Nine Hundred Asteroids in Near-Earth Orbits

SEWilco writes: "This Discovery.com item points out a new estimate of 900 asteroids in orbits closer than Mars. Cornell University's William Bottke did a new study of The Spacewatch Project's small-object search. This estimate says that we've found 40% of the nearby asteroids. Well, I'm glad that we've started looking before a disaster, unlike 'Rendezvous With Rama'." Or "Lucifer's Hammer."

Comments

Re:Off topic: how come gas giants?

[Jon Erikson]

Wouldn't we expect that the greater mass of the large planets, and consequently greater gravity, would compress all their matter into denser (solid) forms?

Whilst it's still an open question thanks to the huge pressures inside Jupiter, it is theorised that Jupiter does have a solid core surrounded by a layer of liquid metallic hydrogen - see this page for some more information. Since Jupiter is so large the gravity at its outer edges isn't enough to overcome centripetal forces and cause the entire planet to collapse to a solid core.

And a related question: our solar system has solid and gaseous planets; is there any fundamental eason that there couldn't be liquid planets, or is that just how it happens to fall in this particular uncharted backwater of the unfashionable end of the western spiral arm?

Well, there aren't that many liquid elements at the temperatures present in the Solar System - the material that formed it would have been mainly simple elements that were either gaseous or solid at those kinds of temperatures. IIRC some of the outer moons have liquid ammonia and methane on their surfaces, but in terms of overal quantity these substances remain rare.

---
Jon E. Erikson

Looks Like They wanted to Copy My website

[szyzyg]

Http://szyzyg.arm.ac.uk/~spm/neo_map.html

Delivering a dose of harsh reality to the world for the last 2 years ;-)

The important thing about the asteroid threat is that it's one of the few dangers to the human races that
(a) Can Kill us All
(b) We Understand
(c) We have a remote chance of avoiding using modern technology

But Fundamental to this all is the fact that we need to get as much wartning as possible - that's why we should be spending more money on telescopes and serach programs.

In fact - we're so underfunded that I've been seduced away from my job of 'saving the world' to go and work at myplay.com.....

So you know which Music serivce provider to blame when armageddon comes calling.

Re:Deflecting asteroids

[petros]

Ok, you find a dinosaur killer on a collision trajectory with the Earth. It will hit us in 18 months. What do you do now?

Why worry? It's not like there are any dinosaurs around anyway...

Tracking asteriods

[michael.creasy]

The article suggests that it is difficult to track the asteriods and see if there is a chance they could hit Earth. Isn't this something that could be done SETI@home style ? I'd much rather be looking for asteriods that could kill millions of people than looking for aliens.

Re:Tracking asteriods

[ZanshinWedge]

Computing power isn't an issue with tracking asteroids. In fact, usually one moderately powered computer is way more than enough for any dedicated asteroid tracking station.

What's needed are more dedicated telescopes (luckily, for tracking asteroids, these don't have to be the huge mega-telescopes, small ones (in comparison) work just fine), more funding, and more staff.

Currently, automated dedicated asteroid finding telescopes are responsible for the largest amount of newly discovered asteroids and comets (as opposed to Amateur astronomers, who tend to discover these things). However, there are just so many huge rocks flying around our Solar System that pass near the Earth from time to time that these automated searches would have to be only the major catcher of asteroids, but they would have to totally dominate the discoveries (in other words, they would have to be responsible for many times the current total rate of asteroid discoveries).

Look at the bright side

[Harald74]

This is not impending doom, it's a business opportunity! Now the Y2K suppliers have somewhere to unload all their stock of water tanks, MRE's and power generators.

BTW, somebody want to buy a 2 KVA generator? Only 6 months old, hardly used. Comes with 200 gallons of petrol. Can optionally throw in a solar panel and radiation proof undies...

The First Might Be in 2022

[Phrogman]

At least according to this article on spaceref.com which states that the eartch approaching asteroid 2000 BF19 has a small probability of impacting Earth. And this press release would seem to counteract the claims made here, since NASA states they have cut their estimate of the total number of large asteriods in the Solar System in half.

Perhaps trusting statistical analysis is the problem? Whats the saying "There are lies, damn lies, and statistics"?

