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On November 24, the National Aeronautics and Space Administration (NASA) will launch a space probe on Wednesday morning, local time, with the goal of deflecting the established trajectory of a pair of distant asteroids, which is also the first human test planetary defense mission < p > < / P > < p > the dual asteroid redirection test (DART), which costs US $324 million, is a test to protect the earth from asteroids and comets in the future. The probe is scheduled to take off from Vandenberg space base in California by SpaceX's Falcon 9 rocket at 1:21 a.m. Eastern time on Wednesday. Dart will travel 9.65 million kilometers in space and arrive at the near earth double asteroid system called Didymos and dimorphos next autumn. Then the probe will hit the smaller dimorphos at a speed of 24000 kilometers per hour < p > scientists predict that the high-speed impact will change the orbit of the double asteroid system. "Man will change the motion of natural objects in space for the first time," said Tom Statler, a scientist of NASA's dart project. The project is managed by the Johns Hopkins University Applied Physics Laboratory in laurel, Maryland on behalf of NASA < p > the earth is surrounded by a large number of cosmic debris such as large pieces of ice, rock and iron. From time to time, they fall from the sky like bricks from a deep space dump. Most of them burned up in the atmosphere, which also makes people worry that a huge space rock may collide with the earth one day < p > in 1908, a mysterious space rock exploded over Siberia, flattening 210000 hectares of forest. In 2013, an asteroid with a diameter of nearly 20 meters exploded 32 kilometers above Chelyabinsk, Russia, shattering the windows of thousands of local buildings and releasing more than 30 times the energy of the atomic bomb dropped on Hiroshima, Japan during World War II < p > at the urging of the US Congress, astronomers have determined and tracked the orbits of about 1000 asteroids with a diameter of more than 1000 meters, which will approach the earth's orbit regularly. Scientists predict that these mountain sized space rocks will not pose a threat to the earth for at least the next few centuries, but it does not rule out that there are still unknown asteroids that may hit the earth < p > Amy Mainzer, an astronomer at the University of Arizona in the United States, is an expert in asteroid detection and Planetary Defense. She said: "although the probability of this kind of thing happening is very low, it is not something we can completely ignore." < / P > < p > according to NASA, humans have identified more than 90% of potentially dangerous asteroids with a diameter of more than 1000 meters. However, for potentially dangerous asteroids with a diameter of more than 140 meters, humans have only identified about 40%. Scientists speculate that there may be as many as 25000 similar asteroids. If they hit the earth, each of them may destroy a large area. < / P > < p > Scientists believe that giant asteroids with a diameter of more than 10 kilometers that may lead to the extinction of dinosaurs on earth will hit the earth once every 15 million years. < / P > < p > in order to facilitate the search for potentially dangerous asteroids, NASA approved the "near earth object survey mission" in June this year (near earth object surveyor). The $500 million instrument is planned to be launched in 2026. < / P > < p > "this is to find near Earth Asteroids large enough to destroy local areas of the earth," said mainzel, who is in charge of the project. "The question is to answer what will happen in the next 100 years. We hope the answer is that nothing will happen." < / P > < p > scientists have come up with various ways to eliminate the threat posed by asteroids, including using missiles equipped with nuclear warheads to destroy asteroids, burning asteroids before falling with lasers, and plans to use the gravity of spacecraft to pull them out of orbit. Some scientists suggest deploying solar sails on asteroids and using light pressure to change the trajectory of asteroids. < / P > < p > Applications Andy Rivkin, the person in charge of monitoring dart task completion in the management laboratory Said that the dart mission will test the simplest of these schemes, which scientists call kinetic energy impact deflection. The specific method is to make a 544kg, car sized detector collide with an asteroid and change its running speed by about one millimeter per second. The dart detector will release a free flying small cube satellite 10 days before the collision and photograph the whole impact process. < / P >

If the test mission is successful, NASA may one day use the impact method to make the asteroid deviate from the orbit of colliding with the earth. < / P > < p > Rifkin said: "if a potential asteroid is really likely to pose a threat, we will learn a lot of knowledge from it and make better preparations for the future." (Chen) < / P > < p >

2023-03-22 10:04:47