Is Mercury a volatile-rich planet?

Mercury: the planet and its orbit

The planet closest to the Sun, Mercury, is the subject of renewed attention among planetary scientists, as two major space missions will visit it within the next decade. These will be the first to return to Mercury, after the flybys by NASA’s Mariner 10 spacecraft in 1974–5. The difficulties of observing this planet from the Earth make such missions necessary for further progress in understandi...

Mercury: Planet of Fire and Ice

Mercury: Introduction to an End-member Planet

This Chapter introduces the major themes of this book. In many ways, Mercury is an extreme planet, and thus it provides a unique benchmark for testing our theories about the origin and evolution of other (particularly terrestrial) planets. Emphasis is given to synthesizing and critiqueing the book's chapters on the planet's origin, its metal-rich composition, its thermal and geophysical evoluti...

Mercury: Planet of Fire and Ice

Mercury’s Exosphere: Mercury’s atmosphere, really an exosphere, is tenuous: The total mass of all known constituents is approximately 15 orders of magnitude less than Earth’s. An exosphere is an atmosphere that has such a low density that collisions between constituents are negligible. Thus, according to Smyth and Marconi, “Mercury has multiatmospheres, with each separate atmosphere forming ind...

What is a planet?

A planet is an end product of disk accretion around a primary star or substar. I quantify this definition by the degree to which a body dominates the other masses that share its orbital zone. Theoretical and observational measures of dynamical dominance reveal gaps of four to five orders of magnitude separating the eight planets of our solar system from the populations of asteroids and comets. ...