Astronomy 330

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Astronomy 330

• Lecture 12

Image of Mars taken from Hubble Space Telescope
http//solarsystem.nasa.gov/planets/profile.cfm?Ob
jectMars
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Astronomy 330

• 4th planet from the sun
• Mars, of the all the planets, is probably the
  most like Earth on its surface
• Length of day is almost identical to Earths,
  Mars also has seasons like Earth
• Maybe had and does have some liquid water???
• Maybe life???

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Astronomy 330

• Mars has 1/10th the mass of the Earth, so we
  expect it to be less active than Earth
  geologically
• Mars is 1.5 AU from the Sun, it has a colder
  surface
• The atmosphere is very thin, U.V. light from the
  Sun reaches Mars surface
• The water on Mars is mostly frozen ice, also much
  CO2 ice (dry ice).
• The atmospheric pressure is so low that liquid
  water cannot exist for very long on the surface,
  it boils or freezes immediately

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Astronomy 330
http//cmex-www.arc.nasa.gov/CMEX/index.html
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Astronomy 330

• Mars, it is thought was much different, in the
  past
• Evidence for large volcanoes, which could have
  released huge amounts of gases (water included)
• River channels indicate that water once flowed
  freely on the surface
• Recent missions to the surface also show
  unequivocal evidence for surface water
• Mars shows climate cycles (only other planet
  besides Earth to show this)

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Astronomy 330 Gusev crater
See http//cmex-www.arc.nasa.gov/CMEX/index.html
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Astronomy 330

• Mars color is red and it is one of the most
  bright objects in the sky
• Little can be seen telescopically except light
  and dark features when Mars is near opposition
  (closest to the Earth).
• Mars also shows polar caps which grow and shrink
  with the seasons on Mars
• Mars also can show transient yellow or white
  clouds

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Astronomy 330 Mars from Hubble
See http//solarsystem.nasa.gov/planets/profile.c
fm?ObjectMars
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Astronomy 330 The Canal Controversy

• Giovanni Schiaperelli (1877) identified linear
  features he called canali, in Italian this means
  channels, but was translated into English as
  canals
• Percival Lowell, by eye, sketched what he thought
  were these canals, developed a whole story about
  a dying civilization on Mars

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Astronomy 330 Lowells canals
http//www.wanderer.org/references/lowell/Mars/cha
p05.html
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Astronomy 330

• Tilt of Mars axis is 25o. This means Mars has
  seasons similar to Earths (recall the tilt of
  the Earths rotational axis is 23.5o).
• Seasons on Mars last twice as long as on Earth
  due to the longer orbital period of Mars
• Polar cap forms and expands in the hemisphere
  undergoing winter phase. Cap also covered in
  clouds. Maximum extent to a a latitude of 65o
• Polar caps recede with onset of summer, a
  permanent cap remains which is only a few hundred
  kilometers across

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Astronomy 330 Variations of Mars orbit,
rotation axis
http//cmex-www.arc.nasa.gov/CMEX/index.html
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Astronomy 330 Missions

• Many observers using telescopes also thought they
  saw seasonal changes in the light and dark
  patches on the surfacedarkening in summer,
  thought this may be due to plant growth, melting
  of a water polar cap
• Mariners 2,4 (first flyby) of Mars (1965)
  shattered this perception

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Astronomy 330 Seasonal Changes from Hubble
http//cmex-www.arc.nasa.gov/CMEX/index.html
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Astronomy 330 Missions

• Mariners showed many impact craters, similar to
  the Moon
• Sending radio signals through Mars atmosphere
  also helped during an occultation of the
  spacecraft showed that the surface pressure was
  0.01 bar, much lower than expected
• Mariners 6, 7 mapped much of the surface, also
  showed Mars to be heavily cratered, but didnt
  map the whole surface and missed very important
  features. Also determined that polar caps have a
  large amount of CO2 ice

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Astronomy 330 South Pole topography, many craters
http//cmex-www.arc.nasa.gov/CMEX/index.html
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Astronomy 330 Mariner 4

