As far as it is known Earth is the only planet suitable for life, with a good temperature, liquid water, and breathable air. Nevertheless, scientist have been searching for similar planets, with little progress thus far. Which is why they are going for the next best thing, Mars and a moon of Saturn, Titan.

Titan is the only moon with conditions similar to Earth, with an atmosphere and clouds. However, these factors are still quite some way from Earths, as the atmosphere consists of about 95% Nitrogen and 5% Methane. Similarly, the clouds, rain, and lakes are made up of methane and ethane. Furthermore, methane contributes to the greenhouse effect on Titan, while water vapor and carbon dioxide are the predominant greenhouse gases on Earth. When the suns rays hit the nitrogen and methane it causes chemical reaction between the two which then create more organic compounds. Some of these products then become carbon chain anions, which are thought to be the building blocks of more complex molecules. These, in turn, are thought to be the basis for the earliest forms of life.

Nevertheless, Titans low temperature of -180 degrees Celsius and complete lack of oxygen in the atmosphere make it an uninhabitable moon. However, scientist have speculated that other life forms could exist that do not rely on water for life, instead they might rely on methane and ethane. They might be able to produce energy from the reaction between acetylene and hydrogen, which are known to be on Titan, through the following exothermic reaction:

C₂H₂ + 2 H₂ C₂H₆ H = 311 kJ/mol

Nevertheless, there have not been any signs of life on Titan. Such low temperatures would make it hard as chemical reaction get slow. Additionally, it takes a very long time to travel to Titan and such technology had not yet been developed.

Mars, on the other hand, is much closer. It would take about seven months to travel to mars. However, Mars too is unsuitable for life with not enough oxygen to breathe and with lot of harmful rays from the sun and little to no protection from them. Furthermore, it is mostly made up of iron dust and rocks, giving it its rusty color. Mars also has an atmosphere about 100 times thinner than Earths which means humans cannot breathe nor is it warm enough for them. In addition, mars has a lack of organic material. However, it does have a lot of iron. Microorganisms, through a reduction-oxidation reaction, can absorb energy. Iron (Fe²⁺, Fe³⁺), hydrogen (H₂), perchlorate (ClO₄^-), and carbon monoxide (CO) are all electron donors and acceptors. Researchers have developed a great amount of technology to sustain life on Mars, such as space suit for the low pressure and dome bubbles that can provide breathable air and protection from the suns harmful rays. They are also trying to find ways to get oxygen from carbon dioxide and water from rocks.

Titan is still being studied, however, because there are many planets similar to Titan. Thus, understanding Titan and potential ways to live on the planet could apply to those planets as well. The study of these two potential candidates for habitability can possibly provide insight to the past, present, and future of life on Earth, with Titan being the past, Earth being the present, and Mars being the future.

After reading the article it seems that chemistry is applicable to other planets as well. It would also seem that, thus far, it is valid. If it were not valid all the progress that has been achieved regarding Mars and Titan will have been for nothing. However, the chemistry of living organisms could differ, if such organisms exist on other planets

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