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Humanity's Mission to Protect Itself from Asteroids: The Science Behind Deep Impact
For the first time in Earth's history, we might be able to prevent an asteroid impact.
Asteroids are one of the few science fiction threats which might actually darken our planetary doorstep. We can probably safely assume that alien invasion, zombies, and killer robots remain in the realm of fiction (at least for now), but we know that asteroids are out there and we know that they’ve sucker punched our planet in the past. On a long enough timescale, an asteroid, comet, or other impactor will come calling, and it’s crucial that we’re ready when it does.
To that end, agencies around the world are hard at work developing planetary defense strategies (not to be confused with planetary protection, which focuses on preventing biological contamination between worlds). By contrast, planetary defense focuses on protecting Earth from impacts by identifying impactors, characterizing them, and planning for an eventual impact.
How NASA and other space agencies are preparing for an asteroid impact
NASA’s Planetary Defense Coordination Office (PDCO) was established in 2016 and utilizes telescopes on the ground and in orbit to search the skies for potentially dangerous impactors in Earth’s vicinity. So far, everything we’ve found is keeping its distance, but if a dangerous impactor was found, the PDCO would be responsible for coordinating a response.
Once a new object is identified, NASA’s Center for Near Earth Object Studies (CNEOS) determines its orbit and calculates any close approaches or impacts. NASA’s Jet Propulsion Laboratory (JPL) also maintains a list of the next five asteroids on close approach at any given time. In most cases, they are relatively small (the size of a car or a house) and they whizz by us or impact the atmosphere without any real consequences. If, however, an especially large asteroid were found to be on a collision course with Earth, here’s what we might do about it.
How to save the Earth from an asteroid
On November 24, 2021, NASA launched its Double Asteroid Redirection Test (DART) on a long journey to the double asteroid Didymos and Dimorphos. The smaller asteroid, Dimorphos, is what’s known as a moonlet because it orbits the slightly larger Didymos. The goal was to impact Dimorphos at high speed and measure the change in its orbit.
About 10 months after launch, DART impacted Dimorphos at 14,000 miles per hour, carrying the energy equivalent of 3 tons of TNT. The impact changed the shape of Dimorphos and shortened the length of its orbit by about 33 minutes. It was the first successful real-world test of an asteroid deflection system. Given enough lead time, we could nudge the orbit of a dangerous asteroid and move it out of an impact path with Earth.
Other options include using a gravity tug to slowly change an asteroid’s orbit. It would work by parking a spacecraft alongside an asteroid for an extended period. The gravitational influence of the spacecraft would subtly pull on the asteroid and shift its trajectory.
We could also use nuclear weapons much like they did in Deep Impact (streaming now on Peacock) with one important change. In the movies, astronauts tend to land on an asteroid, drill into its surface, and deliver an explosive payload underground. Deep Impact correctly suggested that such a plan might simply fracture an asteroid into two or more large pieces, without moving those pieces out of the way. Instead, modern scientists suggest it would be better to detonate the bombs above an asteroid’s surface. Detonated near an asteroid instead of inside it, the blast would vaporize part of the surface, create a temporary atmosphere on one side, and generate thrust away from the blast site.
An asteroid impact might be the only science fiction scenario which could actually threaten humanity, but it’s also the only scenario we’re equipped to handle.
Catch Deep Impact (a planetary protection dress rehearsal) streaming now on Peacock.
