The morning of July 20, 1976, dawned cold and clear on a deserted, rocky plain called Chryse, on the planet Mars. This particular morning was seven years to the day after the first humans had walked on the Moon. The dawn temperature on Mars was around -84°C (-120°F), but by afternoon the air had warmed to about -34°C (-27°F). At about 4:11 p.m., a very unusual thing happened — a spacecraft descended out of the sky.
Size comparison of Earth and Mars. Click here for original source URL
High in the apricot colored sky, a white parachute opened. Beneath the parachute dangled a sturdy, three-legged spacecraft about as tall as a person. As the parachute and its cargo neared the surface, the parachute cut away, and the craft dropped. At the last moment, rocket engines in the underbelly of the probe flared to life, stirring up clouds of reddish dust and depositing the craft onto the surface of Mars. The name of the spacecraft was Viking 1. Covers popped off Viking 1's cameras as the dust settled. Back at the Jet Propulsion Lab in Pasadena, California, scientists controlling the mission waited for Viking's cameras to send back the first surface photos of Mars.
Global view of Mars as seen by the?Viking?1?orbiter in 1980, showing the?Valles Marineris?(center). Click here for original source URL
Viking 1's survey of Mars marked the first successful landing of instruments on the surface of the neighboring planet most like our own planet. From the Earth, scientists had charted moving clouds, polar ice caps, and seasonally changing dark markings on the surface of Mars. Some hypothesized that life existed on the planet, perhaps in the form of vegetation that changed with the seasons. Others even speculated about the existence of intelligent civilizations. The only way to test these theories was to get instruments onto the surface of the red planet. Scientists waited with anticipation as the first images streaked across millions of miles back to Earth. What they saw was a barren, lifeless planet.
Viking 1 was followed a few weeks later by Viking 2. After that, Mars remained unvisited by human machines for 21 years. Finally, on the 4th of July, 1997, Pathfinder landed on a plain at the mouth of a Martian river channel. This little media darling introduced a new generation to Mars. Its three probes sent back numerous images and measured the chemistry of the soil, and a probe also measured the chemistry of six boulders. It's pictures revealed Mars' desolate beauty, with apricot-colored skies tinged by pink air-borne dust, and a surface of sand dunes and scattered boulders. Pathfinder photographed several small dust devils on the horizon, and identified rocks that may have been down the river when billions of years ago Mars surface was still wet and rain still may have fallen from the skies.
Pathfinder represented a return to Mars exploration, and in the following years, mission after mission has gone and explored Mars surface. Following in the tire marks of Pathfinder, the Mars Exploration Rovers, Spirit and Opportunity, launched off the surface of the Earth in 2003 and landed in January 2004. In the more than half decade since their landing they have explored numerous craters sampled rocks and searched for signs of water. In May 2009, the Spirit rover became mired in sand, and became a stationary observation platform. The Jet Propulsion Laboratory lost contact with Spirit in March 2010, and declared the mission complete on May 25, 2011, after being unable to establish contact with the rover for over a year. Opportunity continues to explore and no one quite knows when it will stop bringing new insights into the Martian environments. Joining Spirit and Opportunity, the Phoenix mission landed on Mars in the summer of 2008 and dug into the polar soils finding water. While Phoenix was unable to survive the Martian winter, the short-lived mission proved once and for all Mars does have water ice.
Today's Martian exploration missions are geared at making the way possible for man to venture out to Mars in the coming decades. The current mission is the Mars Science Laboratory, Curiosity. Launched on November 26, 2011, Curiosity landed on Mars on August 6, 2012 after a daring landing sequence that NASA dubbed "Seven Minutes of Terror." Curiosity is an SUV-sized platform from which scientists remotely perform a large variety of chemical, geophysical, and imaging experiments. Also being planned are missions to go to Mars and return again with samples of the Martian soil. Mars may still seem hostile and foreign, but the more we understand about the barren red world, the more possible it becomes to imagine man someday living there.