Strangers in a Strange Land
2013 Dale Alan Bryant
It is felt by many anthropologists, astronomers, chemists, geneticists and zoologists that life on this planet didn't actually originate here; the early Earth wasn't conducive, chemically, to conditions to support life. This thinking has even helped to spawn a relatively new multidisciplinary science (in which I was recently certified), known as Astrobiology, or, the study of the possibilities of life of extraterrestrial origin and how it might relate to Earth-based life forms.
On the early Earth, there wasn't enough oxygen present in the atmosphere to sustain organic compounds or support anything like the multicellular, known-earthly forms of life; also, there was too much water and not enough dry land (today, 75% of the globe is covered by ocean; four-billion years ago, only about 3% of the Earth was terra firma). However, conditions on Mars, our second-nearest planetary neighbor after Venus, were ideal for the necessary organic compounds to have formed. It is now known that large quantities (on the order of ‘oceans’) of liquid water once flowed in ancient Martian rivers. The remaining, now-dried riverbeds have been documented, both photographically by orbital laboratories and chemically by analysis by several roving laboratories. These compounds would have traveled to Earth via the meteoroidal material produced by the ejecta from both asteroid impacts and volcanic eruptions on the Martian surface. Having quickly and easily achieved escape velocity, much of this material would have eventually assumed an orbit around the Earth and eventually impacted the surface. From there, evolutionary processes, e.g., natural selection, would have driven and shaped them to their present, earthly configurations.
Hard as this scenario may be to imagine, the proof that the solar system shares its materials in this way is in the many confirmed fragments of the Martian crust in the form of meteorites that have been found on Earth, particularly lying atop the Antarctic ice-sheet as well as confirmed fragments from the asteroid Vesta and the Moon (I've seen these for myself), that were transported here by the same processes. Accordingly, it shouldn’t be any more difficult to imagine life having emerged elsewhere than it is to imagine it having emerged here on Earth.
This sharing of materials in the solar system is due to repeated bombardment and the overlapping gravitational fields of its many components, e.g., planets, moons, comets, asteroids, etc. In the case of comets, their materials are primordial, or, original, left over from the very formation of the Solar system. Moreover, the chemical composition of early Mars. as mentioned, has been calculated back with great accuracy, thanks mainly to JPL’s Mars Science Laboratory (Curiosity) rover. The chemical signature of each body in the solar system is unique to that particular body (as can be determined even by remote analysis by spectroscope) and its presence here on Earth sticks out like a sore thumb.
But Mars and Earth were formed at the same time; why should they be so different? Simply put, Mars is geologically older than Earth. Not in that Earth and Mars have different times of origin, but in that Mars is one-third the mass of the Earth and this is the cause of many geological differences between the two. Lower mass means a more rapidly cooling interior and therefore declining geologic activity (volcanism), essential for life on Earth. Mars would have lost most of its atmosphere earlier due to its weaker gravity, along with its, at one time plentiful, stores of liquid water because a certain atmospheric pressure is necessary to sustain H2O in the liquid state (the average atmospheric pressure on Earth is 15lbs./p.s.i.; on Mars it is 1.5lbs./p.s.i.). However, interestingly, liquid H2O can and does, exist on the red planet for brief periods- In essence, Mars has aged more rapidly than Earth – but that doesn’t mean that it didn’t thrive at one time. Ancient Mars had a robust atmosphere containing more oxygen than Earth currently does. Just like Earth, Mars’ regolith (rocky surface debris) is a record of its past. Mars did have an atmosphere supporting lots of liquid water and these two things are known to support Earth life. In fact, within its first 45-days of operation, the Curiosity rover had already completed its primary mission of determining whether Mars once had all the necessary conditions to support life. Curiosity confirmed this. It would not be too surprising if, one day, Martian fossils are found buried beneath its surface; it is possible that Mars was once home to a civilization of some kind.
Whether Mars is the origin of life here on Earth, or whether it once supported life of its own – or both – seems certain; so, like strangers in a strange land - we may all be Martians! Whether or not we will one day find intelligent life on Earth remains, as yet, to be seen...