Underground Water

Long ago Mars had water, but where it went is not entirely known.  We do know that one possibility is that the water is underground.  Some proof about this is the underground rivers.  We can tell how old the marks are by looking at the meteors that went through them.  Some scientists believe that if all the water came to the surface it would flood Mars in a depth of 1000 feet.  One scientist thinks that water on Mars may not have been created by rain or snow but by the ground.  Machines have done tests and think the water is so close to the surface that astronauts could dig it up.