An interest in Mars began in the 1870s with the Italian astronomer, Giovanni Schiapparelli, who used a telescope to observe the Martian canals. After that an amateur astronomer and American businessman by the name of Percival Lowell founded an Arizona observatory, where his own observations convinced for years that the Martian canals were being dug by intelligent beings.
The first robotic spacecraft was sent to Mars in the 1960s, followed by a wave of Mars exploration which began with the Viking missiontwo orbiters and two landers heading to the red planet in 1975. Experiments were conducted, combined with chemical testing, which were interpreted by the NASA scientists as negative.
This deflated the hope of a widespread world of any life on Mars. But over the next twenty years developments in Earth studies changed the way these scientists viewed Mars, and about life and Mars. One was a meteorite which the scientists felt may have originated on Mars, and contained ancient microbes.
Second is the possibility that life can thrive and grow in settings different from what we recognize as rich in organic nutrients surviving in the most extreme of environments. Because of this, there are two competing scientific views regarding what form water took on early Mars: the first is the Mars was once much warmer and wetter, with a thicker atmosphere; the second theory states that Mars has always been cold, but with trapped water in the form of underground ice, periodically released when its ice melted by heating, then gushing form onto the surface.
Water in any form is the golden item of NASA, the item that is being chased around by every country that has a space agency in order to find life on Mars or any other planet. Why? Because life requires water for survival, even in the minutest of amounts and the most tiny of life forms. The NASA missions collect data on Earth and other planets about water through rain, floods, and tides. This effects air, water, temperature changes, and the interaction of gravity, which in turn requires new missions to test theories.
NASA feels that billions of years ago, liquid water flowed on Mars because of its outflow channels and geological features on the surface of the red planet. But due to the low temperatures and thin atmosphere, it is impossible for liquid water to exist on the Martian surface, so further testing will be needed under the surface.
Once the 1997 Martian images were sent back to Earth by the Mars Global Surveyor, following the landing of the Mars Pathfinderthe public has been interested in Mars, with NASA seriously studying the possibility of water on the planet in order to sustain some form of life. They feel the key to life's evolution on the planet is understanding the history of its water.
Every 26 months, NASA is able to launch robotic spacecraft to Mars when the alignment of Earth and Mars are jointly suitable. Carrying a wide assortment of payloads, the spacecraft have ventured forth with items such as cameras to robotic arms in order to study the Martian geology, climate, and its history.