Venus and Mars Planetary Geology and Atmospheres

Comprehensive vocabulary flashcards covering the physical characteristics, atmospheric conditions, volcanic formations, surface geology, and moons of Venus and Mars.

Retrograde Rotation of Venus

The clockwise axial rotation of Venus taking $243$ Earth days, opposite to most planets, likely caused by solar tidal interactions with its dense atmosphere and core.

Runaway Greenhouse Effect

The planetary heating process on Venus where an atmosphere rich in $CO_2$ traps infrared radiation, driving surface temperatures hot enough to melt lead. AKA Venusian Greenhouse

Lakshmi Planum

A smooth plateau of old lava plains on Venus marked by two large volcanic calderas named Colette and Sacajawea.

Coronae

Large circular or oval volcanic features found on Venus produced by rising plumes and convection currents of hot magma beneath the crust.

Pancake Domes

Distinctive flat-topped, circular volcanic features on Venus formed by the extrusion of highly viscous, slow-flowing lava.

Shield Volcano

A broad volcano characterized by shallow slopes formed by repeated eruptions of fluid lava from stationary hot-spot volcanism, dominant on Venus and Mars.

Composite Volcano

A steep-sided volcano associated with tectonic plate subduction zones on Earth, entirely absent on Venus and Mars due to lack of plate motion.

Hot-Spot Volcanism

A mechanism where stationary mantle plumes push magma through a non-moving crust, building massive shield volcanoes through repeated eruptions in the same location.

Olympus Mons

The largest shield volcano in the Solar System, located on Mars, measuring approximately $100$ times the volume of Earth's Mauna Loa.

Valles Marineris

A $4000\text{-km}$-long canyon network on Mars formed originally by crustal faulting and down-dropping, later expanded by landslides and erosion.

Splash Craters

Martian impact craters exhibiting fluid-like, lobed ejecta patterns that indicate the presence of volatile water or melted permafrost in the crust at the time of impact.

Martian Hematite Spherules

Small, round mineral concretions, nicknamed blueberries, discovered by the Opportunity rover that formed in the presence of liquid groundwater.

Noachian Period

The earliest geological era of Mars characterized by intense heavy bombardment, extensive lava flooding, and potential presence of liquid surface water.

Hesperian Period

The intermediate geological epoch of Mars marked by widespread lava flows and the formation of massive catastrophic outflow channels.

Amazonian Period

The current and longest geological epoch of Mars, characterized by slow, uneventful evolution, minimal volcanism, and low cratering rates.

Stickney Crater

A prominent impact crater measuring $10\text{-km}$ ($6\text{-mi}$) in diameter situated on Phobos, the inner moon of Mars.

Phobos and Deimos

The two small, non-spherical moons of Mars whose low densities and dark surfaces suggest they are captured asteroids.

Atmospheric Escape Velocity

The gravitational speed threshold determining whether thermal molecular velocities allow gases to escape into space, leading to Mars losing its lighter atmospheric constituents.