Panspermia Theory

Scientists believe this meteorite was probably blasted off of the surface of the planet Mars about 16 million years ago by an impact with an asteroid and traveled through space to the earth, where it landed on Antarctica about 13,000 years ago. Some scientists believe that the rod-shaped structures across the top and center of this image may be tiny fossilized bacteria. Many other scientists believe that the structures were formed by processes other than life.

Panspermia Theory suggests that life seeds came from outer space and planets exchanged life. Panspermia literally means seeds everywhere.

Panspermia suggests that life could have existed on another planet and moved to Earth. Statistics have showed 7.5% of rocks from Mars reach Earth. The rocks would travel between less than 100 years to 16,000 years and more to get to earth.

Some of the proponents include Sales Gyon de Montlivant, who proposed life came from moon, H.E. Richter, who suggested life came from meteorites/comets, and Svante Arrhenius, who came up with Panspermia.

Evidence for Panspermia

1. Bacteria can survive harsh environment of space

a. Ultraviolet radiation

b. Protons bombardments

c. Cold

2. Evidence that meteorites contain life

a. Amino acids (left handed in helicity)

b. Bacteria

c. Carbon

d. Protected inside rocks

3. Bacteria can live for a long time in sleeping state until awakened

4. Mars safer than Earth (less bombardments and less gravity)

5. Mars not as hot as Earth in early development

6. Mars had have had oxygen back then when earth did not

Different Scenarios of Panspermia

Life began once, on Mars, and came to Earth in Martian meteorites. May or may not still exist on Mars (amino acids or bacteria)
Life originated on both Earth and Mars independently. Cross-colonization (cross-fertilization) may subsequently have occurred (a.a. or bacteria)
Life began once, on Earth, and was propagated to Mars, where it possibly established itself (a.a. or bacteria)
Life originated on both Earth and Mars, but in spite of the exchange of rocks and dust, no transfer of viable organisms has occurred
Life originated on neither Earth nor Mars, but somewhere else entirely, such as a comet, Jupiter’s moon Europa, Venus, or body outside the Solar System altogether. It came to earth, perhaps Mars too, via some sort of Panspermia mechanism (a.a. or bacteria)
Life has originated on earth alone and has not (yet) successfully colonized another planet. Mars is, and always was, lifeless

The theory states that after they arrive safely from space, they became protein from amino acids and eventually life (if not already). They would then grow and reproduce, possibly in a warm pond/ocean or underground.

See Davies' Superbugs for further information on Panspermia