This Mid-Autumn Festival, enjoy the moon from a different angle

The Mid-Autumn Festival is a time for families to reunite when the moon is full. From ancient times to the present, there has always been a custom of moon-watching during the Mid-Autumn Festival. When watching the moon with your family, have you ever thought about what secrets are hidden behind this bright moon? This Mid-Autumn Festival, let's look at the moon from a different angle and take a science-based moon-watching trip!

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1. Will the moon be bigger on Mid-Autumn Festival than usual?

There are usually 12 to 13 full moons in a year, and the Mid-Autumn full moon is just one of them. Its size and brightness follow the general law of the moon's changes and are no special compared to other months.

However, the moon does have different sizes. The moon's orbit around the earth is elliptical. If the full moon occurs when the moon is near the perigee, then the full moon at this time is the largest full moon, and the full moon that occurs when it is near the apogee is the smallest full moon. According to calculations, the largest full moon will be about 14% larger than the smallest full moon, but the brightness can be 30% higher than the smallest full moon. However, the naked eye cannot tell whether the moon is larger or smaller.

This year's Mid-Autumn Festival is on the 15th and the moon is full on the 16th. On the second day after the Mid-Autumn Festival, which is the 16th day of the eighth lunar month, we will usher in the second supermoon of 2024, which will also be the largest full moon of the year.

2. What is this “human face” we see on the moon?

Many people, when looking up at the moon, feel that the black spots on the surface of the full moon look like a "human face".

Astronomers once thought that this "human face" was an ocean, so they called it the "Ocean of Storms".

At the beginning, the scientific community generally believed that this "face" was formed by the largest asteroid impact event in the history of the moon, and then some small-scale asteroid impacts occurred, forming small craters similar to human face features such as eyes.

However, in the 21st century, scientists used the observation data obtained by the detector to draw a high-definition picture of this "human face" and found that the edge of this "face" was not circular as previously thought, but polygonal with an angle of about 120 degrees.

If it was an asteroid impact, it should have produced a circular or elliptical crater, so scientists have proposed a new explanation that this "human face" may have originated from volcanic eruptions on the early moon.

3. How old is the Moon?

When the moon was born has always been a controversial issue.

Scientists believe that the moon was formed after a Mars-sized planet hit the Earth and sputtered material into space (first sputtering material into space, then forming rings, and then accreting into balls) A huge ball of molten rock was "thrown" into space. When the magma surface of the object cooled and solidified, silicon crystals called zircons were formed. Due to their ability to adapt to high temperatures and harsh environments, these crystals still exist on the moon and can be used to identify the age of the moon.

In a recent study, scientists discovered through scanning and analysis of crystals brought back from the moon that the moon is 40 million years older than previously thought, reaching 4.46 billion years old.

4. Is there water on the moon?

Many years ago, people believed that there was no water on the moon. It was not until the beginning of the 21st century that the emergence of new detection technology allowed scientists to finally confirm that there is indeed water on the moon.

However, the "water" on the moon that scientists are talking about is not the "water" we drink. Except for a small amount of water ice mixed in the surface weathering layer, it mainly refers to water molecules or hydroxyl groups in minerals, which can only be converted into the water we drink under certain conditions.

In July this year, Chinese scientists discovered the water-containing mineral ULM-1 when analyzing the lunar soil brought back by Chang'e 5. This marked the first time that scientists found molecular water in the returned lunar soil, revealing the true existence form of water molecules and ammonium on the moon.

Subsequently, in August this year, after three years of in-depth research and repeated verification, Chinese scientists proposed a new method to produce a large amount of water using lunar soil. Using this method, one ton of lunar soil can produce 51-76 kilograms of water, equivalent to more than 100 bottles of 500 ml bottled water, which can basically meet the daily drinking water needs of 50 people, and is expected to provide an important design basis for the construction of future lunar scientific research stations and space stations.

5. How are lunar craters formed?

Many scientists once believed that the craters on the moon were mainly caused by volcanic eruptions. After all, the craters are so round, and no meteorites have been seen nearby. More importantly, if the bumpy moon was caused by collisions, then why are there almost no craters on our Earth?

But later, scientists gradually discovered that it was impossible for a volcano to form such a huge crater, and there would be no traces of radial sputtering accumulation. More importantly, after witnessing the example of Comet Shoemaker-Levy 9 hitting Jupiter, everyone finally believed that the impact of small celestial bodies could have such a powerful destructive power.

Today, we are fairly certain that the vast majority of craters on the Moon, as well as on Earth and other solid bodies in the Solar System, were formed by meteorite impacts.

However, there are still a few lunar craters that are caused by volcanoes or other unknown reasons, such as Hyginus Crater and Ina Crater.

Expert support: Liu Xi, researcher at Beijing Planetarium and popular science writer