QUESTION = Why wouldn't life on another habitable planet look similar to Earth's?

GENERATION = There are two main reasons for this: 1. Life on other planets is a very different kind of life than life on Earth. The vast majority of life on Earth has evolved to live in environments that are very similar to Earth. The differences in lifeforms that result in different types of life on other planets are due to the various types of environments that life has evolved to live in. The types of environments that have evolved to live in on other planets are not the same as those that have evolved to live in Earth. The presence of water and other nutrients on other planets makes it much easier for life to develop in different environments, which in turn leads to different types of life. 2. Because of the differences in environments, there are very few chances that life will evolve in a way that is compatible with life on Earth. Therefore, the likelihood of life on other planets is very low. However, life on Earth has evolved to be able to survive in environments that are very similar to Earth, so it is very likely that life will evolve in a way that is compatible with life on Earth. If life is adapted to a different kind of life, then it is very likely that it will evolve in a way 

RETRIEVAL #0 = Astrobiology---other atoms, and the large silicon molecules are monotonous compared with the combinatorial universe of organic macromolecules. Indeed, it seems likely that the basic building blocks of life anywhere will be similar those on Earth, in the generality if not in the detail. Although terrestrial life and life that might arise independently of Earth are expected to use many similar, if not identical, building blocks, they also are expected to have some biochemical qualities that are unique. If life has had a comparable impact elsewhere in the Solar System, the relative abundances of chemicals key for its survival – whatever they may be – could betray its presence. Whatever extraterrestrial life may be, its tendency to chemically alter its environment might just give it away. Section::::Life in the Solar System. People have long speculated about the possibility of life in settings other than Earth, however, speculation on the nature of life elsewhere often has paid little heed to constraints imposed by the nature of biochemistry. The likelihood that life throughout the universe is probably carbon-based is suggested by the fact that carbon is one of the most abundant of the higher elements. Only two of the natural atoms, carbon and silicon, are known to serve as the backbones of molecules sufficiently large to carry biological information. As the structural basis for life, one of carbon's important features is that unlike 

RETRIEVAL #1 = Flammarion (Martian crater)---places, especially craters. This is exactly what would appear if a large lake had slowly evaporated. Moreover, since some layers contain gypsum, a sulfate which forms in relatively fresh water, life could have formed in some craters. 

RETRIEVAL #2 = Superhabitable planet---compliance with the profile seen previously, would be derived from its mass. Its denser atmosphere probably prevent the formation of ice sheets as a result of lower thermal difference between different regions of the planet. Also, it has a higher concentration of clouds, and abundant rainfall. Probably the vegetation is very different due to the increased air density, precipitation, temperature, and stellar flux. For the type of light emitted from the K-type stars, plants may take other colors than green. The vegetation would cover more regions than vegetation here on Earth, making this visible from space. In general, the climate of a superhabitable planet would be warmer, moist, homogeneous and have stable land, allowing life to extend across the surface without presenting large population differences, in contrast to Earth that has inhospitable areas such as glaciers, deserts and tropical regions. If the atmosphere contains enough molecular oxygen, the conditions of these planets may be bearable to humans even without the protection of a space suit, provided that the atmosphere does not contain excessive toxic gases, but would require some adaptation to the increased gravity, such as an increase in muscles and in bone density, etc. Section::::Abundance. Heller and Armstrong speculate that the number of superhabitable planets can far exceed that of Earth analogs: less massive stars in the main sequence are more abundant than the larger and brighter stars, so 

