Asteroid Near-Misses (AKA: Holy Shit! We're All Going to Die)

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Anonymous

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#1
Asteroid Nearly Hit Us—And Nobody Noticed

One of the largest asteroids known to have approached the Earth flew past about 300,000 miles away on March 8, but nobody even noticed it until four days later. When the object, which has been named 2002 EM7, passed closest to the Earth, it was too close to the Sun to be visible. A telescope operated by the Lincoln Laboratory at M.I.T. first recorded the new asteroid on March 12, as it moved away from the Earth and more of its bright side came into view.
Asteroids approaching from a blind spot cannot be seen by astronomers. If an object passed through this zone on a collision course with Earth, it would not be identified until it was too late for any intervention.

Astronomers have made numerous pleas in recent years for more funds to catalogue near-Earth objects and their orbits. This would reduce the number of unknown objects that could possibly take us by surprise, and give us early warning about potential future collisions.

Further observations by Timothy Spahr of the Harvard- Smithsonian Center for Astrophysics revealed that 2002 EM7 has a 323-day orbit. It is invisible to the naked eye, and is too small to be classed as a “potentially hazardous asteroid.” But it’s probably between 55 and 100 yards across, meaning it’s bigger than the object that exploded in 1908 over the Tunguska region of Siberia, flattening trees for 1,200 square miles.

Brian Marsden of Harvard-Smithsonian says preliminary calculations indicate that 2002 EM7 will have several more chances to hit the Earth during the next century, with odds of one in six million to one in a billion of an actual impact.

NASA announced this week a new Web-based asteroid monitoring system called Sentry that can monitor and assess the threat of space rocks that could possibly strike the Earth. It will help scientists communicate with each other about their discoveries of new, potentially threatening asteroids.

While no large asteroid is currently known to be on a collision course with our planet, experts say an eventual impact is inevitable and the consequences could be serious, up to and including global devastation that might destroy civilization as we know it. The odds of such an impact in any given decade are extremely low, and most experts agree that there would likely be at least 10 years of warning if such an object were ever spotted.

However, smaller asteroids like 2002 EM7 are more likely to hit Earth in any given year and could cause significant local or regional damage. The odds of a locally or regionally destructive asteroid hitting an inhabited area in a given 50- year period are about 1-in-160, according to experts.

In recent years, asteroid experts worldwide have struggled to develop a system to catalogue and track newly spotted Near Earth Asteroids and communicate any possible threats to the public.

However, asteroids move so slowly against the background of stars that when one is first discovered, astronomers cannot pin down its exact path. Recent false alarms, when scientists said there was a threat that a particular asteroid would hit Earth in a certain year, have made headlines and frightened the public.

The new Sentry system, developed over the past two years, is operated out of NASA's Jet Propulsion Laboratory. The system's online “Risks Page” listsed 37 asteroids last week.

“Objects normally appear on the Risks Page because their orbits can bring them close to the Earth’s orbit and the limited number of available observations do not yet allow their trajectories to be well-enough defined,” says JPL’s Donald Yeomans, manager of NASA’s Near-Earth Object Program Office, which oversees Sentry. “By far the most likely outcome is that the object will eventually be removed as new observations become available, the object’s orbit is improved, and its future motion is more tightly constrained.” Several new asteroids will be added to the list each month, only to be removed to the “no-risk” page soon afterwards.

A color-coded measurement called the Torino Scale, developed in 1999, gives each asteroid a number. Zero or one represents a remote risk, and a 10 means there will be an impact. All but one of the asteroids currently on the Sentry list are zeros on the Torino Scale. At the top of the list, however, is space rock 2002 CU11, discovered February 7. It presently has a 1-in-100,000 chance of hitting the Earth on August 31, 2049. But as its orbit is refined, it’s possible this asteroid, like many others, will be re- categorized as harmless.

Asteroid detections have increased in recent months because Congress has asked NASA to find 90 percent of all Near Earth Objects larger than 0.6 miles by 2008. About 500 of the these asteroids have been found, and an estimated 500 remain undiscovered.
 

harlequin2005

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#2
This from the New Scientist:-

Story Link

Asteroid buzzes Earth from "blind spot"


16:22 15 March 02

NewScientist.com news service

One of the largest asteroids known to have approached the Earth zipped past about 450,000 kilometres away on March 8 - but nobody recorded it until four days later.

The object, now called 2002 EM7, was hard to spot because it was moving outward from the innermost point of its orbit, 87 million km from the Sun. When it passed closest to the Earth - just 1.5 times the distance to the Moon - it was too close to the Sun to be visible.

Asteroids approaching from this blind spot cannot be seen by astronomers. If a previously unknown object passed through this zone on a collision course with Earth, it would not be identified until it was too late for any intervention.

Astronomers have made numerous calls in recent years for more funds to catalogue near-Earth objects and refine their orbits. This would reduce the number of unknown objects that could catch us unaware, and give early warning of potential future collisions.


