AnnouncementsAnnouncements

● Passing out marks-so-far today with assignmentsPassing out marks-so-far today with assignments● ½ of available marks now given out½ of available marks now given out● Can always do `bonus assignments' (worth 2 credits)Can always do `bonus assignments' (worth 2 credits)

– Find current news article relevent to the Find current news article relevent to the course (1 credit)course (1 credit)

– Briefly describe it and its relevence to the Briefly describe it and its relevence to the course (1 credit)course (1 credit)

The Search: MarsThe Search: Mars● A Short Biography of MarsA Short Biography of Mars

– The Planet and its HistoryThe Planet and its History● The History of Mars ExplorationThe History of Mars Exploration

– PastPast– CurrentCurrent– Future?Future?

● The Search for (past) Life on MarsThe Search for (past) Life on Mars

– Viking ExperimentsViking Experiments– Microbial FossilsMicrobial Fossils

A Portrait of Mars as a Small PlanetA Portrait of Mars as a Small Planet

● MarsMars● The atmosphere of MarsThe atmosphere of Mars● How it came to be that wayHow it came to be that way

MarsMars

● Red planet between Earth and Red planet between Earth and Asteroid BeltAsteroid Belt

● Half again as far away from Sun Half again as far away from Sun as the Earth isas the Earth is

– Expect it to be ~100Expect it to be ~100oo F F colder than Earth on averagecolder than Earth on average

– Average too cool for waterAverage too cool for water– Peak temps ~ 70Peak temps ~ 70o o F (but -130 F (but -130

at night!)at night!)

MarsMars

● Near asteroid beltNear asteroid belt

– Likely more collisions than Likely more collisions than EarthEarth

● Large impacts can blow off Large impacts can blow off significant rocky material significant rocky material

– MeteoritesMeteorites● As well as gases (atmosphere)As well as gases (atmosphere)

MarsMars

● ~1/2 radius of Earth~1/2 radius of Earth● ~1/10 mass~1/10 mass● ~40% surface gravity~40% surface gravity

– Force of a 1 lb weight less Force of a 1 lb weight less than ½ lb on Marsthan ½ lb on Mars

– Less gravity holding the Less gravity holding the atmosphere in placeatmosphere in place

MarsMars

● Too little gravity to be able to hold Too little gravity to be able to hold onto a significant atmosphereonto a significant atmosphere

● Atmospheric pressure less than Atmospheric pressure less than 1% of Earth's1% of Earth's

EvaporationEvaporation

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

EvaporationEvaporation

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

● Fastest moving water (say) Fastest moving water (say) molecules can escape into molecules can escape into atmosphereatmosphere

● Water molecules in atmosphere Water molecules in atmosphere can collide into water and become can collide into water and become part of the liquidpart of the liquid

● Balance is reached when Balance is reached when evaporating water = condensing evaporating water = condensing waterwater

EvaporationEvaporation

● Can change balance:Can change balance:

– Little water in atmosphere, Little water in atmosphere, evaporation happens fasterevaporation happens faster

● (Why feel so sticky on a (Why feel so sticky on a humid day)humid day)

– If air pressure is very low, If air pressure is very low, evaporated water molecules evaporated water molecules can move very far away from can move very far away from pool of waterpool of water

● Fewer around to condenseFewer around to condense● Faster evaporationFaster evaporation

EvaporationEvaporation

● Effect of atmospheric pressure Effect of atmospheric pressure happens on our own planethappens on our own planet

● Reason for `high-altitude cooking Reason for `high-altitude cooking instructions' on some boxesinstructions' on some boxes

● Higher altitude -> lower air Higher altitude -> lower air pressure -> evaporation is easier -pressure -> evaporation is easier -> lower boiling point> lower boiling point

0 2000 5000 7500 10000100

120

140

160

180

200

220

Boiling Point at Altitude

Altitude (ft)

Boilin

g P

t of

Wate

r (F

)

EvaporationEvaporation

● Martian atmospheric pressure < Martian atmospheric pressure < 1% of Earth's1% of Earth's

