Earthlike planets

Speculation about life on other planets probably began when humans discovered that the Earth Is not unique. We know that several other planets of the solar system bear at least some resemblance to our own. Why, then, should there not be life on Mars, or Venus, or perhaps on undiscovered Earthlike planets orbiting some other star ... 

The structure of energy makes the emergence of life inevitable if the proper reaction conditions prevail. This, the determinist s clarion always sounds true because its score is chiseled into the structure of energy manifest in atoms. It also is a useful sound for it tells us that, if we should learn how to get to another earthlike planet, our test for life should be based upon the very principles that led to life on this planet. 

At least one other Earthlike planet has been discovered, and it is possible that many more may exist. In 2011, NASA s Kepler space telescope discovered a planet (named Ke-pler-22b for now) orbiting a star about 600 light years from Earth (rectdl that a light year is the distance light travels in one year, so that s extremely far away). This planet is estimated to be about 2.4 times the size of Earth and exists in an area known as a habitable zone, which means that it is in an area that could potentially serve as a host to life as we know it. Little is known at this time about the atmosphere or composition of this planet, but it is nonetheless interesting that it exists. How many more Earthlike plan-... 

Unlike water, there is no cold trap for methane or H2 on an earthlike planet. Rather, methane and H2 diffuse to the top of the atmosphere and disassociate from photolysis. The H then escapes to space. The remaining carbon makes it back to the surface where it eventually reacts to form more methane. The hydrogen to do this ultimately comes from water. The net reaction is equivalent to disassociating water and having the hydrogen escape to space. 

Photosynthesis supplied and maintains the oxygen we breathe. We must look to the Earth s interior and to space to see why this bounty exists. One must look at the other reservoirs, as the oxygen in the air is only 1.6% of the total available oxygen. Like with the American Revolution, it is futile to search for a single simple cause. Rather, there is interplay of multiple processes, all of which are expected on an earthlike planet. I begin with the long-term cycles. 

The range of characteristics of planets is likely to exceed our experience with the planets and satellites in our own Solar System by far. Models of planets more massive than our Earth - rocky Super-Earths - need to consider the changing atmosphere structure, as well as the interior structure of the planet. Also, Earthlike planets orbiting stars of different spectral type might evolve differently. Modeling these influences will help to optimize the design of the proposed instruments to search for Earth-like planets. 

Grenfell JL, Stracke B, von Paris P, Patzer B, Titz R, Segura A, Rauer H (2007) The resptuise of atmospheric chemistry on earthlike planets around F, G and K Stars to small variations in... 

The physical processes that have allowed oxygen in our air are those of an earthlike silicate planet I extrapolate in generalities from biology. Life can evolve biochemical pathways for multiple modes of photosynthesis. 

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