Eagle is a 22-metre long impact crater located on the Meridiani Planum extraterrestrial plain, situated within the Margaritifer Sinus quadrangle (MC-19) portion of the planet Mars.

Scientists were delighted that the rover landed there, as the crater contains rocky outcroppings that helped prove that Meridiani was once an ocean floor.

Upon closer, in-situ examination of the outcrops, whose layers are no thicker than a finger, it was confirmed that Meridiani Planum was once the location of an ancient, somewhat acidic and salty sea,[3] though much more information on the history of this area would start being collected more than three months later, when Opportunity visited the much larger crater Endurance to the east.

The hematite observed from orbit, whose presence decided the landing site in the first place, was found to be encased in millions of tiny hematite spherules, nicknamed "blueberries", by mission scientists, due to their shape, although they are actually much smaller than real blueberries.

Images from the rover's microscope discovered blueberries at several stages of this process, with most completely separated, but some still attached by a thin "stalk".