Thread: 2011 MD: 30' to 100' Asteroid to Pass Earth at an Altitude of 7,500 Miles

Name: 2011 MD
Date: June 27, 2011
Time: 1:14 pm EDT
Location: Coast of Antarctica

Article.

Why does this miss concern me? Simple: 50,000 years ago, a 150 ft wide nickel-iron meteorite created a crater (Meteor Crater) nearly a mile wide in the Arizona desert. It impacted with a force of 10 Megatons. A similarly dense object 100 ft across would impact with 1/3 of that force.

A 3 megaton blast would never plunge us into any sort of nuclear winter, but it would pretty much wipe out most of LA or New York.

But that's not what concerns me. What concerns me is that it was discovered just 5 days before it's point of closet approach.

I'm also concerned that while LINEAR telescopes are giving it's size as ranging between 29' and 98' wide, the folks at Asteroid Watch are minimizing that to an extreme by repeatedly saying "it's only 10 meters wide" and that "Stony asteroids less than 25 m would break up in Earth's atmosphere & not cause ground damage."

Yeah, well, that's IF it's not at the upper end of the range of its estimated size.

It would definitely wipe out a lot of a big city if it scored a direct hit, but then I have to wonder, what is the probability that it would do so?

Originally Posted by mugaliens

A 3 megaton blast would never plunge us into any sort of nuclear winter, but it would pretty much wipe out most of LA or New York.

Some would say "No big deal. We can do without LA and/or NY"

Originally Posted by mugaliens

But that's not what concerns me. What concerns me is that it was discovered just 5 days before it's point of closet approach.

Seems as if someone was asleep at the wheel. Why wasn't it noticed before this?

Originally Posted by mugaliens

Yeah, well, that's IF it's not at the upper end of the range of its estimated size.

And since "they" did such a poor job in finding this, what if "they" underestimated its size?

Originally Posted by Coelacanth

It would definitely wipe out a lot of a big city if it scored a direct hit, but then I have to wonder, what is the probability that it would do so?

Armed with the current information we have of it's trajectory: 0%

Armed with the information available in the first few minutes after it was discovered this past Thursday: Still very low, as there aren't that many big cities compared to the land area of the Earth.

Originally Posted by mugaliens

..."Stony asteroids less than 25 m would break up in Earth's atmosphere & not cause ground damage." ...

That sounds silly to me. Same mass still making collision. But remember, the populated areas are really quite small. Lots of sea, desert, ice etc.

Originally Posted by RayTomes

That sounds silly to me. Same mass still making collision. But remember, the populated areas are really quite small. Lots of sea, desert, ice etc.

Well, if you heat rocks unevenly, they crack. Not so with either iron-nickel meteors, which remain largely intact throughout atmospheric entry.

Originally Posted by mugaliens

Well, if you heat rocks unevenly, they crack. Not so with either iron-nickel meteors, which remain largely intact throughout atmospheric entry.

Does this alter the size of the explosion? If so, why?

I lack any kind of expertise on such things, and perhaps this post will reflect that, but isn't the idea that, if it breaks up, the surface area exposed to atmosphere is increased, resulting in greater friction? (And possibly also in still further break up?)

Seems like the amount of kinetic energy is the same either way, but maybe much of the kinetic energy is absorbed "gradually" in the atmosphere, rather than in an instant as it hits the ground.

Personally, I'd have to defer to Ray but it does sound logical that 10 smaller ones would have a better chance of burning up than one large one...but still you'd have some that would make it through, I should think... Ray?

Originally Posted by RayTomes

Does this alter the size of the explosion? If so, why?

I does not alter the total energy that's released. It does alter how that energy is dissipated. Smaller chunks would be more likely to burn up in the atmosphere, creating dust/soot and heating the atmosphere. The shock wave created by the incoming chunks may still cause serious local devastation, much like that of the Tunguska Event. However, if the meteor could be fragmented further out in space, instead of having many chunks entering over a small area (like a wall of many speakers at a rock concert), they'd enter spread out over a large area, thereby reducing or eliminating a combined shockwave front.

One large chunk would melt some rock and send ejecta flying for miles, while creating a more horizontal shock wave upon impact.