11c. Red Planet Mars
Mars Data (Table 13-1)
•  Mars data
•  Earth-based observations of Mars
•  Early observations mistaken as evidence of life
•  Spacecraft find craters, volcanoes & canyons
•  Surface features indicate flowing water
•  Earth & Mars began alike, evolved differently
•  Rovers explored the Martian surface
•  The Martian atmosphere changes seasonally
•  Martian moons resemble captured asteroids
Mars Data: Numbers
•  Diameter:
6,794 km
0.53
Mars Data: Special Features
.
Earth
•  Mass:
6.4 . 1023 kg 0.107 . Earth
•  Density:
3.9 . water
•  Orbit:
2.3 . 108 km 1.52
•  Day:
•  Year:
0.72
.
Earth
AU
24h.37m 23s
1.02
.
Earth
686.98 days
1.88
.
Earth
•  Mars is farthest terrestrial planet from the Sun
•  Mars is the second smallest terrestrial planet
•  Mars has < 1% the Earth’s atmosphere
–  Mars’ atmosphere is ~ 95% CO2 & 3% N2
•  Mars has rapidly changing polar ice caps
•  Mars has two very different hemispheres
–  The “north” is covered with volcanoes & lava flows
–  The “south” is covered with numerous craters
•  Mars holds some Solar System records
–  Olympus Mons: The tallest mountain (a volcano)
–  Valles Marineris: The longest canyon
•  Mars will be the first planet visited by humans
Earth-Based Observations of Mars
•  Mars is the closest superior planet to Earth
–  Conjunction
Always superior [far side of the Sun]
•  Mars is overhead at local solar noon
•  Mars isfarthest fromEarth & appears smallest
–  Opposition
•  Mars is overhead at local solar midnight
•  Mars is closest to Earth & appears largest
•  Mars’ orbit is rather highly elliptical
–  Mars oppositions vary in favorability
•  August
oppositions are most favorable
–  28 August 2003 closest in nearly 60,000 years
•  February oppositions are least favorable
–  Mars looks very small even at favorable oppositions
•  Hubble Space Telescope cannot identify impact craters
Future Mars Oppositions
May 22, 2016
July 27, 2018
October 13, 2020
Orbits of Earth & Mars
Mars: Hubble Space Telescope
Old Mars Observations From Earth
Observations As Evidence of Life
•  Giovanni Schiaparelli
1877
–  Winter
–  Reported seeing canali on Mars
•  Italian
⇒ Means
“channels” &
is ambiguous
–  Natural stream channels
•  English ⇒ Translated “canals”
•  Seasonal color changes do occur on Mars
& has implications
–  Artificial shipping routes
–  Long viewing sessions & poor seeing conditions
•  He “saw” what was not actually there
•  He incorrectly interpreted what he did not actually see
Fine red dust settles on large lava flows
•  Areas look relatively light
–  Summer
Field stubble on Earth
Wind removes thin cover of dust
•  Areas look relatively dark
Verdant fields on Earth
•  The human eye plays tricks
–  Astronomers stare at bright red areas on Mars
•  Most of Mars has a distinct red color
–  Astronomers see cyan [blue-green] in dark areas
•  Tendency of retinal fatigue to see complementary color
•  Misinterpretation
–  “Canals” + summer greening = Intelligent life
Martian Canali & Craters
Martian Global Topography
Spacecraft Find Craters & Volcanoes
•  Mariner 4, 5 & 7
–  First close-up pictures of Mars
–  Two distinctly different hemispheres on Mars
•  Boundary tilted ~ 30° to the Martian equator
•  Northern hemisphere Relatively low & relatively smooth
•  Southern hemisphere Relatively high & heavily cratered
•  Unusual features
–  Valles Marineris
Fly-over
•  Longest, widest & deepest canyon in the Solar System
–  Would reach from San Francisco to New York
–  Many side canyons are as large as the Grand Canyon
–  Mars shows no evidence of plate tectonics
•  As on Venus, lack of oceans may be critical here
–  Olympus Mons
Fly-over
•  Solar System’s largest volcano
•  Clear evidence of hot-spot volcanism
Valles Marineris: Hemispheric View
