Here is a pretty cool video I found on youtube (http://www.youtube.com/watch?v=yjiGH9QNiU0) that is a spoof that shows was Mars will look like in 2020. As you can see they do not show any sign of human presence besides robots. Obviously it is still believed that humans will not touch Mars by 2020 as shown in this movie, but we will litter Mars with our broken robots.