• First spacecraft to fly by Mars
• Discovered first evidence of running water
• Studied interplanetary fields, particles
• First close up pictures of Mars, surprisingly
  like Moon (impacts)
• Studied atmosphere of Mars by beaming radio
  signals through atmosphere

http//solarsystem.nasa.gov/missions/profile.cfm?S
ortTargetTargetMarsMCodeMariner_04
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Astronomy 330 Mariner 6 7

• Identical spacecraft which flew by Mars in 1969
• Took more pictures
• Revealed surface features such as depressions not
  related to impacts, deserts

http//solarsystem.nasa.gov/missions/profile.cfm?S
ortTargetTargetMarsMCodeMariner_06
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Astronomy 330 Mariner 9

• First spacecraft to orbit another planet (1971)
• Atmosphere very dusty on arrival, but being in
  orbit allowed it to wait
• Imaged 80 of surface
• Discovered river beds, craters, Vallis Marinaris
• Evidence of wind and water erosion, fog, weather
  fronts

http//solarsystem.nasa.gov/missions/profile.cfm?S
ortTargetTargetMarsMCodeMariner_09
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Astronomy 330 Missions

• Mariner 9, first orbiter
• Discovered first volcanoes on Mars
• Discovered the largest volcano in the Solar
  System
• Discovered the largest canyon and largest canyon
  system
• Discovered vast drainage channels
• Repeated occultations allowed to make detailed
  observations of the structure of Mars atmosphere.

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Astronomy 330 Vallis Marinaris
http//cmex-www.arc.nasa.gov/CMEX/index.html
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Astronomy 330 Viking 1 2

• Viking 1 and Viking 2 launched within weeks of
  each other in 1975, landed 1976
• Consisted of orbiter and lander
• Imaged entire planet
• Water vapor measurements, infrared thermal
  mapping
• Landers collected and analyzed soil (rich in
  iron, devoid of life)
• Monitored temperature, winds
• Seismometers did not function

http//solarsystem.nasa.gov/missions/profile.cfm?S
ortTargetTargetMarsMCodeViking_02
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Astronomy 330 Viking
http//nssdc.gsfc.nasa.gov/planetary/viking.html
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Astronomy 330 Missions

• Several Soviet and U.S. missions failed (e.g.
  Mars Observer) in the 80s and early 90s
• 1996, Mars Pathfinder landed Sojourner rover,
  obtained data on elemental composition of rocks
• Mars Global Surveyor obtained high resolution at
  very high resolution, first topographic map of
  Mars

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Astronomy 330 Missions

• The next two U.S. missions in 1999 failed due to
  the mixups of units (some people were using
  English system, others using metric!).
• Mars Odyssey successfully in orbit in 2001,
  discovered large amounts of subsurface ice.

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Astronomy 330 Fobos 1 2

• Russian orbiters and landers (1988)
• Designed to orbit and study Mars and moons of
  Mars (Phobos and Deimos)
• Mission lost due to programming error

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Astronomy 330 Mars Observer

• Mission to study geology, geochemistry (1992)
• Mission lost due to fuel line rupture (most
  likely cause) 2 days before orbit insertion

http//solarsystem.nasa.gov/missions/profile.cfm?S
ortTargetTargetMarsMCodeMarsObserver
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Astronomy 330 Pathfinder (Sojourner)

• First rover mission (1996-1997)
• Consisted only of a self-righting, tetrahedral
  lander
• Landed in Ares Vallis, found evidence of running
  water from images of rocks
• Showed rocks are similar in composition to
  terrestrial volcanic rocks
• Also collected weather data

http//solarsystem.nasa.gov/missions/profile.cfm?S
ortTargetTargetMarsMCodePathfinder
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Astronomy 330 Nozomi

• Japanese orbiter (1998)
• Orbiter lost due to malfunctions, ran out of
  fuel, placed in solar orbit

http//solarsystem.nasa.gov/missions/profile.cfm?S
ortTargetTargetMarsMCodeNozomi
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Astronomy 330 Mars Climate Orbiter

