Lecture 9: Terrestrial Planets and Geological Activity

Terrestrial Planets

Rocky planets with solid surfaces, like Earth.

Geologically Active

Surface reshaped by volcanoes, earthquakes, and erosion.

Lithosphere

Cool, rigid outer layer of a planet.

Core

Innermost layer, composed of nickel and iron.

Mantle

Layer of rocky material between core and crust.

Crust

Outer layer of rock, includes granite and basalt.

Seismic Waves

Waves generated by earthquakes, probing Earth's interior.

Accretion

Heat generated from collisions of planetesimals.

Differentiation

Sinking of heavy elements, generating internal heat.

Radioactivity

Decay of elements releasing heat through emitted particles.

Potassium-40

Radioactive isotope with a half-life of 1.25 billion years.

Argon-40

Stable product of Potassium-40 decay.

Meteorites

Chunks of rock providing age data for the solar system.

Solar System Age

Determined to be approximately 4.6 billion years.

Earth-Moon Distance

Average distance of 3.84 × 10^8 meters.

Craters

Surface features indicating geological activity.

Volcanoes

Geological formations resulting from molten rock eruptions.

Riverbeds

Eroded paths indicating past water flow.

Cliffs

Steep rock formations shaped by erosion.

Atmospheres

Gaseous layers surrounding terrestrial planets.

Gravitational Potential Energy

Energy from the position of mass in a gravitational field.

Kinetic Energy

Energy of motion, converted from emitted particles.

Density

Mass per unit volume, varies in planetary layers.

Half-Life

Time taken for half of a radioactive substance to decay.

Earth's Interior

Comprised of core, mantle, and crust layers.

Internal Heat Sources

Include accretion, differentiation, and radioactivity.

Formation Clues

Organized orbits and rotation patterns of planets.

Water Molecules

Repel oil molecules due to electrical properties.

Slipperiness of Oil

Oil is more slippery, rising to water's surface.

Oil Molecule Size

Oil molecules are larger than water molecule spaces.

Heat Transfer

Internal heat moves to planetary surface.

Convection

Hot molten rock rises; cool rock falls.

Mantle Convection Cycle

Completes in 100 million years on Earth.

Planet Size

Larger planets retain internal heat longer.

Surface-Area-to-Volume Ratio

Determines cooling time of a planet.

Cooling Time

Shorter for larger surface-area-to-volume ratios.

Venus Geological Activity

Shows volcanic features and recent resurfacing.

Mars Characteristics

Smaller than Earth, with ancient river beds.

Perseverance Rover

Investigates Mars' past habitability and water evidence.

Mars Atmosphere

Thin CO2 atmosphere leads to minimal greenhouse effect.

Recurring Slope Lineae (RSL)

Dark streaks indicating subsurface water flow on Mars.

MESSENGER Mission

Revealed geological activity on Mercury.

Planetary Magnetic Fields

Created by moving charged particles in the core.

Earth's Magnetosphere

Protects from solar wind, preserving the atmosphere.

Aurorae

Charged particles create northern lights in Earth's atmosphere.

Geological Activity Factors

Determined by internal heat and heat transfer.

Magnetic Field Requirements

Requires conducting fluid, convection, and rapid rotation.

Mars vs. Earth

Mars is 50% Earth's radius, 10% its mass.

Planetary Cooling

Larger planets take longer to cool off.

Surface Area of Sphere

Calculated as 4πR².

Volume of Sphere

Calculated as 4/3πR³.

Mars' Past Climate

Once warmer and wetter before cooling.

Planetary Differentiation

Converts gravitational energy to heat during sinking.