The leading hypothesis for how the moon formed involves a collision between a Mars-sized object and Earth that would have boiled away elements like carbon, making its discovery on the moon a mystery
Source:
https://www.newscientist.com/article/2242725-the-moon-is-emitting-carbon-raising-questions-about-how-it-was-formed/?utm_campaign=RSS%7CNSNS&utm_source=NSNS&utm_medium=RSS&utm_content=home