Stealth Asteroid Misses Earth

Paradoxish writes: "Gah. According to cnn.com an asteroid hiding in an astronomical blindspot nearly blindsided Earth. The scary part is that scientists didn't notice it until four days AFTER it passed by. Apparently, it would've been similiar to the Tunguska explosion. Scary." As long as they keep missing Earth, we're OK.

Comments

Does anyone know

[linzeal]

What would happen if an asteroid of a given size hit the moon? A place with equations on velocity, density, and angle of entry for the meteor would be nice.

I would imagine that impact material from the moon could make secondary impacts on earth and the ocean would be a little whacky. Could a tsunami be born out of such an event if the asteroid was large enough?

Re:Does anyone know

[SrlKlr]

What would happen if an asteroid of a given size hit the moon?

What is more interesting is if you think about what would happen if the moon was to go away (like maybe knocked out of orbit or something like that). Forget the simple things like screwing up light at night and night time criters. Think about tides and how they are directly affected by the moon. And since the weather is extremely dependant upon the temperature of the ocean, this would completely, change the weather across the globe. Colder areas would become colder and warmer areas would become warmer without some type of climate circulation. Lots of factors for a hunk of rock flying around the globe...

Re:Does anyone know

[denzo]

Equation for momentum: m_a*v_a + m_b*v_b = m_a*v_a' + m_b*v_b'

The LHS is initial velocities, and RHS is final velocities. Since an asteroid collision would likely be a plastic collision (i.e., object stick together), the final velocities for objects A & B would be the same. Assume that the moon's velocity is zero, since we are determining the relative change in velocity. Thus you would get an equation like thus to find the final velocity of both objects combined:

v' = (m_asteroid * v_asteroid)/(m_asteroid + m_moon)

Where m_moon = 7.35E22 kg. Assume that v_asteroid = 10km/s, and in order to get a significant change in the moon's velocity (say 1 m/s), the asteroid would need to be going 7.35E18 m/s. If the asteroid was the same density as the moon (3340 kg/m^3), then that would mean a spherical asteroid of a diameter of 16 km. (assuming that I did that all right).

Pretty big asteroid, I think a global killer is considered to be a 1 km long asteroid. Recalculate the above equation for different assumptions.

It seems like

[DeltaBlaster]

It seems like we are starting to hear about some asteroid missing us a few times a year now. Has anyone ever heard of Nasa having any sort of plan on what to do if an asteriod ever was going to hit earth? (Even though according to that article the odds are currently 1 in 10 million")

Re:It seems like

[Tackhead]

> Has anyone ever heard of Nasa having any sort of plan on what to do if an asteriod ever was going to hit earth?

Has anyone ever heard of Congress giving NASA the budget required to come up with any plan more effective than "Put your head between your legs and kiss your ass goodbye."

The dinosaurs are extinct because they lacked a space program.

More the pity homo sapiens, who was smart enough to invent rockets, smart enough to realize the nature of the threat, but too dumb to do anything about it.

Prediction: 24 hours after the asteroid impact, the surviving Congresscritters call upon the surviving sheeple to burn down and lynch all aerospace industry personnel because "NASA should have been able to warn us!"

Maybe our descendants, 500 years after the Great Burn, will do better.

Re:It seems like

[Darby]

I think that the airport security should have been able to prevent Sept 11, and I don't see a big hue and cry to lynch the metal detector jockeys and their bosses.

Well, since the government knew about it beforehand they could have prevented it but chose not to. This is not conspiracy theory or speculation, since they warned many VIPs not to fly that day.

I love their artist's rendition

[Macrobat]

They say the asteroid is a little bigger than the Tunguska object, but they depict something that looks a little bit smaller than the moon. It's a file picture, though, because it's their conception of the asteroid that allegedly did the dinosaurs in. Still seems like something THAT big would be even more devastating.

Re:Calculations

[PD]

The asteroid was spotted only after it passed us. If we knew the trajectory of the asteroid, then we would have been able to calculate that it would miss us. If the asteroid was going to hit us, then depending on how far out, they might be able to guess which ocean it would fall into, or which continent might get hit.

