Asteroid 2004 MN4 May Hit Earth After All

ControlFreal writes "Asteroid 2004 MN4 was introduced earlier on Slashdot, and although scientists are now fairly certain that is will miss earth on April 13th, 2029, the modification to its orbit caused by Earth's gravity may still cause an impact one or a couple of orbits further down the road, the Times reports; the impact probabilities in 2035, 2036 of 2037 will not be known until the exact modification to its orbit is known; in 2029, that is. By then it may be too late for effective counter-measures. An impact would cause an energy release equivalent to about 1 Gigaton of TNT (~4e+18 Joule), and while that won't cause a massive extinction event, it causes widespread devastation. More info on 2004 MN4 can be found here and here."

NASA's impact risk summary

[Aspasia13]

The following NASA page contains an impact risk summary of several near-earth object:

http://neo.jpl.nasa.gov/risk/ [nasa.gov]

Note that this one is in the top three, but with due respect to Douglas Adams, "Don't Panic" appears to be in order.

Actual energy yields:

[product byproduct]

0.865 gigaton for 2004 MN4 impact [nasa.gov]
vs
32 gigaton for Indian Ocean quake/tsunami, 2004 [wikipedia.org]

Re:Good!

[AKAImBatman]

without some new propulsion technology i doubt even by 2029 we will have this option.

New propulsion technology? You mean like Nuclear Pulse [wikipedia.org], Nuclear Thermal [wikipedia.org] (also in Trimodal [nuclearspace.com] for low atmospheric work), Nuclear Salt Water [wikipedia.org], M2P2 [wikipedia.org], and hundreds of other mature, semi-mature, or proposed methods that we haven't used because it's "too damn expensive to get off this rock"?

Propulsion is *not* the problem.

Re:Other effects

[Anonymous Coward]

How is "0.1 lunar distance" not closer than the moon?

Re:Other effects

[Rorschach1]

Well, it's only going to intersect the proper altitude at two points, right? Remember that geosynchronous satellites occupy a very narrow band over the equator. The asteroid may not intersect that plane at all. Even if it did, it'd be unlikely to hit anything.

I'm not sure what standard spacing is out there, but I'm sure it's at least a few hundred km. The chance of a 1 km object hitting one of these widely spaced, small objects is not great.

As for perturbation, I'm sure it's negligible. Even if it wasn't, the satellites should have sufficient station keeping ability to stay put.

Re:Good!

[delong]

The problem with those designs is legal - the US, Britain, and (through the former USSR) Russian are prohibited by the Limited Test Ban Treaty and the Outer Space Treaty from exploding nuclear devices in space. That prohibition may also cover engines like Nuclear thermal if it releases radiactive material. I'm all for nuclear propulsion, but those pesky international treaties get in the way.

Bush planning astronomy cuts

[drewzhrodague]

Bush is planning cuts [space.com] in astronomy budgets.

What about 2046? Distance r(earth)=0.05

[chopper749]

4x more likely to hit then in 2035. Impact risk [nasa.gov]

Re:Other effects

[stlhawkeye]

I wonder if anyone's thought about the effects if the asteroid doesn't directly strike earth. Could it cut a swath through the geosynchronous satellites, destroying one, two or dozens directly? Might it perturb their orbits enough to destabilize the whole lot of them?

That's a lot of space. Geosynch orbit is 22,000 miles. Tack on 4,000 miles for the earth's radius, and it's a shell of space with a surface area of 8.5 billion square miles. Let's pretend we've got 50,000 satellites in that area by 2030. That means 1 sallite per 170,000 square miles. That suggests one satellite occupying a square of space 500 miles x 500 miles, and this thing is under a half mile across, probably less than a quarter-mile. The chances of it impacting anything in that orbit is incredibly tiny.

Caveat: my math may be off, but the point stands. This object occupies a TINY region of space, and satellits occupy an even TINIER region of space. There's no cloud of buzzing satellites around the planet, they're sparsely populating a huge shell around the planet.

Re:Good!

[back_pages]

Explanation [onelook.com]

Re:Orion Project

[Anonymous Coward]

Several tons of Uranium per hydrogen bomb? No offence batman, but I don't think you exactly understand how those work.

A critical mass of Uranium-235 is somewhere around 112lbs. If you had several tons of uraniumin one spot you'd have one very large uncontainable spontaneous reaction going on.

H-bombs (also called thermonuclear bombs) don't typically use uranium. They use a smallish bit of Plutonium, perhaps a bit of deutrium or tritium to boost the initial fission reaction, and a material called lithium deuteride. Neutrons and heat created from the fission reaction cause spontaneous fusion of the lithium and deuterium atoms.

