Mars has a rich history of exploration, the richest of all planets in our solar system. The first missions were simply flybys, where the early Mariner spacecraft would take as many pictures as possible as they flew past Mars and transmit this data back to Earth. Subsequent missions, such as Mariner 9 and the Mars Global Surveyor, took the process a step further: orbiting the planet and allowing long-term, global studies for the first time.
In 1975 the first rovers destined for Mars were launched, Viking I and II, and became the first US missions to safely land on the surface of Mars and transmit images back to earth. For the first time, scientists were able to study detailed images of Martian soil, which resulted in the controversy of Martian microfossils. Further missions, including Pathfinder, Spirit and Opportunity, and Phoenix, have all been enormously successful, outliving their expected lifetimes and even finding evidence that the Martian soil was at one time wet and likely capable of supporting life.
The Mars Science Laboratory, also called the Curiosity rover, is the most recent and most sophisticated lander to reach Mars. Its mission is to study the Martian soil and determine if Mars ever had an environment capable of supporting microbial life. Recent evidence, such as the smooth river rock-type pebbles shown in the image (above left), provide further indications that Mars did at one point contain flowing water.