Water is the main element of life on Earth. All forms of life depend on water. It was the place where life first evolved on this planet. So finding water on another planet suggests that same form of evolution can take place there as well. This is why astronomers were greatly excited when they found water on Mars. The long held theories of Martian life may be a truth after all.
However the life forms that may come to light from Mars will be far more different from most of the stuff mentioned by science fiction writers. There is no chance that there is anything more than microbial forms to exist on Mars under current environment conditions. But the discovery of water gives hope of finding bacterial or similar forms of life and this will be the first time any sort of life being discovered outside Earth.
For many years astronomers were on the debate that there was water on Mars at some part of its history. Some even believe that there were oceans and large rivers and the majority of the planet was in fact, under water. Nobody is sure what happened to all this water. There are some in the polar ice caps in the form of ice. Then what happened to the rest of the water?
For many years, scientists were not sure what happened to the rest of the water. The only explanation was that it was lost to the space as Mars lost its atmosphere, but the recent images taken from Mars Global Surveyor (MGS) indicated that there is ice below the Martian surface, far away from the poles than previously thought. The images of recent craters and gullies showed signs of ice coming to surface and even the flow of liquid water. This new evidence has risen the hopes of astronomers to new heights.
There are another group of scientists who believe that there can be liquid water under the thick layers of polar ice caps. There can be life in these waters but it may be much different from life forms that are observed here on Earth. But the heat coming from the core of the planet, may in fact create a much friendlier environment beyond the ice caps, than on the surface of the planet.
With all this evidence, what does the water really mean to the astronomers? Other than the hope of finding life outside Earth, it has a few additional importances. First of all, finding water will allow the future astronomers to plan colonies on Mars, where water can be used to make both oxygen as well as hydrogen. Hydrogen will power the future spacecrafts taking off from Mars and it will be a better base than Earth for the missions to the distant places of the solar system, both due to the shorter distance as well as the lower gravity.
If the astronomers can find water on Mars it may indicate that water is not a scarce element in the universe after all and it will rise up the hopes of finding more planets with liquid water, outside the solar system. Wherever there is water, there is a high chance of finding life, which is similar to what is seen on Earth.
If Mars was once having oceans and if they disappeared with time, the same fate may take hold of Earth one day. It is important to find out the causes of these changes and try out whatever methods available to prevent the same thing happening to this planet. Finding water will be a new chapter in finding the actual geographical history and mystery of Mars.
In summary, Mars is believed to have had large amounts of water in its past. There are signs of erosion and dried up ocean and river beds to suggest this. Then recent evidence on polar ice caps, gullies and craters with evidence of underground ice, has raised the hopes that there is in fact ice beneath the Martian surface and liquid water still flows on the surface from time to time.
If these evidences are true then the astronomers believe that there can be some form of life to be found on Mars. It will also indicate that this water can be used to establish future colonies and bases for future space expeditions. If the astronomers are able to solve the mystery of the disappearance of water from the surface of Mars, it will be of great use to prevent the same fate taking hold of Earth.