The habitability of natural satellites describes the study of a moon's potential to provide habitats for life, though is not an indicator that it harbors it. Natural satellites are expected to outnumber planets by a large margin and the study is therefore important to astrobiology and the search for extraterrestrial life. There are, nevertheless, significant environmental variables specific to moons.
It is projected that parameters for surface habitats will be comparable to those of planets like Earth - stellar properties, orbit, planetary mass, atmosphere and geology. Of the natural satellites in the Solar System's habitable zone —the Moon, two Martian satellites (though some estimates put those outside it) and numerous Minor-planet moons — all lack the conditions for surface water. Unlike the Earth, all planetary mass moons of the Solar System are tidally locked and it is not yet known to what extent this and tidal forces influence habitability.
Research suggests that deep biospheres like that of Earth are possible. The strongest candidates therefore are currently icy satellites such as those of Jupiter and Saturn—Europa and Enceladus respectively, in which subsurface liquid water is thought to exist. While the Lunar surface is hostile to life as we know it, a deep Lunar biosphere (or that of similar bodies) cannot yet be ruled out deep exploration would be required for confirmation.
Exomoons are not yet confirmed to exist and their detection may be limited to transit-timing variation which is not currently sufficiently sensitive. It is possible that some of their attributes could be found through study of their transits. Despite this, some scientists estimate that there are as many habitable exomoons as habitable exoplanets. Given the general planet-to-satellite(s) mass ratio of 10,000, gas giants in the habitable zone are thought to be the best candidates to harbour Earth-like moons.
Tidal forces are likely to play as significant a role providing heat as stellar radiation.
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vignette|Vue d’artiste représentant Kepler-186 f, une exoplanète qualifiée de Terre jumelle. alt=La Terre |vignette|La planète Terre vue depuis Apollo 17. Une planète analogue à la Terre ou analogue terrestre (en anglais Earth analog), (planète) jumelle de la Terre (Earth Twin), Terre jumelle (Twin Earth), seconde (ou deuxième) Terre (Second Earth), Terre extrasolaire ou exo-Terre (Alien Earth), ou , ou encore planète (de type) terrestre (Earth-like planet ; distincte de planète tellurique, terrestrial planet en anglais), est une planète ayant des caractéristiques et des conditions semblables à celle de la planète Terre.
The theorized habitability of red dwarf systems is determined by a large number of factors. Modern evidence indicates that planets in red dwarf systems are unlikely to be habitable, due to their low stellar flux, high probability of tidal locking and thus likely lack of magnetospheres and atmospheres, small circumstellar habitable zones and the high stellar variation experienced by planets of red dwarf stars, impeding their planetary habitability.
vignette|Vue d'artiste depuis une exolune. Sa planète hôte ainsi que son étoile sont visibles. vignette|Vue de Pandora et Polyphème de l'univers d'Avatar. Une lune extrasolaire, exolune, un satellite extrasolaire, ou encore un exosatellite, est un satellite naturel qui orbite autour d’une exoplanète ou d'un autre corps extrasolaire plus grand que lui. Bien qu'aucun objet de ce type n’ait encore été formellement découvert, il est raisonnable de penser que leur existence est très probable et qu'ils existent en très grand nombre, d'après l'étude empirique des satellites naturels de notre Système solaire ; quelques candidats sont déjà suspectés d'être des exolunes.
Explore la définition, la formation, les méthodes de découverte et la recherche de la vie des exoplanètes, y compris l'histoire des découvertes et l'équation de Drake.
Explore le contenu de la matière dans l'univers, y compris la cartographie de la matière noire et l'exploration des exoplanètes.
Explore la force gravitationnelle, le potentiel énergétique, les orbites satellitaires et le système solaire.
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Dwarf galaxies in groups of galaxies provide excellent test cases for models of structure formation. This led to a so-called small-scale crisis, including the famous missing-satellites and too-big-to-fail problems. It was suggested that these two problems ...
As part of a long-term project to determine abundances and astrophysical properties of evolved red stars in open clusters, we present high-precision DDO photoelectric observations for a sample of 33 red giant candidates projected in the fields of nine Gala ...