[ti:Methods for Protecting Earth against an Asteroid Strike]
[al:Science & Technology]
[ar:VOA]
[dt:2025-03-13]
[by:www.voase.cn]
[00:00.00]Astronomers following asteroid activity in space estimate there is a very small chance an object large enough to destroy a whole city could strike Earth in 2032.
[00:17.70]But space agency officials say even if such an asteroid keeps heading on a path toward Earth, the world is now much better-equipped to defend itself against such a threat.
[00:32.87]The American space agency NASA recently estimated there was a 3.1 percent chance that asteroid 2024 YR4 would hit Earth on December 22, 2032. 
[00:48.86]That is the highest probability predicted for such a large space rock in modern times.
[00:57.31]Richard Moissl is head of the European Space Agency's (ESA) planetary defense office. 
[01:05.36]While recognizing the risk the asteroid could present, he told the French news agency AFP people should not panic over such predictions.
[01:17.07]Astronomers have noted that the more data they gather, the odds of a direct asteroid hit are expected to keep rising over time. 
[01:27.92]However, scientists say at a certain point the odds will likely drop down to zero.
[01:35.26]Moissl said he thinks it is important to remember that even in the unlikely event the probability keeps rising to 100 percent, the world is "not defenseless."
[01:48.74]Here are some methods currently being considered as defensive measures to keep humanity safe in case there is a real threat.
[01:58.24]Only one planetary defense method has been tried against an asteroid. 
[02:04.34]In 2022, NASA's Double Asteroid Redirection Test (DART) sent a spacecraft into the 160-meter-wide Dimorphos asteroid.
[02:17.33]The effort successfully changed the asteroid's orbit around a larger space rock.
[02:23.36]Bruce Betts is chief scientist for the nonprofit Planetary Society. 
[02:29.38]He told AFP that space agencies could hit the 2024 YR4 asteroid with several spacecrafts, observing how each one changed the path.
[02:41.22]The asteroid discovered in December is estimated to be 40-90 meters wide -- about half the size of Dimorphos.
[02:50.56]"You have to take care not to overdo it," Moissl warned. 
[02:55.22]He said this is because if a spacecraft only partly destroys an asteroid, it could send smaller pieces of the space rock heading toward Earth.
[03:06.46]A separate idea would involve sending a large spacecraft to fly alongside a threatening asteroid.
[03:14.27]The spacecraft would not touch the asteroid, but would use its gravitational force to pull it away from Earth.
[03:21.66]Moissl said another non-contact plan would put a spacecraft near the asteroid to eject a continuous flow of atoms to push the asteroid off course.
[03:35.39]Scientists have also considered painting one side of the asteroid white. 
[03:40.83]They believe this could increase the light the object reflects to make it slowly change course.
[03:48.90]One idea is to use a nuclear weapon against a threatening asteroid.
[03:53.64]In laboratory tests, researchers found that X-rays from a nuclear blast could move a rock. 
[04:00.66]But this is considered more of a plan for kilometers-wide asteroids like the one that killed off the dinosaurs. 
[04:10.23]And this method also carries the risk that a nuclear explosion could send additional pieces of the asteroid falling toward Earth.
[04:19.59]A similar method - but one considered less dangerous - would involve shooting laser beams from a spacecraft to destroy the side of an asteroid in an effort to push it away from Earth.
[04:34.46]Moissl said that if all else fails, at least the world will have a good idea where a threatening asteroid would strike.
[04:42.45]Since astronomers believe most asteroids would at most threaten to destroy one city, efforts could be organized to get people out of an area before a strike.
[04:54.19]"Seven-and-a-half years is a long time to prepare," Moissl added.
[04:59.32]He also noted that even with the rising odds involving 2024 YR4, there is still about a 97 percent chance the asteroid will miss Earth.
[05:12.88]I'm Jill Robbins.