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Brazil Nut Effect Explains Mystery of the Boulder-Strewn Surfaces of Asteroids
KentuckyFC (1144503) writes When Japan's Hayabusa spacecraft gently maneuvered into a parking orbit around the asteroid Itokawa in September 2005, it conducted a comprehensive photographic survey, the most detailed ever taken of an asteroid. This survey revealed that Itokawa is covered in large boulders that look like ejecta from craters in other parts of the asteroid. But when astronomers added up the total volume of these boulders, it turned out to be greater than the volume of the craters there were supposed to have come from. Other asteroids also show a similarly skewed distribution of large boulders. That has caused some significant head-scratching among astronomers who are at a loss to explain where the boulders come from.
Now an international team has solved the mystery. They say the boulders float to the surface of asteroids in an astrophysical example of the Brazil nut effect. This is the long observed phenomenon in which shaking a mixture of big and small particles causes the larger ones to rise to the top. That's because the shaking creates gaps beneath the large particles that small particles fall into. The result is that the large particles float. The team simulated the shaking effect that collisions between asteroids would produce and say that these vibrations would cause large boulders to float to the surface in a few hours, finally explaining why asteroids have such boulder-strewn surfaces. Problem solved!
Now an international team has solved the mystery. They say the boulders float to the surface of asteroids in an astrophysical example of the Brazil nut effect. This is the long observed phenomenon in which shaking a mixture of big and small particles causes the larger ones to rise to the top. That's because the shaking creates gaps beneath the large particles that small particles fall into. The result is that the large particles float. The team simulated the shaking effect that collisions between asteroids would produce and say that these vibrations would cause large boulders to float to the surface in a few hours, finally explaining why asteroids have such boulder-strewn surfaces. Problem solved!
Where the biggest nuts rise to the top.
That's kind of what I was thinking.
I heard about this in Geology class 20+ years ago. It's why farmers fields keep producing rocks, because the bigger pieces move up and work their way to the surface.
I thought this was pretty well understood for quite some time.
Lost at C:>. Found at C.
I never stopped to think if the Brazil nut is on top, but more how the heck do I crack open the shell. A triangle is one of the strongest shapes. The Brazil nut shell is in a nice triangle. Thus my approach is smashing it to pieces, and eating the nut in little fragments.
If something is so important that you feel the need to post it on the internet... It probably isn't that important.
But does the process work when the gravity field is tiny? That is what needed to be found out before saying that that is definitely the process at work.
These comments are my personal opinions and do not necessarily reflect the opinions of the other voices in my head.
Why is this called the "Brazil Nut Effect?" This is just normal buoyancy, science teachers have been doing demonstrations like this for years. You can do the same thing if you put a golf ball in the bottom of a container full of shredded bark and shake it.
I shake 'er up. The big pieces float to the top. I scoop them out. Brazil nut effect. Asteroid problem solved. It took an international team to sort this out? Come on! :D
It's the same in an organization -- shake it up -- the management rises to the top.
Any similarity to a litter box is purely coincidental
I thought it was going to relate it with nuts causing small amounts of player activity.
Ezekiel 23:20
I would have intuitively said the other way around.
Since the gravity is so small I would have expected the motion of the smallest particles to be close to random, perhaps close to Brownian motion if you looked at the system over a long enough period of time.
I guess, even though there isn't much to pull the material together, once a small particle is in a crack or void it is very unlikely to ever escape and so the crack does eventually fill in, it seems to me that the process should exist but be much slower than when compared to the effect in a strong gravity field.
As you said, "Intuitively, which we all know is probably wrong"
These comments are my personal opinions and do not necessarily reflect the opinions of the other voices in my head.
Easy enough to check. Send up a can of mixed nuts to the space station and put it in a slow centrifuge. Spin it for a few days then open it up and... shit, someone ate all the cashews and almonds, and reluctantly the peanuts, leaving only the brazil nuts. FAIL.
More music, fewer hits
My problem with these kind of articles is how they state it as 'case closed'. All this is is a theory of what is happening. Maybe it has a lot of solid science behind it, maybe it is even right, but right now it is still just a theory for us to explain what is happening. Using words like "Now an international team has solved the mystery" makes it sound like there is no debate, this is the answer, and anyone who says otherwise is an idiot. While I am not a scientist, I come close enough, and this fails the scientific method, at least in how the reporting represents it.
OK, I feel better now.
Never thought of that. Probably because I don't like buying popcorn at $5.00 for a small that tastes like wood shavings covered in bromide.
Well.. maybe. Or Maybe not. But Definitely not sort of.
If a collection of boulders/rocks have the same shape and density (individually), then they will have the same space between them regardless of their size. This is ignoring the conflicts with the walls of your hypothetical box. However, asteroids in space have no walls. Your experiment should not show what you think.
It might be more accurate to say that smaller rocks settle down more readily than larger boulders (in the spaces between), and the effect perceptively "floats" the boulders to the surface.