Oxygen is one of the essential criterions for life to exist. Or so has been thought till date.
Now, a Japanese researcher has dispelled that notion by presenting a novel hypothesis arguing that it could be possible for far-off planets to hold huge quantities of abiotic or non-biologically produced oxygen.
Norito Narita, assistant professor at the Astrobiology Center of National Institutes of Natural Sciences (NINS), has brought to light the possibility of production of abiotic oxygen through the photocatalytic reaction of titanium oxide, known to be abundant on distant planets and the moon.
According to Narita, “To search for life on extrasolar planets through astronomical observation, we need to combine the knowledge from various scientific fields and promote astrobiological researches to establish the decisive signs of life.”
Narita also argues the necessity of looking for new biomarkers besides oxygen from the present result, although oxygen still stands as one of possible biomarkers.
On Earth, plants continuously produce oxygen through photosynthesis.
Therefore, if a planet has an environment similar to the Sun-Earth system, a continuous photocatalytic reaction of titanium oxide on about 0.05 percent of the planet’s surface could enable it to produce the amount of oxygen found in the Earth’s current atmosphere.
The team also estimated the amount of possible oxygen production for habitable planets around other types of host stars with various masses and temperatures.
Another remarkable finding was the discovery that even in a least efficient production case of a low-temperature star, the photocatalytic reaction of titanium oxide on about 3 percent of the planetary surface could maintain this level of atmospheric oxygen through abiotic processes.
The author also noted that it was possible for a habitable extrasolar planet to maintain an atmosphere with Earth-like oxygen, even without organisms present to perform photosynthesis.
The paper, which appeared in the Scientific Reports journal, is a good example of an inter-disciplinary study which combines knowledge from different fields of science and promote astrobiology in the search for life on extra-solar planets.