Astro 6 Flashcards
What are the two main types of planets in the Solar System?
Terrestrial (rocky, inner) planets and Jovian (giant, outer) planets.
Name the terrestrial planets.
Mercury, Venus, Earth, and Mars.
What are the main characteristics of terrestrial planets?
Rock/metal composition, similar size to Earth, few/no moons, thin/no atmosphere, close to the Sun.
Which terrestrial planets have a substantial atmosphere?
Earth and Venus; Mars has a thin atmosphere; Mercury has almost none.
Name the Jovian planets.
Jupiter, Saturn, Uranus, Neptune.
List 3 key properties of Jovian planets.
Large size, made mostly of hydrogen/helium, many moons, far from the Sun, no solid surface.
What causes differences in planetary atmospheres?
A planet’s temperature and surface gravity (escape velocity) determine what gases it can retain.
What is escape velocity for Earth?
11 km/sec.
Why can’t small, hot planets keep light gases like hydrogen?
Light molecules move faster at a given temperature and may exceed the planet’s escape velocity.
How did Earth get an atmosphere if it couldn’t keep hydrogen/helium?
Outgassing from volcanic activity and impacts by comets supplied atmospheric gases.
What is Kepler’s Third Law?
a^3 ∝ P^2, relating orbit size (a) and period (P).
What are common sources of impact evidence on Earth?
Craters (Barringer, Gosses Bluff, Manicouagan), meteorites, historical events (Tunguska, Chelyabinsk).
How often does a 1 km object hit Earth?
About every 100,000 years, causing catastrophic effects.
What do zircon crystals from Jack Hills, WA reveal about early Earth?
They show evidence for liquid water over 4.4 billion years ago, suggesting early wet/cool conditions.
List two processes responsible for water on Earth.
Outgassing (volcanic) and cometary impacts.
What is outgassing?
The release of gases from a planet’s interior, often through volcanoes.
What is the main factor that distinguishes terrestrial from jovian planets?
Terrestrial: rocky, small, close to Sun; Jovian: gaseous, massive, far from Sun, many moons.
Why are Saturn’s rings and hexagon storm scientifically interesting?
Their formation and stability remain mysterious.
What are ‘Brownlee particles’?
Tiny comet dust particles captured in the upper atmosphere of Earth.
What evidence do we have for constant impacts on Earth today?
Continuous dust/micrometeorite influx, window craters on spacecraft, visible meteor showers.