– (Earth's atmosphere at 15 (Earth's atmosphere at 15 miles / 80,000 ft)miles / 80,000 ft)

● Water boiling point is so low that Water boiling point is so low that any liquid water evaporates any liquid water evaporates immediatelyimmediately

● No free water possible on surfaceNo free water possible on surface

EvaporationEvaporation

● But water ice DOES exist on But water ice DOES exist on Mars:Mars:

– Polar ice capsPolar ice caps● Mostly (on top) dry ice Mostly (on top) dry ice

(frozen CO2)(frozen CO2)● Underneath, visible when Underneath, visible when

CO2 has sublimated, water iceCO2 has sublimated, water ice

– Quite likely some trapped Quite likely some trapped under surface: `permafrost'under surface: `permafrost'

Atmospheric PressureAtmospheric Pressure

● Atmospheric pressure is Atmospheric pressure is seasonalseasonal

● Dry ice caps meltDry ice caps melt

– Increase COIncrease CO22 in in

atmosphereatmosphere– Increase atmosphere Increase atmosphere

pressurepressure● Dry ice caps re-freezeDry ice caps re-freeze

– Pressure decreasesPressure decreases

The Reasons for the SeasonsThe Reasons for the Seasons

● Earth's (and Mars') axis is Earth's (and Mars') axis is tiltedtilted

● Earth: 23.5Earth: 23.5oo (Mars: 25.9 (Mars: 25.9oo))● Tilt stays in same direction Tilt stays in same direction

as planet orbits Sunas planet orbits Sun

The Reasons for the SeasonsThe Reasons for the Seasons● Sun comes in at different Sun comes in at different

angle when planet is at angle when planet is at different positionsdifferent positions

● Summer:Summer:

– Light most directLight most direct– Sun closest to being Sun closest to being

overheadoverhead● WinterWinter

– Comes in at angle:Comes in at angle:● Same amount of light Same amount of light

covers larger areacovers larger area

– Increased reflectionIncreased reflection

Summer

Winter

The Reasons for the SeasonsThe Reasons for the Seasons● Orientation changes over Orientation changes over

course of yearcourse of year● Another effect: Earth is Another effect: Earth is

slightly further from Sun in slightly further from Sun in (Northern Hemisphere) (Northern Hemisphere) Winter than in SummerWinter than in Summer

– Only ~1% effect (5Only ~1% effect (5ooF)F)– Effect of orientation Effect of orientation

~16% effect (90~16% effect (90ooF)F)

Fall: Cubs win (effective 2003)

Spring: Bulls Lose

Win

ter:

Bea

rs L

ose

EclipticEcliptic

● Because of Earth's tilt, equator Because of Earth's tilt, equator (and rotation) do not line up with (and rotation) do not line up with plane of the solar systemplane of the solar system

● Solar system objects (Sun, Moon, Solar system objects (Sun, Moon, planets) apear to lie along an arc – planets) apear to lie along an arc – eclipticecliptic

EclipticEcliptic

● Planets are along plane of solar Planets are along plane of solar systemsystem

● Appear on Earth to along an arcAppear on Earth to along an arc● Mars visible these days early at Mars visible these days early at

night towards the East, even from night towards the East, even from ChicagoChicago

– Bright reddish `star'Bright reddish `star'– Near a bright greenish-Near a bright greenish-

yellow `star' (Venus)yellow `star' (Venus)

Starmap for tonight, 9pm

How Mars Came to Be This WayHow Mars Came to Be This Way

● Distance from Sun makes global Distance from Sun makes global liquid water difficult but not liquid water difficult but not impossibleimpossible

● NO ATMOSPHERENO ATMOSPHERE

– Liquid water quickly Liquid water quickly evaporatesevaporates

– No greenhouse effect to warm No greenhouse effect to warm planet, regulate temp.planet, regulate temp.

