Why do humans want to explore asteroids?

Asteroids are celestial bodies that orbit the sun in the solar system but are much smaller in size and mass than planets. At present, humans have observed nearly one million asteroids, which are widely distributed from low-Earth orbit to the asteroid belt, Kuiper belt, and even more distant space. Asteroids preserve the original information of the formation and evolution of the solar system, contain vast resources, and pose a real threat to the earth. Their detection helps to reveal the origin of life, develop natural resources, promote technological progress, and protect the safety of the earth. They are currently a hot spot in international deep space exploration.

Uncovering the secrets of the evolution of the solar system and the origin of life

How are asteroids formed? Current theories suggest that in the early days of the solar system, solid matter was continuously condensed from the primordial solar nebula and was attracted and captured by nearby large planets. During its formation, Jupiter produced increasingly larger gravitational disturbances, driving the remaining matter to continuously collide and break, eventually forming a large number of asteroids between the orbits of Mars and Jupiter.

This process is basically synchronized with the formation of the solar system. Large celestial bodies in the solar system, such as the Earth and Mars, have undergone billions of years of complex evolution and are now completely different. However, most asteroids have a low degree of internal evolution and still roughly maintain the appearance of their early birth, thus recording the initial state of the solar nebula, the nebula evolution process, and the growth process of the planets, which can be called the "fossils" of the solar system. Detecting the chemical composition, surface material characteristics, and internal structure of asteroids provides a good way to study the origin and evolution of the solar system.

How did water and life on Earth come into being? Some scholars believe that they may have been brought to Earth by small celestial bodies such as asteroids and comets, because they also contain organic components and water ice. The exploration of asteroids can provide important clues for studying the origin of life on Earth.

ESA's Rosetta-Philae probe used isotope measurements to conclude that water on Earth did not come from comets; Japan's Hayabusa 1 and 2 probes collected samples from the Itokawa and Ryugu asteroids, respectively. Analysis found that the organic matter contained in the former was of non-biological origin, while the latter's dust samples contained more than 20 kinds of amino acids, adding weight to the hypothesis that asteroids spread life.

There are many types and numbers of asteroids and they are widely distributed. With the continuous improvement of detection technology and more in-depth and systematic research on asteroids, it will provide more help for studying the formation and evolution of the solar system, the origin of life on Earth and other issues.

Broad prospects for resource development

Asteroids are rich in mineral resources and are an important target for space mining.

According to spectral characteristics, asteroids can be divided into C-type (carbonaceous), S-type (rocky), and X-type asteroids. Among them, C-type asteroids are rich in carbon, hydrogen, oxygen, nitrogen and other elements, and many S-type and X-type asteroids contain huge amounts of mineral resources, and some asteroids are very rich in metal elements.

The largest M-type asteroid detected so far, Psyche, is about 250 kilometers in diameter and contains about 90% metal, mainly iron, nickel and pyroxene. The near-Earth asteroid 3554 is about 2.5 kilometers in diameter and is estimated to contain platinum and metal deposits worth more than $20 trillion, which may be important resources for future human survival and development.

Even asteroid impacts have brought mineral deposits to Earth. In the Sudbury region of Canada, a small celestial body impact formed a 100-kilometer-diameter impact crater, which contains super-large copper-nickel and platinum group element mines. In the Yucatan Peninsula of Mexico, a large copper deposit was left in a 180-kilometer-diameter impact crater.

In addition, asteroids have little gravity, so resource mining is relatively easy, and they can easily change their orbits. With the continuous advancement of human space technology, in the future, we can mine asteroid mineral resources and send them back to Earth, or capture smaller asteroids and send them to near-Earth orbit or lunar orbit for development and utilization, or directly process them in situ to produce energy and materials needed for space activities, which can significantly reduce the need for launches from Earth and reduce costs and risks.

The development of asteroid resources has become an important means for major powers in the space age to gain strategic resources and expand new frontiers. It will also lead the development of space economic industrial chains such as the Earth-Moon economic circle and space manufacturing, and has extremely broad prospects.

Deep space exploration test site

Asteroid exploration plays an important role in driving technology. Compared with large celestial bodies, asteroids have the characteristics of "microgravity and uncertainty". "Microgravity" means that the gravity on the surface of an asteroid is extremely small, making it difficult to establish an orbit around it. Its exploration requires high-precision and highly reliable autonomous navigation capabilities. The probe cannot be attracted to land by the gravity of the asteroid, and it needs to precisely control the propulsion system to achieve an adhered landing. Another reason is that the escape velocity is low, so the probe can easily take off from the surface of the asteroid.