Bigger than Tunguska


An asteroid-hunting telescope operated by the MIT Lincoln Laboratory first recorded the new asteroid on March 12, as it moved away from the Earth and more of its bright side came into view.

Further observations allowed Timothy Spahr of the Harvard-Smithsonian Center for Astrophysics to calculate its orbit. He found that it has a 323-day orbit that takes it as far as 188 million km from the Sun.

Invisible to the unaided eye, 2002 EM7 is too small to be classed as a "potentially hazardous asteroid". But it is probably between 50 to 100 metres across, making it larger than the object that exploded in 1908 over the Tunguska region of Siberia, flattening trees over 2000 square kilometres.

The approach puts it among the 10 closest known approaches by minor planets, says Brian Marsden of Harvard-Smithsonian. More ominously, only one of the 10 closest objects was larger. This was 1996 JA1, which passed only slightly closer to the Earth on 19 May 1996.

The discovery adds to the list of asteroids which are long shots to hit the Earth in the next century. Preliminary calculations indicate 2002 EM7 has Several chances to hit the Earth in that period, with odds of one in six million to one in a billion, Marsden told New Scientist. Further observations are likely to lengthen the odds.


Jeff Hecht
 

ninja_cat

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Originally posted by harlequin
Asteroids approaching from this blind spot cannot be seen by astronomers. If a previously unknown object passed through this zone on a collision course with Earth, it would not be identified until it was too late for any intervention.
Exactly what kind of intervention did they have in mind? I would have thought that at present we have nothing that is capable of reaching an asteroid in enough time and with the capability to do any serious damage. (Unless we launch Bruce Willis at it :) )
 

ninja_cat

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Trouble is, what is the range of an ICBM. Probably not enough to travel any great distance in space as they are designed as ballistic missiles, not guided missiles a la air to air etc. They could probably reach into the upper atmosphere, but no way could the even reach the moon. I suppose if the math were done you could knock it of course.
 
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Anonymous

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But all in all smacking it with a nuke is also a dubious business. You could risk just making matters worse.
 
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Anonymous

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#8
Xanatic said:
But all in all smacking it with a nuke is also a dubious business. You could risk just making matters worse.
Yeah, instead of getting hit by a giant rock you now get hit by a giant radioactive rock! :p

Seriously though, I don't think we have anything that we could get moving quickly enough that'd have any effect on one of these things.
 

rynner2

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#9
I thought this story sounded familiar! I posted a link to it a few days ago on this thread

(Perhaps we should cut the waffle from this site, so everyone gets a chance to see all the new posts...)
 

harlequin2005

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#10
Oops... missed that one .As a cold comfort, I didn't see the New Scientist quoted on the Asteroid thread so at least I brought something new to the game :)

8¬)
 
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Anonymous

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#11
The problem with throwing nukes at it is our calculations could be wrong. Maybe the asteroid wouldn't have hit us. But if we now have turned it into 100 smaller pieces, we got a lot bigger chances for getting hit.
 
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Anonymous

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#15
Not even that. Just a 15 year old hanging around the house during the Easter Holadays.
 
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Anonymous

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#16
you should be treating yourself to some crunchy nut cornflakes if your just about to die, forget just the plain ones

the problem is they taste to good
 

FelixAntonius

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#17
So why should I worry about my great x umpteen grandchildren?

They've never worried about me, so maybe, they can look after themselves!!!!!
 

ogopogo3

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#18
Future Asteroid Impact: Even with the Nuke Option, We'd be S

http://www.science-frontiers.com/sf127/sf127p03.htm

Ok, this ain't exactly new news. It comes from early 2000, but it's just become available, as William Corliss puts a two year gap between his free and pay articles.

Still, I don't ever remember hearing of this, do you?

Not too long ago, geologists adamantly denied that there were any large meteor craters pockmarking our planet. Now, they find 100-kilometer craters on a regular basis. And scientists are casting worried looks at those near-earth asteroids, knowing that one day one will be on a collision course.

Not to worry, say the modern-day Technocrats, we will launch nuclear-armed rockets that will nudge such cosmic threats into harmless trajectories.

These Pollyannas are presumptious. They assume that asteroids are hard, cohesive objects that will be shoved aside by a few megatons of explosive energy. There are two things wrong with this idea, and these reveal how radically our ideas about the nature of asteroids have changed in just 10 years.

First, most astronomers will now agree that asteroids are orbiting rubble piles rather than monolithic objects. For example, the near-earth asteroid Mathilde, 53 kilometers in diameter, has a density of only 1.3 grams/cubic centimeter. Its porosity must be greater than 50%. It is not a hard, coherent object. Instead of a bullet, it is more like a cloud of shotgun pellets. It would be hard to divert all this debris with a nuclear blast.