– No ozone to protect from UVNo ozone to protect from UV

Large Enough for Atmosphere

Not Large Enough for Atmosphere

The History of Martian ExplorationThe History of Martian Exploration

● Past explorationsPast explorations● Current Rover MissionsCurrent Rover Missions● Future PlansFuture Plans

Exploration of Mars TodayExploration of Mars Today

● So many recent missions to So many recent missions to Mars that it's becoming Mars that it's becoming almost anticlimaticalmost anticlimatic

● News filled with discoveries News filled with discoveries from current roversfrom current rovers

● Still very difficult:Still very difficult:

– Success rate low!Success rate low!– Scientists can't go there Scientists can't go there

at whim yetat whim yet

Observations of Mars from EarthObservations of Mars from Earth

● Early telescope observations:Early telescope observations:

– `observations' of canals`observations' of canals– Improved telescopes Improved telescopes

showed this not to be the showed this not to be the casecase

● Later, radio observationsLater, radio observations

– Surface temperatureSurface temperature– Crude radar maps of Crude radar maps of

surfacesurface

1960-2: Korabl (`Marsnik')1960-2: Korabl (`Marsnik')

● Attempted Russian Probes Attempted Russian Probes ● 4 attempted flybys, 1 attempted landing4 attempted flybys, 1 attempted landing● Most barely made it past Earth orbit, Most barely made it past Earth orbit,

one was lost between Earth and Marsone was lost between Earth and Mars

1964: Mariner, Zond1964: Mariner, Zond

● Mariner 3, 4 (USA): attempted flybyMariner 3, 4 (USA): attempted flyby

– Mariner 3: Couldn't make it to Mariner 3: Couldn't make it to MarsMars

– Mariner 4: First flyby, close up Mariner 4: First flyby, close up picturespictures

● Zond 2 (USSR): Russian flyby, descentZond 2 (USSR): Russian flyby, descent

– Lost on its way to MarsLost on its way to Mars

1969: Mariner, Mars 19691969: Mariner, Mars 1969

● Mariner 6,7: Identical flyby craftMariner 6,7: Identical flyby craft

– Mariner 4: First flyby, close up Mariner 4: First flyby, close up picturespictures

● Mars 1969A/B: Russian flyby, descentMars 1969A/B: Russian flyby, descent

– Didn't survive takeoffDidn't survive takeoff

1971: Mariner, Mars 2/3: Orbiters1971: Mariner, Mars 2/3: Orbiters

● Mars 2/3 (USSR): First orbiter of Mars 2/3 (USSR): First orbiter of another worldanother world

– Measured temps, magnetic fieldsMeasured temps, magnetic fields– Sent probe, 1 crashed too fast, Sent probe, 1 crashed too fast,

other survived 20 hours Mariner other survived 20 hours Mariner 8 didn't make it8 didn't make it

● Mariner 9: Orbited, obscured by stormsMariner 9: Orbited, obscured by storms

– First close-up views of moons of First close-up views of moons of MarsMars

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

● Mars 4: Brakes didn't work; flew by Mars 4: Brakes didn't work; flew by instead of orbitedinstead of orbited

● Mars 5: Successful Orbit, picturesMars 5: Successful Orbit, pictures● Mars 6: Descent, sent data from Mars 6: Descent, sent data from

atmosphere before shutting down, but atmosphere before shutting down, but data garbleddata garbled

● Mars 7: Missed Mars entirelyMars 7: Missed Mars entirely

1975: Viking 1,2 (USA)1975: Viking 1,2 (USA)

● Identical Orbiter + landerIdentical Orbiter + lander

– Orbiters searched for safe Orbiters searched for safe landing placeslanding places

– Extensive weather Extensive weather measurements, chemistry/biology measurements, chemistry/biology experimentsexperiments

– Sent several thousand images, Sent several thousand images, datadata

1988: Phobos 1,2 (USSR)1988: Phobos 1,2 (USSR)

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

1988-19921988-1992

● 1988: Phobos 1, 2 (USSR)1988: Phobos 1, 2 (USSR)

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

● 1992: Mars Observer (USA)1992: Mars Observer (USA)

