At present, there are 79 1 384 known asteroids and 3559 known comets.
In the early days of our solar system, before the existence of the earth, Jupiter and Pluto, a huge vortex cloud composed of dust and gas surrounded the sun. The dust particles in the dust tray collide with each other to form a larger rock mass. This process continues until they become the size of boulders. Eventually, the evolution of this accumulation layer formed the planets in our solar system.
Billions of small space rocks have never evolved. Miraculously, most of these magical "small universes" have hardly changed in these 4.6 billion years since their formation. The relatively primitive state of comets, asteroids and some meteors makes them good storytellers. They can tell a lot about the early solar system. They can reveal the secrets of our origin. They may provide clues to the sources of water and raw materials that make life on earth possible.
Current data:
Known asteroid: 79 1, 384.
Known comets: 3559
Exploration of machines
Nasa's robotic spacecraft allows us to visit comets, asteroids and dwarf planets at close range and even bring back samples for research. We are just beginning to understand what these places are like, what they are made of and how they are formed.
The raw material of life?
Comets and asteroids may have sent some water and other substances, which made the complex chemical reactions that produced life unfold on the earth. Glycine amino acids were found in the comet dust brought back to earth by the Stardust mission. Glycine is used by organisms to produce protein. This discovery confirms the hypothesis that some living matter formed in space was brought to the earth by meteors and comets long ago.
Just like forensic investigation, scientists pieced together the story of our origin along the clues of what happened when the solar system was young. What we know will also let us know about planetary systems in other galaxies and how life develops in some places.
Future resources
We also explored asteroids to understand the difficulties and resources in the solar system that will affect human colonization in space. What challenges will we face when we venture away from the earth? Can we find new sources of raw materials and natural resources that can be used on the earth? Can humans use asteroids and comets as gas stations one day? Can we find new and cleaner energy in space to help us protect the environment?
Impact is a process that can end life or promote life in the solar system. These cosmic collisions are naturally like rain, although they occur more frequently when the solar system is young. Scientists believe that the separated objects and fragments produced by early collisions in the past hit the earth and played an important role in the evolution of our planet.
With the increase of regularity, scientists are discovering asteroids and comets with unusual orbits, which enables scientists to get closer to the earth and the sun. Only a few such celestial bodies pose a threat to the earth, but the more we know and understand them, the more prepared we are to take appropriate measures when they attack us.
Knowing the size, shape, mass, composition and structure of these celestial bodies can help us decide the best way to transfer space rocks that threaten the earth's orbit. Missions to comets and asteroids provide valuable information about their composition and structure, and help scientists get the best solutions to those celestial bodies in threatening orbits.
By tracking NEOs with potential threats in real time, we can gain more time to study potential threats. NASA's NEO program was launched in 1998 to cooperate with a series of research initiated by NASA to detect, track and describe potentially dangerous asteroids and comets that may approach the Earth.