How NASA battles against our fear of planet-killer asteroids

TWENTY five million kilometres sounds like a lot, but it's a close shave in astronomical terms.

That's how close to Earth a 2.6km wide asteroid will come when it flies past us this weekend at close to 60,000 km/h.

There are media claims the massive space object would destroy the ozone layer and trigger 91m tsunamis if it hit, potentially ending life as we know it.

In other words, its potential for devastation is straight out of Hollywood sci-fi blockbusters Deep Impact and Armageddon (although the fictional Armageddon asteroid was much bigger: 'about the size of Texas').

But while 25 million kilometres is scarily close, NASA is reportedly quite relaxed this planet killer won't deviate at the last minute and hit us.

North Coast astronomer Dave Reneke described the event as a "close shave" but "not a brush".

KNOW YOUR SPACE STUFF

  • COMET: A chunk of ice and rock and a little gas originating from outside the solar system, accompanied by a visible "coma and tail" when they pass close to the sun. Comets have a much larger (and therefore longer) orbit path around the sun, meaning we only get to see them every few decades.
  • ASTEROID: A space rock larger than 10m across, born of the asteroid belt between Mars and Jupiter, which occasionally get flung out this side of Mars with the very rare potential of striking Earth.
  • METEOROID: A space rock that's bigger than a piece of dust but smaller than 10m across.
  • METEORITE: A meteoroid which has hit earth.

He said despite its size it was too small to see from the Northern Rivers with a regular telescope.

"You would need to have a very high powered telescope with tracking capabilities, and you would need to know its coordinates exactly," Mr Reneke said.

Mr Reneke said if a meteor that big if it was to come within the orbit of the moon, its flight path might be altered and it could end up impacting the Earth due to orbital changes.

"It would wipe out an entire continent... it could easily take out the eastern side of Australia in one fell swoop," he said..

"We've had them come inside the orbit of the moon before.

"These (scenarios) have been played out in computer profiles.

"This one's a big one, but it's well outside the orbit of our moon and far enough away for us not to be concerned about it."

NASA's Near Earth Object program tracks hundreds of asteroids whose path through space takes them near Earth's orbit, and there's sometimes three or four per day (most which are under 100m across) passing close by.

This phenomenon gives doomsday theorists such a stockpile of ammunition to make bold claims about the end of human civilisation on a regular basis, forcing NASA to routinely deny these well-publicised claims.

Recent predictions that an asteroid would slam into earth in the vicinity of Puerto Rico causing wanton destruction compelled NASA to put our one such denial.

In a media statement Paul Chodas, manager of NASA's Near-Earth Object office at the Jet Propulsion Laboratory in California, said "there is no existing evidence that an asteroid or any other celestial object is on a trajectory that will impact Earth."

"In fact, not a single one of the known objects has any credible chance of hitting our planet over the next century."
But that doesn't mean NASA isn't keeping a close watch on them.

Their monitoring of these so-called Potentially Hazardous Objects is evidence enough to show their concern.

You can even get an official desktop "widget" called Asteroid Watch from the NASA Jet Propulsion Lab website, as well as an unofficial smartphone app called AsteroidAlert.

And recently NASA has ventured into the realm of science fiction, hatching a plan to slam a spaceship into an asteroid to see if it can force a deviation to its flight path.

Sounds like a risky move.

But the Asteroid Impact and Deflection Assessment, a joint NASA and European Space Agency project, will involve some careful surveying of the target asteroid first with a satellite inserted into the asteroid's orbit.

Only then will NASA send a 320kg spacecraft smashing into it at 22,500kmh to produce a "minimal change" in the object's orbit around the sun.

That's scheduled to happen in 2020.

Mr Reneke said asteroid related missions were a worthy cause. "The big ones on their way, they all say, and we've got to have a plan to do something about it."



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