How many meteorites hit the Moon each year?

When sending humans to the Moon in 1969, one of the many risks that NASA had to take into account was a meteor piercing through astronauts’ clothing or equipment. Unlike Earth, which has a protective atmosphere (an atmosphere that burns many meteorites), the Moon is vulnerable to any kind of space rock, including small debris.

Fortunately, astronauts are not in too much danger, according to Bill Cooke, head of the Office of Meteoric Environments at NASA’s Marshall Space Flight Center. “The odds of an astronaut being hit by a millimeter-sized object is 1 in 1,000,000 per hour per person,” Cooke said.

NASA is preparing to return humans to the Moon by 2025 and plans to build a base on this natural satellite orbit or surface. Therefore, understanding how often the Moon is hit by meteorites is extremely important.

So how many objects hit the Moon every day or every year? The answer depends on the size of the object, Cooke said. NASA’s Office of Meteorite Environment studies the space around the Earth and Moon to understand the behavior of meteorites. As a result, Cooke knows a lot about objects that collide with the Moon every day.

It is not possible to accurately quantify the number of objects smaller than a millimeter, Cooke said. However, experts estimate that between 10 and 1,000 tons (equivalent to 5.5 cars) of dust collide with the Moon every day. With larger meteorites, estimates are also clearer.

“There are about 100 ping-pong ball-sized meteors hitting the Moon every day, that’s about 33,000 meteors a year. No matter how small, each rock the size of a ping-pong ball will impact the Moon’s surface with great force. equivalent to 3.2 kg of explosives,” Cooke said.

Large meteorites also hit the Moon, but more sparsely. Cooke estimates that larger meteors, such as 2.5 meters in diameter, hit the Moon about every four years. They hit the Moon with the force of 900 tons of TNT. The Moon is about 4.5 billion years old, so it’s not surprising that its surface is riddled with all sorts of craters.

Scientists study impacts on the Moon in many ways. From the Earth’s surface, they pointed their telescopes toward the Moon to observe the collisions. The meteorite can plunge to the surface of this place at a speed of 72,400 – 257,500 km / h, according to NASA. The collision produced a flash of light visible from Earth.

Scientists can also use spacecraft orbiting the Moon, such as NASA’s Lunar Reconnaissance Orbiter (LRO), to observe the craters left by the impacts. Because it moves very quickly, a meteor that weighs only 5 kg can create a crater up to 9 meters wide, and cause 75,000 kg of rock and soil to shoot up. LROs can easily detect these depressions after they have formed.

The Moon experiences many collisions each year, but this does not necessarily prevent humans from being present. “Considering the surface area of ​​​​the Moon is about 38 million square kilometers, if you choose an area of ​​one square kilometer, this place will be hit by a meteor the size of a ping-pong ball about every 1,000 years,” Cooke said. So the opportunity is still wide open for future lunar explorers and spacecraft.

Thu Thao (According to Live Science)