Before space exploration, telescopic observations played a major role in understanding Mars. Unlike Venus, whose thick haze of clouds obscured its surface, Mars offered a spectacle of shifting light and dark markings with its changing seasons.
Over the past few decades, the robotic spacecraft we've sent to Mars — orbiters, landers, and rovers — have vastly deepened our understanding of the Red Planet. We've come to know Mars not just as an image through a telescope, but also as a unique and intriguing world.
Right: This NASA Hubble Space Telescope view of the planet Mars is the clearest picture ever taken from Earth, surpassed only by close-up shots sent back by visiting space probes. The picture was taken on February 25, 1995, when Mars was at a distance of approximately 103 million km (65 million miles) from Earth. Morning clouds appear along the planet's western (left) limb. These form overnight when Martian temperatures plunge and water in the atmosphere freezes out to form ice-crystal clouds.