What To Do About an Asteroid That Has a 1 In 625 Chance of Hitting Us In 2040? 412
The Bad Astronomer writes "The asteroid 2011 AG5 is 140 meters across: football-stadium-sized. Its orbit isn't nailed down well enough to say yet, but using what's currently known, there's a 1 in 625 chance it will impact the Earth in 2040. It's behind the Sun until September 2013, and more observations taken then will probably reduce the odds of impact to something close to 0. But does it make sense to wait until then to start investigating a mission to deflect it away our planet? Astronomers are debating this right now, and what they conclude may pave the way for how we deal with an asteroid threat in the future."
Re:I will be doing one thing about it. (Score:5, Informative)
140 meters diameter doesn't sound like much. Depends on the composition and speed, it will be reduced even further before making it to the ground. I immagine it shouldn't be much worse than a Tunguska event and seeing how majority of the planet is uninhabited, chances are good that no major number of lifes will be lost.
And if it occurs at a location where we can monitor/record, it will bring awareness that rocks in space do indeed end up on our planet in our lifetimes, thus worthwile to think about. Therefore having this pebble hit us might not be such a bad thing after all.
Re:I will be doing one thing about it. (Score:5, Informative)
140 meters diameter doesn't sound like much. Depends on the composition and speed, it will be reduced even further before making it to the ground. I immagine it shouldn't be much worse than a Tunguska event and seeing how majority of the planet is uninhabited, chances are good that no major number of lifes will be lost.
And if it occurs at a location where we can monitor/record, it will bring awareness that rocks in space do indeed end up on our planet in our lifetimes, thus worthwile to think about. Therefore having this pebble hit us might not be such a bad thing after all.
Just some numbers for reference:
This one is 140 meters across.
Re:I don't see the problem. (Score:5, Informative)
If it hit the water, it may cause a tsunami wave. Depending on where that wave makes landfall, it could disrupt anywhere from dozens to millions of people.
But weren't the tsunami's (2004 and Japan's) caused when large (kilometers long) sections of the seabed were suddenly raised up, displacing the seawater? The displacement of a 140 m meteor doesn't seem like it would be as much.
Further reading:
The energy released on the Earth's surface only (ME, which is the seismic potential for damage) by the 2004 Indian Ocean earthquake and tsunami was estimated at 1.1×1017 joules,[24] or 26 megatons of TNT. This energy is equivalent to over 1500 times that of the Hiroshima atomic bomb, but less than that of Tsar Bomba, the largest nuclear weapon ever detonated. However, this is but a tiny fraction of the total work done MW (and thus energy) by this quake, 4.0×1022 joules (4.0×1029 ergs),[25] the vast majority underground.
While the wikipedia [wikipedia.org] page doesn't say how much water was displaced, it does say this:
the earthquake had made a huge impact on the topography of the seabed. 1,500-metre-high (5,000 ft) thrust ridges created by previous geologic activity along the fault had collapsed, generating landslides several kilometers wide. One such landslide consisted of a single block of rock some 100 m high and 2 km long (300 ft by 1.25 mi). The momentum of the water displaced by tectonic uplift had also dragged massive slabs of rock, each weighing millions of tons, as far as 10 km (6 mi) across the seabed.
Re:I will be doing one thing about it. (Score:5, Informative)
True, but the remaining variables are the composition and how much actually makes it down to the surface.
Lets use some numbers in the calculator from the quick Google search:
http://impact.ese.ic.ac.uk/ImpactEffects/ [ic.ac.uk]
- We are hit with 140 meters perfect sphere of dense stone
- Speed of projectile is 17 km/s (Calculator states that it is the typical speed for asteroid impace)
- Entry angle of 45% (Again based on the caluculator stated most likely)
- Rock lands into 1000 meter depth water. Random figure
Results:
1 km away [ic.ac.uk]
20 km away [ic.ac.uk]
100 km away [ic.ac.uk]
Reading the descriptions, it honestly doesn't sound like such a calamity. At 100 km distance it is hardly felt.
Re:I will be doing one thing about it. (Score:5, Informative)
Um. Not really. http://idisk.mac.com/mpaineau-Public/paine_tsunami_asteroid99.pdf [mac.com]
The assumption people make is that all the kinetic energy goes into a wave. That's not a given. It can dissipate as heat as the meteor falls through the water, or create incoherent waves. The Indian Ocean tsunami was so bad because the plate "flicked" up, splashing the water. It might be more like punching the water, which would still make a bit of a splash; but it might not make a huge wave.
That said, I wouldn't be swimming anywhere near it.
Re:I will be doing one thing about it. (Score:5, Informative)
Huh? It says 72 Megaton explosion. That's bigger than than the largest nuclear bomb ever detonated.
Re:I will be doing one thing about it. (Score:2, Informative)
Yes, but those results are for a water impact, not land. Impact on water is vastly different against a land hit, where debris ejection is a certainty regardless of asteroid composition due to this ones size. All of this is conjecture though. If it's a loose aggregate asteroid, it'll detonate in air like tunguska and airblast the land. That's probably the best case if it is land bound. Worst case? I don't really want to consider that.
Also, there is that 22.1ft amplitude tsunami at the 100km link. Pretty good surf at the beach, if your up for it! Did you even read your links all the way through?