Wu Weiren, the chief designer of China's lunar exploration project, recently revealed that China is planning to carry out a kinetic energy impact demonstration and verification mission on an asteroid to verify the feasibility of the asteroid defense plan. This means that China will become the second country after the United States to conduct practical verification of asteroid kinetic energy impact. Why actively impact asteroids? What are the difficulties and significance of this verification task? In this regard, Tang Zhenghong, a researcher in the Optical Astronomy Technology Research Office of the Chinese Academy of Sciences Shanghai Astronomical Observatory, said that the mission was mainly to test and verify the technical feasibility of potentially threatening asteroids through kinetic energy impact deflection, and prepare for the future defense of the Earth. After all, theoretical calculations and ground simulations have limitations, and only a real collision can obtain the most accurate data. Tang Zhenghong emphasized that China's asteroid defense program is a deep space exploration mission that combines significant scientific significance and technological challenges. This plan will be promoted within the framework of relevant United Nations initiatives, and the data and research results obtained will be shared with the global scientific community, helping humanity to jointly enhance planetary defense capabilities and system construction. Active impact is currently the optimal solution. Near Earth asteroid impact has been listed by the United Nations as the top 20 disasters threatening human survival. From the Gulf of Mexico impact 65 million years ago, to the Tunguska explosion in 1908, to the Chelyabinsk meteorite fall in 2013, near Earth asteroids have always posed a threat to the safety of Earth and life. In February of this year, an asteroid named 2024 YR4 continued to attract global attention - according to scientists' calculations, there is a certain risk of impact on Earth, and after multiple observations, the probability of impact has been adjusted to "close to zero". Tang Zhenghong pointed out that although highly destructive near Earth asteroid impacts are extremely rare events, once they occur, they will cause great impact, and their severity is directly related to the size of the asteroid. He gave an example that an asteroid with a diameter of 10 meters colliding with Earth has the energy equivalent to a typical nuclear warhead, and such events occur approximately once every 10 years; If an asteroid with a diameter of 10 kilometers collides with Earth, it will trigger a global disaster and mass extinction of species - dinosaurs probably have a deep understanding of this. Actively colliding with asteroids to eliminate their potential threat to Earth is currently recognized as the optimal solution in the world. ”Tang Zhenghong introduced that there are currently multiple international organizations dedicated to near Earth object research, and the space mission planning advisory group composed of national space agencies is responsible for formulating the initiation and execution of asteroid impact response missions, clarifying response plans and time limits. Under current technological conditions, kinetic energy impact is considered the most effective and feasible way to address the potential threat of asteroid impact. Other technologies such as bomb directed detonation, aircraft capture, gravitational traction, laser ablation, etc. are still in the exploratory stage and are not yet mature. It is reported that the asteroid impact verification mission is planned to adopt a "companion flight+impact+companion flight" mission mode, launching observers and impactors. One of its core tasks is to launch a composite spacecraft in the near future to perform kinetic energy impact on a near Earth asteroid, and then conduct close range observation and evaluation of the impact effect. Simply put, it means actively colliding to see to what extent the asteroid's orbit can be altered. ”Tang Zhenghong likened this process to "threading embroidery needles" in space. First, launch a mother ship carrying an impactor. As it approaches the target asteroid, the impactor separates from the mother ship and collides with the asteroid at a very high speed (about 6.5 kilometers per second). It is a technical difficulty to collide with a small target with a diameter of only about 50 meters at such a high relative velocity in the vast space. At the same time, the distance between Earth and asteroids is millions of kilometers, and how to accurately hit the preset position is also a huge challenge. Tang Zhenghong explained that since asteroids are spherical, different impact points have different effects on their orbital changes. If only the edge collision occurs, it may only change its rotational speed rather than effectively deflect its orbit. For this purpose, the task involves cutting-edge technologies such as ultra high precision autonomous navigation and guidance (accurately hitting a small celestial body with high-speed motion, irregular shape, and weak gravity), long-distance high-speed communication, and intelligent autonomous management of spacecraft. In September 2022, the National Aeronautics and Space Administration (NASA) conducted the Double Asteroid Refraction Test (DART) mission to combat a more threatening asteroid. Through kinetic energy impact, the target asteroid "Dimofos" shortened its orbital period around its parent star "Didymos" by 33 minutes. This is the first attempt in human history to change the orbit of an asteroid through kinetic energy impact, verifying the feasibility of kinetic energy impactor technology. However, this task has obvious limitations: the various manifestations during the DART impact process rely on ground-based telescopes and a small cubic star accompanying it for observation. Due to limitations in payload performance and observation time, it is impossible to comprehensively evaluate the impact of ejecta generated by the collision. The task planned and implemented in our country can be seen as a supplement and upgrade. ”Tang Zhenghong stated that China plans to use multiple powerful payloads carried by the main spacecraft to conduct close range and long-term fine observations, which is expected to obtain more detailed data on the entire impact process. In addition, the goal of the DART mission is a binary asteroid system, which evaluates impact effects by measuring changes in its orbital period; And our country's target for this impact is a single near Earth asteroid, which will directly measure its changes in orbit around the sun. Relatively speaking, the probability of a single asteroid colliding with Earth is higher and more threatening. Of course, some people are concerned that asteroids that originally posed no threat to Earth may actually fly towards Earth after being impacted? Regarding this, Tang Zhenghong stated that the asteroid selected for this plan is millions of kilometers away from Earth, and no matter how its orbit is changed by impact, it is impossible to collide with Earth. Its safety has been fully verified. It's far more than just a simple collision. Although asteroids are dangerous, they also contain great scientific value, hiding the oldest secrets of the solar system. It is understood that there are over billions of asteroids in the solar system, which are "living fossils" that record the formation and evolution of the solar system. They are rich in resources of significant economic value such as iron, nickel, platinum group metals, and water ice. Regardless of the type of asteroid targeted this time, close range observations will provide valuable information for studying the early formation and evolution of the solar system. Tang Zhenghong described the impact as an "active seismology" experiment: by analyzing the size, shape, quantity, and velocity of the impact crater, the composition and structure of the material on the surface and inside of the asteroid can be inferred, which is crucial for evaluating the impact force required to deflect other asteroids in the future. In addition, completing this mission will significantly enhance China's technological level in the field of deep space exploration, accumulating experience and data for more complex asteroid sampling and return, as well as asteroid mining missions in the future. The ultra high velocity impact experiment conducted in the microgravity environment of space will also provide extremely valuable data for planetary physics research. The value of this mission will be enormous and multifaceted, far beyond just a 'collision'. ”Tang Zhenghong emphasized. Because asteroids contain abundant scientific research resources, China launched its first asteroid exploration mission this year. In May of this year, the Tianwen-2 mission probe of China's planetary exploration project was successfully launched. At present, Tianwen-2 probe has been in orbit for more than three months. (New Society)