Paper Review on “Under Pressure: How the Density of Exoplanets’ Atmospheres Weighs on the Odds for Alien Life”

Paper Review on “Under Pressure: How the Density of Exoplanets’ Atmospheres Weighs on the Odds for Alien Life”
The article “Under Pressure: How the Density of Exoplanets’ Atmospheres Weighs on the Odds for Alien Life” explorers how atmospheric pressure on earthlike planets would leads to the planets being habitable. Anyone who would wish to estimate habitability according to Giovanni Vladilo of the Trieste Astronomical Observatory in Italy and lead author of the paper published in the Astrophysical Journal should put atmospheric pressure into consideration as atmospheric pressure affects the liquid water temperature that is used to define habitability (Hadhazy, 2013).
Atmospheric pressure is the air molecules that weigh heavily on us at around one kg per square centimeter, but as humans, we cannot feel it as we have adapted to live in these conditions. Atmospheric pressure impacts water boiling point when it changes from liquid to gas. At higher attitudes, the atmospheric pressure is lower than at sea levels and water boils at lower temperatures and vice versa. According to Vladilo, this happens because temperature is an indicator of how fast molecular motion is, boiling point occur only when the molecules are fast enough to allow other molecules to escape from each other. Pressure keeps the molecules tight and at high pressures, high temperatures are needed to allow evaporation (Hadhazy, 2013).
In Vladilo’s paper, he and his colleagues modeled a planet similar to earth in terms of atmospheric pressure then run computer simulations which varied the planets atmospheric pressure from 100 to 6 times more than earths. The distance from the planets sun like star was also varied from two thirds to an additional third. The habitability of these planets were gauged on the latitudes that could have surface the atmospheric pressure increased the habitable zone increased in width. When the atmospheric pressure was lowered to about a tenth that of earth, the outer edge of the habitable zones reached two percent further than earths but as the atmospheric pressure were increased to thrice that of earth the habitable zone increased to 18 percent (Hadhazy, 2013).
These results indicate that a planet similar to earth with a higher atmospheric pressure and closer to the sun by 5 percent would be habitable but a lower pressure planet would not be habitable. Higher pressure is denser and so they transport heat better and thus promote a greenhouse effect where atmospheric gases absorb heat. Plants that are further from their stars than how the earth is from the sun receive less sunlight than earth. They trap heat better at higher atmospheric pressures and their polar zones retain water than freezing it. Thus, this planet will remain warm though it is far from its star. On the hand, exoplanets with lower atmospheric pressure and closer to their star will have its water boil as at lower atmospheric pressure water boils at a lower temperature (Hadhazy, 2013). At higher atmospheric pressure where the planet is closer to its star, the water will not boil and the planet could still be habitable.
Although these planets that are closer to their star with higher atmospheric pressure are habitable, the temperatures are too high for humans and other thermophiles to survive. What would survive in such a planet are bacteria that thrive in temperatures higher than 45 degrees Celsius. Humans would survive in a planet that is further from the sun. Atmospheric pressure also affects biodiversity. High temperature exoplanets would have almost similar surface temperatures due to efficient transfer of heat among their latitudes and the life forms living in these exoplanets would be few as they would need to be adapted to the similar temperatures. On the other hand, low pressure exoplanets will have more varied temperatures than earth and they would have many more life forms than earth with organisms more adapted to their varied temperatures (Hadhazy, 2013).
Habitable zones that depend on pressure are only studied academically as the zones of exoplanets being studied do not have atmospheric pressure as one of their components but Vladilo believes that working with super earths which are planets larger than earth is where the atmospheric pressure insights could be applied. Atmospheric pressures of planets through observations can only determine the chemical properties of these pressures. The major reason for this is that exoplanets development of pressures and the densities they develop is not well understood (Hadhazy, 2013). Different planets with different atmospheric pressures have different densities. Vladilo and his colleagues plan to do a follow up of this model.
The information in this article is relevant to astrobiology as it adds to the knowledge of the subject. Terrestrial life is believed to exist in an environment where there is water and in modern day, astrobiologists concentrate on the habitual zone where the water in this zone does not freeze or boil away. Such a zone according to the article can be achieved by increasing atmospheric pressure in an earthlike planet. The fact that earth like planets with higher atmospheric pressures could be habitable will lead to more astrobiologists doing more research on this subject. The article also goes on to explain the kind of environment that would be necessary for life to survive in high atmospheric pressures and explains the extremes that would lead to life dying in this environment. Another area of astrobiology that the article looks into is the kind of life that can survive in high atmospheric environment (Hadhazy, 2013). The writer also explains how far the habitable environment would stretch and areas not habitable under these circumstances.
It is obvious that following this article more astrobiologists will research more on the possibility of habitable environment in higher atmospheric pressures. The writer also asserts that the atmospheric pressure properties are not well known and the formation of atmospheric pressures and their densities are not well understood as different planets have different densities. The area of atmospheric pressure has not been extensively studied and it will be exciting to see what other astrobiologists can research and tell the general public on this topic (Hadhazy, 2013).
One of the critic of the article is that the writer use of planets similar to earth in terms of humidity, size and all other aspects is not rational this kind of planet would be difficult to find out there in the space as all the other planets that have been discovered are not similar to earth.
Another critic of the article is that atmospheric pressure cannot be controlled or predicted and we don’t know the source of atmospheric pressure very little has been studied or known about atmospheric pressure. Vladilo and his colleagues do not include density that comes with atmospheric pressure in his theory. Different atmospheric pressures come with different densities and this can affect the habitability of the planet even with the right atmospheric pressure at the right distance from the sun.
Hadhazy, A. (2013). Under Pressure: How the Density of Exoplanets’ Atmospheres Weighs on the Odds for Alien Life, accessed 26 March 2014,


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