| First is the classical scenario in which the giant planets begin roughly in their final locations and the disk of planetesimals and embryos in the terrestrial planet region extends all the way into the outer asteroid belt region. |
| Liquid water is one of the most important materials affecting the climate and habitability of a terrestrial planet. |
| Jupiter is orbited by Io, a body wracked by intense volcanism, while Saturn's largest moon, Titan a body larger than the terrestrial planet Mercury exhibits a primitive atmosphere denser than that of Earth. |
| Scientists see Titan as a complex world, closer to a terrestrial planet than a moon typical of the outer planetary systems. |
| Anglada-Escudé and his colleagues estimate that Proxima b is at least 1.3 times as big as Earth and is most likely a terrestrial planet, with a surface. |
| Statistically speaking, this means that a randomly placed alien outside the solar system has a 1 in 40 chance of observing a single terrestrial planet in our solar system. |
