Landing On an Asteroid Might Cause an Avalanche

coondoggie writes "As if landing on an asteroid wouldn't be dangerous enough, a new microgravity experiment on the forces generated by an asteroid and its make-up suggests landing on one may cause a big avalanche. The rubble and dust covering asteroids and comets can feel changes in what is known as 'force-chains' between particles over much larger distances than on Earth, making these surfaces less stable than previously imagined, said Dr. Ben Rozitis of the Open University, who presented his experiment's findings (abstract) on July 4 at the National Astronomy Meeting."

Comments

Oh no!

[Speck'sBacon]

Now how are we going to shoot Bruce Willis and a bunch of B-list character actors into space to stop a giant asteroid from smashing into earth?

Re:Oh no!

[microbox]

Steve Buscemi is not a B-list character actor.

independant research?

[Anonymous Coward]

Just another flawed Monsanto study...

Re:Bullshit

[I'm New Around Here]

It's OK if you RTFA, but at least RTFS(ubmission), since it is right on this same page.

The rubble and dust covering asteroids and comets can feel changes...

(emphasis mine)

Re:Bullshit

[Lunix Nutcase]

Couldn't even make it to the 2nd sentence of the summary?

so if a mountain is 50% of the objects width..

[gl4ss]

it might come down easier? who would have though.

though, in the asteroids microgravity, so what?

Re:so if a mountain is 50% of the objects width..

[I'm New Around Here]

I'm guessing it is about having the dust cover scientifically important parts of the craft, such as lenses and clean sample bins. Also clogging filters or joints could cause issues.

Re:so if a mountain is 50% of the objects width..

[ackthpt]

I'm guessing it is about having the dust cover scientifically important parts of the craft, such as lenses and clean sample bins. Also clogging filters or joints could cause issues.

So you just take along a little compressed air and repel the stuff before it gets there. This would be one very, very slow avalanche.

Re:so if a mountain is 50% of the objects width..

[drinkypoo]

So you just take along a little compressed air and repel the stuff before it gets there. This would be one very, very slow avalanche.

Right now, spacecraft are made out of sheet metal and tin foil. Maybe someday when we discover how to tap the vacuum energy we'll build them sturdier. Reminds me of Futurama where they're underwater or something (obviously my memory is a steel trap, with significant rust) and the question comes up as to how many atmospheres of pressure the ship can withstand. And since it was designed to operate between Earth and space, where there is no pressure, the answer is between zero... and one. Even slow-moving rocks have the potential to completely ruin our current vehicles.

Re:so if a mountain is 50% of the objects width..

[ShanghaiBill]

I'm guessing it is about having the dust cover scientifically important parts of the craft, such as lenses and clean sample bins. Also clogging filters or joints could cause issues.

If there is no atmosphere to suspend it, particles of dust will follow the same trajectory as any other object. So if your lens is in the path of the dust, it would also be in the path of the boulders, and the dust would be the least of your concerns.

Re:so if a mountain is 50% of the objects width..

[ackthpt]

So you just take along a little compressed air and repel the stuff before it gets there. This would be one very, very slow avalanche.

Right now, spacecraft are made out of sheet metal and tin foil. Maybe someday when we discover how to tap the vacuum energy we'll build them sturdier. Reminds me of Futurama where they're underwater or something (obviously my memory is a steel trap, with significant rust) and the question comes up as to how many atmospheres of pressure the ship can withstand. And since it was designed to operate between Earth and space, where there is no pressure, the answer is between zero... and one. Even slow-moving rocks have the potential to completely ruin our current vehicles.

Maybe we already have the materials, but the convention is to stick (ha) with what works.

Perhaps also a little static generator could polarize dust so it is more attracted to the asteroid than a craft.

Re:so if a mountain is 50% of the objects width..

[drinkypoo]

Maybe we already have the materials, but the convention is to stick (ha) with what works.

We don't, though. In order to make the ship significantly stronger we have to spend more mass. Carbon fiber might one day be the right material, but right now it's still prone to cracking in many terrestrial applications.

Perhaps also a little static generator could polarize dust so it is more attracted to the asteroid than a craft.

