Question

1. To boldly go. (a) It can be argued that if life were to exist elsewhere in the universe, it would require some process like photosynthesis. Why is this argument reasonable? (b) If the starship Enterprise were to land on a distant planet and find no measurable oxygen in the atmosphere, could the crew conclude that photosynthesis is not taking place?

2. A crucial prereq. Human beings do not produce energy by photosynthesis, yet this process is critical to our survival. Explain

Answer 1

1a)....Photosynthesis. is important to living organisms because it is the number one source of oxygen in the atmosphere. ... Green plants and trees use photosynthesis to make food from sunlight, carbon dioxide and water in the atmosphere: It is their primary source of energy...... If there was no photosynthesis, plants and animals likely could not exist. In addition the atmosphere would have very little oxygen because photosynthesis releases a large amount of oxygen into the air. ... Otherwise, the Earth would be a pretty barren lifeless place without photosynthesis....

1b). No plants is not the only basis of oxygen in other plants ... as A recent study conducted by National Observatory in Japan says that Titanium oxide photcatalysis is abiotic source of oxygen...... The Earth's atmosphere contains oxygen because plants continuously produce it through photosynthesis. This abundant supply of oxygen allows life forms like animals to flourish. Therefore, oxygen had been thought to be an essential biomarker for life on extrasolar planets. But now, a research assistant professor Norio Narita of the Astrobiology Center of NINS, which was founded in April 2015, and an associate professor Shigeyuki Masaoka, of the Institute of Molecular Science of NINS, have presented a novel hypothesis that it could be possible for planets to have large quantities of abiotic (non-biologically produced) oxygen........

Until now, it had been thought that if a planet has oxygen, that must mean that some form of plants are producing it through photosynthesis. Therefore, it had been assumed that when searching for signs of life on habitable extrasolar planets, the presence of oxygen in the atmosphere could be considered a definitive biomarker. However, non-biological chemical reactions can also affect atmospheric compositions of extrasolar planets. Now, the research team led by Dr. Narita has shown that, abiotic oxygen produced by the photocatalytic reaction of titanium oxide, which is known to be abundant on the surfaces of terrestrial planets, meteorolites, and the Moon in the Solar System, cannot be discounted.

For a planet with an environment similar to the Sun-Earth system, continuous photocatalytic reaction of titanium oxide on about 0.05 % of the planetary surface could produce the amount of oxygen found in the current Earth's atmosphere. In addition, the team estimated the amount of possible oxygen production for habitable planets around other types of host stars with various masses and temperatures. They found that even in the least efficient production case of a low-temperature star, the photocatalytic reaction of the titanium oxide on about 3% of the planetary surface could maintain this level of atmospheric oxygen through abiotic processes. In other words, it is possible that a habitable extrasolar planet could maintain an atmosphere with Earth-like oxygen, even without organisms to perform photosynthesis......

2).Ultimately, all of the carbon atoms of which we are made, not just carbohydrates, enter the biosphere through the process of photosynthesis . Moreover, the oxygen that we required is produced by photosynthesis......