Subject: Planetary Space Travel

I've heard that one of the main problems with interplanetary space 
travel is the fact that it takes so long and the astronauts would run 
out of supplies such as fuel, oxygen, food, etc.  My question is the 
following:  consider we are going to Mars.  Why can't we send up an 
unmanned probe or something that can carry supplies to Mars and send 
them into orbit around Mars or land the supplies down so that when the 
astronauts get there they can replinish their supplies and come back 
home???

Re: Planetary Space Travel