this island earth - exploring the solar system reading: marshak, ch. 1 & 2

This Island Earth - Exploring the Solar System

Reading: Marshak, Ch. 1 & 2

Sol – Giver of Life

* Bright enough but not too bright; massive enough, but not too massive.

* Light emitted mostly in visible spectrum

Welcome to the ’Hood

Odd one Out – Pluto: a dirty snowball

The Gas Giants

Saturn and its Moons

Jupiter

•2.5 x as massive as all other planets combined, but low density (Sp. Gr. ~1.3)

•Composed mostly of hydrogen & helium.

• Fastest spin of any planet (10 hours).

• Ferocious wind storms (Great Red Spot)

Io – one of just four volcanically active bodies in the solar system.

Asteroid Impact!

The Terrestrial Planets

• No atmosphere• No hydrosphere• Tectonically “Dead” • Heavily Cratered•Slow rotation 179 days• Noontime temps 800oF; nighttime temps –280oF.

Mercury

Venus

• Resembles Earth in size, density, mass, etc.

•Tectonically Active

• Dense Atmosphere 90x Earth’s air pressure

• CO2-rich atmosphere

• “Runaway Greenhouse”: 475oC (900oF)

Mars

• Tectonically “dead” today, but active in distant past.

•Much smaller than Earth with <1% Earth’s atmospheric pressure

• Can’t retain heat, avg. temps. Down to –125oC (-193oF).

• Contains some water – mostly in polar ice.

• Signs of water: rivers, oceans in past; where did water go?

This Island Earth – The Just-right Planet

• Close, but not too close to sun.

•Size – large enough to hold atmosphere, but not too much

• Tectonically active; magnetic.

• Atmosphere – dense, but not too dense; unusually oxygen-rich.

• Temperature – well-regulated in “livable range.”

• Water in three phases, oceans.

• Life!

A Look Inside the Earth

Oceanic Crust –Thin (~5 km); dense (3.0); lower; younger (<180 my)

Continental Crust –Intermediate composition on average; thicker (~20 – 80 km); less dense (~2.7); higher; older (up to 4.0 b.y.)

Rigid Lithosphere

Plastic Asthenosphere

Core – Fe & Ni

Mantle – Ultramafic Rock

Solid

LiquidRigid