Asteroid may hit Mars, 1 in 75 chance. Tunguska sized

deapfreeze · Jan 3, 2008

" instead of one large asteroid, we'd be bombarded by a few medium ones " Or we would have an amazing meteor shower. It would be safer than having a city killer hit the ground... <div class="Discussion_UserSignature"> William ( deapfreeze ) Hooperhttp://deapfreeze-amateur-astronomy.tk/ </div>

brigandier · Jan 3, 2008

Both are possible, I guess

h9c2 · Jan 3, 2008

I'm sure "nuking" a small rock like this would leave sufficiently small fragments to significantly reduce its destructive power. nonetheless, how feasible is it, considering the timeframe, and the size of the rock to "Drop a couple of nukes on it"?

MeteorWayne · Jan 3, 2008

Well the situation is different for a mars impactor vs an earth one. It's a very small object, heading away from us toward Mars, so is a pixel or two of brightness when spotted from earth with a scope. So the position error bars are substantial. For an object heading toward earth, it would be getting larger and closer in the images, so we would be gaining much better information. Yes there are defenses possible against impactors if you have enough time (i.e. decades). For an object like this, that was discovered only a few weeks ago, there would be no defense. <div class="Discussion_UserSignature"> But the Krell forgot one thing John. Monsters. Monsters from the Id. I really, really, really, really miss the "first unread post" function </div>

shadow735 · Jan 3, 2008

How so? what is the rock composed of, is it solid? is it rubble? is it crumbly porous rock? If we dont know the composition of a meteor that is set to impact its not a good idea to just lob nukes at it expecting it to blow up into millions of harmless pieces. If its a rubble pile held together by gravity it could just scatter massive rocks creating an even larger area of devistation. If its a very dense rock the blast from a nuke could be absorbed. Same if it is pourous or spongey rock. the Idea of lobbing a nuke is great as long as you know what type of rock your lobbing it at. As for the rock headed toward mars I hope it does hit, it will mean great advances in science and understanding of impacts. <div class="Discussion_UserSignature"> </div>

MeteorWayne · Jan 3, 2008

Really? Where would we get the nukes? How would we get them to the asteroid in 3 weeks? Would things be mmade worse if you disrupted the object, spreading it over a larger area? You thinking is about a decade or so behind the times. <div class="Discussion_UserSignature"> But the Krell forgot one thing John. Monsters. Monsters from the Id. I really, really, really, really miss the "first unread post" function </div>

MeteorWayne · Jan 3, 2008

Or 20 cities would be destroyed instead of one. <div class="Discussion_UserSignature"> But the Krell forgot one thing John. Monsters. Monsters from the Id. I really, really, really, really miss the "first unread post" function </div>

centsworth_II · Jan 3, 2008

"Or 20 cities would be destroyed instead of one." Given that the chance of ocean impact is great, the tsunami caused by one large impactor could destroy many, many cities. But I don't hold much hope of nuclear bombs being able to blow an asteroid apart. Wouldn't most -- or almost all -- of the force of the blast be directed into empty space? <div class="Discussion_UserSignature"> </div>

silylene old · Jan 3, 2008

And, whether the asteroid is in 1 piece, 10 pieces or 100 pieces, the same amount of energy will be deposited into Earth's upper atmosphere as the incoming rocks decelerate and burn up, since their total mass and velocity is unchanged. As MW said, it doesn't help that much to have the asteroid broken up. <div class="Discussion_UserSignature"> <div class="Discussion_UserSignature" align="center">- - - - - - - - - - - - - - - - - - - - - - </div><div class="Discussion_UserSignature" align="center">I really, really, really miss the "first unread post" function. </div> </div>

tyguy · Jan 3, 2008

so they know where it would hit, but still can only give a 1 in 75 chance?

shadow735 · Jan 3, 2008

I guess we will find out for sure later in this month <div class="Discussion_UserSignature"> </div>

centsworth_II · Jan 3, 2008

Actually, the odds had gone up to about 1 in 25, but now have dropped to 1 in 28 and are predicted, with more measurements, to "quickly drop to zero." http://neo.jpl.nasa.gov/news/news154.html <div class="Discussion_UserSignature"> </div>

