## Introducing Asteroid 2004 MN4 633

Numerous readers wrote in with bits about a potential asteroid collision:

*"The recently discovered asteroid 2004 MN4 is currently listed as having a 1/233 chance of hitting the Earth. It is 420 m across and if it strikes the Earth it will release an energy of 1,900 Megatons of TNT (the largest nuclear weapon ever detonated, Tsar Bomba had a yield of only 50 Megatons). It is also the only asteroid that currently has a Torino scale value of 2."*So, in summary, there's a 1-in-233 chance of the worst disaster in recorded history happening on April 13, 2029, and a 232-in-233 chance of nothing happening. Have a nice day!**Update: 12/24 22:14 GMT**by**M**: The rock is now rated a 4 on the Torino scale, or a 1-in-62 chance of impact.
## Re:Like a car on a turn... (Score:1, Informative)

## Re:According to google define (Score:2, Informative)

Regards,

Steve

## Re:Thanks for the breakdown ... (Score:5, Informative)

----

Your Inputs:

Distance from Impact: 100.00 km = 62.10 miles

Projectile Diameter: 1320.00 m = 4329.60 ft = 0.82 miles

Projectile Density: 3000 kg/m3

Impact Velocity: 17.00 km/s = 10.56 miles/s

Impact Angle: 45 degrees

Target Density: 2500 kg/m3

Target Type: Sedimentary Rock

Energy:

Energy before atmospheric entry: 5.22 x 1020 Joules = 1.25 x 105 MegaTons TNT

The average interval between impacts of this size somewhere on Earth during the last 4 billion years is 9.2 x 105years

Major Global Changes:

The Earth is not strongly disturbed by the impact and loses negligible mass.

The impact does not make a noticeable change in the Earth's rotation period or the tilt of its axis.

The impact does not shift the Earth's orbit noticeably.

Crater Dimensions:

What does this mean?

Transient Crater Diameter: 13.1 km = 8.12 miles

Transient Crater Depth: 4.63 km = 2.87 miles

Final Crater Diameter: 18.4 km = 11.4 miles

Final Crater Depth: 0.711 km = 0.441 miles

The crater formed is a complex crater.

The volume of the target melted or vaporized is 3.22 km3 = 0.772 miles3

Roughly half the melt remains in the crater , where its average thickness is 24 meters = 78.6 feet

Thermal Radiation:

What does this mean?

Time for maximum radiation: 0.95 seconds after impact

Visible fireball radius: 15.2 km = 9.45 miles

The fireball appears 34.6 times larger than the sun

Thermal Exposure: 2.29 x 106 Joules/m2

Duration of Irradiation: 20.8 seconds

Radiant flux (relative to the sun): 110

Effects of Thermal Radiation:

Much of the body suffers second degree burns

Deciduous trees ignite

Seismic Effects:

What does this mean?

The major seismic shaking will arrive at approximately 20 seconds.

Richter Scale Magnitude: 8.0

Mercalli Scale Intensity at a distance of 100 km:

VII. Damage negligible in buildings of good design and construction; slight to moderate in well-built ordinary structures; considerable damage in poorly built or badly designed structures; some chimneys broken.

VIII. Damage slight in specially designed structures; considerable damage in ordinary substantial buildings with partial collapse. Damage great in poorly built structures. Fall of chimneys, factory stacks, columns, monuments, walls. Heavy furniture overturned.

Ejecta:

What does this mean?

The ejecta will arrive approximately 144 seconds after the impact.

Average Ejecta Thickness: 26.1 cm = 10.3 inches

Mean Fragment Diameter: 11.8 cm = 4.65 inches

Air Blast:

What does this mean?

The air blast will arrive at approximately 303 seconds.

Peak Overpressure: 157000 Pa = 1.57 bars = 22.3 psi

Max wind velocity: 242 m/s = 540 mph

Sound Intensity: 104 dB (May cause ear pain)

Damage Description:

Multistory wall-bearing buildings will collapse.

Wood frame buildings will almost completely collapse.

Highway truss bridges will collapse.

Glass windows will shatter.

Up to 90 percent of trees blown down; remainder stripped of branches and leaves.

## Re:The problem (Score:3, Informative)

## Re:Ever Wonder... (Score:1, Informative)

http://newton.dm.unipi.it/cgi-bin/neodys/neoibo

## Re:Nothing to worry about? (Score:3, Informative)

Even though 30 years is a drop in the universe's bucket in terms of time, there is a lot that could possibly alter the course.Other than human interference? No, not really. The chances of its running into some other body are probably far less than its running into the earth, and it's not like there's a lot of commuter traffic to get in the way. Space is rather empty -- pardon the cliché.