That's a good or even great idea, but it won't help with rocks for the foreseeable future.

Empirical results differ

[simonbp]

NEAR-Shoemaker "landed" on Eros perfectly fine. Likewise Hayabusa "landed" on Itokawa perfectly fine. Neither saw any sort of "avalanche".

Re:Empirical results differ

[Lunix Nutcase]

Are either Eros or Itokawa tiny asteroids made up almost entirely of granular materials (which was the parameters of this paper)? Otherwise you didn't really refute them.

Murdoch said many smaller asteroids are thought to be entirely granular in nature -- piles of rock and gravel held together by gravity. Understanding the physics of granular materials is important for interpreting spacecraft images of these small bodies, to understand their evolution, and also to help design space missions that will interact with their granular surfaces.

Re:Empirical results differ

[simonbp]

Yes, they are both rubble piles; nearly everything smaller than a few hundred kilometers across is. Eros is relatively large for NEA at 34 km on its long axis, while Itokawa is only 535 m on its long axis (about the size of the International Space Station). The regolith of both objects was very similar.

Re:Empirical results differ

[Jmc23]

ah, you just had to take away his happiness with logic didn't you! He was so proud of himself too because people who 'quote' everything have to work extra hard.

Re:Empirical results differ

[CreamyG31337]

Eros is not a rubble pile. I hate quoting wikipedia, but "The asteroid 433 Eros, the primary destination of NEAR Shoemaker, was determined to be riven with cracks but otherwise solid. Other asteroids, possibly including Itokawa, have been found to be contact binaries, two major bodies touching, with or without rubble filling the boundary."
http://en.wikipedia.org/wiki/Rubble_pile

Re:Empirical results differ

[kermidge]

I haven't done due diligence in searching, so I have to wonder how long ago the possibility of avalanches on the assorted rubbled asteroids was raised. You knew, but that may not qualify as being able to assume it was a notion up for wider discussion. Perhaps the author of the piece that led to the submission didn't bother searching either.

I think it's an interesting question and I admire that bit of mind that first asked it. Now I have to wonder just who first wondered about it. Geez, thanks, hey.

But very slowly

[Anonymous Coward]

In microgravity just how fast could that avalanche be?

Less than one millimeter an hour?

The effect would resemble plant growth more than 1/2 a mountain falling on you in a second or two.

Re:Bullshit

[Mente]

Armageddon was an asteroid. Deep Impact was a comet.

Not a rocket scientist but....

[k31bang]

Only read the summary, but couldn't we just send a dense object to hit it first, causing the "avalanche" then safely land?

Re:Not a rocket scientist but....

[Rich0]

Hit an asteroid like one being described here with a dense object, and you just end up with 5 million asteroids. Maybe in a million years they'd have re-aggregated back to what they look like today.

These things aren't really "solid objects" as you'd think of them. Imagine putting up a square frame and filling the space inside with billiard balls, then remove the frame and repeat until you miraculously get most of them to stay together. Then try to stand on top of it. That's basically what you're trying to land on, minus the 1G gravity.

You're trying to land on a lump of gravel, the largest component of which could be picked up with your hands and thrown such that it will never come back down. It probably took a billion years for that lump to grow to the size it is by virtue of little bits and pieces just happening to collide in a way that didn't blow the whole thing apart.

Re:Not a rocket scientist but....

[aix tom]

Of course, then what's even the point of "landing" on something that has almost no gravity?

I would describe that more as some sort of "docking" instead of "landing".

You could fly your vessel up to 1-2 meters distance and extend a sampling arm, or do you EV mission from there without even touching the asteroid with your spacecraft. It feels a little lie "Oh, noes! We can't land on objects where it makes absolutely no sense to try to land on anyway!"

Re:Bullshit

[AJH16]

Personally, I just read the comments... the summaries are always worthless anyway.

Microgravity = microacceleration

[edibobb]

If it does cause a landslide, it will be a very slow landslide because the gravity is so low on an astroid. The kinetic energy of the sliding "land" will be correspondingly low, and would have little in common with a landslide or avalanche on earth. It would be unstable, but unlikely to smash anything.