To keep track lets take a trip to 'Imagination Land' (no not the south park version!). Now imagine that the 8 planets and pluto in the solar system are places where humans can live, would the age rate differ from planet to planet? Now lets get back to reality. We may be able to send humans to mars so would be interesting to see if 'Martian Humans' Live longer than 'Earthling Humans', but to be honest I dont have a couple of centuries to live to see how the age rate over generations evolve on Mars. BUT isn't it possible to send micro living organisms to other planets, in a safe container which MUST not contaminate the planet it visits, and study the age rate of cells and compare... this could be done surely?