Atmosphere …

Gives us the air we breathe

Protects us from meteorites and harmful cosmic radiation

Blanket covering the Earth from heat at day and cold at night

Bye-bye, Earth!

4.6 billion years ago:Heavy Bombardment

Barringer crater, Arizona49,000 yr oldIron meteorite of size 50 m, mass 300,000 tonImpact velocity 11 km/sec

Our Earth is a target, too!

150 known impact sites on Earth

Diameters from 50-70 m to 200 km

65 million years ago a huge meteorite of 10 km size hit the Earth

• World-wide fires• 1-km-hign tsunamis• Acid rains and atmospheric pollution• Darkness and severe winter for many decades

¾ of all living species have been killed

Our Moon could have been formed in a giant collision4.5 billion years ago

The Peekskill meteorite

October 9, 199212 kg stony meteorite hit the Earth

Venus the Beautiful

The goddess of beauty

Fig. 17-3a, p.349Greenhouse for trapping heat

Runaway greenhouse effect

Atmosphere lets the visible sunlight in, but traps infrared radiation and prevents rapid cooling of the surface at nights

"It will be possible to see cities on Mars, to detect navies in [its] harbors, and the smoke of great manufacturing cities and towns... Is Mars inhabited? There can be little doubt of it ... conditions are all favorable for life, and life, too, of a high order. Is it possible to know this of a certainty? Certainly."

Samuel Leland 1895

Seasons on Mars?Channels for irrigation ???

Sorry, no channels – just dry canyons, lava flows and dusty deserts …

Dry riverbeds, traces of flooding

No water, just dry desert …

Salty rocks on Mars: former sea bottom

8 billion miles through space!

Jupiter – the biggest planet

The Red Spot

Io Europa Ganymede Callisto

Total 61 moons discovered so farMost are captured small asteroids

Galilean moons:

Europa – a giant skating rink

Io – giant volcanoes

Saturn – second largest planetSo fluffy – it could float in water

Enormous winds: 1800 km/hr !!

The Great White Spot: huge storm

Thickness: less than 1 km

Extend from 74,000 to137,000 km

Discovered by Huygens in 1659

Saturn rings

Flying through the rings

Titan, the mysterious moon of Saturn

Uranus

What happened to Miranda?

Neptune

Triton

Pluto and Charon

The Kuiper Belt – home for short-period comets??

Starting in 1992, astronomers have become aware of a vast population of small bodies orbiting the sun beyond Neptune. There are at least 70,000 "trans-Neptunians" with diameters larger than 100 km in the radial zone extending outwards from the orbit of Neptune (at 30 AU) to 50 AU.