Mars

Mars, named after the Roman god of war, is the fourth planet from the sun.

Background
Before the Great War, the United States Space Administration planned to launch a manned mission to Mars by July 2078, which was called the Mars Shot Project. However, the project was delayed by a year due to unrest overseas. In 2077, after public outcry over a reporter being killed in a test of the XMB booster engine, the USSA attempted to garner support for the Mars mission by investing in the popular television show, The Adventures of Captain Cosmos. In the end, it would all be for nought, and the project would never be carried out due to the nuclear war of 2077.

Mentions
At the Museum of Technology, a film named The Long Road to Mars was playing before the war. Also at the museum, a list of space facts mentions that a volcano on the planet, Olympus Mons, is the tallest known mountain in the solar system, three times the height of Mount Everest.

A model of the solar system appears in the REPCONN headquarters, which includes a model of Mars.

In issue #6 of Grognak the Barbarian, the titular character faces off against Maula, the war maiden of Mars.

On Mothership Zeta, one of the abducted humans asked if a device on the ship was a Martian sex machine.

Vice President of the Enclave Daniel Bird claims that they have pictures of Mars that show canals and water on the planet's surface, which he believes means that there is also oxygen, so humans could breath on the planet.

The finale of The Adventures of Captain Cosmos was titled Captain Cosmos vs. the Giant Cockroach from Mars. Additionally, the set for the finale was supposed to be the surface of the planet.

At the Bloomfield Space Center, the Hermes-13 was designed for a mission to Mars, before being repurposed to carry a power reactor to an orbital nuclear missile platform.

The Vault Dweller can claim to be from the planet, "proving" it by showing Jason Zimmerman their firelance.

Appearances
Mars is mentioned in Fallout, Fallout 2, Fallout 3 and its add-on Mothership Zeta, Fallout: New Vegas, Fallout 4 and its Creation Club content Captain Cosmos, and Fallout 76, and would have been mentioned in Van Buren, Black Isle Studios' cancelled Fallout 3.