Knowing when to delete chapters?

This question is for all the writer folk out there! I sometimes have trouble deciding if my chapters have enough weight to drive the plot forward and should remain in the book. The chapter I'm contemplating taking out has some important elements. The characters are traveling in a wasteland and have located a town, and while doing so they stumble across a dead alien. However, this alien finding only foreshadows what will happen in a later book, and doesn't necessarily need to happen at that exact moment. The chapter is short, and if need be, I could smash most of it into the next chapter. For me, the line of whether or not a chapter is absolutely necessary is blurred. I have some that I KNOW I need, and others that the story wouldn't exactly be the same without, yet feel too light to stand on their own. Is this foreshadowing enough to make the chapter stand on its own? Any tips or advice would be much appreciated!