After the moon formed, Earth was probably left with an ocean of molten rock, which may have given the planet a thick atmosphere full of carbon dioxide like the one on Venus
Source:
https://www.newscientist.com/article/2260767-earths-early-atmosphere-may-have-been-toxic-like-the-one-on-venus/?utm_campaign=RSS%7CNSNS&utm_source=NSNS&utm_medium=RSS&utm_content=home