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Ch 06--Other Terrestrial PlanetsCh 06--Other Terrestrial Planets

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Terrestrial PlanetsTerrestrial Planets

• Is the temperature on Mercury, the closest planet to the Sun, higher than the temperature on Earth?

• What planet is most similar to Earth?• What is the composition of the clouds surrounding

Venus?• Does Mars have liquid water on its surface today?• Is life known to exist on Mars today?

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Terrestrial PlanetsTerrestrial Planets

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MercuryMercury

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MercuryMercury

• Proximity to Sun makes for a hot planet– daytime 700 K (800 F)– nighttime 100 K (-280 F) (actually quite cold)

• Some regions of Mercury’s poles are permanently shaded– Water ice on the poles!

• Magnetic field similar to Earth, therefore, must have an iron core

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Mercury’s InteriorMercury’s Interior

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Mercury’s Violent PastMercury’s Violent Past

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VenusVenus

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Venus AtmosphereVenus Atmosphere

• Greenhouse effect--carbon dioxide prevents infrared light from escaping, thus heating up the atmosphere

• Mostly sulfuric acid clouds shrouding the planet’s surface

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Venus AtmosphereVenus Atmosphere

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VenusVenus

• Mapped by the Magellan spacecraft in 1990--radar!

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VenusVenus

• Mapped by the Magellan spacecraft in 1990--radar!

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MarsMars

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Mars--Martians?!Mars--Martians?!

• 1877, Schiaparelli reports seeing “canali” (channels, not canals)– some thought these were

a planetary irrigation system

• 1898, H. G. Wells “War of the Worlds”

• 1938, Orson Wells radio broadcast

• 1976, Viking Orbiter 1 photo

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MarsMars

• Life? Probably not.

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MarsMars

• Life? Maybe in the past.– There was abundant water!

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Mars--Recent DiscoveriesMars--Recent Discoveries

• Life? Maybe in the past.– There still may be abundant water!– Images from Mars Global Surveyor

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MarsMars

• 1997, Analysis of pieces of Mars found in Antarctica suggest fossil remains of microbial life! (maybe)

• 1979, Viking 1 lander had inconclusive (controversial) results regarding organic material

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MarsMars

• Mars atmosphere often active:– ~1% as dense as

Earth’s

– 95% CO2

• Oxygen reacted with iron (rust colored surface!)

– Dust storms seasonally– Snow fall near the poles

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Terrestrial PlanetsTerrestrial Planets

• Is the temperature on Mercury, the closest planet to the Sun, higher than the temperature on Earth?– Higher in the day side, colder in the night side

• What planet is most similar to Earth?– Venus in size, chemistry, and distance. Mars in length of day

and seasons

• What is the composition of the clouds surrounding Venus?– Primarily sulfuric acid

• Does Mars have liquid water on its surface today?– No, some water ice, though. Probably lots of water in the past

• Is life known to exist on Mars today?– No, but not ruled out. Hints that it may have had life in the

past

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Questions for thoughtQuestions for thought

• Discuss the existence of life on Mars, in the past and at the present time.