Module 9: Meteorite Impacts – Key Vocabulary

Vocabulary flashcards covering key terms and definitions from Module 9: Meteorite Impacts, spanning solar-system formation, bolides, impact craters, mass extinctions, and hazard management.

Supernova

The explosive death of a star at the end of its life cycle, capable of disturbing nearby gas and dust clouds.

Nebular Hypothesis

The theory that the solar system formed 4.6 billion years ago from a collapsing, rotating cloud of gas and dust triggered by a supernova.

Solar Nebula

A flattened cloud of gas and dust whose center became the Sun while outer material clumped into planets.

Galaxy

A massive collection of billions of stars; our solar system occupies a tiny part of the Milky Way.

Milky Way Galaxy

The spiral galaxy containing our solar system; about 100,000 light-years across.

Star

A hot, glowing ball of gas that generates energy by fusing hydrogen into helium.

Sun (core temperature)

The Sun’s core reaches about 15 million °C, driving nuclear fusion.

Photosphere

The Sun’s visible outer layer with a temperature of roughly 6,000 °C.

Solar System

Consists of 8 planets, 214 moons, and millions of smaller bodies orbiting the Sun.

Order of the Planets

Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune.

Life Cycle of Stars

Stages a star passes through, ending in a supernova for large stars; the Sun’s life expectancy is ~10 billion years.

Bolide

Any extraterrestrial body (asteroid, meteoroid, or comet) that originates in space.

Asteroid

Rocky-metallic object 10 m–1000 km in diameter, mainly from the Asteroid Belt between Mars and Jupiter.

Meteoroid

Small asteroid-like body up to 10 m in diameter traveling in space.

Meteor

A meteoroid that enters Earth’s atmosphere and produces a visible streak of light.

Meteorite

A meteor that survives passage through the atmosphere and strikes Earth’s surface.

Comet

Icy body that releases gas and dust, forming a glowing tail when heated by the Sun; likely originates in the Kuiper Belt.

Kuiper Belt

Region beyond Neptune believed to be the source of many comets.

Halley’s Comet

Famous periodic comet visible to the naked eye every ~75 years; next appearance in 2061.

Airburst

Explosion of a bolide in the atmosphere (12–50 km altitude) producing intense light and shockwaves.

Tunguska Airburst

1908 Siberian event where a 25–50 m bolide exploded, flattening ~2,000 km² of forest without leaving a crater.

Chelyabinsk Airburst

2013 Russian meteor explosion that injured ~1,500 people, the largest since Tunguska.

Impact Crater

Depression formed when a meteorite strikes a surface, often surrounded by an ejecta blanket.

Ejecta Blanket

Layer of fragmented rock deposited around a crater during impact.

Breccia

Angular rock fragments that fall back into a crater shortly after impact, filling and shallowing it.

Simple Crater

Small (< a few km) bowl-shaped crater without an uplifted center.

Complex Crater

Large (> 6 km) crater with a collapsed rim and a central uplifted floor.

Manicouagan Crater

100 km wide complex crater in Quebec formed 214 million years ago; now a ring-shaped lake.

Chesapeake Crater

Submerged crater off Virginia’s coast, 35.5 million years old, nicknamed the “Eye of Quebec.”

Shoemaker-Levy Comet

Comet whose 21 fragments impacted Jupiter in 1994, confirming large impacts can occur in the solar system.

Mass Extinction

Rapid, global loss of a large proportion of species, often tied to climate shifts, volcanism, or bolide impacts.

K-T Boundary Mass Extinction

Event 65 million years ago that wiped out dinosaurs and 70 % of species due to bolide-induced global cooling.

Iridium Anomaly

Unusually high iridium levels in 65-million-year-old rock, evidence for an extraterrestrial impact at the K-T boundary.

Chicxulub Crater

180 km wide impact structure on Mexico’s Yucatan Peninsula, source of the K-T extinction event.

Asteroid Belt

Region between Mars and Jupiter where most asteroids orbit; bolides there pose no threat unless their paths are disturbed.

Magnitude-Frequency Relationship

Concept that large bolide impacts occur less frequently than small ones (e.g., Tunguska-sized every 1,000 years).

Spaceguard Survey

Program cataloguing near-Earth objects > 1 km in diameter; now extending to bodies ≥ 100 m.

Dimorphos Test Mission

2022 spacecraft impact that successfully altered the orbit of asteroid Dimorphos, demonstrating deflection technology.

Bolide Deflection Strategy

Preferred hazard-mitigation method: ram a spacecraft to nudge an asteroid off course rather than blow it up.