To make matters worse, asteroids like Mathilde are stickier than a cloud of buckshot. This fact is deduced from photos of asteroids showing many to be marked by huge craters. (Mathilde has one 33 kilometers wide.) K.R. Housen et al, using laboratory tests and scaling data, argue that asteroid craters were not blasted out by collision. (Mathilde is not "shattered" as one would expect given such a huge crater.) Rather, the craters are "dents" instead of holes! Cosmic rubble piles are like sponges. Collisions with other rubble piles result in compression of the target surface and accretion of the smaller object. In effect, asteroids are energy absorbers and will hardly be fazed by a nuclear detonation.

(Asphaug, Erik; "Survival of the Weakest," Nature, 402:127, 1999.)

Comment. We are doomed -- but not right away.
Hollywood fiction lied. I will not trust it again...for six weeks.
 
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Anonymous

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#19
A very interesting pice of writing, thank you for bringing it to our attention at last.

I have a question though, if indeed these Near-Earth objects absorb other objects like a sponge, will they not eventualy become a solid mass and become hardened through Impact, Heat, and Gravity?

And will this effect the orbit of the objects turning them into Planet killers?

Lets face it, by the time we see it coming it will be too late anyway.

For all our technology we cant even launch the Space shuttle if the weathers not right.

My advice is not to worry about it, enjoy what time you have left and get out more.
 
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Anonymous

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#20
they wernt seen as a problem before hundreds of rocket builders and nuke people were threatened with redundancy by the collapse of the "cold War"....... i just wonder
 

intaglio

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#21
If you've something the size of Everest barrelling towards you at 500 m per sec it doesn't much matter if it weighs 10,000,000 megatonnes or 20,000,000 megatonnes, the energy it deposits onto our planet will be of the same order of magnitude. Kinetic energy is mass x velocity^2, in this case 2.5 to 5 x 10^18 megajoules or about 1000 megatons energy deposited in a fairly insignificant time in a miniscule area. :eek!!!!:

Mind you the "blow it up with nukes" concept was never on. The best you would do with that idea would be to substitute a bullet with radioactive scattershot :monster:
 

rynner2

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#22
More subtle responses to the asteroid threat (assuming we get enough warning) include ideas like wrapping the asteroid in reflective foil - this would increase the pressure of sunlight on it, slowly but steadily changing its orbit.

Looking for links to this, but instead I found this, which is a detailed proposal for a space based telescope for locating dangerous asteroids. Long and detailed, but at least it gives plenty of facts and statistics.
 
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Anonymous

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#23
So the asteroids is just a big conspiracy by nuke-makers? :) It is just only recently we have realised what big a threat they are. And sadly nukes won't help us much. For one thing they aren't powerful enough. And also it will mean we suddenly have 8000 pieces of asteroid heading in our direction instead of one big. Much bigger chance of hitting us.
 

rynner2

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#24
Xanatic said:
And sadly nukes won't help us much. For one thing they aren't powerful enough. And also it will mean we suddenly have 8000 pieces of asteroid heading in our direction instead of one big. Much bigger chance of hitting us.
Not necessarily. If nukes were used, it would probably be to try to divert the asteroid rather than destroy it. Caught early enough, a small deflection would result in sufficient orbit change to either miss Earth's orbit altogether, or to cross it a short time before or after the earth has passed. (The Earth moves its own diameter along its orbit in about 7 minutes.)

But if an asteroid was exploded, the resultant shower of debris would still be less disastrous than the complete asteroid, because the smaller fragments would burn up in the atmosphere. Those that did reach the surface would also have been abraded and decelerated, so that the total impact energy at the surface would be far less than that of the original asteroid (even assuming that none of the fragments miss Earth altogether). The fragile nature of an asteroid (as mentioned earlier) means that it might be quite easy to blast it to smithereens.
 
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Anonymous

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#25
It is true that due to the greater surface, the small asteroid pieces would burn in the atmosphere. What I mean was more, our calculations could be a bit off and the asteroid wouldn't have hit us. But if we smash it to a thousand pieces, we are suddenly much more likely to be hit. In the same way as being shot at with a gun, and a shotgun.

We could of course try and divert the orbit, but then we would need to see it quite early. I don't know if we have good chances for that, just look at those two near-misses that we just had. Of course blowing a nuke besides it might still be enough.
 
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Anonymous

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#27
good to see the "new" system of measurment... a footbal pitch sized chunk, a dophin, a whale, a fag packet, the head of a pin and the eye of a needle.... lets get rid of this metrication rubish and go back to the good old measurments
 
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Anonymous

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#28
They should fire all the astronomers. What use are they if they can't see these things coming! :confused:
 

intaglio

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#30
Just wondering. If such an object fell onto the US (somewhere relatively uninhabited for preferably, though there are times when I think Washington DC might be an option) would the president declare a "War against Astrophysics"?
 
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