• U.S., 1998 mission
• Orbiter to study surface and atmosphere,
  communications relay for Mars Polar lander and
  Deep Space 2
• Burned up in Mars atmosphere, incorrect units
  used resulting in navigation error

http//solarsystem.nasa.gov/missions/profile.cfm?S
ortTargetTargetMarsMCodeMCO
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Astronomy 330 Mars Polar Lander

• 1998 U.S. mission
• Supposed to land near pole
• Communications lost as descent begun

http//solarsystem.nasa.gov/missions/profile.cfm?S
ortTargetTargetMarsMCodeMPL
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Astronomy 330 Deep Space 2

• U.S. 1998
• Twin micro-probes released from Mars Polar Lander
• Intended to penetrate surface at high speed and
  take sub-surface data
• Mission lost

http//solarsystem.nasa.gov/missions/profile.cfm?S
ortTargetTargetMarsMCodeDS2
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Astronomy 330 Beagle 2

• European, 2003
• Release from European orbiter Mars Express
• Was to have landed on surface to look for signs
  of life-past or present
• Mission lost

http//solarsystem.nasa.gov/missions/profile.cfm?S
ortTargetTargetMarsMCodeBeagle_02
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Astronomy 330 Mars Global Surveyor

• First success in more than 2 decades !
• U.S. 1997
• Polar orbit, observed Mars from low altitude
  orbit
• Observed evidence for recent liquid water flows
• 3-d profiles of North pole
• Still in operation

http//solarsystem.nasa.gov/missions/profile.cfm?S
ortTargetTargetMarsMCodeMGS
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Astronomy 330 Mars 2001 Odyssey

• U.S., 2001
• Mission to map surface, search for signs of water
  ice
• Found a vast amount of subsurface ice, results
  suggest that 10 of near surface could be water
• Radiation levels 2-3 times those near Earth
• Still in operation, serves as communications
  relay for Spirit and Opportunity

http//solarsystem.nasa.gov/missions/profile.cfm?S
ortTargetTargetMarsMCodeOdyssey
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Astronomy 330 Mars Express

• European, 2003
• Search for subsurface water, study atmosphere
• Dramatic evidence of methane (life?)
• Was supposed to work with Beagle 2
• Mission still operating

http//solarsystem.nasa.gov/missions/profile.cfm?S
ortTargetTargetMarsMCodeMarsExpress
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Astronomy 330 Spirit and Opportunity Rovers

• U.S. 2004
• Currently operating
• Designed to move and examine mineralogy of rocks
• Look for evidence of water (have found a lot of
  evidence!)

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Astronomy 330 Bulk Properties of Mars

• Diameter, 6,787 km, half the size of the Earth
• Surface area is equal to all the continents on
  Earth
• Mass is 11 the Earths, 9 times the Moon
• Therefore, Mars has geologic activity roughly
  half way between the Earth and the Moon

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Astronomy 330

• Mars density is 3.9 g/cm3 and its uncompressed
  density is about 3.8 g/cm3
• This indicates that Mars is probably deficient in
  metals.
• Maybe Mars is more representative of the Silicate
  to Metal ratio in the early Solar nebula
  (remember that we think that the Earth suffered a
  giant impact)
• Or maybe the part of the Solar Nebula where Mars
  formed had less metals

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Astronomy 330

• Spacecraft orbital data indicates that Mars
  probably has a somewhat dense core
• Core is probably composed of FeS (not iron nickel
  as on Earth) (Iron Sulfide) with a diameter of
  2400 km, 40 of total diameter.
• The core takes up a similar volume relative to
  the total as does the Earths core
• Core is probably solid, not liquid as deduced
  from calculations
• Mars has no strong magnetic field (not
  surprising), but does show a primordial field

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Astronomy 330

• Magnetometers do detect some residual fields
  coming from specific areas of Mars
• This indicates Mars probably did have a strong
  field in its past and a liquid core
• Magnetism is found where rocks on Mars are the
  oldest
• The Solar wind interacts directly with the
  Martian atmosphere

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Astronomy 330 Reading

• Read Chapter 11 of Morrison and Owen