On October 11, 2022 local time, the asteroid small moon “Dual Form” seen by the Double Asteroid Redirection Test (DART) spacecraft 11 seconds before impact. DART’s onboard DRACO imager took this image from a distance of 42 miles (68 kilometers).
The National Aeronautics and Space Administration (NASA) announced on the 11th local time that in a test conducted in September, the “Double Asteroid Redirection Test (DART)” spacecraft successfully collided with the target asteroid and changed its original orbit. It is reported that this is the first time in human history that humans have consciously changed the trajectory of a celestial body, and it is also considered a watershed moment in defending the earth from planetary impact.
For the first time, the movement of celestial bodies has been successfully changed
According to reports, the DART spacecraft was launched from California, USA on November 24, 2021, and flew towards the asteroids “Dimorphos” and “Didymos”. The mission aims to test whether future asteroid collisions with Earth can be avoided through human intervention. It is also the world’s first planetary defense test.
According to NASA, “Dimofors” is about 160 meters in diameter and about 11 million kilometers away from the earth. “Didimos” is an asteroid with a diameter of 780 meters. “Dimovus” revolves around “Didimos”, which can be simply understood as the relationship between the moon and the earth. Neither asteroid poses a threat to Earth.
Observation results show that on September 26, the DART spacecraft with a total weight of 600 kilograms successfully hit the asteroid “Dimovus” at a speed of 22,500 kilometers per hour, and finally shortened its orbital period by 32 minutes. Images recorded by the telescope show a spectacular explosion of debris on the asteroid following the impact.
According to NASA’s measure, the minimum requirement for a DART mission to succeed is to change the orbital period of the target asteroid by 73 seconds, which means that the actual achievement of the mission has reached more than 25 times the minimum baseline.
Lori Glaze, director of NASA’s Planetary Science Division, said the current observations are an important step toward understanding the impact of the DART spacecraft’s impact. “We are ushering in a new era for humanity, in which we may be able to protect ourselves from dangerous asteroid impacts.”
NASA Administrator Bill Nelson (Bill Nelson) called this “a watershed moment for planetary defense missions.” moment”, “We all have a responsibility to protect our planet, which is our only home after all… This mission shows that NASA is working hard to prepare for whatever the universe throws at us”.
Some people may think, what is the probability of an asteroid hitting the earth, why do humans actively change the trajectory of other celestial bodies in the universe, is it unfounded worry?
In fact, impacts of asteroids, comets, space rocks and other celestial bodies are not uncommon. Some people also joked that in the long history of mankind, there are actually many “passing by dangers”.
However, most impacts are harmless, mainly because the objects are not large enough. Since there are fewer asteroids with larger diameters in space, the probability of them hitting the Earth is lower, so most impacts have not caused much impact.
It is reported that what usually falls on the earth are some extremely small space rock particles, only the size of sand grains or peas, which are the meteors we see. Larger meteoroids, about the size of a basketball, can sometimes survive their passage through the atmosphere and become meteorites.
According to NASA, an asteroid the size of a car hits the atmosphere about once a year. Most of these several-meter-long space rocks will burn up before reaching the surface and cause no major disasters. In the historical records of mankind, the attack of extraterrestrial celestial bodies is not an isolated case. In 2013, in Chelyabinsk, Russia, an asteroid with a diameter of about 20 meters exploded and fragmented in the sky 30 kilometers above the ground. At that time, the windows of many houses were shattered by the shock wave of the explosion, some buildings were damaged, and more than a thousand people were indirectly injured. According to scientists’ estimates, the probability of such a large-scale asteroid impact event is very low, and there will be no more than two in a century.
According to other records, in 1908, a meteorite explosion occurred near the Tunguska River in Russia. The shock wave shattered the window glass within a radius of 650 kilometers, and burned more than 2,000 square kilometers of trees. The scientific community generally believes that the “perpetrator” of the Tunguska explosion was a rocky asteroid with a diameter of about 65 meters.
Scientists pointed out that if a larger celestial body hits the earth, the consequences may be immeasurable.
An asteroid 1km in diameter could wreak havoc on an area the size of France, triggering earthquakes, fires, toxic gases and more, the study said. If the asteroid had a diameter of 5 kilometers, the shock wave from the impact would be strong enough to shatter windows across Europe. If the asteroid reaches a diameter of 10 kilometers, it will cause mass extinction.
Nancy Chabot, head of DART mission coordination and an expert at the Applied Physics Laboratory of Johns Hopkins University in the United States, said that the DART mission has provided a large amount of data on the nature of asteroids and the effectiveness of kinetic energy impacts, ” The mission team is continuing to study this rich dataset to fully understand the process of the first asteroid deflection test.”
NASA stated that the survey team will continue to use observation facilities in various places to improve the measurement accuracy of the orbital period through frequent observations. NASA astronomers will study images of Dimovos taken by the DART spacecraft and the Italian LICIACube cube star to more precisely estimate the asteroid’s mass and shape. In addition, the European Space Agency also plans to launch a probe called “Hera” in 2024 to launch new probes to the “Dimofors” and “Didymos” asteroid systems. The probe is expected to arrive at its target in 2026 to further observe the impact crater of the DART spacecraft on “Dimofors” and try to accurately measure the mass of the asteroid.
Astronomers noted that the project has great implications for near-Earth asteroid defense. The astronomical community generally regards asteroids 200 million kilometers away from the earth as near-Earth asteroids, and believes that they are at risk of colliding with the earth.