On February 14, according to foreign media reports, a new crater will appear on the moon on March 4 this year, because the Falcon 9 rocket of American space exploration technology company SpaceX will hit the moon. The impact raised many concerns, including craters left by the impact and biological pollution < p > < / P > < p > the rocket was launched in 2015 to send NASA's dscovr probe to a position facing the sun 1.5 million kilometers away from the earth. The rocket entered the earth's atmosphere independently, but it did not return to the earth's atmosphere at enough speed. According to the normal procedure, the superior rocket should be burned during re-entry, so as to reduce the space waste in low earth orbit < p > however, since February 2015, the abandoned Falcon 9 rocket, which is 14 meters long and weighs nearly 4 tons, has been operating in a broad orbit around the earth. Its precise motion has always been difficult to predict because it is affected by both the gravity of the moon and the sun and the gravity of the earth. But now it can be concluded that it will hit the moon at a speed of 2600 meters per second on March 4 and will create a crater about 19 meters in diameter < p > "man-made" crater < / P > < p > for the earth, the end-of-life rocket hitting the moon must be more environmentally friendly than dispersing in the earth's upper atmosphere in the form of metal oxide particles, which are produced when the rocket re-entry burns. But the moon lacks an atmosphere to protect it from space debris, so it has countless craters formed by natural impact < p > NASA Lunar Reconnaissance Orbiter (LRO) photographed the formation of a 19 meter diameter lunar crater in March 2013. At that time, a half ton space rock hit the surface of the moon at about 10 times the speed of the Falcon 9 rocket. In the past decade, NASA's lunar impact monitoring program has found hundreds of smaller impacts caused by space rocks weighing only half a kilogram < p > the upcoming impact will happen on the back of the moon, so we can't see the impact scene with our own eyes. But then spacecraft orbiting the moon will be able to take images of the crater < p > in 2009, NASA's Lunar Crater Observation and remote sensing satellite (LCROSS) mission achieved an accurate directional impact. At that time, LCROSS and its rocket stage hit the lunar polar crater, forming a smaller crater on its frozen surface and throwing out a plume, proving that the lunar surface contained water as speculated < p > biological pollution < / P > < p > leaving New craters on the moon is not the most worrying. After all, there are about 500 million craters with a diameter of 10 meters or more on the lunar surface. What we should worry about is that living microorganisms or molecules will pollute the moon, which may be mistaken for evidence of the existence of life on the moon in the future < p > most countries have signed planetary protection agreements, seeking to minimize the risk of biological pollution of the earth to other celestial bodies (and other celestial bodies to the earth). The implementation of these agreements has both ethical and scientific reasons. The ethical argument is that organisms brought from earth may endanger any ecosystem that exists on another celestial body. The scientific argument is that we want to study and learn more about the natural conditions on celestial bodies, but we should not at the cost of wanton pollution or even destruction < p > the biggest recent violation of the COSPAR agreement occurred in 2019, when the privately funded Israeli lunar lander beresheet crashed on the moon with DNA samples and thousands of water bear insects. These half millimeter long organisms can tolerate the vacuum environment in space, although they are not active in space. These water bear worms and other microorganisms living in their intestines are now scattered at the beresheet crash site < p > most likely, these creatures will not appear in an environment conducive to their survival. There may not be enough water to revive and activate them, but this is not a risk we should take. Falcon 9 rocket, which launched dscovr, was not sterile when it took off, but it has been in space for seven years, so the risk of biological pollution is minimal so far. However, as we send more and more things to the moon, we must be careful enough. (small) < / P > < p >