A rain of 40 stones fell from the sky in 1911 near Nakhla in Egypt. One meteorite hit and killed a dog. The stones ranged in size from 20g to 1813g, and it is estimated a total weight of 10kg (22 pounds) had fallen. Meteorites from Mars are classed as "SNC meteorites", refering to the places where meteorites of their kind where found (Shergotty-Nakhla-Chassigny).

"A Princess of Mars", first of eleven "John Carter on Mars" novels, is published by Edgar Rice Burroughs in 1911.

Donald Menzel concludes in 1925 that air pressure on Mars would be less than 66 millibars. Walter S. Adams determines in 1926 that Mars is very dry. Large day/night temperature differences are measured on Mars during 1927 by William Coblentz and Carl Lampland. Bernard Lyot concludes in 1929 that an upper limit to the atmospheric pressure on Mars is about 24 millibars.

October 30, 1938: Orson Welles broadcasts War of the Worlds, at least 1 million people believe it was real.

Carbon dioxide was detected by Gerard Peter Kuiper on Mars in 1947.

In 1947 Werner Von Braun proposed Das Mars Projekt. A fleet of ten ships would go to Mars, explore, and return in about 520 days. By 1962 Werner von Braun considers the "Mars Project" to be 15-20 years away.

The Martian Chronicles by Ray Bradbury is published in 1950. Hyron Spinrad and co-workers report measurements of water in the atmosphere of Mars from spectroscopic observations in 1963. The following year Lewis Kaplan reports that the pressure of carbon dioxide on Mars is low, about 4 millibars.