Terrestrial Planets: Atmospheres, Water, and the Carbon Cycle

Terrestrial Planets

Small, rocky planets with relatively thin or no atmosphere; examples include Mercury, Venus, Earth, and Mars.

Craters

Cavities found on Mercury and the Moon, created by high-speed impacts.

Volcanism

The eruption of molten rock from the mantle to the surface, which shapes planetary landscapes.

Escape Velocity

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

Greenhouse Effect

The process by which greenhouse gases absorb and emit infrared radiation, warming a planet's surface.

Photodissociation

The breaking apart of molecules due to energy from ultraviolet light, allowing lighter atoms to escape a planet's atmosphere.

Carbon Cycle

The process involving the exchange of carbon among the atmosphere, oceans, soil, and living organisms, maintaining a balance in atmospheric CO2 levels.

Atmospheric Pressure

The force exerted onto a surface by the weight of the air above it, measured in bars.

Methane (CH4)

A hydrocarbon gas made of one carbon atom and four hydrogen atoms, which affects atmospheric dynamics.

Mass of Oxygen

16, indicating that oxygen is heavier than hydrogen and contributes to atmospheric density.

Venus' Atmosphere

Characterized by extremely high pressure (90 bar) and 95% CO2, contributing to a very high surface temperature.

Mars' Atmospheric Loss

Result of the lack of a magnetic field and solar wind stripping away its atmosphere, leading to loss of liquid water.

The Role of Planetary Size

Influences volcanic activity and the capacity to hold an atmosphere, where smaller planets experience more atmosphere loss.

Chemical Composition of Atmospheres

Mainly made up of oxygen, nitrogen, carbon, and hydrogen, with different ratios affecting the atmosphere's characteristics.

Oceans' Impact on Earth's Atmosphere

Dissolved CO2 forms carbonate rocks, impacting the levels of atmospheric CO2 and contributing to oxygen production.

Radiative Heating

The balance between absorption of sunlight and emission of infrared light that determines a planet's temperature.

N2 (Nitrogen)

The most abundant gas in Earth's atmosphere, making up approximately 78%.

Atmospheric Erosion

The process by which atmospheric conditions lead to the removal of surface material, affecting a planet's landscape.

Tectonic Activity

Movement of the Earth's plates that can create mountains and change the planet's surface.

Burning Fossil Fuels

Human activity leading to an increase in CO2 levels, affecting climate and contributing to global warming.

Hydrogen's Escape

Due to its light mass, hydrogen easily escapes a planet's atmosphere, particularly on Mars.