By virtue of being the closest to Earth, Mars has been mythologized more than than any other planet in the solar system. Fly-by satellites photographed much of its surface and took atmospheric readings; short-lived surface probes revealed a climate habitable by human beings, albeit with temperature swings in the extremes that no unsheltered human being could survive. Canals were detected, suggesting the presence (at least formerly) of water, which in turn suggested the presence of life. That was intensified by the infamous photograph of the “Cydonian face” on Mars, leading to renewed calls for another surface landing, this one intended to last longer than a couple minutes.

On this day, July 4, in 1997 Mars Pathfinder lands on the surface of Mars, carrying the first rover to another planet. The mission was intended to be more a proof of concept of vehicle delivery to other planets, but it still brought back reams of new data.

The Mars rover, named Sojourner for Sojourner Truth, the Civil War activist, lasted over three months, three times longer than its expected maximum. Over the course of its mission it returned more than 16,500 images from the Pathfinder lander and 550 images taken by itself. The results of more than 15 chemical analyses of rocks and soil, as well as weather conditions were also transmitted to Earth. No martians were ever found.