Extraterrestrial Life - Planetary Habitability in The Solar System

Planetary Habitability in The Solar System

See also: Planetary habitability and Natural satellite habitability

Some bodies in the Solar System have been suggested as having the potential for an environment that could host extraterrestrial life, particularly those with possible subsurface oceans. Though due to the lack of habitable environments beyond Earth, should life be discovered elsewhere in the Solar System, astrobiologists suggest that it will more likely be in the form of extremophile microorganisms.

The planets Venus and Mars, along with several natural satellites orbiting Jupiter and Saturn, and even comets, are suspected to possess niche environments in which life might exist. A subsurface marine environment on Jupiter's moon Europa might be the most suitable habitat in the Solar System, outside of Earth, for multicellular organisms.

Panspermia suggests that life elsewhere in the Solar System may have a common origin. If extraterrestrial life was found on another body in the Solar System, it could have originated from Earth just as life on Earth may have been seeded from elsewhere (exogenesis). The Living Interplanetary Flight Experiment, developed by the Planetary Society launched in 2011 was designed to test some aspect of these hypotheses, but it was destroyed along with the carrier Fobos-Grunt mission. The first known mention of the term Panspermia was in the writings of the 5th century BC Greek philosopher Anaxagoras. In the nineteenth century it was again revived in modern form by several scientists, including Jöns Jacob Berzelius (1834), Kelvin (1871), Hermann von Helmholtz (1879) and, somewhat later, by Svante Arrhenius (1903). Sir Fred Hoyle (1915–2001) and Chandra Wickramasinghe (born 1939) were important proponents of the hypothesis who further contended that lifeforms continue to enter the Earth's atmosphere, and may be responsible for epidemic outbreaks, new diseases, and the genetic novelty necessary for macroevolution.

Directed panspermia concerns the deliberate transport of microorganisms in space, sent to Earth to start life here, or sent from Earth to seed new solar systems with life. The Nobel prize winner Francis Crick, along with Leslie Orgel proposed seeds of life may have been purposely spread by an advanced extraterrestrial civilization, but considering an early "RNA world" Crick noted later that life originating may have originated on Earth.

Proponents of Intelligent Design creationism (ID) attempting to evade objections to religious views being introduced into science education have claimed that the "designer" might be aliens rather than God. The movie "Expelled" promoting ID featured narrator Ben Stein asking Richard Dawkins about ID, and presented his response as an endorsement of panspermia. In an op-ed on 18 April 2008, shortly before the film opened, Dawkins explained that he was going through this science fiction scenario as the nearest ID got to science, to show that even if evidence could be detected that life on Earth had been seeded by intelligent aliens, the designers themselves would have had to have evolved.

In a virtual presentation on Tuesday, April 7, 2009, Stephen Hawking discussed the possibility of building a human base on another planet and gave reasons why alien life might not be contacting the human race, during his conclusion of the Origins Symposium at Arizona State University. Hawking also talked about what humans may find when venturing into space, such as the possibility of alien life through the theory of panspermia.