Mars: The Red Planet

• Roman God of war – Blood

• Reflects 30% of its incident sunlight

• 2 small ‘moons’: Phobos and Deimos

Property Earth MarsRadius 6378km 3394km ~ 0.51RE

Mass 6.42x1023 kg = 0.11 ME

Average Density 5520kg/m3 3930kg/m3

Gravity 1 0.38 Earth’s

Escape Speed 11.2km/s 5.0km/s

AverageTemperature

210K / -63C (~150-310K)

5.97x1024 kg= 1 ME

290K / 17C

Eccentricity 0.017 0.093

Other Physical Properties

• Sidereal Rotation speed: 24hrs 37mins• Sidereal orbital period: 686.9 solar day

(or 1.881 tropical years)• Perihelion 1.38AU, Aphelion 1.67AU• Axis tilt: 24°• Orbital inclination to ecliptic 1.85°• Magnetic Field: 1/800 of Earth’s

Seasons - like Earth – but complicated due to orbital eccentricity.

Views of Mars

Left: Hubble 1997 Right: Viking 1976

Martian Surface

• Huge Volcanoes

• Deep canyons

• Vast Dune Fields

Mars Global Surveyor

Contrasting Hemispheres

• Northern Hemisphere: Volcanic planes (like lunar maria)

Enormous lava flow in its history.Less Cratered: Younger? 3 Billion Yrs

• Southern Hemisphere: heavily cratered highlands. Older? 4 Billion yrs

Tharsis: the Martian Continent.

• Lies on the equator ~ size of North America.• Rises ~10km above surface• To its East: Chryse Planitia – ‘Plains of Gold’• To its West: Isidis Planitia – ‘Plains of Isis’

Both wide depressions ~3km deep ‘oceans’• NO sign of Plate tectonics: Geologically Dead• Few craters on Tharsis: 2 – 3 Billion yrs old?

Hellas Planitia

• Lowest point on Mars• ~3000km across• Basin is ~9km below rim• > 6km below average

level of Mars • Huge Impact feature in

early history!• Maybe ~4Billion yrs old.

Volcanism:Olympus Mons

• Largest volcano in the solar system.

• ~25km high 3x taller than Mt Everest

• 700km across at base. ~Texas

• Extinct.At least for ~100

Million years!

Ancient Flows from Olympus Mons

Volcanoes on Mars

• All are shield volcanoes - Venus

• Many 100’s of smaller volcanoes

• Tall due to small surface gravity.2.5x that of Earth

• No signs of activity.

Craters on Mars and the Moon

• Lunar crater Copernicus: ejecta blanket dry powdery material.

• Mar’s Crater Yuty.• ~18km diameter• Ejecta was liquid in nature –

‘splash crater’• Permafrost of water ice just

below surface –liquefied in impact explosion

A Mars Rover begin to explore Victoria Crater

Sand Dunes on Mars

Martian ‘Grand Canyon’

• 4000km long, ~120km wide, ~7km deep(Grand Canyon ~20km wide, ~2km deep)

• Tectonic Fracture – not water channel!

Formed over 2 billion yrs ago.

Odyssey’s View of Valles Marineris

On Earth, it would stretch right across Canada!

Valles Marineris

Water on Mars?• Photographic evidence that liquid water once

existed in great quantities on surface.• “Runoff Channels”: Dried up Rivers• Water now locked in sub-surface permafrost

From ~ 4 billion yrs ago

~400 km long

up to 5 km wide

“Outflow” Channels

Remnants of catastrophic flooding with >100x flow rate of the Amazon

~3 billion years ago.

Frozen Lake in Martian Crater

Polar Caps• Mainly frozen CO2 (‘dry ice’) < –120C 150K• Seasonal cap – shrinks and grows each

year. • South ~4000km, North ~3000km diameter. • 1m thick. • Residual cap – permanently frozen.• South ~350km, North ~ 1000km across.• North cap warmer ~-75C and mainly water• Seasonal freezing reduces atmospheric

pressure by up to 30%!

North Polar

Cap on Mars

Frozen Water

and CO2

Martian South Pole

Melting ices in summer

Atmosphere on Mars

Thin: ~1/150 pressure of Earth.95.3 % CO2

2.7% N2

1.6% Argon0.13% O2

0.07% CO0.03% H2O (changes)

Martian Weather• Noon in summer surface

temperature can reach 300K / +27C.

• At night temperature drops by 100C!

• ‘Fog’ in early morning• Large violent Dust

storms in season• No rain or snow

Sand Storms on Mars and Earth

Martian Evolution• Why is Mars the way it is?

Reverse Runaway ‘Greenhouse’ Effect.• In the past, a stable temperature of ~0C, dense

atmosphere, heavy rain all possible…• Liquid water dissolved CO2 and formed

carbonates in rocks – hence cooling planet.• Eventually water freezes out of atmosphere…

• Due to lack of greenhouse gases, tectonic motion and few volcanoes: CO2 is not replenished.

View from Viking Lander 1

Large Rock ~2m big covered with fine grain debris. Dunes formed by ‘sand’ storms.

Views from Viking Landers 1 & 2

Red Rocky Desert : High iron content (iron oxide)

Views from Martian Rovers

Columbia Hills (Above), Endurance Crater (Below).

Unusual Rock Formation on the lower slopes of ‘Endurance Crater’.

Cracking and alteration

processes -. caused by H20?

Rover Opportunity plans a closer

look! October 4, 2004

Panoramic Views fromSpirit and Opportunity (2005)

Life on Mars?

No signs of bacterial activity in rock samples – though interesting inorganicchemistry

Is there life from meteoritic rocks from Mars? Inclusive!

Two Martian ‘Moons’

Phobos ‘fear’, Deimos ‘panic’ : Mythical horses that drew the chariot of the Greek God of war.

Discovered in 1877 by Asaph Hall

Phobos• ~28km x 20km with huge 10km wide crater.• Circular, equatorial orbit of 9378 km

(Just 3 Mars radii)

• Sidereal Period 7hrs 39mins – much faster than Martian day – races across the sky every 5.5 hrs.

• Rotates synchronously.

Both moons reflect ~6% of sunlight: Hard to see

Phobos from Mars Global

Surveyor

Thermal Emission

Spectrometer

Deimos

• ~16km x 10km with large 2.3km wide crater.• Circular, equatorial orbit of 23,457 km

(~7 Mars radii)• Sidereal Period 30hrs 18mins. Moves across

the Martian sky every ~3 days.• Also Rotates synchronously.Both moons have average densities of ~2000kg/m3

Unlike mars – hence captured Asteroids