mars: the red planetweb2.uwindsor.ca/.../physics/reddish/teaching/190/mars-w.pdf · 2008-11-28 ·...
TRANSCRIPT
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.
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!
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
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.
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.
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%!
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
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.
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
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