usage of earth analogs

Just need a short paragraph for a discussion board!

We use what we know about Earth, its structure, atmosphere, geologic activities, and processes to prove or disprove our theories of other planets. For example, we used Google Earth in Week Four’s lab to examine rivers on Earth, and then will apply what we know of Earth’s rivers to explore evidence for past rivers on Mars in this week’s lab. Describe one other such example of our usage of Earth analogs to determine the circumstances elsewhere and how it might influence our extraplanetary explorations in the future. And for the last time this term, don’t choose one that has already been posted.