Olympus Mons: Solar System Champ
Surface Features Indicate Water
Dendritic Stream Channels on Mars
•  Earth-like streamflow
clearly existed on Mars
–  Dendritic stream channels flow down mountains
•  Most of these appear to be
–  Parallel
relatively old
stream channels flow down
slopes
•  Many of these appear to be remarkably young
•  Permafrost may be just beneath the Martian surface
•  Catastrophic floods
clearly existed on Mars
–  Teardrop-shaped islands around crater rims
•  Remarkably similar to Glacial Lake Missoula floods
•  ≥ 109 floods from ~ 15,500 to ~ 13,500 years ago
•  Biggest floods ~ 500 cubic miles of water past Portland
•  Evidence for a Great Northern Ocean
–  Strandlines on northern hemisphere slopes
•  Notches cut by wave action along shorelines
Mars Orbiter: “Dao Valley”
Mars Orbiter: “Reull Channels”
A Possible Water History on Mars
Earth & Mars Evolved Differently
Teardrop-Shaped
Island
Evidence of Sheet Flow on Mars
Water Flow Direction
Parallel Stream Channels on Mars
•  Historic observations
–  1800’s
–  1965
Astronomers saw Martian clouds
Mariner 4 measured very high CO2 levels
•  Martian cirrus clouds contain both H2O & CO2 ice crystals
•  Atmospheric warming effects
–  CO2 on Earth raises temperature ~ 36°C
•  Much terrestrial CO2 is locked in carbonate rocks
–  Subduction recycles CO2 back into Earth’s atmosphere
–  CO2 on Mars raises temperature ~ 5°C
•  Mars quickly cooled & solidified because it is so small
Ancient
Modern
–  No subduction recycling of CO2 back into Mars’ atmosphere
•  Rainfall dissolved CO2 & removed it from the atmosphere
–  Runaway icehouse effect on Mars
–  Stabilized at present levels
The Martian Atmosphere
•  Early
Atmospheres of Earth & Mars
atmosphere
–  Probably very similar for Venus, Earth & Mars
•  Abundant volcanic activity during Mars’ early history
•  Abundant H2O, CO2 & SO2
–  Being very small, Mars ran out of heat & magma
•  Once outgassing decreased, the oceans disappeared
–  Water dissociated into H & O, which escaped Mars’ weak gravity
•  Remaining volcanic gases entered the atmosphere
•  Present atmosphere
–  Chemically
Remarkably
similar to
Venus
•  ~ 95.3% CO2 & ~ 2.7% N2
–  Expected due to little remaining volcanic outgassing
–  Physically
Remarkably different from Earth
•  ~ 0.63% as much atmospheric gas as Earth
–  Expected due to weak gravity & little replenishment
Viking & Pathfinder Explored Mars
•  Viking spacecraft
Mars Viking Lander
1976
–  Experiments looking for signs of life
•  Water
•  Nutrients
•  Heated
•  C14 added
Peroxides & superperoxides released O2
No obvious organic waste products
Mass spectrometer analyzes gases
None taken up by possible organisms
•  Mars Pathfinder spacecraft
4 July 1997
–  Sojourner was the small rover on Mars Pathfinder
•  Controlled from Earth with some autonomous functions
•  Discovered an abundance of andesite
–  Volcanic rock moderately rich in quartz
–  Rock type first described in South America’s Andes Mountains
•  Surprisingly different from Mars’ southern basalt
–  Volcanic rock
very poor
in quartz
–  Common in Earth’s ocean basins & the Moon’s maria
http://en.wikipedia.org/wiki/File:Sagan_Viking.jpg
Mars Pathfinder & Sojourner Rover
Mars Exploration Rovers
•  Overall mission
–  Search for clues to ancient water
•  2 rovers on opposite sides of Mars
•  Expected operating lifetime of 3 months
–  Ultimately a search for life
•  Mars Exploration Rover – A
Spirit
–  Landed 4 January 2004
•  Crater Gusev
Appears to have been affected by water
•  First intentional grinding of a rock on Mars
–  Operated until 22 March 2010
•  Mars Exploration Rover – B
Opportunity
–  Landed 25 January 2004
•  Landed in Meridiani Planum
•  Came to rest in Eagle Crater, a small impact crater
