Project Hail Marys ending makes one big change from the book. Heres why.

Like any book-to-film adaptation, Project Hail Mary makes some changes to its source material.

SEE ALSO: How did Harry Styles' 'Sign of the Times' wind up in 'Project Hail Mary'? Thank Sandra Hüller.

In most cases, Project Hail Mary's changes look like removing elements of Andy Weir's novel in order to streamline the film. For example, in the book, a key part of finding astronauts for the Hail Mary mission is determining whether they have a very rare coma resistance gene...