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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.
I thought this was going to relate to nuts with high amounts of radioactivity.
Damn_registrars has no butt-hole. Damn_registrars has no use for a butt-hole.
...
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
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.
Jellomizer for president 2016
Wow, the World Cup of Brazil really left a mark all the way into space! Now all I need for today is a scientific article, which explain complex physics by using the Mexican Wave!!
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.
Well yeah, every person that goes to movies is well aware of this effect, that is why during the movie you hear the rustle of boxes of popcorn being shaken to bring the large tasty choice kernels to the top.
explains the mystery of why people think we'll be mining asteroids?
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.
Odd; My first thought would be that those surface boulders were just the more recent micro-asteroids that were drawn to the larger asteroids gravity. I'm not sure why a more complicated explanation is necessary? But I'm open to learning.
The large boulders rise due to a density disparity. If you take the smallest box that would hold a large boulder, you will find a lot of airspace in it. The same sized box filled with smaller rocks would have less airspace. The larger box is therefore lighter than the smaller box.
This can be experimentally verified by making the large boulders out of a material that is much more dense than the small rocks, such that the cubic density would still be higher for the large boulders, even including the airspace. In this case, the large boulders should sink when the system is shaken.
Your countries thought is good steady footing.
John McAfee 'It was like that time I hired that Bangkok prostitute; to do my taxes, while I fucked my accountant'
Another explanation is that the asteroid got showered by a significant amount of other material that was not part of the primary body of the crater making asteroid. Perhaps when a nearby moon or planet exploded like the fictitious planet of Alderan in the popular Star Wars movie A New Hope.
This type of astronomical event would also explain why one side of Mars is the flattest place in the solar system and has a crust thickness of only 1km and the other side hosts the tallest mountains in the solar system and has a crust thickness of 20 km. Also can offer a plausible explanation for why phobos and deimos are not round like one would expect moons to be.
Is that when you meet up with a hot Brazilian chick but then it turns out she has a monster cock and a bigger ballsack than you?
This was known as the Cesspool Theory of Managment.
"The big chunks rise to the top."
Banach-Tarski in action?
What is it with the army of medium.com lovers lately?
There is possibly some confusion in parent post between granular convection and frost heaves.
In New England and other climes that have a winter freeze and spring thaw, the winter freeze pushes rocks upward as the water in the soil expands into ice. In the spring thaw, the ice under the rocks melts from the periphery inward, and slurries of ice water mud fill the voids. As a result, the rocks stay in their higher place as the soil settles back to its spring level.
One of my chores when I was growing up was to help with digging the big and deep holes in the garden next to the emerging boulders that were too large to remove. We'd roll the boulder into the deeper hole and bury it, and be able to use the rototiller and tractor over it for a few years before it would rise again.
Will
TFA describes the situation on a dry asteroid.
An asteroid or comet that contains water as well as stone is likely to behave differently. If its ice is melted by impact or increased exposure to sunlight, then frost heaves might cause a faster migration of big stones to the surface than would happen by granular convection. But if the ice is acting as a concrete binding agent, then there will be no frost heaves and no granular convection. Probably on a lot of asteroids both processes will be active.
I'm thinking that determining whether frost heaves or granular convection has been at work is going to be important in figuring out how to deflect any asteroid or comet. I'n guessing this will need to be done on a case by case basis.
Will
This also explains why all the big nuts and bolts rise to the top of my bolt bucket!
My ism, it's full of beliefs.
The apparent discrepancy of the total volume of large boulders being greater than that of the visible craters they have supposedly come from is not resolved by the BNE. In the paper, this paradox is only mentioned in passing, and no definite resolution is offered. No-one seems to have ruled out the possibility that there are additional craters beneath the rubble, or that the excess includes remnants of the impactors. Perhaps there is an assumption that, absent the BNE, the boulders formed by early impacts should now be buried.
American cretins. You can't even write 'they' properly.
And you get REALLY confused when you have to write 'they're', 'their' or 'there'. How the hell is your country still standing?
We stand on our feet, silly.
It's harder to do that while your head is up your ass.
Your obsessing on typos, homophones, homonyms during a Slashdot banter about Brazil nuts and asteroids is either an emotional disorder or you are from the Land of Trolls that can't walk and talk at the same time.
Hurling vituperative disparagements in grammatically correct English has nothing to do with this story and discussion so please take your meds. .