Physical features on Mars

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Many of the channels flowed into a basin called Acidalia Planitia, which is the dark area in the extreme north.

The three Tharsis volcanoes (dark red spots), each about 25 kilometers (16 miles) high, are visible to the west.

Slide 18

Changes in color across Mars’ Surface

- first thought to be vegetation!

- changes over seasons (growing seasons?)

now understood physically:

- changes in the surface features (i.e. plains, volcanoes, crater beds)

- changes in the surface

chemical composition (rock, soil types – e.g., basalt) determined from spectroscopy (radar) of reflected light from the surface

- albedo – measure of the

reflectivity of a planet

Slide 19

Mars Global Surveyor

- NASA launched in December 1996

- 6 instruments including

MOC – high resolution camera

MOLA – laser altimeter (first 3D look!)

TES – high-resolution temperature detector

Magnetic field detector

How do we measure the height of features on Mars?

Laser Altimeter (MOLA)

bounce laser beams off surface

time delay between signals gives height measure

Slide 20

The “Face” on Mars (Viking Image from 1976)

Slide 21

Radar map of Martian surface

MOLA

(Mars Orbiter Laser Altimeter)

Color indicates elevation

(Blue =low, red= high)

Slide 22

Mars Topographic Map (MOLA radar 1998/99)

Mars Topographic Map (MOLA radar 1998/99)

Slide 23

Mars’ Crustal Dichotomy =

noticeable differences between N and S hemispheres

- Altitudes (N lowlands, S highlands)

- Cratering (age of surfaces?)

Various Explanations:

- large impact (asteroid) on Mars

- plate tectonics (although Mars too small for hot core)

- volcanic eruptions which smoothed parts of the planet

Slide 24

Hellas Impact Basin

ü 2000 km diameter, 9 km deep!

ü Probably formed by asteroid impact

ü Debris from collision would cover US with layer 3 km thick

Slide 25

Olympus Mons – largest volcano in S.S.

rises 15 miles above

surrounding flat plains

three times as tall as

Mt. Everest

“hot spot” volcanism

like in Hawaiian Islands