Chapter 10: Mars

10.1 Orbital Properties

10.2 Physical Properties

10.3 Long-Distance Observations of Mars

10.4 The Martian Surface

10.5 Water on Mars

Life on Mars?

10.6 The Martian Atmosphere

10.7 Martian Internal Structure

10.8 The Moons of Mars

Units of Chapter 10

Mars’s orbit is fairly eccentric which affects amount of sunlight reaching it

When viewed from Earth, Mars can be located either in the general direction of the Sun (conjunction) or away from it (opposition).

10.1 Orbital Properties

Radius: 3394 km

Moons: Deimos, Phobos

Mass: 6.4 x 1023 kg

Density: 3900 kg/m3

Length of day: 24.6 hours

10.2 Physical Properties

From Earth, can see polar ice caps that grow and shrink with the seasons

Much better pictures from Mars missions, close-up

10.3 Long-Distance Observationsof Mars

• Changing polar ice caps are frozen carbon dioxide; water ice is permanently frozen

• Shifting dust cover makes surface look like it is changing

• Frequent dust storms, with high winds

Major feature: Tharsis bulge, size of North America and 10 km above surroundings

Minimal cratering; youngest surface on Mars

10.4 The Martian Surface

This map shows the main surface features of Mars. There is no evidence for plate tectonics.

• Northern hemisphere (left) is rolling volcanic terrain

• Southern hemisphere (right) is heavily cratered highlands; average altitude 5 km above northern

• Assumption is that northern surface is younger than southern

• Means that northern hemisphere must have been lowered in elevation and then flooded with lava

Valles Marineris: Huge canyon, created by crustal forces Top right: Grand

Canyon on same scale

• 4000 km long• Maximum 120 km wide, 7 km deep

Mars has largest volcano in solar system: Olympus Mons

• 700 km diameter at base• 25 km high• Caldera is 80 km in diameter

Three other Martian volcanoes are only slightly smaller

Was there running water on Mars?

Runoff channels resemble those on Earth

Left: Mars

Right: Louisiana

10.5 Water on Mars

Current thinking: Open water (rivers, lakes) once existed on Mars

This may be an ancient Martian river delta (or it may not)

Much of northern hemisphere may have been ocean

Impact craters less than 5 km across have mostly been eroded away

Analysis of craters allows estimation of age of surface

Crater on right was made when surface was liquid

Recently, gullies have been seen that seem to indicate the presence of liquid water; interpretation is still in doubt

More intriguing, this pair of images appears to show that gully formation is ongoing

Some water may now be permafrost under polar ice capsLeft: Southern polar cap, mostly carbon dioxideRight: Northern polar cap, mostly waterBoth images taken during local summer

Viking landers both landed in low-latitude northern plains

Rocky surface, red due to iron content

Viking 1

Viking 2

The landing site for Opportunity was chosen to maximize the chances of finding water, or evidence for water

Discovery 10-1: Life on Mars?Viking landers looked for evidence of living organisms; did not find anything conclusive

Discovery 10-1: Life on Mars?Two Martian meteorites found in Antarctica show possible signs of microbial life, but evidence is disputed

Three-part figure frm right page of Discovery 10-1 goes here

Martian atmosphere is mostly carbon dioxide, and very thin

Too thin to retain much heat; temperature drops sharply at night

10.6 The Martian Atmosphere

Fog can form in low-lying areas, as sunlight strikes

Mars may be victim of runaway greenhouse effect in the opposite sense of Venus’s.

As water ice froze, Mars became more and more reflective and its atmosphere thinner and thinner, freezing more and more water and eventually carbon dioxide as well.

As a result, Mars may have had a thicker atmosphere and liquid water in the past, but they are now gone.

• No seismic studies have been done

• From behavior of crust, it is estimated to be 100 km

thick

• No magnetic field, so core is probably not metallic,

not liquid, or neither liquid nor metallic

10.7 Martian Internal Structure

Mars has two tiny moons:

Phobos (left, 28 km x 20 km)

Deimos (right, 16 km x 10 km)

Both probably captured from the asteroid belt

10.8 The Moons of Mars

The oldest regions on the Martian surface are those with

A. polar caps.B. volcanoes.C. impact craters.D. arroyos. 

The Earth has a strong planetary magnetic field, in contrast to Mars, which has a very weak field, if any at all. in the context of the dynamo model, we can explain this difference by noting that

A. Mars rotates very slowly.B. Mars is farther from the sun than the

Earth.C. the interior of Mars is very hot.D. the interior of Mars is mostly rocky

materials. 

The density of Mars is:

A. about like that of the Earth.B. the lowest of the terrestrial

planets.C. the lowest of all planets.D. the greatest of the

terrestrial planets. 

A major feature of the atmosphere of Mars is

A. very dense clouds shrouding most of the planet.

B. strong winds and dust storms.C. very high temperatures and

pressures.D. chemical mixture very similar to

that of Earth.

Which of the following did not, directly or indirectly, result from large-scale volcanic eruptions on Mars in the past?

A. Large shield volcanoes.B. Water vapor in the atmosphere.C. Polar icecaps.D. Impact craters, mostly in the

southern hemisphere.E. Carbon dioxide in the atmosphere. 

Mars is orange because

A. dust in the atmosphere reflects orange light the most effectively.

B. the surface is littered with orange peels from an ancient (and stupid) civilization.

C. the soil is radioactive and therefore glows orange.

D. the soil is rusty because of the presence of ferrous oxide.

Olympus Mons is

A. the widest canal discovered on Mars.

B. a Martian sea, although it no longer has water in it.

C. a Martian volcano, twice the height of Mt. Everest.

D. the largest impact crater on Mars. 

We would expect Mars to undergo seasonal changes much like those on Earth because

A. Mars is about the same distance from the sun as Earth.

B. Mars' equator is inclined to its orbital plane about the same as Earth's.

C. the same calendar is used on Mars as on Earth.

D. Mars rotates about as fast as the Earth does.

In general, impact craters on the surface of Mars are shallower than those on our moon, and its moons Deimos, and Phobos . This fact implies that

A. smaller objects hit the surface of Mars.B. the Martian surface is harder than the

others.C. more erosion has occurred on Mars than

the moons.D. Mars quakes have made the crater walls

collapse.E. objects hit Mars with a lower velocity. 

• Mars’s orbit is more eccentric than Earth’s

• Rotates in 24.6 hours; axial tilt similar to Earth’s

• Atmosphere very thin, mostly carbon dioxide

• Temperature averages 50 K below Earth’s, but seasons are otherwise similar

• Mars landers have yielded substantial amounts of data

Summary of Chapter 10

• Northern and southern hemispheres are very different

• South is higher and heavily cratered

• North is lower and relatively flat

• Major features: Tharsis bulge, Olympus Mons, Valles Marineris

• Crater ejecta provide evidence for permafrost layer under surface (easily liquidized)

• Two small moons, probably captured asteroids

Summary of Chapter 10 (cont.)