## Re:Nothing to worry about? (Score:2, Informative)

## Updated to a Torino value of 4. Uh oh. (Score:5, Informative)

It looks like it's up to a 4, now.

## Re:Ever Wonder... (Score:5, Informative)

I guess I'd just like to see the math on how they come up with these numbers.Nobody's stopping you; it's not a secret. Go get it.

But get ready for some heavy lifting; as you dig into it you'll very quickly realize why they didn't try to put any in a popular news article.

I'm not too up on it myself but you can start with phase spaces [wolfram.com], I think, though that hardly touches the real fun, which is the probabilistic aspect of determining the path of an object through all of the influences of the solar system... while I'm not up on the details I

doknow they don't use naive formulations of that problem, they've got some powerful and brain-bending tricks to prevent the estimate from diffusing too quickly.## Re:Why don't we know if it will hit? (Score:1, Informative)

>For example, we predict the trajectories of space probes through space decades in advance with very tiny margins of error.It's a good question. The answer is that space probes have radios mounted on them which broadcast at *very* precise frequencies. When receiving the probe's telemetry one can watch the frequecncy of the carrier wave. Any difference between the designed frequency and the actual frequency is a measure of the probe's velocity difference with respect to Earth. Factor out the Earth's motion and a few other well known factors, and you get an astonishingly precise velocity value. A photograph gives poor X and Y resolution, measuring Dopler shift gives excellent delta-Z resolution.

Sadly asteroids lack tuned transitters.

## Re:Why don't we know if it will hit? (Score:3, Informative)

We are clearly capable of tracking things through space with very, very low margins of error.To know where something is

nowdoesn't mean you canpredictwhere it will be in the future. Not within a "space is big" margin of error.So what's the bottleneck here?The very thing that makes it want to hit us: gravity. That is, the Three-Body Problem [wolfram.com], an 3 is at the lower end of influences that come into play over the next 25 years.

## Re:Updated to a Torino value of 4. Uh oh. (Score:5, Informative)

## Re:Why don't we know if it will hit? (Score:5, Informative)

So what's the bottleneck here? Poor imaging?Yes. The image on the telescope is not a theoretical point, but has a certain diameter depending on the telescope diameter, atmospheric distortion, ccd resolution, etc. So you cannot pinpoint the asteroid position precisely, but only give a bounding box.

Combining multiple observations will give you more data, and you can start narrowing down the estimate. Right now the error on the position, projected to year 2029, is about 200 times bigger than the diameter of Earth, so we say that there's a 1/200 probability of impact. A planet is a very tiny target.

When the precision is sufficient to say that, for example, the asteroid will pass by the left side, it will suddenly drop to zero. If it is actually going to impact the Earth, the probability will slowly going up until it will reach 1.

## Re:Why don't we know if it will hit? (Score:2, Informative)

There are so many factors we don't know after 2-3 sightings of such a meteor to make more accurate prediction.

## torino is now at 4 (Score:3, Informative)

## Re:Updated to a Torino value of 4. Uh oh. (Score:1, Informative)

So, I would not start planning the apocalypse party just yet.

## Re:In numerology... (Score:5, Informative)

Not so fast!The number 4 in Japanese is "shi" (U+56DB), but "shi" also means death (U+6B7B)!

It's just as unlucky as 13 in western culture, and more specific about our fate.

## Re:Maybe (Score:2, Informative)

> with a rock this size, which is about enough to flatten a fairly large city,

> if I'm understanding this correctly. If it's going to hit, we probably won't

> learn where exactly until the last approach, at which point it's too late

> to evacuate Calcutta or wherever.

If it's large enough to flatten a large city, you don't want it to hit

anywhere, not even in the middle of the Pacific.

However, 25 years is a long time; we can afford to just *watch* it for fifteen

years, and that still leaves ten years more, *plenty* of time to alter its

orbit if necessary so that it doesn't hit. (All this malarke about blowing

it to pieces with nukes is just so much movie-plot nonsense. It would be much

easier and safer to mount a few rockets on it and push it off course so it

misses. Especially if we have several years to work out the details.)

Honestly, something that we see coming 25 years ahead of time isn't going

to be scary unless it's *entirely* too large to move (i.e., sized more like

a small planet than an asteroid), which seems unlikely -- and this little

bitty thing isn't even close to that category. If you want to get yourself

all worked up over the possibility of a large asteroid plowing into the

Earth, think about one coming from a strange angle far out of the plane of

the eccliptic so that we don't notice it until a few hours before it hits.