SETI@Home asteroid prediction

[ajdavis]

Does this fall under the category of obligatory Beowulf comment? Does that mean we can dispense with it for this story? =)

I believe the problem with long-range asteroid prediction is not computational power. The N-body problem with only a few dozen good-sized gravity wells in the system is easily simulated with a desktop machine. The problem is the accuracy of our measurements. The magnitude of the error term dominates the significant result pretty quickly as you extrapolate measurements centuries into the future.

What are we to make of the lack of public response to the problem of protecting against meteor collisions? With--what?--3 movies two summers ago about major collisions (okay, one was about a comet, which I don't think anyone would survive), still no one has much of a reaction. I don't know whether to revive my faith in humanity, since those execrable had so little effect on the national consciousness, or to leave it dead, because we never wake up and try to save ourselves until it's too late.

hmmm

[nomadic]

See, we should have kept those iridium satellites up as shielding...

Re:Looking for potential collisions

[Xenu]

The tracking of space debris is performed by the U.S. Space Command's Space Surveillance Network, not NASA.

Re:Wow

[XNormal]

I'm curious though, why should we believe that scientists/astronomers can track _every_ asteroid in a near-earth orbit, when they can't even track _every_ piece of space debris in orbit around earth now?

Objects in Earth orbit that could cause damage to a satellite or space station can be as small as a speck of dust. Asteroids that could cause serious damage in case they hit the earth are dozens of meters or more in size. It's not easy to track them becasuse there is a lot of sky to cover, but it is feasible.

----

Asteroids kill more people than plane crashes

[prot0z]

I've read that a 1kilometer asteroid falls on earth every 1e6 years, and that an asteroid of that size would kill 1e9 humans.
So, we can say that the mean is 1000 people/years. This is more than plane crashes (which is about 500 people/year).

40% a little bit to positive?

[Lion-O]

Researches like this have been going on for quite some time now; it isn't due to the movie Armageddon that people started worrying about it. But I wonder if 40% is accurate enough; next to mars, between the 'solid' planets and the gas giants, are a lot of asteroids orbiting the sun. I know a lot of them have been spotted allready, you can even follow their tracks with programs like Redshift, but since there are so many of them I would not be surprised if they miss a few. Not to mention small asteroids from out of space colliding with one in the asteroid belt and forming even new particles which may follow different orbits.

But I really wonder; if you don't know how many are out there how can you tell that you cought 40% allready ?

Re:Deflecting asteroids

[Mark F. Komarinski]

Which begs the question:

What's wrong with many small pieces coming into the atmosphere?

The reason that a big asteroid makes it through the atmosphere is that there's so little surface area. It's like saying that a large block of ice takes 1 day to melt, while a similar block smashed into pieces takes 2 hours. Since the surface area is higher, there's:

a) A higher chance that the pieces burn up in the atmosphere (this happens all the time).
b) Less damage since the resulting pieces don't have the same amount of kinetic energy (Would you rather be hit by a car going 20 MPH, or a bicycle going 20MPH?). There have been numerous stories of meteors falling out of the sky and punching a hole in a roof of a building with no other damage. Surely you'd rather pay to fix everyone's roof than have all life on Earth wiped out.

Deflecting asteroids

[XNormal]

Ok, you find a dinosaur killer on a collision trajectory with the Earth. It will hit us in 18 months. What do you do now?

It looks like the only technology that could possibly pack enough energy to deflect an object with such momentum is a nuclear bomb. Isn't it ironic that the same technology that brought us the possibility of destroying life on planet Earth could also save it?

A few years ago I did a few back-of-the-envelope calculations to see what would be required to deflect an object a few kilometers in size. Naturally, the delta-V you need to deliver depends on how early you can catch it. If it's still very far you need just a little nudge to ensure it won't collide. It also depends on what margin for error you want to tolerate i.e. how far from Earth do you want it to pass.

It looks like some of the bigger H-bombs have the energy to do it. The problem is how to convert it efficiently to kinetic energy. If you blow up a nuclear bomb in space all you get is a fantastic flash. The relatively small mass of the device itself evaporates and disperses into the vacuum in a matter of milliseconds. You need mass to convert this energy into motion. Using the mass of the asteroid itself is dangerous - if you blow up your bomb too close to the object it could break into many fragments with different orbits. Many of them could still hit the Earth. Splitting it neatly in half Armageddon-style is not very likely :-).

So you need to bring your own reaction mass. The bomb will be accompanied by some big tanks of water. I don't remember the calculations, but you need quite a lot of reaction mass. It appeared to be more than what current launch vehicles can handle.

Have a nice day.


----