Mercury (planet)
Mercury is one of four terrestrial planets in the Solar System, and is a rocky body like Earth. It is the smallest planet in the Solar System, with an equatorial radius of . Mercury is also smaller—albeit more massive—than the largest natural satellites in the Solar System, Ganymede and Titan. Mercury consists of approximately 70% metallic and 30% silicate material. Mercury's density is the second highest in the Solar System at 5.427 g/cm, only slightly less than Earth's density of 5.515 g/cm. If the effect of gravitational compression were to be factored out from both planets, the materials of which Mercury is made would be denser than those of Earth, with an uncompressed density of 5.3 g/cm versus Earth's 4.4 g/cm.
Gliese 1132
As of June 12, 2018, there are two confirmed planets and one candidate planet orbiting GJ 1132. Gliese 1132 b is the innermost planet of the Gliese 1132 system, as well as the smallest. It is very similar in size and mass to Earth, with a radius of 1.13 and a mass of 1.66 . It is slightly denser than Earth with 30% more surface gravity, meaning it has a rocky composition. Despite its physical similarities to Earth, it is considered too hot to be habitable, getting 19 times more sunlight due to its 1.6 day orbital period. In April 2017, it was revealed that the planet has an atmosphere, potentially rich in water vapor and methane.