Because of the "microgravity", it is difficult to carry out detailed advance detection of asteroids. Due to the long distance, Earth observation can only obtain the basic orbital parameters and a small amount of information of the asteroid, but it is difficult to grasp its physical properties such as size, topography, motion characteristics, gravitational field, etc. This brings "uncertainty" in understanding, making it more difficult for the probe to rendezvous with and land on the asteroid.

Therefore, asteroid exploration plays an irreplaceable role in driving the development of aerospace technology. It requires breakthroughs in a number of new core technologies, including precise orbit measurement and control and autonomous navigation, low-thrust transfer orbit, surface sampling of weak-gravity celestial bodies, and multi-mode long-life electric propulsion. The development of these technologies will enhance human deep space exploration capabilities.

Asteroid exploration is also a highly comprehensive space mission, which places high demands on mission design, delivery systems, space propulsion, and space measurement and control. Many near-Earth asteroids are easy to reach, easy to detect, and inexpensive, making them very good technology testing grounds. The United States, Europe, Japan, and other countries have tested a large number of new solutions and technologies in their asteroid exploration missions.

For example, the European Space Agency has verified technologies such as multi-planetary leverage and comet surface landing through its comet exploration mission. NASA has verified technologies such as solar electric propulsion, autonomous navigation, and spectral imaging with tiny cameras during its asteroid exploration. These have laid an important foundation for future deep space exploration and are an advance rehearsal for humanity's journey into deep space.

Protecting the peace of the earth

The impact of small celestial bodies on the Earth is an inevitable event. It has caused environmental disasters and biological extinctions on Earth many times in history. It is a major potential threat that humanity must face.

Astronomy defines asteroids with a minimum distance of 0.3AU (1AU is the distance between the sun and the earth) as near-Earth asteroids. More than 20,000 asteroids have been discovered so far, some of which have orbits that intersect with the Earth's orbit and have the potential to collide with the Earth. Asteroids with a minimum distance of 0.05AU and a diameter greater than 140 meters are defined as threatening near-Earth asteroids, accounting for one-tenth of the total.

What is more complicated is that when an asteroid enters a certain distance from the Earth, it is possible for it to be captured by the Earth's gravity, change its orbit and hit the Earth. Their orbits are also constantly changing due to the gravitational perturbations of other large celestial bodies in the solar system. Therefore, the number of asteroids that threaten the Earth is not constant, and the degree of threat often changes.

The threat to humanity is very serious. An asteroid with a diameter of more than 140 meters can hit the Earth with enough force to destroy a medium-sized country. There are nearly 200 confirmed meteorite craters on Earth, of which about a quarter are more than 10 kilometers in diameter. The asteroid impact that caused the extinction of the dinosaurs 65 million years ago left a 150-kilometer-diameter impact crater in Mexico.

In 2013, an asteroid with a diameter of about 17 meters entered the atmosphere and exploded 90 kilometers above the Chelyabinsk region of Russia, with an explosion equivalent to 13 times the atomic bomb dropped on Hiroshima. The incident injured more than 1,600 people and damaged more than 1,000 houses.

In July 2019, an asteroid with a diameter of 57-130 meters passed by the Earth at a distance of 720,000 kilometers. If its orbit had changed more and hit the Earth, it would have produced an explosion 5,000 times the power of the Hiroshima atomic bomb. The asteroid flew toward the Earth from the position of the sun, and its shadow was obscured by the strong sunlight. Scientists suddenly discovered its traces one day in advance, and they were shocked.

Therefore, monitoring, early warning and defense of near-Earth asteroids are closely related to human survival and are also one of the major technical challenges facing the international aerospace community. In order to protect the peace of the Earth, it is necessary to conduct sky surveys of near-Earth asteroids to discover all potential threats; to continuously monitor threatening asteroids and promptly determine changes in risks; to conduct asteroid exploration and sampling activities to study their material composition and orbital mechanisms, and ultimately eliminate potential threats.

my country has announced the establishment of a near-Earth asteroid defense system to jointly respond to the threat of near-Earth asteroid impacts with other countries. This is an important measure for us to fulfill our obligations as a major country and demonstrate our responsibility as a major country. It is also an inevitable choice to protect the survival and development of mankind and build a community with a shared future.