We are only about 4.4 billion years too late. Mars has be bombarded by Earth rocks (ejecta from large meteor events) for billions of years. Some of these rocks were ejected under conditions where bacterial spores inside them can survive the trip to Mars. I fully expect we will find life on Mars that looks just like Earth life.<p>There is actually a good case to be made that life originated on Mars given that it had liquid water on the surface earlier than the Earth.