*2.3.3 Terrestrials*

Terrestrials are exoplanets that are similar in structure to the inner planets of the Solar System including Mercury, Venus, Earth, and Mars. These exoplanets have compositions that are dominated by elements including carbon, oxygen, magnesium, silicon, and iron [9, 26]. Terrestrials are interesting because these bodies present the possibility of finding a planet similar to Earth that could support life.

A sub-classification of terrestrials is Super-Earths. Super-Earths are rocky planets that have a mass greater than the Earth, but usually defined to be less than 10 Earth masses. Given their mass, some Super-Earths may be similar to Solar System planets Neptune and Uranus [23].

Exo-Earths are terrestrial exoplanets that have similarities to Earth in terms of their mass, radius, and temperature. Their orbits would reside within the habitable zone where liquid would water could exist [23].

Chthonian Planets are a proposed class of exoplanets that began as gas giants. During subsequent evolution, their orbits were altered to bring these planets in proximity to their host star. This proximity caused their atmosphere to be removed with only the rocky core remnant remaining. Given their similarity, some Super-Earths could be Chthonian Planets [23].
