A Hyper-Velocity Impact In the Asteroid Belt?

astroengine writes "Astronomers have spotted something rather odd in the asteroid belt. It looks like a comet, but it's got a circular orbit, similar to an asteroid. Whether it's an asteroid or a comet, it has a long, comet-like tail, suggesting something is being vented into space. Some experts think it could be a very rare comet/asteroid hybrid being heated by the sun, but there's an even more exciting possibility: It could be the first ever observation of two asteroids colliding in the asteroid belt."

Re:Asteroids boring?

[camperdave]

Relax! That was Long Ago in a Galaxy Far, Far Away. Our asteroid belt is boring, with every rock more or less tidally locked to each other. Their asteroid belt is dynamic and exciting, and filled with hungry, hungry space eels.

Why there's a difference.

[argent]

There's a reason you don't normally see icy bodies in circular orbits in the asteroid belt: they'd be blown clean of the ice within a fairly short period of time, astronomically speaking. that's what the tail consists of, dust embedded in the ice being released as the ice sublimes. Which means that the ice here has to have been exposed fairly recently.

Re:Lateral spray

[Anonymous Coward]

The tail isn't a debris spray. It's a spray of sublimating ice that was recently exposed by an impact, but had previously been covered by less volatile material.

Priorities are a function of Probabilities

[Orne]

Scenario 1: Asteroid strike. I defer to NASA JPL [nasa.gov], the Tunguska event (100-meter class = ~ 15 mil tons TNT) asteroid occurs once or twice / 1000 years. A 1000-meter class is 1 in 15 million years. An 8000-meter class (dinosaur killer) is 1 in 50-100 million years.

Scenario 2: Earthquake. San Francisco [usgs.gov] has an annual forecast of earthquake probabilities, and they predict a 68% probability of a 6.7 Magnitude or greater in the next 30 years. Wikipedia [wikipedia.org] gives a probability scale for earthquakes, where a Magnitude 7 (similar to what struke Haiti) occurs 18 / year. A single 6.7 earthquake (P = 120/year) is equivalent to 16 kilotons of energy, or about 1 Tungaska event (P = 0.004/year).

Given the disparity in the probability of asteroid strikes (on populated areas, no less) vs earthquakes, it should be no surprise that the world governments believe money is better spent on earthquake prediction and evacuation relief, not on asteroid strike detection. The "bang for the buck" is clearly higher in earthquake spending.

Two asteroids colliding

[xupere]

Well, where do you think baby asteroids come from?

Re:Hyper-Velocity

[camperdave]

Okay. Apparently hypervelocity [wikipedia.org] is an actual astronomy and/or material sciences term:

The term hypervelocity usually refers to a very high velocity, approximately over 3,000 meters per second (6,700 mph, 11,000 km/h, 10,000 ft/s, or Mach 8.8). In particular, it refers to velocities so high that the strength of materials upon impact is very small compared to inertial stresses. Thus, even metals behave like fluids under hypervelocity impact. Extreme hypervelocity results in vaporization of the impactor and target.

Re:Hyper-Velocity

[Convector]

Only in Newtonian mechanics. However, if the objects' velocities are so fast that they would sum to more than the speed of light, then you need to use relativity. In no reference frame does the velocity of one relative to the other exceed c. I'm afraid I'm too lazy to look up the formula. The shelf with all my physics books on it must be 10 feet away from me (although at 0.8c it's only 6 feet).

Re:Probably not

[Rick Genter]

Those who moderated the parent "Insightful" should be meta-moderated as either "Clueless" or "Humorless".

Re:Probably not

[ByteSlicer]

Actually, they mostly do it to reward the poster since Funny mods don't increase karma, but Informative or Insightful mods do. Something that's modded to +5 Funny and then modded Overrated a few times will even burn the poster's karma. But yes, it's also humorous in most cases.