Life is a very adaptable thing.  Living things have been found in some areas where no one expected anything could live.  Bacteria and small animals living in hot springs.  Animals living in the coldest areas.  Flowers that survive in the harshest deserts.  
    Life is a powerful force, as irresistible as gravity.  Since the life force is everywhere, it will find a way to bring life to the non-living matter somehow.  So since life exists almost everywhere on Earth, it is certain that it exists on other planets as well, in one form or another.  We may not recognize it as life because it may be very different from life here, but it exists.