Innri Reikistjörnur

Hvað heldur þú?

• Er hitastig á Merkúr, reikistjörnunni sem er næst sól, hærra en á jörðinni?

• Hver er samsetning skýja sem umlykja Venus?

• Er fljótandi vant á Mars í dag?

• Er líf á Mars í dag?

Myndir frá Mariner 10

sýna hve líkt yfirborð

Merkúr er því sem er á Tunglinu

Mercury Moon

Caloris Basin

Note the edge of a huge crater on the left, mostly

in shadow.

Unusual, Hilly Terrain

The tiny, fine-grained wrinkles are actually closely spaced hills.

Mercury has an iron core and a magnetic field like Earth

Mercury rotates in 176 Earth days, barely enough to have a dynamo created magnetic field -- yet, Mercury still has a magnetic field. Its source is a great mystery.

Mercury’s temperature range is the most extreme in the solar system

• Mercury’s slow 176 day rotation and the lack of an appreciable atmosphere means temperatures vary enormously from one side of the planet to the other.

• Daytime with the Sun overhead reaches 700K (or 800°F)• Midnight with the Sun completely obscured is 100K (or

-280°F)• Earth typically has temperature differences between day

and night of about 11K (or 20°F)

The surface of Venus is

completely hidden beneath

permanent cloud cover

Venus

• Atmosphere is 96% CO2

• Temperature is 750K– much higher than Mercury– daytime AND nightime– caused by the greenhouse effect

The greenhouse effect heats Venus’s surface

Venus is covered with gently rolling hills, two “continents,” and numerous volcanoes

The Venusian Surface

Impact Craters

on Venus

Mars as viewed from Earth

Like Earth, Mars has polar ice caps that grow and shrink with the changing seasons.

Valles Marineris is many times larger than the Grand Canyon

Enormous shield volcanoes

Olympus Mons - the largest volcano in the solar system has a base larger than the state of Colorado

Early space probes to Mars found no canals but did find some

controversial features

Surface features indicate that water once flowed on Mars

Ohio River valley on Earth

River channels on Mars

Viking I Lander Picture from 1976

1999 Picture from the Mars

Pathfinder Lander - Sagan

Station

Note the remote-control rover,

Sojourner, next to a Martian rock

Martian air is thin and often filled with dust

• Mars’ thin atmosphere is 95% CO2

• Mars’ atmospheric pressure is about 1% as high as Earth’s

• Mars’ coldest temperatures occur at the poles at about 160K (-170°F)

• Typical Mars temperatures range between 50°F and -80°F

The Martian meteorite found in Antarctica has not provided conclusive

evidence about life on Mars

Mars’ two moons, Phobos and Deimos, look more like potatoes than spheres

What did you think?• Is the temperature on Mercury, the closest planet to the Sun, higher than

the temperature on Earth?The temperature on the daytime side of Mercury is much higher than on Earth, but

the temperature on the nighttime side of Mercury is much lower than on Earth because Mercury rotates so slowly and has little atmosphere to retain heat.

• What is the composition of the clouds surrounding Venus?The clouds are composed primarily of sulfuric acid.

• Does Mars have surface liquid water today?No, but there are strong indications that it had liquid water in the distant past.

• Is life known to exist on Mars today?No life has yet been discovered on Mars.

Self-Check1: Compare and contrast the atmospheres of the terrestrial planets in terms of temperature,

pressure, and chemical composition.

2: List the properties that Mercury has in common with the other terrestrial planets with the Moon.

3: Compare and contrast the surfaces of Mercury, Mars, and Venus with that of the Earth in terms of geologic structures and evidence regarding tectonic activity.

4: Describe plausible explanations for the absence of water vapor in the Venusian and Martian atmospheres.

5: Discuss the contributions of the various spacecraft missions to our understanding of the terrestrial planets.

6: Discuss the evidence for the existence of water on Mars surface in the past and the location and form of that water today.

7: Compare the magnetic fields of Mercury, Venus, and Mars with that of Earth.