Announcements

1
Announcements

• Passing out marks-so-far today with assignments
• ½ of available marks now given out
• Can always do bonus assignments' (worth 2
  credits)
• Find current news article relevent to the course
  (1 credit)
• Briefly describe it and its relevence to the
  course (1 credit)

2
The Search Mars

• A Short Biography of Mars
• The Planet and its History
• The History of Mars Exploration
• Past
• Current
• Future?
• The Search for (past) Life on Mars
• Viking Experiments
• Microbial Fossils

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A Portrait of Mars as a Small Planet

• Mars
• The atmosphere of Mars
• How it came to be that way

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Mars

• Red planet between Earth and Asteroid Belt
• Half again as far away from Sun as the Earth is
• Expect it to be 100o F colder than Earth on
  average
• Average too cool for water
• Peak temps 70o F (but -130 at night!)

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Mars

• Near asteroid belt
• Likely more collisions than Earth
• Large impacts can blow off significant rocky
  material
• Meteorites
• As well as gases (atmosphere)

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Mars

• 1/2 radius of Earth
• 1/10 mass
• 40 surface gravity
• Force of a 1 lb weight less than ½ lb on Mars
• Less gravity holding the atmosphere in place

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Mars

• Too little gravity to be able to hold onto a
  significant atmosphere
• Atmospheric pressure less than 1 of Earth's

8
Evaporation

• What causes evaporation of liquid, and what
  prevents it?

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Evaporation

• What causes evaporation of liquid, and what
  prevents it?
• Fastest moving water (say) molecules can escape
  into atmosphere
• Water molecules in atmosphere can collide into
  water and become part of the liquid
• Balance is reached when evaporating water
  condensing water

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Evaporation

• Can change balance
• Little water in atmosphere, evaporation happens
  faster
• (Why feel so sticky on a humid day)
• If air pressure is very low, evaporated water
  molecules can move very far away from pool of
  water
• Fewer around to condense
• Faster evaporation

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Evaporation

• Effect of atmospheric pressure happens on our own
  planet
• Reason for high-altitude cooking instructions'
  on some boxes
• Higher altitude -gt lower air pressure -gt
  evaporation is easier -gt lower boiling point

12
Evaporation

• Martian atmospheric pressure lt 1 of Earth's
• (Earth's atmosphere at 15 miles / 80,000 ft)
• Water boiling point is so low that any liquid
  water evaporates immediately
• No free water possible on surface

13
Evaporation

• But water ice DOES exist on Mars
• Polar ice caps
• Mostly (on top) dry ice (frozen CO2)
• Underneath, visible when CO2 has sublimated,
  water ice
• Quite likely some trapped under surface
  permafrost'

14
Atmospheric Pressure

• Atmospheric pressure is seasonal
• Dry ice caps melt
• Increase CO2 in atmosphere
• Increase atmosphere pressure
• Dry ice caps re-freeze
• Pressure decreases

15
The Reasons for the Seasons

• Earth's (and Mars') axis is tilted
• Earth 23.5o (Mars 25.9o)
• Tilt stays in same direction as planet orbits Sun

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The Reasons for the Seasons

• Sun comes in at different angle when planet is at
  different positions
• Summer
• Light most direct
• Sun closest to being overhead
• Winter
• Comes in at angle
• Same amount of light covers larger area
• Increased reflection

Summer
Winter
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The Reasons for the Seasons
Fall Cubs win (effective 2003)

• Orientation changes over course of year
• Another effect Earth is slightly further from
  Sun in (Northern Hemisphere) Winter than in
  Summer
• Only 1 effect (5oF)
• Effect of orientation 16 effect (90oF)

Winter Bears Lose
Spring Bulls Lose
18
Ecliptic

• Because of Earth's tilt, equator (and rotation)
  do not line up with plane of the solar system
• Solar system objects (Sun, Moon, planets) apear
  to lie along an arc ecliptic

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Ecliptic

• Planets are along plane of solar system
• Appear on Earth to along an arc
• Mars visible these days early at night towards
  the East, even from Chicago
• Bright reddish star'
• Near a bright greenish-yellow star' (Venus)

Starmap for tonight, 9pm
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How Mars Came to Be This Way
Large Enough for Atmosphere

• Distance from Sun makes global liquid water
  difficult but not impossible
• NO ATMOSPHERE
• Liquid water quickly evaporates
• No greenhouse effect to warm planet, regulate
  temp.
• No ozone to protect from UV

Not Large Enough for Atmosphere
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The History of Martian Exploration

• Past explorations
• Current Rover Missions
• Future Plans

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Exploration of Mars Today

• So many recent missions to Mars that it's
  becoming almost anticlimatic
• News filled with discoveries from current rovers
• Still very difficult
• Success rate low!
• Scientists can't go there at whim yet

