Liquid water on Mars has not yet actually been observed, although there does seem to be evidence there was once water there. Recently some scientists announced that they have seen signs that water is still changing the surface of Mars even today, but they have not actually caught it in the act.

We have observed frozen water ice near the poles on Mars. According to this article there is enough to fill Lake Michigan twice over:
Ice on Mars
http://science.nasa.gov/h...02/28may_marsice.htm

Here is a place where you can learn more about Mars
http://mars.jpl.nasa.gov/funzone_flash.html


Terry