Ominously the movie "Mission to Mars" in the final sequence reveals that an advanced civilization that lived on Mars emigrated from spiritual form the center of the galaxy, but not before his DNA sent to Earth to cause the evolution of life and reach point of being sentient beings-we-we discover that we are them.
Similarly MIT and Harvard scientists have launched a major investigation to find out if life on Earth descended from organisms that originated on Mars, reaching Earth in meteorites.
for signs of past or present life on Mars the best bet DNA or RNA is to look below the surface, particularly sequences of molecules that are nearly universal in all forms of life on Earth.
The investigation, called "Search for Extra-Terrestrial Genomes' (SETG) is carried out within the Department of Earth Sciences, Planetary and Atmospheric MIT and has the participation of Harvard University.
The premise of the research is based on that in the early solar system, the climate of Mars and the Earth was much more similar than it is now, so life was stopped on a planet could presumably have survived in the other. In addition, an estimated one billion tons of rock have traveled from Mars to Earth, scattered in asteroid impacts and it is known that some microbes can survive a trip of this magnitude could survive and even thousands of light years between different star systems.
Additionally, orbital dynamics make it 100 times easier for rocks to travel from Mars to Earth than vice versa. Therefore it is not so unreasonable to think that the origin of life on our planet is the panspermia of the red planet in the blue planet floating in cosmic twins outer sea: Mars sperm, the egg Earth.