Mars: The Red Planet Roman God of war - Blood Reflects 30% of its incident sunlight 2 small 'moons': Phobos and Deimos
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Mars: The Red Planet • Roman God of war – Blood • Reflects 30% of its incident sunlight • 2 small ‘moons’: Phobos and Deimos
Property Earth Mars
Radius 6378km 3394km ~ 0.51RE
Mass 5.97x1024 kg 6.42x1023 kg =
= 1 ME 0.11 ME
Average Density 5520kg/m3 3930kg/m3
Gravity 1 0.38 Earth’s
Escape Speed 11.2km/s 5.0km/s
Average 210K / -63C
Temperature 290K / 17C (~150-310K)
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 ~4 Billion 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 explosionA Mars Rover begin to explore Victoria Crater
Sand Dunes on Mars
Martian ‘Grand Canyon’
Formed
over 2
billion
yrs ago.
• 4000km long, ~120km wide, ~7km deep
(Grand Canyon ~20km wide, ~2km deep)
• Tectonic Fracture – not water channel!Odyssey’s View of Valles Marineris On Earth, it would stretch right across Canada!
Valles Marineris
The floor of Ius Chasma's southern
trench, located in the western region
of Valles MarinerisWater 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 summerAtmosphere on Mars Thin: ~1/150 pressure of Earth. 95.3 % CO2 2.7% N2 1.6% Argon 0.13% O2 0.07% CO 0.03% 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, 2004Panoramic Views from Spirit and Opportunity (2005)
Life on Mars? No signs of bacterial activity in rock samples – though interesting inorganic chemistry Is there life from meteoritic rocks from Mars? Inclusive!
Two Martian ‘Moons’ Discovered in 1877 by Asaph Hall Phobos ‘fear’, Deimos ‘panic’ : Mythical horses that drew the chariot of the Greek God of war.
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 seePhobos from
Mars Global
Surveyor
Thermal
Emission
SpectrometerPhobos
Phobos.. ..up close White-ish whispy streaks could be younger material.
Solar Eclipse of Phobos from seen from the surface of Mars!
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
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