–  Still operating as of 22 February 2013
Mars Opportunity Before Launch
Mars Spirit & Opportunity Rovers
http://en.wikipedia.org/wiki/File:Opportunity_Lander_Petals_PIA04848.jpg
http://en.wikipedia.org/wiki/File:NASA_Mars_Rover.jpg
Mars Opportunity “Blueberries”
Mars Opportunity “Meridiani Meteorite”
Mars Opportunity “Escher Rock”
Mars Opportunity at Endurance Crater
Mars Curiosity Rover
MSL Cruise Stage Before Launch
•  Mars Science Laboratory (MSL) mission
–  Spacecraft components
•  Earth–Mars fueled cruise stage
•  Entry–descent-landing (EDL) system
•  Curiosity rover with instrument package
Skycrane
–  Soft-landed in Gale Crater on 6 August 2012
•  Unique “sky crane” landing strategy
•  General mission objectives
–  Assess Martian climate & geology
–  Assess favorability of conditions for microbial life
–  Assess habitability for future human exploration
•  Specific Curiosity objectives
–  Biological
–  Geological & geochemical
–  Planetary process
–  Surface radiation
Opportunity, Sojourner & Curiosity
http://en.wikipedia.org/wiki/File:MSL-Cruise_Stage_Test.jpg
Mars’ Atmosphere Is Very Dynamic
•  Diurnal changes
–  Mars Pathfinder
–76°C to –10°C
–  Daytime heating generates dust devils
•  Weak clear-air tornadoes
•  Pressure dropped as dust devils passed Pathfinder
•  Seasonal changes
–  Basic patterns
•  Winter
•  Spring
•  Summer
•  Fall
~ 20% seasonal pressure changes
Frigid temperatures freeze out much CO2
Warm temperatures thaw out much CO2
Frigid temperatures freeze out much CO2
Warm temperatures thaw out much CO2
–  Hemispheric differences
•  Northern summer
Mars is at aphelion
–  Clear skies warm northern summer much more than expected
•  Southern summer
http://en.wikipedia.org/wiki/File:Mars_Science_Laboratory_mockup_comparison_.jpg
Martian Dust Devil From Above
http://lightsinthedark.files.wordpress.com/2012/03/dustdevil.jpg
Mars is at perihelion
–  Dust storms cool southern summer much less than expected
Mars Global Dust Storm
http://science.nasa.gov/media/medialibrary/2001/10/11/ast11oct_2_resources/0131w.jpg
Cloud Caps on Martian Volcanoes
Cloud Cap On Mount Hood
http://fox12weather.files.wordpress.com/2010/09/lenticular-cropped1.jpg
Mars Craters & Mounds at Sunset
Mars’ Moons Resemble Asteroids
•  Discovery
–  Asaph Hall
Favorable opposition of 1877
•  Named after chariot horses of the Greek god of war
•  Might be captured asteroids
•  Details
–  Phobos
Fear
•  Closest to Mars & largest in size
•  Orbital period of ~ 7 hours 39 minutes
–  Races from West to East from horizon to horizon in ~ 5.5 hours
–  Comparable to artificial satellites in low Earth orbit
•  Several times brighter than Venus appears from Earth
–  Deimos
Panic
•  Farthest from Mars & smallest in size
•  Orbital period of ~ 6 days
–  Creeps from East to West from horizon to horizon in ~ 3.0 days
•  About as bright as Venus appears from Earth
Mars Odyssey (Themis scanner)
The Martian Moons (Asteroids?)
Important Concepts
•
Mars data
–
–
–
–
•
Early Mars observations
–  Schiaparelli reported seeing canali
–  Seasonal color change was confusing
•  Seasonal dust storms rearrange dust
•  Retinal fatigue produces cyan color
•
•
Diameter only ~ 53% that of Earth
Mass 10.7% & density 72% of Earth
Highly elliptical orbit
Same day & axial tilt as Earth
Many spacecraft have visited Mars
–  Mariner 4, 5 & 7
•  Two very different hemispheres
–  Viking landers
•  Looked for signs of life; none found
–  Mars Pathfinder
•  Included the Sojourner rover
–  Mars Orbiter
Mars’ dynamic atmosphere
–  Diurnal changes
–  Seasonal changes
•  Atmospheric pressure varies ~ 20%
•  H2O & CO2 clouds can occur on Mars
•
Mars has two small natural satellites
–  Phobos
Fear
•  Fast West-to-East sky crossing
–  Deimos
Panic
•  Slow East-to-West sky crossing