Just for a moment, think of what is most important in your life. What can you not live without today? Is it a family member or a special friend? Could it be your computer or a video game? A special music CD? A favorite pet?

Obviously, it is easy to think of something with which you cannot live. Any choice you make is obviously the most important choice to you. But, do you think you missed a choice that should be the most important choice for everyone? You don't think so?

How about - WATER!

Scientists know that having available water is absolutely necessary when planning for space exploration. Any considerations for finding some type of life in space seem to require water to be present - well, at least by earthbound scientists who believe life elsewhere can't live without water.

Mars truly seems to be the only other planet within our solar system that we can most easily explore (and on which we can possibly live). NASA and the Russian Space Agency have sent more unmanned space probes to Mars than to any other planet. We study Mars with telescopes that show it really is the Red Planet! These same views show that the entire planet is not red. There are areas of white at both poles. Hmmmm - are they ice caps? ... made of frozen water? ... or something else?

In the late 1800's, astronomers saw lines on Mars they even named "canals," which they believed must have contained water. Missions to Mars began in the 1960s. These space probes sent back pictures of the Martian surface showing it as a dusty desert covered with craters as well as extinct volcanoes. These pictures destroyed the idea that Mars was warm and wet and could harbor life today.

In April 2001, NASA launched a special spacecraft to Mars. The trip to Mars took 6.5 months. This craft is named 2001 Mars Odyssey. It continues to orbit and study Mars.

Mars Odyssey's main job is to take measurements that can help scientists know what kinds of elements and minerals make up the surface of Mars. Odyssey looked for hydrogen, which is obviously connected to finding water on Mars (Now you know why it is always important to know that the chemical formula for water is H2O.)

Hydrogen on Mars is detected in a unique way. High-energy particles from space (called cosmic rays) continually strike the surface of all our solar bodies. When they hit Mars, particles called gamma rays (high energy light particles) and neutrons (an important part of an atom's nucleus) are kicked out. Materials near the surface of Mars leave their "fingerprint" on the collection of ejected gamma rays and neutrons. Scientists study these particles with instruments on Mars Odyssey and conclude there is a lot of water in the surface layer on Mars.

It is now possible to report that the 2001 Mars Odyssey spacecraft was successful in its search for water on Mars! As expected, the low temperatures there have turned the water into ice, but we can be excited to know that water was truly discovered on Mars in 2002! Actually, this ice is mixed with the soil on Mars just below the surface. Scientists estimate there may even be enough water ice mixed in the soil to fill up two water bodies the size of Lake Michigan.

A Mars mission in 2000 took pictures of hundreds of objects on the surface of Mars that look like "gullies" on the Earth - a feature formed by moving water. Many of these features are close to the polar ice caps. Interestingly, these ice caps are actually made of "dry ice" (solid carbon dioxide). Since the mission in 2000, other Mars space missions have discovered what look like old rivers, floodplains, lakes, and perhaps an ocean! These pictures continue to give us more evidence that Mars once had liquid water. Today, Mars is too cold to have anything but ice.

2001 Mars Odyssey also measured radiation levels to help scientists know whether astronauts traveling to Mars will need extra protection from dangerous radiation levels.

Why should we worry about whether there is water or even water ice on Mars? If we ever expect to successfully land people on the Martian surface - and even live on it - we will need either to make or find materials there to help us survive. We can never take enough water to last for the return trip. Why not use the water we now know is on Mars?

Just imagine - you could be the first person to step on Mars - live on Mars - and yes, even the first person to drink water formed on another planet.