Comparative Planetology: The Terrestrials

These flashcards cover key vocabulary terms related to comparative planetology, focusing on the characteristics and formation of terrestrial planets and the Moon.

Orbital radius (AU)

The average distance from a planet to the sun measured in astronomical units.

Equatorial diameter (km)

The diameter of a planet measured at its equator, indicating its size.

Sidereal rotation period

The time it takes for a planet to complete one full rotation on its axis relative to the stars.

Surface gravity (m/s²)

The acceleration due to gravity experienced at the surface of a planet.

Escape speed (km/s)

The minimum speed needed for an object to break free from a planet's gravitational pull.

Crater

A bowl-shaped depression formed by the impact of a meteoroid or other celestial object.

Volcanism

The process of eruption of molten rock, gases, and other materials from a planet's interior to its surface.

Obliquity (degrees)

The angle between a planet's rotational axis and its orbital axis.

Giant-Impact theory

A hypothesis explaining the Moon’s formation from a collision between the early Earth and a Mars-sized body.

Eccentricity

A measure of how much an orbit deviates from being circular; values close to 0 indicate a more circular orbit.

Exosphere

A thin layer of gases surrounding a planetary body, where the atmosphere transitions to space.

Mare

Large, dark, basaltic plains on Earth’s Moon formed by ancient volcanic eruptions, often referred to as 'seas'.

Density (water = 1)

A comparative measure of a planet's density relative to water, where water has a density of 1.

Thermal energy

The energy that originates from the temperature of matter, often produced by the movement of tectonic plates.

Planetary core

The innermost layer of a planet, typically composed of metal and responsible for a planet's magnetic field.