MeteorWayne · Jan 3, 2008

No the point is they don't know. Among the possible positions, only 1 in 28 intercepts Mars. However, due to the orbit, if it does hit, they have a good idea where that will happen; along the path of possible positions. <div class="Discussion_UserSignature"> But the Krell forgot one thing John. Monsters. Monsters from the Id. I really, really, really, really miss the "first unread post" function </div>

comga · Jan 3, 2008

No, they don't know where it would hit. Check out the link http://neo.jpl.nasa.gov previously posted by myself and centsworth_II. It shows the uncertainty ellipse, which looks more like a line, of the possible paths through a plane through Mars normal to the direction of motion. This ellipse is centered off of the surface of Mars but slices across it. 3.6% of the ellipse, in a probability weighted sense, lies across the "impact zone" which is slightly larger than the planet itself, due to its gravity. It is now possible to state with high confidence where it will NOT impact on Mars, which include the locations of the rovers. The reason for the imprecision is that the asteroid is moving almost straight away from us. Therefore, the uncertainties in the third dimension, along the line of sight, are the greatest. This uncertainty diminishes slolwy as its motion departs from that straight away line. The Jan 2 plot shows Mars more than half way from the nominal intercept point to the edge of the ellipse. On December 30 it was ~1/7 of the way from the center to the edge. This is not so much because the center point moved as it is because the ellipse has shrunk. It is likely that the next refinement will shrink the ellipse enough to exclude Mars entirely. (Bummer!)

MeteorWayne · Jan 3, 2008

I said they have a good idea of where it woul hit, not that they know where it would hit. <img src="/images/icons/smile.gif" /> The "good idea" is along the most likely path. What I was trying to say was the same as your "It is now possible to state with high confidence where it will NOT impact on Mars, which include the locations of the rovers. ", though perhaps I didn't say it as clearly as you did. MW <div class="Discussion_UserSignature"> But the Krell forgot one thing John. Monsters. Monsters from the Id. I really, really, really, really miss the "first unread post" function </div>

comga · Jan 3, 2008

Actually, I was responding to tyguy. You understand the issues, but I thought a bit more detail was wanted.

tdamskov · Jan 5, 2008

<blockquote>In reply to:<hr />And, whether the asteroid is in 1 piece, 10 pieces or 100 pieces, the same amount of energy will be deposited into Earth's upper atmosphere as the incoming rocks decelerate and burn up, since their total mass and velocity is unchanged. As MW said, it doesn't help that much to have the asteroid broken up.<hr /></blockquote> The total mass and velocity will be unchanged. However, a more fragmented object would present a larger surface area to the atmosphere and thus more energy deposited due to drag. I suspect small (50 m and below) rubble/ice objects would be prime targets for fragmentation. If it could be induced to explode in the upper atmosphere (tunguska) that would mean a lot less energy to reach the ground.

MeteorWayne · Jan 5, 2008

Tim, Yeah, kind of busy right now with the Quadrantid meteor shower data reduction. What would be the effect of a nuke? It depends on the composition of the asteroid involved. Which asteroid is it? Is it Rocky, a rubble pile, a comet body? How will a nuclear blast affect it? How would we get the nukes there in time? Current ideas are (assuming enough time): Landing a mass driver on the surface and throwing mass away. Landing a thruster of the surface and thrusting. Using a spacecraft as a gravity Tug. Changing the albedo of the surcae in some way to let the sun do the work. Possible attaching a solar sail. All work by very slightly changing the velocity of the asteroid to ensure that the asteroid and the earth do not occupy the same space at the same time. I'll go into more detail later. This has been discussed (to the beating a dead horse level) in a number of other threads here. When I have time I'll do a search for them Wayne <div class="Discussion_UserSignature"> But the Krell forgot one thing John. Monsters. Monsters from the Id. I really, really, really, really miss the "first unread post" function </div>

