The Amazonian is a geologic system and time period on the planet Mars characterized by low rates of meteorite and asteroid impacts and by cold, hyperarid conditions broadly similar to those on Mars today. The transition from the preceding Hesperian period is somewhat poorly defined. The Amazonian is thought to have begun around 3 billion years ago, although error bars on this date are extremely large. The period is sometimes subdivided into the Early, Middle, and Late Amazonian. The Amazonian continues to the present day.

Mars is the fourth planet from the Sun. The surface of Mars is orange-red because it is covered in iron(III) oxide dust, giving it the nickname "the Red Planet". Mars is among the brightest objects in Earth's sky and its high-contrast albedo features have made it a common subject for telescope viewing. It is classified as a terrestrial planet and is the second smallest of the Solar System's planets with a diameter of 6,779 km (4,212 mi). In terms of orbital motion, a Martian solar day (sol) is equal to 24.5 hours and a Martian solar year is equal to 1.88 Earth years. Mars has two natural satellites that are small and irregular in shape: Phobos and Deimos.