According to the paper published in the journal Science Advances, the group of researchers affiliated with multiple institutions in Japan describes their study of carbon data from the KAGUYA lunar orbiter and what they learned from it.
The work involved studying a year and a half of data from the KAGUYA lunar orbiter, focusing specifically on carbon emissions. They found that the moon was emitting more carbon than has been thought, and more than could be accounted for by new carbon additions, such as the solar wind or collisions with micrometeoroids. They also found that some parts of the moon have been emitting more carbon than others the basaltic plains, for example, emit more carbon than the highlands. The researchers suggest this is because surface material on the plains is newer than material in the highlands and thus has had less time to vaporize.
The findings by the researchers suggest that the moon has a large amount of ancient carbon beneath its surface, and it has likely been there since the moon was formed.