Water and Life on Mars

Mars perhaps first caught public interest in the late 1870s, when Italian astronomer Giovanni Schiaparelli reported using a telescope to observe canali, or channels, on Mars. By the turn of the century, popular songs told of sending messages between Earth and Mars by means of huge signal mirrors. On a darker side, H.G. Wells' 1898 novel The War of the Worlds portrayed an invasion of Earth by technologically superior Martians desperate for water. (1) In the early 1900s novelist Edgar Rice Burroughs, who is best known his creation of the jungle hero Tarzan, also entertained young readers with tales of adventures among the exotic inhabitants of Mars, which he called Barsoo. (2)
It was hoped that Mars had ample
Although Mars shows some promise in terms of habitability, it also shows some handicaps. Mars is half of an astronomical unit beyond the Sun's habitable zone and water is therefore frozen on its surface, though probable liquid water flows in the past emphasize the planet's potential. The planets lack of a magnetosphere and extremely thin atmosphere are an even greater challenge. The planet has little heat transfer across its surface, poor insulation against bombardment and the solar wind, and insufficient atmospheric pressure to keep water in liquid form. Also, Mars is nearly or is a geologically dead planet.
There is no general agreement, however, on what form water took on the early Mars. Two competing views are currently popular in the science community. According to one theory, Mars was once much warmer and wetter, with a thicker atmosphere. (9) According to the other theory, Mars was always cold, but water trapped as underground ice was periodically released when heating caused ice to melt and gush forth onto the surface.
In either case, the question of what happened to the water remains a mystery. Most scientists do not feel that Mars' climate change was necessarily caused by a cataclysmic event such as an asteroid impact that, perhaps, disturbed the planet's polar orientation or orbit. Many believe that the demise of flowing water on the surface could have resulted from gradual