Our planet has been continually bombarded by asteroids since its formation, 4.5 billion years ago. While the frequency of large impacts has decreased, many potential Near-Earth Object (NEO) threats remain undiscovered, so if or when they will impact Earth remains unknown.
Most of the time, an impacting asteroid will simply burn up in the atmosphere, giving those on the ground a pleasant meteor shower display. However, depending on the size, composition, and impact location of the asteroid, the results could be catastrophic.
Fortunately, if an Earth-threatening asteroid is discovered in time, there are ways to mitigate or even prevent a disaster. Astronomers now discover over 2000 new near-Earth asteroids a year. So far, none pose a significant risk.
However, if an asteroid is found to be on a collision course with Earth, it can be diverted by a few different methods. For long warning times (and asteroids that are not too big), a heavy “kinetic impactor” spacecraft can be used to impact the asteroid at high speeds, giving it a slight nudge so that it safely misses Earth. When warning times are short, or the asteroid is large, kinetic impactors cannot provide enough momentum for the asteroid to miss Earth. In these cases, a nuclear device can be sent to melt and vaporize enough surface material to deflect the asteroid, while keeping the bulk of it intact. Very short warning time scenarios, where deflection is impossible, can be handled by using a similar device to fragment the asteroid into many small, well-dispersed pieces.
If none of the prevention options are possible, then evacuation and other emergency response measures will be put to use. In these cases, it is essential to know what areas would be affected by the impact in order to minimize casualties and damage. Scientists at LLNL provide simulation support in preparation for all the above scenarios so if the time comes where an asteroid is headed our way, we will be prepared.
Speaker: Megan Bruck Syal, Lawrence Livermore National Labs
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