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Observations of Mars from Earth

• Early telescope observations
• observations' of canals
• Improved telescopes showed this not to be the
  case
• Later, radio observations
• Surface temperature
• Crude radar maps of surface

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1960-2 Korabl (Marsnik')

• Attempted Russian Probes
• 4 attempted flybys, 1 attempted landing
• Most barely made it past Earth orbit, one was
  lost between Earth and Mars

25
1964 Mariner, Zond

• Mariner 3, 4 (USA) attempted flyby
• Mariner 3 Couldn't make it to Mars
• Mariner 4 First flyby, close up pictures
• Zond 2 (USSR) Russian flyby, descent
• Lost on its way to Mars

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1969 Mariner, Mars 1969

• Mariner 6,7 Identical flyby craft
• Mariner 4 First flyby, close up pictures
• Mars 1969A/B Russian flyby, descent
• Didn't survive takeoff

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1971 Mariner, Mars 2/3 Orbiters

• Mars 2/3 (USSR) First orbiter of another world
• Measured temps, magnetic fields
• Sent probe, 1 crashed too fast, other survived 20
  hours Mariner 8 didn't make it
• Mariner 9 Orbited, obscured by storms
• First close-up views of moons of Mars

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1973 Mars 4/5/6/7 (USSR)

• Mars 4 Brakes didn't work flew by instead of
  orbited
• Mars 5 Successful Orbit, pictures
• Mars 6 Descent, sent data from atmosphere
  before shutting down, but data garbled
• Mars 7 Missed Mars entirely

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1975 Viking 1,2 (USA)

• Identical Orbiter lander
• Orbiters searched for safe landing places
• Extensive weather measurements, chemistry/biology
  experiments
• Sent several thousand images, data

30
1988 Phobos 1,2 (USSR)

• Lost due to human error (Phobos 1), computer
  malfunction (Phobos 2)

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1988-1992

• 1988 Phobos 1, 2 (USSR)
• Lost due to human error (Phobos 1), computer
  malfunction (Phobos 2)
• 1992 Mars Observer (USA)
• All contact lost 3 days from Mars

32
Very Recent Mars Missions

• 1996
• Mars 96 (USSR) Didn't successfully leave Earth
• Mars Global Surveyor (USA)
• Looking for places to send Pathfinder
• Still sending back data
• Mars Pathfinder
• Probe with some sensors
• Test of new technologies, techniques

33
1998 Less Successful

• Nozomi (Japan)
• Navigation problems
• Could not reach Mars at expected time
• Unable to orbit Mars
• Mars Climate Orbiter (USA)
• Crashed into Mars after mistake in converting
  units in probe computer programming

34
1998-9 Less Successful

• Nozomi (Japan)
• Navigation problems
• Could not reach Mars at expected time
• Unable to orbit Mars
• Mars Climate Orbiter (USA)
• Crashed into Mars after mistake in converting
  units in probe computer programming
• Mars Polar Lander (USA)
• Signal lost near Mars Navigation errors?

35
2001 Mars Odyssey(NASA)

• Orbiter
• Build global map of telements, minerals on the
  Mars surface
• Determine the abundance of hydrogen in
  subsurface. -gt hidden deposits of water ice?
• Structure of the Martian surface.
• Radiation environment between the Earth and Mars
  and in low Mars orbit (radiation-related risk to
  human exploration)
• Communication relay Spirit/Opportunity/Beagle

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2001 Mars Express(Europe)

• Orbiter Lander/Rover (Beagle)
• Beagle lost
• Image globe in 3D
• Build accurate picture of meteorology/climage
• Communications Relay

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2003 Spirit, Opportunity(USA)

• Search for/study many types of rocks and soils
  that might hold clues to past water activity.
• Maps showing the locations of different kinds of
  rocks and soils around the landing sites.
• What forces have shaped the landscape
• Search for minerals that contain water/formed in
  water.
• Identify minerals, how made
• Clues to what environment was like in past

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The Search for Life on Mars

• Pictures of surface
• Viking biology experiments
• Meteoritic fossils'
• Future?

39
Venus

• Closest to Earth
• ¾ as far away from Sun as Earth is
• Very similar to Earth's size, density
• Covered by thick, opaque clouds

40
Reading for Next Class (Apr 16)

• Chapter 15 The Outer Solar Systen
• History of Outer Solar System Exploration
• The Nature of Gas Giants
• Atmosphere
• Chemistry
• The Moons of Jupiter, Saturn, Uranus, Neptune
• Chapter 16 How Unique is Earth?
• Necessary Resources
• On Having a Large Moon
• Staying alive by accident