While we have yet to make it to Mars, maybe in my lifetime we'll spot another Earth? So far we've discovered 300 planets outside of our solar system so the odds are in our favor:
Solar System's 'look-alike' found
"Astronomers have discovered a planetary system orbiting a distant star which looks much like our own. They found two planets that were close matches for Jupiter and Saturn orbiting a star about half the size of our Sun. Martin Dominik, from St Andrews University in the UK, said the finding suggested systems like our own could be much more common than we thought.
And he told a major meeting that astronomers were on the brink of finding many more of them."