Gas from massive lunar volcanic eruptions once gave the moon an atmosphere.
What kind of atmosphere did the moon have?
The only moon in the solar system that is known to have a dense atmosphere is Titan, Saturn's largest moon. Today, our moon only has traces of an atmosphere—in fact, it's not even technically an atmosphere. The more accurate name for it is “exosphere”. This exosphere is made up of molecules that are gravitationally bound to the moon, but are too sparse to behave like actual gas.
However, about three to four billion years ago, our moon had an actual atmosphere. This discovery has certainly come as a surprise, since astronomers have long thought that the moon was very dry. A new study has now found that volcanic eruptions on the moon actually released hot vapors, which then formed an atmosphere. This atmosphere was able to stick around for about 70 million years before dissipating away into space.
All the moon has now are remnants of its atmosphere.
The moon has had a storied past. Just some hundred million years after its birth, it went through something called Late Heavy Bombardment. During this period, which occurred three to four billion years ago, the moon endured a lot of impacts from planetary debris. This triggered several volcanic eruptions, which then spewed large amounts of lava that covered huge stretches of the surface. Nowadays, the surface of the moon is peppered with long-dead volcanoes and dark maria, which are plains of hardened lava.
During the Late Heavy Bombardment period, the moon's atmosphere was at its densest. However, even then, the moon's atmosphere wasn't much if compared to the Earth's atmosphere. The moon's atmosphere was able to exert pressure measuring just about one kilopascal. On Earth, however, the atmosphere can exert pressure measuring about 100 kilopascals at sea level.
Astronomers studied the ancient dark maria on the moon's surface to determine how much gas had been in its atmosphere. They also analyzed volcanic glass samples taken by the Apollo missions in the 1970s. These samples allowed the researchers to determine which gases were present in the atmosphere, while mapping the flow of lava allowed them to determine the volume of gas.
We may be better prepared for future trips to the moon.
Eventually, the researchers determined that the moon once had an atmosphere made up of hydrogen, oxygen, carbon monoxide, sulfur, and several other volatile gases. Most of these gases dissipated into space, though researchers say that some of the gases may have settled into the dark, icy craters around the lunar poles.
These findings can also benefit future lunar landings. Now that we know that some atmospheric gases may have settled into the moon's craters, future lunar missions may be able to find ice in the said locations. With a known ice source, missions would be able to sustain their exploration programs.
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