RETRIEVAL #3 = Circumstellar habitable zone---conservative habitable zone. Geothermal energy sustains ancient circumvental ecosystems, supporting large complex life forms such as "Riftia pachyptila". Similar environments may be found in oceans pressurised beneath solid crusts, such as those of Europa and Enceladus, outside of the habitable zone. Numerous microorganisms have been tested in simulated conditions and in low Earth orbit, including eukaryotes. An animal example is the "Milnesium tardigradum", which can withstand extreme temperatures well above the boiling point of water and the cold vacuum of outer space. In addition, the plants "Rhizocarpon geographicum" and "Xanthoria elegans" have been found to survive in an environment where the atmospheric pressure is far too low for surface liquid water and where the radiant energy is also much lower than that which most plants require to photosynthesize. The fungi "Cryomyces antarcticus" and "Cryomyces minteri" are also able to survive and reproduce in Mars-like conditions. Species, including humans, known to possess animal cognition require large amounts of energy, and have adapted to specific conditions, including an abundance of atmospheric oxygen and the availability of large quantities of chemical energy synthesized from radiant energy. If humans are to colonize other planets, true Earth analogs in the CHZ are most likely to provide the closest natural habitat; this concept was the basis of Stephen 

RETRIEVAL #4 = Ramaria---shown that "Ramaria" is not monophyletic, and that the characteristic coralloid shape has likely evolved several times from different ancestors. Section::::Species. BULLET::::- "R. abietina" BULLET::::- "R. acrisiccescens" BULLET::::- "R. acutissima" BULLET::::- "R. aenea" BULLET::::- "R. africana" BULLET::::- "R. albidoflava" BULLET::::- "R. albocinerea" BULLET::::- "R. alborosea" BULLET::::- "R. altaica" BULLET::::- "R. ambigua" BULLET::::- "R. americana" BULLET::::- "R. amyloidea" BULLET::::- "R. anisata" BULLET::::- "R. anziana" BULLET::::- "R. apiahyna" BULLET::::- "R. apiculata" BULLET::::- "R. araiospora" BULLET::::- "R. arcosuensis" BULLET::::- "R. argentea" BULLET:::: 

RETRIEVAL #5 = Exoplanetology---the Sun. The lack of water also means there is less ice to reflect heat into space, so the outer edge of desert-planet habitable zones is further out. Rocky planets with a thick hydrogen atmosphere could maintain surface water much further out than the Earth–Sun distance. Planets with larger mass have wider habitable zones because the gravity reduces the water cloud column depth which reduces the greenhouse effect of water vapor, thus moving the inner edge of the habitable zone closer to the star. Planetary rotation rate is one of the major factors determining the circulation of the atmosphere and hence the pattern of clouds: slowly rotating planets create thick clouds that reflect more and so can be habitable much closer to their star. Earth with its current atmosphere would be habitable in Venus's orbit, if it had Venus's slow rotation. If Venus lost its water ocean due to a runaway greenhouse effect, it is likely to have had a higher rotation rate in the past. Alternatively, Venus never had an ocean because water vapor was lost to space during its formation and could have had its slow rotation throughout its history. Tidally locked planets (a.k.a. "eyeball" planets) can be habitable closer to their star than previously thought due to the effect of clouds: at high stellar flux, strong convection produces thick water clouds near the substellar point that greatly 

RETRIEVAL #6 = Faint young Sun paradox---deposits. A primary sink for carbon in the Earth atmosphere is the carbonate-silicate cycle. It is however hard for CO to build up in the Martian atmosphere in this way because it would likely condense out before reaching partial pressures necessary to produce a sufficient greenhouse effect. An alternative possible explanation posits intermittent bursts of powerful greenhouse gases, like methane. Carbon dioxide alone, even at a pressure far higher than the current one, cannot explain temperatures required for presence of liquid water on early Mars. Section::::On other planets.:Venus. Venus's atmosphere is composed of 96% carbon dioxide, and during this time, billions of years ago, when the Sun was 25 to 30% dimmer Venus's surface temperature could have been much cooler, and its climate could have resembled current Earth's, complete a hydrological cycle – before it experienced a runaway greenhouse effect. Section::::See also. BULLET::::- Cool early Earth BULLET::::- Effective temperature – of a planet, dependent on reflectivity of its surface and clouds. BULLET::::- Isua greenstone belt BULLET::::- Paleoclimatology BULLET::::- Snowball Earth BULLET::::- Carbonate–silicate cycle BULLET::::- Gaia Hypothesis