Los Alamos National Laboratory

WATCH: This Is What an Asteroid Impact in The Ocean Could Mean For You

And how to survive.

PETER DOCKRILL
16 DEC 2016
 

When we think about the prospect of an asteroid impact on Earth, it's easy to imagine the cataclysmic death and destruction that would result if a space rock smashed into a large city or urban area.

But given that more than 70 percent of the globe is covered in water, it's more likely that an asteroid would touch down somewhere in the world's oceans – but what would that mean for land dwellers like you and me?

 

The answer, according to new modelling from scientists at the Los Alamos National Laboratory, is complicated.

The team ran a series of 3D simulations to see just what kind of shock waves and water dispersion would result from an asteroid crashing into the high seas – and whether it would be enough to trigger a tsunami.

While an initial asteroid impact in the ocean could generate splash waves ranging from hundreds of metres to even kilometres high, unless the collision occurred close to the coast, the simulations suggest a tsunami devastating the shoreline is unlikely.

That's because the shockwaves generated by one-off impacts like an asteroid are relatively short compared to more widespread disruptions such as an earthquake.

The difference means that the waves resulting from an asteroid impact wouldn't actually propagate very far – although you certainly wouldn't want to be close by.

 

If an asteroid were to land in the ocean within 10 to 20 kilometres of a populated coastline, the effects would be devastating, the researchers say, resulting in severe flooding, shockwaves in the air, high temperatures and hurricane-force winds.

Another factor to consider is if an asteroid were to explode in the air into a bunch of smaller fragments before making impact – called an airburst – the effect would be modified.

While this would spread more moderate impacts over a much wider area, the ripples in turn generated by these smaller collisions with the water would be reduced in size, making tsunami-style waves even less likely.

But even if the waves generated by a large asteroid never came close to hitting our shores, that doesn't mean an impact taking place far out at sea wouldn't be dangerous.

efa6c35196a9095e027c62ccb647b01d55266e4aLos Alamos National Laboratory

Another threat asteroids pose when landing in oceans is water vapour, which can be lofted into the atmosphere. If this water vapour makes it up to the stratosphere, it could linger for months to years.

In one of the team's simulations, some 250 metric megatonnes of water vapour were lifted into the atmosphere. Since water vapour is a greenhouse gas, that could lead to climate warming effects lasting years after the asteroid's initial threat has subsided.

The findings were presented this week at the American Geophysical Union Fall Meeting in San Francisco, but have yet to be published.

Once other scientists have a chance to peer-review the research, we'll have a better idea of what we're dealing with here. But it's clear already that asteroids and Earth don't mix well, although a water impact in most instances would probably result in less lives lost.

Here's hoping new efforts to counter this space-borne menace actually take shape – and mean we don't have to run through these virtual asteroid simulations in real life.

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