silylene old · Jan 5, 2008

Hicup and tdadamsov, of course it depends on how far the fragments are dispered. In this particular case, I was assuming that an ICBM nuke was launched at the last moment at an asteroid similar to the one which may strike Mars. Assume an ICBM were launched from today's existing inventory, and exploded next to the asteroid not that far above the earth's surface - perhaps 300-500km high (isn't that the upper trajectory limit of a TOPOL or a Minuteman 3 or Poseidon or D5A?). Since this asteroid is moving 30 km/s, that means it would be exploded only perhaps 10-15 seconds before fragments begin entering the upper atmosphere. How far would the asteroid fragment 'cone' disperse in only 10-15s? Maybe 5 km? I can't imagine much more than that. So all the kinetic energy would be released in a patch of the upper atmosphere 5km in diameter. I am thinking that the damage radius on the surface below would be 5x to 10x the size of the fragment cone, or 25-50km. And the total energy reaching the surface is perhaps about about 20% of the original kinetic energy, or about 3-5 MT. And if the asteroid were not targeted , it would breakup in the upper atmosphere, and the models and reports I have read suggest an energy release at the ground below of 3-5 MT and a damage radius of 20-50 km. I really don't see much difference. Nuke interception would only work if it were to occur weeks or months before the asteroid hit, so that the fragment cone was *much* greater in size, and if none of the surviving individual fragments were large. Even better would be to nudge the asteroid aside so it misses. In this case, it requires a surprisingly small nudge if it is done at the correct part of the trajectory and the asteroid was still years away. Our planet's existing ICBM inventory is not built with the reliability or battery duration or or thermal control or targeting capability to travel months in the solar system to meet the asteroid ta <div class="Discussion_UserSignature"> <div class="Discussion_UserSignature" align="center">- - - - - - - - - - - - - - - - - - - - - - </div><div class="Discussion_UserSignature" align="center">I really, really, really miss the "first unread post" function. </div> </div>

tdamskov · Jan 5, 2008

Silylene, I agree completely on the scenario you suggest. Actually, detonating one (or multiple) nuclear warheads in the upper atmosphere just prior to an asteroid strike would be topping the list of things not to do. The EMP strike at that altitude destroys any means of mounting an emergency relief operation after the disaster. A bit like shooting yourself in the foot before a marathon <img src="/images/icons/wink.gif" /> Nukes might be somewhat useful at nudging an object, but it's a waste of energy just detonating it nearby. Almost all energy disperses without effect. The nuke needs to be inside the object (bunker buster?) to do some real damage. And as you mention, a specialized vehicle capable of travelling for years in interplanetary space would be required.

comga · Jan 5, 2008

All of you who are so interested in turning this discussion into one of defending Earth from an approaching asteroid should go to places like http://planetarydefense.blogspot.com/2006_02_01_archive.html , www.b612foundation.org , http://spaceguard.esa.int/ or http://www.outofthecradle.net/archives/2005/12/cosmic-collision-insurance-rusty-schweickart-and-the-b612-foundation/ There is a lot of background, including thoughtful criticism by Clark Chapman of SwRI on why nukes are a poor choice, assuming that we have a choice. The rest of us can just watch the odds of an impact dwindle but keep our hopes up.

Philotas · Jan 5, 2008

It was starting to become interesting though. <img src="/images/icons/smile.gif" /> <div class="Discussion_UserSignature"> </div>

silylene old · Jan 6, 2008

On a side note, asteroid 2007VK184 has just been rated a Torino Scale 1 concern by JPL and NEODYS based on 100 observations spanning 54 days. The object is 0.13 km in diameter, and is a danger to earth in the year 2048. Please understand that as more observational data is acquired in the next few months, the chance of an earth strike very likely diminish to nil. Still s2007VK184 is something to watch, since as you said "It was starting to become interesting though." <div class="Discussion_UserSignature"> <div class="Discussion_UserSignature" align="center">- - - - - - - - - - - - - - - - - - - - - - </div><div class="Discussion_UserSignature" align="center">I really, really, really miss the "first unread post" function. </div> </div>

icemanmd · Jan 7, 2008

oct 31st. 2041 it makes a much closer pass I wonder why they do not mention that.

h9c2 · Jan 7, 2008

I must be misunderstanding the minimum passing distance. It is explained as the distance from geocenter to object in earth radius, so can it be less than 1, and not hit? From this page: http://neo.jpl.nasa.gov/risk/2007vk184.html

Asteroid may hit Mars, 1 in 75 chance. Tunguska sized

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