The number of galaxies in our universe cannot be exact. There are billions of galaxies. Some galaxies are too far (or too faint) for us to see. Within 3.34 billion light years away, billions of individual galaxies exist. With new information found by the Hubble space telescope, there are approximately 50 billion galaxies nearby. And that's just what we can see. There are probably hundreds of billions more that are too far away to see.

A nice online page on galaxies is: http://www.sciam.com/1998/1098issue/1098laham.html Nobody knows when people will go to Mars. It's very far away, and takes about two years to get there and back in the fastest ship. Mars travellers would have to take enough air and water, and fuel to last two years and to get back. There are people figuring out how to do this however. Check out the Mars Society at http://www.marssociety.org/ and Scientific American at http://www.sciam.com/2000/0300issue/0300alpert.html