I learned about Planet Impact from TechLearning.  It’s a series of engaging online activities where students can learn about comets and their affect on planets.

It’s presented in relatively simple English that’s accessible to Intermediate English Language Learners.  There are several games students can plan, including ones where they calculate angles to determine if their comet will hit or miss planets.

I’ve placed the link both on my Science page and my English Themes For Beginners page under Planets and Space.