Although Dimorphos is similar to many other near-Earth asteroids, the DART team chose it as the target because it is a junior member of the asteroid binary. It is called the “small satellite” and it orbits its larger partner Didymos every 11 hours and 55 minutes like a clockwork. DART will hit Dimorphos at an angle of about 17 degrees from its orbit, and scientists plan to measure how much its orbit has shifted as a result. In other words, they can easily compare its movement with the movement of another nearby object. If they choose to strike an isolated asteroid, then the slight deflection of its orbit will be insignificant for several years before it passes the earth at close range. But due to the proximity of its partners, any changes to Dimorphos’ orbit can be confirmed within a few days.
“It’s really a clever and ingenious method, and it’s cost-effective. And it’s also very safe: You push the satellite a little bit near the asteroid it has orbited,” Chabot said. She and her team predict that DART can shorten the asteroid’s orbit by 5 to 15 minutes, so that it may only take 11 hours and 45 minutes to orbit Didimos. NASA considers a deflection of 73 seconds or longer to be a successful mission.
Before March 2023, the pair of asteroids will be close enough to be accurately measured on Earth using a telescope. After that, they will travel farther, because part of their path around the sun extends beyond the orbit of Mars. Although the asteroid looks like a single point of light at this distance, scientists will be able to measure the frequency at which the brightness of the reflected sunlight reflected from Didymos dims—a representative of the duration of the orbit of Dimorphos.
These asteroids, like many other asteroids and some meteors (space rocks that enter the Earth’s atmosphere), are not as dense and solid as billiard balls.They may be large pieces of rock, gravel, and ice, arranged loosely together, called “gravel piles”, and have a stony composition similar to asteroids Dragon Palace with ErosAnd to Meteor exploding over Chelyabinsk, Russia, 2013. In fact, the small satellites of Dimorphos may only be formed by rotating from the side of Didymos. If Dimorphos were gravel, the impact of DART might form a crater instead of throwing debris and propelling the asteroid significantly. But this uncertainty is one of the reasons for the execution of the task.
In order to conduct a more detailed inspection of the crash site, the European Space Agency’s Hera Next comes the task. The spacecraft is scheduled to launch in 2024. When it reaches the Asteroid Duo in 2026, its optical camera, lidar tool, infrared scanner and two CubeSat assistants will draw detailed maps of the Dimorphos surface and structure.
If a dangerous asteroid does fly to the earth, hitting a spacecraft-or “kinetic impactor”-into it is only a tool that humans can use. NASA, ESA, and other space agencies have also been exploring other methods, such as placing the spacecraft nearby as a “gravity tractor” to pull it to different routes, or detonating a nuclear explosion nearby to force it to leave. (The use of nuclear weapons on asteroids inherently risks failure because it may turn them into many Lori Glaze, director of NASA’s Planetary Science Department, said at a media conference on Sunday: “The kinetic impactor is by far the most mature of these technologies.”