky" (1978). Can you name others?
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Photos: All about asteroids




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Searching for all asteroid threats


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NASA asks public to hunt asteroids


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Meteorite pulled from Russian lake

The probability of it striking Earth currently stands at 1:63,000, and even those odds are fading fast, as scientists find out more about the asteroid.
"This is a relatively new discovery," said Don Yeomans, manager of NASA's NEO Program. "With more observations, I fully expect we will be able to significantly reduce, or rule out entirely, any impact probability for the foreseeable future."
2013 TV135 was discovered on October 8, while NASA was closed during the government shutdown. And already it looks to soon be joining the ranks of the more than 10,000 known near-Earth objects that are virtually certain to cause us no harm.
But until then, it has the distinction of having a danger rating of 1 out of a possible 10 on the Torino Impact Hazard Scale, the system that gauges the danger of impact destruction by asteroids.
The 1 rating means that it poses "no unusual level of danger." There is "no cause for public attention or concern."
Almost all other asteroids that scientists have discovered rank a 0 on the scale. There is another asteroid with a danger rating of 1. And it, too, is no cause for alarm, NASA says.
September's close pass



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The close pass 2013 TV135 made on September 16 was not a near miss. At a distance of 4.2 million miles as it flew by, it was more than 15 times as far away from Earth as the moon.
That pales by compare to the closest shave the Earth got from an asteroid of considerable size in recorded history.
On February 15 this year, asteroid 2012 DA14, which measured 150 feet wide, slipped in below the moon's orbit and squeaked by our planet just 17,200 miles from its surface.
The one that passed by in September is big, with a diameter of 1,300 feet. That's the size of four football fields, but it does not quite make it an Earth crusher.
An asteroid needs to be at least twice as large to advance into that league.
"We believe anything larger than one to two kilometers (about 0.6 to 1.2 miles) could have worldwide effects," NASA said in a statement.
Russian divers find huge suspected meteorite chunk
Near passes daily
Two behemoths in that size range will pass by planet Earth in the next three months at similar distances as 2013 TV135. NASA says that neither will hit us.
Near asteroid passes are common. They pretty much occur daily, if not two or three times a day, NASA says.
They come, and they go, and they leave the Earth in peace.
In addition, particles from space bombard our planet every minute -- at a rate of 100 tons a day, NASA says.
You eat them; you drink them; you breathe them. Much of you and everything else on Earth contains them.
Distant catastrophe
Though it seems Earth is safe for now, there is such a thing as a doomsday asteroid.
Scientists say it is likely that the impact of an asteroid over six miles wide wiped out dinosaurs along with much of the life on Earth 65 million years ago.
More like it will come, NASA says.
But they only turn up once every "few million years."
That may give humanity some time to find a way of dealing with it.
Follow @CNNLightYears on Twitter for more science news updates
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