How to take out an asteroid and save Earth

“Ground truth” information from NASA’s OSIRIS-REx rendezvous could save Earth from a killer asteroid.

Bringing rock samples back from asteroid Bennu on the OSIRIS-REx mission will help computer modelers refine plans for deflecting an asteroid or comet on target for Earth.

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Never fear, an oceanic asteroid impact wouldn’t cause apocalyptical tidal waves

Asteroid deflection | Los Alamos National LaboratoryWhen a team of LANL scientists modeled what would happen if an asteroid struck Earth, they discovered a Hollywood-worthy tsunami wouldn’t be the problem. Long-term effects on the climate might.


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Never fear, an oceanic asteroid impact wouldn't cause apocalyptical tidal waves


But it could have long-term effects on the climate



By Danny Lewis


Fans of apocalyptic disaster movies are probably familiar with the scene: a rogue asteroid spiraling in from outer space lands in the middle of the ocean, triggering massive tidal waves and throwing the world into chaos. But when a group of scientists decided to put this scenario to the test, they found that a real life Deep Impact would have very different results, Maddie Stone reports for Gizmodo.


A team of data scientists at the Los Alamos National Laboratory (LANL) modeled what would happen if an asteroid struck Earth’s vast oceans. They found that while one might expect a giant hunk of space rock to trigger enormous, Hollywood-worthy tsunamis, big waves aren’t the problem to fear.


The waves themselves would likely quickly dissipate out in the ocean. Imagine dropping a rock into a lake—the first ripples might be large, but as they spread out they get smaller and smaller. The same thing would happen in the case of an asteroid or comet impact, Stone reports, but it would still have a larger effect than dropping a pebble into a pond.


But while waves may not be the biggest threat from an asteroid impact, that doesn’t mean it wouldn’t affect our planet.


“The most significant effect of an impact into the ocean is the injection of water vapor into the stratosphere, with possible climate effects,” study leader Galen Gisler said while presenting his results at the American Geophysical Union meeting this week, Stone reports.


An asteroid impact in the ocean could vaporize hundreds of megatons of water, much of which would end up in the atmosphere. While a fair amount of that water vapor would likely turn into rain, some of it could linger slightly higher in what is known as the stratosphere. “And because it’s a potent greenhouse gas, this could have a major effect on our climate,” writes Stone.


Of course, this isn’t the only scenario possible. Many asteroids never make it to the ground, and the water would absorb much of the blast from even a fairly large asteroid exploding, Robinson Meyer reports for The Atlantic.


While that wouldn’t harm human civilization too much, an explosion over a coastal city would be a very different thing. Either way, it might not be a bad idea to figure out ways to stop space rocks before they get too close.




This article originally appeared on Smithsonian.com


Published Research

Three-dimensional simulations of oblique asteroid impacts into water

By Galen Gisler, Catherine Plesko, et al
ABSTRACT

Waves generated by impacts into oceans may represent the most significant danger from near-earth asteroids and comets. For impacts near populated shores, the crown splash and subsequent waves, accompanied by sediment lofting and high winds, are more damaging than storm surges from the strongest hurricanes. Asteroids less than 500 m in diameter, impacting deep water far from shores, produce waves that may be detectable over large distances, but are probably not significantly dangerous. We present new three-dimensional simulations of oblique impacts into deep water, with trajectory angles ranging from 27° to 60° (where 90° is vertical). These simulations are performed with the Los Alamos Rage hydrocode, and include atmospheric effects including ablation and airbursts. These oblique impact simulations are specifically performed in order to help determine whether there are additional dangers from the obliquity of impact not covered by previous two-dimensional studies. Water surface elevation profiles, surface pressures, and depth-averaged mass fluxes within the water are prepared for use in propagation studies.

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Options and uncertainties in planetary defense: Mission planning and vehicle design response

By Galen Gisler, Catherine Plesko, et al
ABSTRACT

This paper is part of an integrated study by NASA and the NNSA to quantitatively understand the response timeframe should a threatening Earth-impacting near-Earth object (NEO) be identified. The two realistic responses considered are the use of a spacecraft functioning as either a kinetic impactor or a nuclear explosive carrier to deflect the approaching NEO. The choice depends on the NEO size and mass, the available response time prior to Earth impact, and the various uncertainties. Whenever practical, the kinetic impactor is the preferred approach, but various factors, such as large uncertainties or short available response time, reduce the kinetic impactor’s suitability and, ultimately, eliminate its sufficiency.

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Videos

How we are going to deflect an asteroid
Crashing a spacecraft into an asteroid could shift its orbital path. The spacecraft DART will be test-crashed on an asteroid, providing insight into future deflection.

Visualization of Threats from Asteroid Ocean Impacts
Here's what would it would look like if an asteroid struck the ocean—and what would happen to the planet as we know it.

OSIRIS-REx, bringing back a bit of an asteroid
The OSIRIS-REx mission will help determine the timeframe within which we must launch a kinetic impactor or a nuclear explosive carrier.

Los Alamos Asteroid Killer
LANL scientists use a supercomputer to model what would happen if we used nuclear energy to deflect an Earth-threatening asteroid.

Photos

    Black download iconScientists from Los Alamos National Laboratory are using high performance computing to investigate how an asteroid’s kinetic energy is transferred to the atmosphere and ocean. (Download an animation by astrophysicist Galen Gisler.)

    Black download icon How would the detonation of a nuclear energy source affect an incoming asteroid? 3D supercomputer simulations help address ways to prevent objects in space from colliding with Earth.


    Expert

    Cathy Plesko  is a computational geophysicist with Los Alamos National Laboratory.

    Cathy Plesko

    Cathy Plesko is a Research Scientist in Applied Physics
    at Los Alamos National Laboratory. She uses the hydrodynamic codes on supercomputers to study what happens when asteroids and comets hit a planet and how to prevent them from hitting Earth.

    Contact

    Charles Poling, (505) 257-8006,  cpoling@lanl.gov

    Nick Njegomir, (505) 665-9394, nickn@lanl.gov

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