In a rare reversal, archaeologists have determined that a Maya book written almost 900 years ago is genuine—after decades of believing it was fake. This does not, however, have anything to do with aliens. There may well have been alien landings in Maya, but we have not received any evidence of any landings elsewhere, so how would we know?
Ancient people used a variety of explanations to explain natural events, such as the phases of the moon or the tides. It makes far more sense that what they Mayans saw was natural science, and that they came up with alien explanations in their own minds. This would justify the events to the Mayan people and make them feel safe.
Modern science has proven that the Grolier Codex is authentic in provenance. Grolier being an encyclopedia in past decades. While the acquisition may have cloudy origins the actual pages are true by scientific standards including the paper itself and the Mayan blue ink used to mark upon it. Astronomy and calendar recording from the Maya civilization lives on another day.
I don't think it's likely that there were alien landings in Ancient Maya, because if Aliens exhisted we would have more proof than ancient book, but I believe anything is possible. It is more likely the book is genuine but fictional or that it involves myths and folklore of the Mayans.