Why is Mars the most tempting planet for human exploration? No other planet in our solar system is more likely to harbor life. And it's close enough to get there in less than a year using currently available technology.
For many scientists, the main reason to go to Mars is simple: to look for life. Today, Mars is cold and dry, but millions of tons of liquid water once flowed on its surface--meaning life could have thrived there. And there could still be liquid water underground, where some form of life might linger to this day.