Extraterrestrial liquid water extrasolar planetary systems appear to have very different compositions to the Solar System, though there is probably sample bias arising from the detection methods. Liquid water has a distinct absorption spectroscopy signature compared to other states of water due to the state of its hydrogen bonds. Despite the confirmation of extraterrestrial water vapor and ice, however, the spectral signature of liquid water is yet to be confirmed outside of Earth. The signatures of surface water on terrestrial planets may be undetectable through thick atmospheres across the vast distances of space using current technology. Seasonal flows on warm Martian slopes, though
Planetary core Planetary core The planetary core consists of the innermost layer(s) of a planet; which may be composed of solid and liquid layers. Cores of specific planets may be entirely solid or entirely liquid. In the Solar System, core size can range from about 20% (Moon) to 85% of a planet's radius (Mercury). Gas giants also have cores, though the composition of these are still a matter of debate and range in possible composition from traditional stony/iron, to ice or to fluid metallic hydrogen. Gas giant cores are proportionally much smaller than those of terrestrial planets, though theirs can be considerably