Planet consists mostly of planets the size of Neptune and smaller, down to smaller than Mercury. There are types of planets that do not exist in the Solar System: super-Earths and mini-Neptunes, which could be rocky like Earth or a mixture of volatiles and gas like Neptune—a radius of 1.75 times that of Earth is a possible dividing line between the two types of planet. There are hot Jupiters that orbit very close to their star and may evaporate to become chthonian planets, which are the leftover cores. Another possible type of planet is carbon planets, which form in systems with
Outer Planet Flagship Mission Outer Planet Flagship Mission The Outer Planet Flagship Mission is a type of NASA program to research larger size missions to the outer solar system, and some examples of this type of mission are Galileo or Cassini-Huygens. In 2013 after encounter some technical issues and funding in the early 2010s, development was paused although overall research continued. One issue is the other big NASA missions such as in astrophysics and another is availability of RTG's One proposal was a joint mission between NASA and ESA to send a probe to study the icy satellites of the outer Solar System. There