When viewing the Moon through a telescope, how can you differentiate maria from craters?

The correct answer is that maria appear darker. When viewing the Moon through a telescope, maria are the large, flat, basaltic plains that were formed by ancient volcanic eruptions and are less reflective than the surrounding highlands, which are covered with a lighter, more rugged terrain consisting of many craters. This contrast in brightness allows observers to easily distinguish maria from craters.

Craters, formed by the impacts of meteoroids, typically have brighter and more prominent edges compared to the relatively smooth and darker surfaces of the maria. Therefore, the darker appearance of maria compared to the brighter highlands is a key characteristic that helps in their identification during lunar observation.