A recent study found that the moon is losing its atmosphere.

The moon is slowly losing its atmosphere, according to a new study published in the journal Geophysical Research Letters. Scientists have long known that the moon’s surface has very little atmosphere, but they weren’t sure exactly how much was lost over time. To find out, researchers at MIT and Boston University used data from NASA’s Lunar Atmosphere and Dust Environment Explorer (LADEE) mission to measure the amount of argon gas in the lunar atmosphere. Argon gas is a noble gas that doesn’t react with other elements, so it can be used as a way to track how much material has been lost over time.

The team found that about 2.5 tons of argon escapes from the moon every year. This means that an estimated 100 tons of argon has been lost since LADEE stopped collecting data in 2014. The team also found that Earth’s magnetic field shields lunar astronauts from most of this escaping gas.