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• Introduction

• Vital statistics

• Interior

• Surface

• Water, water, anywhere?

• Atmosphere

• Life

Lecture 5: Mars

(God of War)

Actual Imagined

Schiaparelli (1879),

Lowell, …

Canali and Canals

Mars - vital statistics

Orbital semi-major axis 1.524 AU

Orbital period 686.98 days

Rotational period 24 hours 37 min 22 sec

Eccentricity of orbit 0.093

Inclination of rotation axis 25.19º

Diameter (at equator) 0.533 dEarth (6788 km)

Mass 0.107 MEarth

Mean density 3940 kg m-3 (0.71 Earth)

Interior of Mars – the models

1) Iron core contaminated by

sulphur so may always have

been liquid. But, fast rotating

so why no convection

currents? No crystallisation?

2) MGS data suggest only

remnant magnetic field. If

sulphur <15% of core, it may

have mostly solidified.

Thermal+gravity models suggest some of core is molten.

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The surface of Mars (MGS)

Tharsis

Hellas

Elysium

Valles Marineris

MGS: Mars gravity map

Tharsis Montes & Olympus Mons

Shield volcanoes on edge of Tharsis

Olympus

Ascraeus

Pavonis

Arsia

Olympus Mons

700 km wide at base; 24 km above plain

Caldera: 80 km wide; 2.5 km deep

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Mars Express: Albor Tholus caldera

3-D view. Caldera 30 km wide, 3 km deep.

Entire volcano 160 km across, 4.5 km deep.

Mars Global Surveyor Magnetic map

Clear evidence for “magnetic stripes” very similar to

those on Earth – more evidence for past tectonic activity.

Valles Marineris

Tectonic origin but many features:

lava layering, weathering, (water?)

– erosion very important on Mars.

Mars Express, high

res. image – 12m/pixel

Fluidized ejecta?

Left - Copernicus (Moon)

Right - Yuty (Mars)

Water on Mars? - Past

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Ares Vallis

Streamlined islands?

Water on Mars? - Past

Ravi Vallis

Chaotic terrain + 300 km flows

Today?No surface liquid water.

Water-ice can exist just

below the surface down to

few km. Depth upper limit

depends on soil and latitude.

MGS images of gully flow

inside a crater in Terra

Sirenum. The “deposit” is

several hundred meters

long. Older ones can also

be seen.

Atmospheric surface

pressure 1/150 of Earth.

No stratosphere (no O3).

Large surface temperature

range: ~273 K (day) ~150 K

(night). Mean 218 K.

Greenhouse effect: ∆T +8 K

The Atmosphere

Mesosphere

Thermosphere

Mars

CO2 95.3 %

N2 2.7 %

Ar 1.6 %

O2 0.13 %

CO 0.27 %

H2O <0.003 %

Present-day Atmosphere of Mars

Martian atmospheric composition similar to Venus but

with a CO2 column 104 less massive (<1% Earth).

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Atmospheric Circulation• Mars rotates rapidly but has little atmosphere, no oceans

and large polar regions. Circulation is complex.

• Seasonal, “Hadley cell” at sub-solar point– condensation

flows to/from the poles. Also day/night “thermal tides”.

• Winds up to 10 m s-1 can drive massive dust storms.

Mars Earth

Martian CO2 (+H2O) polar caps

South higher

thus always

colder – North

varies more.

North South

Mars Express –

Martian South Pole

Right: visible image

Centre: CO2

Left: H2O

Phobos and Deimos – probably captured asteroids. Both

exhibit synchronous rotation, i.e. they keep the same face

towards Mars (like our own Moon).

Deimos (size ~15 km)

Martian Moons

Phobos (size ~20 km)

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Postcards from Mars Viking

Spirit

Opportunity

Curiosity rover: landed 2012 August 6

Curiosity: a 900kg habitability probe(biological potential; geological and atmospheric evolution; surface radiation)

abrasion rasp drill

White veins: Calcium Sulphate?

Life on Mars?• Viking – null result?

• Martian Meteorites –

ALH84001 is 4 Gyr old; in

space for 16 Myr; on Earth

for 13000 yr.

• Claim for fossil life based

on carbonate globules:

implies bacteria smaller

than most on early Earth.

• Methane recently

discovered in atmosphere…

The End