Tunguska Meteorite is nonsense

[MSG]

Everyone knows that the Tunguska explosion was a result of Nikola Tesla's experiments:

http://www.frank.germano.com/tunguska.htm

One of my favourite conspiracy theories

[Edmund Blackadder]

The Tunguska explosion was not caused by an asteroid.

1) there was no crater
2) noone has been able to find any asteroid materials in the area.
3) plants in the area have been discovered to have mutated DNA.

It is quite clear to me that the Tunguska explosion was caused by a miscalculated experiment of the great eccentric inventor Nicola Tesla.

BTW the official theory is that the asteroid consisted of nothing but water, it flew down to close to the surface, and then it exploded. Thats as difficult to believe as the Tesla theory imo.

Re:Chances are still pretty slim.

[coyote-san]

The moon's orbit is used for a couple reasons, most noticably the "lensing" effect both the earth and moon have on close misses. Something that passes this closely is going to have its orbit affected by the gravitational attraction.

As for the impact of the rock, we no longer have the luxury of only caring about the area immediately adjacent to the impact point. During the first Gulf War there was a brilliant flash seen by military satellites from an impact that exploded over the Pacific Ocean. Had circumstances been slightly different the flash would have been seen over the Persian Gulf or Middle East, and it's virtually certain that the flash would have been initially interpreted as a nuclear detonation. (Watching for such flashes is exactly why these satellites were launched.)

If the error was not quickly determined -- and it could be very difficult with another Tunguska-level event where the *only* way to distinguish it from a nuke is the lack of radiation -- then the deaths from the subsequent "retaliation" could easily dwarf the deaths from the initial impact.

Books for your reading pleasure

[teamhasnoi]

This fine book is about this very thing happening (asteroid hitting earth). Lucifer's Hammer by Larry Niven & Jerry Pournelle. (Both kick-ass authors) Another book by them, that is somewhat similar (aliens throwing the asteroids at us) is Footfall. Both are very good. If you don't have time to read 600 pages, here is a slightly shorter version.

Tunguska? NOT!

[tuxlove]

An impact by an asteroid of similar size to the Tunguska asteroid is not possible. Siberia was not hit by an asteroid in 1908 - it wasn't even "hit" technically. The destruction was caused by a comet.

Hunters have looked for the remains of the asteroid that hit Siberia for years, but have found nothing, and for a very good reason. Simulations have shown that the blast pattern on the Siberian landscape could only have been caused by an object moving moving at a particular angle and exploding at elevation over the ground.

Asteroids do not explode like that, but a comet would quite possibly. Made mostly of frozen liquid, the heat of atmospheric entry could cause a comet to explode as it rapidly vaporized. This would leave little or no large remains as an asteroid would, would probably not cause a crater, and would throw up less debris than an asteroid. All of this seems consistent with the Tunguska event.

I'm no expert by any means, but if an asteroid of the same size as the Siberian comet hit the earth, my guess is that it would be much more destructive and have more worldwide effect.

We need a NEAR@HOME...

[jhesse]

Hmm... A 12-inch SC telescope contained in a small roof-mounted dome with servos and a CCD hooked up to your computer. With a hundered of these, we should be able to get at least half of the sky.
Something like this, only smaller: http://www.ll.mit.edu/LINEAR/

Whaddaya think, sirs?

Australian Skies

[skware]

Aint it great how in 1996 the aussie government withdrew all funds from a asteroid mapping program.

This pretty much leaves noone gaurding the southern skies.

There was a story on this on 60 minutes (aussie version) 3 days ago. A transcript of it can be found at http://news.ninemsn.com.au/sixtyminutes/stories/20 02_03_17/story_531.asp

Some Perspective

[Militant Apathy]

1.2 Lunar diameters is not the relevant number here. 288,000 miles is 72 Earth radii.

That means that if you draw a circle around the Earth with a radius at the distance of closest approach, the Earth's cross-sectional area fits into that circle 5,200 times.

In other words, even if someone were heaving rocks at us at distances this close or closer at a rate of one per year (a grotesque overestimate), we would expect to get hit once every five millenia or so, neglecting gravitational attraction effects (which don't contribute much).

As "near misses" go, that's not so near. The Earth isn't that big a target. This is a nice frothy story for CNN, especially the "blind side" angle, but not a great reason to start repenting sins.