They can use depleted uranium (u-238), this is part of the third stage of the bomb. Because of the heat of the fusion, the normally un-fissionable uranium can be fissioned to give the bomb an extra kick at the cost of making a normally relatively clean bomb much more radioactive.

It's much more practical to scale the amount of lithium deuteride in the bomb (which is only limited to the vehicle carrying it, and it's much lighter than uranium, obviously), because once the fusion has started it keeps going till there's no more fuel.

Re:Actual energy yields:

[imsabbel]

Difference:
The energy of the MN4 impact would be delivered into the athmosphere, a VASTLY less stable enviroment than the earth mantle.
Not to mention dust|chemical alteration problems...

Not so

[rk]

While you're right that Hubble wouldn't be too useful for tracking this asteroid, Hubble is perfectly good for looking at things [nasa.gov] in our [racine.ra.it] solar [vias.org] system [hubblesite.org].

Re:Bunkers?

[Glock27]

Your simulation was a bit flawed. For the actual numbers given, and 45 deg. angle of impact (considered most likely), effects look fairly severe at 30 km. range, not so bad at 75 (this was for impact into sedimentary rock). If it were to hit in the ocean, I'd say there's potential for a fairly bad tsunami, especially if it were to hit close to shore. Here was my run:

Your Inputs:

Distance from Impact: 30.00 km = 18.63 miles
Projectile Diameter: 320.00 m = 1049.60 ft = 0.20 miles
Projectile Density: 2681 kg/m3
Impact Velocity: 12.59 km/s = 7.82 miles/s
Impact Angle: 45 degrees
Target Density: 2500 kg/m3
Target Type: Sedimentary Rock
Energy:
Energy before atmospheric entry: 3.65 x 1018 Joules = 8.71 x 1e2 MegaTons TNT
The average interval between impacts of this size somewhere on Earth during the last 4 billion years is 2.0 x 1e4years

Relevant figures for a 75 km. distant sedimentary rock hit:

Ejecta:

The ejecta will arrive approximately 125 seconds after the impact.
At your position the ejecta arrives in scattered fragments
Average Ejecta Thickness: 3.5 mm = 0.138 inches
Mean Fragment Diameter: 5.62 cm = 2.21 inches

Air Blast:
The air blast will arrive at approximately 227 seconds.
Peak Overpressure: 11900 Pa = 0.119 bars = 1.69 psi
Max wind velocity: 26.8 m/s = 59.9 mph
Sound Intensity: 82 dB (Loud as heavy traffic)
Damage Description:

Glass windows will shatter.

For 30 km. range:

Ejecta:

The ejecta will arrive approximately 78.5 seconds after the impact.
Average Ejecta Thickness: 5.47 cm = 2.15 inches
Mean Fragment Diameter: 63.7 cm = 25.1 inches

Air Blast:
The air blast will arrive at approximately 90.9 seconds.
Peak Overpressure: 59800 Pa = 0.598 bars = 8.5 psi
Max wind velocity: 115 m/s = 257 mph
Sound Intensity: 96 dB (May cause ear pain)
Damage Description:

Multistory wall-bearing buildings will collapse.
Wood frame buildings will almost completely collapse.
Glass windows will shatter.
Up to 90 percent of trees blown down; remainder stripped of branches and leaves.

Doesn't sound like too much fun at 30 km.!

Re:Good!

[lgw]

The actual amount of radioactive materials released by these designs is pretty trivial - only of political importance, not environmental. However, the risk of disaster is large. A uranium-based fission pile can be made quite safe if it's never been used: uranium is a *lot* safer than most rocket fuels. Once you start using a fission pile you start building up dangerous decay products, but even that might not be a problem for an engine that wasn't re-used.

Orion is the exception, but orion is silly for moving anything smaller than a city into space.

Earth Impact Effects Calculator Link

[Baldrson]

The Earth Impact Effects Calculator [arizona.edu] lets you calculate the destructive effect of various asteroid impacts.

Re:Orion Project

[Anonymous Coward]

You're right, about the mark iv bomb, but you're wrong in the fact that it's simply an implosion type fission weapon, with a yield of 20kt. It's the same thing we dropped on Nagasaki. Very big, very clumbsy, pretty heavy, and for a nuclear weapon, relatively low yield. Contrast that with a device that was made about 10 years later: the W-31. Weight 900-1000lbs. Yield: 1-40kt, depending on the build..

We have in our stockpile weapons that weigh as little as 2800lbs that can do 5 megatons. We certianly don't need a saturn V to loft those.