After astronomers reduced the chances of 2024 YR4 – a recently discovered city-killer asteroid – colliding with Earth in 2032 from 3.1% to 1%, some may have breathed a sigh of relief, but are we truly out of the woods yet?
Indeed, many weren’t even aware of how much danger the 2024 YR4 posed to humanity, but astronomers are keeping a watchful (and worried) eye on it (and other asteroids) until its threat subsides entirely, according to a report by Scientific American published on March 26.
Scope of possible city-killer asteroid destruction
As for the asteroid itself, astronomers with NASA’s Center for Near Earth Object Studies in California, European Space Agency’s (ESA) Near-Earth Object Coordination Center (NEOCC), and the privately owned Near Earth Objects Dynamics Site in Italy observed it to be between 40 and 90 meters in size and, after the initial odds of 3.1% of it impacting Earth on December 22, 2032, reduced them to 1%.
In terms of devastation it could’ve caused if it were to directly strike a city, a 40-meter asteroid would lead to significant damage and some fatalities, but it wouldn’t wipe it off the map.
According to Kathryn Kumamoto, head of the planetary defense program at the nuclear physics-focused Lawrence Livermore National Laboratory, “If it’s on the smaller end, and it’s going to hit in the middle of the ocean, maybe that’s fine.” It would result in a strong shockwave but in an uninhabited area and there might not even be a tsunami because the asteroid would likely fall apart and burn to ashes in Earth’s atmosphere.
However, if it were a 90-meter space rock, then its destruction would be much larger, vaporizing the impact site, triggering mass casualties, and spreading the effects tens of miles further. If it were to target a populated area, the option would be to evacuate the locality and “take the hit,” or to try to divert or destroy it before it could hit.
In the words of Juan Luis Cano, an aerospace engineer with the ESA’s NEOCC in Italy, stopping an asteroid from hitting Earth is difficult as it is, and doing it in less than eight years would’ve pushed our capacities to the limit. As he explained, “this would have been a delicate case.”
Can we prevent it?
According to Patrick Michel, principal investigator of Hera, an ESA mission helping to test and characterize asteroid deflection techniques, a successful mission to divert or destroy 2024 YR4 was “not infeasible, (…) but it would not have allowed us any error.” He added:
“This is effectively something we didn’t really say to the public because we were pretty sure the risk would be removed, but if it didn’t, the situation was not really ideal.
Destroying it would involve breaking it into pieces, provided that the resulting debris misses Earth or is able to burn up in the atmosphere with no consequences. On the other hand, deflecting it with a series of small nudges could be better as it’s the only mitigation method that astronomers tested on an actual space rock, in 2022 NASA’s Double Asteroid Redirection (DART) mission.
That said, it would take 10 years for this strategy to work so, given the short timeframe of merely eight years, dealing with 2024 YR4 would require both deflection and disruption.
Then, there’s the nuclear option, and some lab-based experiments suggest that going this route would be highly effective, with recent Lawrence Livermore research suggesting that a one-megaton nuke would be able to vaporize a 100-meter asteroid. Nukes could also be used in a more subtle, deflection scenario. That is, if we manage to overcome current legal obstacles with using them in space.
And while we’re not in the clear yet from 2024 YR4, scouting it further could determine its precise dimensions and mass, as well as gather information about its structure, which astronomers believe could range from “weakly bound rubble pile” to “mechanically rigid, monolithic rock.”
Other threats and dealing with them
Meanwhile, researchers have discovered about 16,000 asteroids similar in size to this one in near-Earth orbits, including 887 Alinda (over four kilometers in diameter and could cause a global extinction event), and it is estimated that there might be about as many as 215,000 more out there undiscovered so far, increasing the chances of finding another threat on a possible collision course with us.
To this end, NASA is building the Near-Earth Object (NEO) Surveyor, a $1.4 billion infrared telescope to discover comets and asteroids that could threaten our world.
All things considered, time remains our best friend or our worst enemy when dealing with asteroid threats. If the above asteroid was a more significant threat, we’d only have years to deal with it. Still, technological advances might help avoid similar hazards decades down the line.
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