Planetary human habitability
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Planetary human habitability refers specifically to the conditions/parameters needed to support human life on so-called habitable planets or on so-called habitable moons.
The planet Earth's temperature extreme records are:
- The hottest temperature measured was 57.8°C (136°F) at El Azizia, Libya on 1922-09-13
- The coldest temperature measured was -89.2 °C (-128.5 °F), recorded on 21 July 1983 in Vostok, a Russian Antarctic research station located at the center of the East Antarctic Ice Sheet. Some scientists like to use the terms "Earth-Like" and "habitable" for the sake of popular acceptance or to improve a theory's apparent validity [citation needed], but as can be seen from these records, even the planet Earth itself can be inhospitable to human life. For example, each year multitudes of people die from dehydration due to extreme heat.[citation needed] Similarly, many people freeze to death every year in sub-zero winter temperatures.[citation needed]
Human life is rare
While human life on Earth is intelligent, developing advanced technologies such as communication satellites, intelligent life in our galaxy as a whole is relatively rare. Some estimates suggest that about 1% of all Sun-like stars possess Earth-like planets. [citation needed] The nearest star with intelligent or human-like life on an Earth-like planet is estimated to be at least 200 light years away[citation needed]. Complicating the issue is that the development of human life was a very complex, time-consuming process[citation needed]. Some estimates suggest that intelligent life requires at least 3.5 billion years in order to develop to human-like levels.[citation needed] Furthermore, the star itself must not be too massive, else the star will die before intelligent life can evolve.
Factors
In order to support human-like life, a planet must orbit around a star that falls somewhere between Spectral types F and K[citation needed], and it must be located at a distance from its parent star that falls within the star's habitable zone. The planet must be somewhat similar in characteristics to Earth, including an atmosphere with a pressure of at least 900 but less than 3000 millibars[citation needed], suitable surface gravity, suitable partial pressures of gases, adequate surface temperature, an adequate amount of oxygen, an axial tilt of between 10 and 30 degrees[citation needed], and of course a suitable climate. The mass should be between one-half and 3 times that of Earth[citation needed] and the diameter somewhere between 10,000 and 15,000 km[citation needed]. The planet must posess a mixture of water and forests[citation needed]. It may also be helpful for the planet in question to have at least one large moon, to minimize the variation in climate and axial tilt.[citation needed]
Parameter list
- Extremes of temperature:
- Hypothermia [1]- Cryosphere variance and size.
- Dehydration - Hydrosphere size.
- Habitable/Survivable atmosphere pressures.
- Habitable/Survivable gravity range
- Habitable/Survivable Hydrosphere size and precipitation.
- Habitable/Survivable atmopshere constituents (IPP).
- Insolation vs. Greenhouse gases
- Eccentricity, affects of: Seasonality, Cryosphere size variability, Desert sizes.
- Axial tilt, affects: mild or extreme seasonality, cryosphere size, desert sizes.
Search
See main articles: Methods of detecting extrasolar planets, Extraterrestrial life
Finding extraterrestrial life is a task which has, thus far, met with limited success.[citation needed] Finding any sort of life first requires finding stars with orbiting planets, then narrowing those down to stars with planets that have suitable characteristics as outlined above. The latter part has proven to be a very difficult task as well. [citation needed] Once a suitable planet has been found, astronomers may then use radio telescopes or other technology to observe the planet. In the meantime, the only method we have for searching for exterrestrial life, aside from alleged UFO encounters, is to search the sky using radio telescopes, picking and choosing interesting targets, as is the case with SETI and SETI@home.
Habitable moons
According to astronomers, there may also be habitable moons orbiting around Jupiter-like gas giants.[citation needed] Unlike planets, a moon may not have to lie within the main star's habitable zone, because a moon may pick up heat due to (or in addition to) tidal forces from its parent planet, as with Jupiter's moons Io and Europa. The moon must, however, orbit far enough away from the planet's radiation belt or it may not develop life.[citation needed] Some scientists believe that these kinds of moons may be the most likely candidates for extraterrestrial life.[citation needed]
References
- ^ [www.usps.org/national/ensign/uspscompass/compassarchive/compassv1n1/hypothermia.htm]
See also
- Human
- Human ecology
- Behavioral ecology
- Ecophysiology
- Deep ecology
- Planetary habitability
- Biosphere
- Hydrosphere
- Temperature extremes
- Marginal value theorem
- Rare Earth hypothesis
- Drake equation
- Fermi paradox
- Plenitude principle
- Anthropic principle
- Mediocrity principle
- Extraterrestrial life
- Happy Planet Index
- Earth's atmosphere
- Celestial body atmosphere