Mars is the fourth planet from the Sun — a dusty, cold, desert world with a very thin atmosphere. Mars is also a dynamic planet with seasons, polar ice caps, canyons, extinct volcanoes, and evidence that it was even more active in the past.

No other planet has captured our collective imagination quite like Mars.

In the late 1800s when people first observed the canal-like features on Mars’ surface, many speculated that an intelligent alien species resided there. This led to numerous stories about Martians, some of whom invade Earth, like in the 1938 radio drama, The War of the Worlds. According to an enduring urban legend, many listeners believed the story to be real news coverage of an invasion, causing widespread panic.

Countless stories since have taken place on Mars or explored the possibilities of its Martian inhabitants. Movies like Total Recall (1990 and 2012) take us to a terraformed Mars and a struggling colony running out of air. A Martian colony and Earth have a prickly relationship in The Expanse television series and novels.

Internet: <www.solarsystem.nasa.gov> (adapted).