Final Review for ASTR/GEOL 2040: Life and Habitability

Definition of life

Self-contained chemical system undergoing Darwinian evolution.

Key life detection criteria

Growth, reproduction, metabolism, movement observed.

Life cycle of stars

Form from gas, burn hydrogen, explode, die.

Age of Earth

4.5 billion years old, oldest rocks 3.8 billion.

Biogenic elements

Essential elements for life: SPONCH (S, P, O, N, C, H).

Types of organics

Sugars, fatty acids, amino acids, nucleotides.

Extremophiles

Organisms thriving in extreme conditions (temperature, pressure).

Tree of life

Classification of life: bacteria, archaea, eukarya.

LUCA

Last Universal Common Ancestor of all life.

Miller-Urey reactions

Experiments simulating early Earth conditions to create organics.

Plate tectonics

Movement of Earth's plates recycling CO2 and shaping geology.

CO2 cycle

Releases and recycles CO2 through volcanic activity and rain.

RNA world hypothesis

RNA as both information carrier and catalyst for life.

Cambrian explosion

Rapid emergence of complex life forms 570 million years ago.

Venus's early conditions

More conducive to life before runaway greenhouse effect.

Mars's current state

Cold, dry, thin atmosphere; past water evidence present.

Europa

Moon with potential global ocean beneath icy crust.

Enceladus

Saturn's moon with geysers ejecting water vapor and organics.

Titan

Moon with thick atmosphere and methane hydrologic cycle.

Panspermia

Theory that life originated from extraterrestrial sources.

Extrasolar planets

Planets outside our solar system, detected indirectly.

Habitable zone (HZ)

Region around a star where liquid water can exist.

Continuously habitable zone (CHZ)

Smaller zone where conditions remain stable for life.

Drake equation

Estimates number of intelligent civilizations in the galaxy.

Fermi's paradox

Questioning why we haven't encountered extraterrestrial life.

Rare Earth hypothesis

Complex life may require unique conditions and advantages.

SETI

Search for Extraterrestrial Intelligence via radio signals.

Galactic colonization

Theoretical spread of civilizations throughout the galaxy.

Snowball Earth

Hypothesis of Earth's extreme glaciation affecting climate.

Thermophiles

Extremophiles thriving in high-temperature environments.

Chemotrophs

Organisms obtaining energy from chemical compounds.