The Inner Planets The Inner Planets to Scale

The Inner Planets

The Inner Planets to Scale 3, 031 mi 5. 4 g/cm 3 7, 521 mi 7, 926 mi 5. 2 g/cm 3 5. 5 g/cm 3 4, 222 mi 3. 9 g/cm^3

Inner Planet Similarities • • • All are a few thousand miles across All are made of rock, with an iron core All are dense (b/c made of rock) They are called terrestrial (rock) planets Why do the inner planets share these similarities?

• Only planet known to have liquid water • Only planet known to have life – What features of Earth allow it to sustain life? Earth

Mercury • Diameter: 3, 031 mi – The smallest planet • Orbits once every 88 d • Rotates once in 59 d – How long is it from Sunset to Sunrise? • Virtually no atmosphere • Closest to the sun

Mercury’s Surface • What causes these craters? • Why do we see so many of them?

Temperature Extremes on Mercury • Daytime Temp: 900°F extremely hot • Nighttime Temp: -250°Fextremely cold • Why the temp. extremes? – Long time without sunlight (~176 d) – No atmosphere to hold or transfer heat

Venus • Similar in size and density to Earth • Earth’s twin • Nearest planet to Earth • Thick atmosphere (95 XEarth) of CO 2 • Hottest surface of any planet • Completely covered in clouds of sulfuric acid – How can you study the surface the clouds?

Venus’ Surface • Sent spacecraft to take pictures from the surface • Lasted 2 hr 7 min – Found out it was 865°F at the surface! – Why so hot?

“Greenhouse Effect” • CO 2 reflects heat back to the surface • Sunlight gets in, heat can’t escape – just like a greenhouse • Similar to greenhouse effect on Earth, only 10, 000 X more CO 2 – What would Al Gore say? • Heat & pressure destroy spacecraft sent to the surface – How then can you study its surface?

Venus Through the Clouds • You look through the clouds – with RADAR! • Bounce sound waves off the surface & study the echo

Mars • Red/Pink color • Called the red planet • caused by “rust in the dust” (iron in rocks) • 68°F to -200°F • Seasons like Earth’s • Thin CO 2 atmosphere – If CO 2, why isn’t Mars hot like Venus? – Low pressure means water cannot be a liquid

Martian Valcanoes • Largest (extinct) volcano in the S. S. – Olympus Mons-9 miles high! • Shield volcano, similar to Hawaii • Astronomers think Mars lacks tectonic plate movements; how could this explain the large volcanoes?

Martian Canyons • Largest canyon – 3, 000 miles long and 5 miles deep – Rocks shrink when they cool. Astronomers think Mars may have cooled quickly after its formation; how might this be used to explain the large canyon?

Martian Surface • Many spacecraft sent to the surface • Searched for life, evidence of liquid water – Why would astronomers be interested in liquid water? – If liquid water can’t exist at low pressure, why do astronomers still look for evidence of liquid water on Mars?

Martian Water? Martian Life?

Life on Mars?

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Inner Planets