– All contact lost 3 days from MarsAll contact lost 3 days from Mars

Very Recent Mars MissionsVery Recent Mars Missions

● 1996:1996:

– Mars 96 (USSR): Didn't Mars 96 (USSR): Didn't successfully leave Earthsuccessfully leave Earth

– Mars Global Surveyor (USA)Mars Global Surveyor (USA)● Looking for places to send Looking for places to send

PathfinderPathfinder● Still sending back dataStill sending back data

– Mars PathfinderMars Pathfinder● Probe with some sensorsProbe with some sensors● Test of new technologies, Test of new technologies,

techniquestechniques

1998: Less Successful1998: Less Successful

● Nozomi (Japan)Nozomi (Japan)

– Navigation problemsNavigation problems– Could not reach Mars at expected time Could not reach Mars at expected time – Unable to orbit MarsUnable to orbit Mars

● Mars Climate Orbiter (USA)Mars Climate Orbiter (USA)

– Crashed into Mars after mistake in Crashed into Mars after mistake in converting units in probe computer converting units in probe computer programming programming

1998-9: Less Successful1998-9: Less Successful

● Nozomi (Japan)Nozomi (Japan)

– Navigation problemsNavigation problems– Could not reach Mars at expected time Could not reach Mars at expected time – Unable to orbit MarsUnable to orbit Mars

● Mars Climate Orbiter (USA)Mars Climate Orbiter (USA)

– Crashed into Mars after mistake in Crashed into Mars after mistake in converting units in probe computer converting units in probe computer programmingprogramming

● Mars Polar Lander (USA)Mars Polar Lander (USA)

– Signal lost near Mars: Navigation errors?Signal lost near Mars: Navigation errors?

2001: Mars Odyssey2001: Mars Odyssey(NASA)(NASA)

● OrbiterOrbiter● Build global map of telements, minerals on the Build global map of telements, minerals on the

Mars surfaceMars surface● Determine the abundance of hydrogen in Determine the abundance of hydrogen in

subsurface. -> hidden deposits of water ice?subsurface. -> hidden deposits of water ice?● Structure of the Martian surface.Structure of the Martian surface.● Radiation environment between the Earth and Radiation environment between the Earth and

Mars and in low Mars orbit (radiation-related risk Mars and in low Mars orbit (radiation-related risk to human exploration)to human exploration)

● Communication relay Spirit/Opportunity/BeagleCommunication relay Spirit/Opportunity/Beagle

2001: Mars Express2001: Mars Express(Europe)(Europe)

● Orbiter + Lander/Rover (Beagle)Orbiter + Lander/Rover (Beagle)● Beagle lostBeagle lost● Image globe in 3DImage globe in 3D● Build accurate picture of meteorology/climageBuild accurate picture of meteorology/climage● Communications RelayCommunications Relay

2003: Spirit, Opportunity2003: Spirit, Opportunity(USA)(USA)

● Search for/study many types of rocks Search for/study many types of rocks and soils that might hold clues to past and soils that might hold clues to past water activity.water activity.

● Maps showing the locations of Maps showing the locations of different kinds of rocks and soils different kinds of rocks and soils around the landing sites.around the landing sites.

● What forces have shaped the What forces have shaped the landscapelandscape

● Search for minerals that contain Search for minerals that contain water/formed in water.water/formed in water.

● Identify minerals, how madeIdentify minerals, how made● Clues to what environment was like in Clues to what environment was like in

pastpast

The Search for Life on MarsThe Search for Life on Mars

● Pictures of surfacePictures of surface● Viking biology experimentsViking biology experiments● Meteoritic `fossils'Meteoritic `fossils'● Future?Future?

VenusVenus

● Closest to EarthClosest to Earth● ¾ as far away from Sun as ¾ as far away from Sun as

Earth isEarth is● Very similar to Earth's size, Very similar to Earth's size,

densitydensity● Covered by thick, opaque Covered by thick, opaque

cloudsclouds

Reading for Next Class (Apr 16)Reading for Next Class (Apr 16)● Chapter 15: The Outer Solar SystenChapter 15: The Outer Solar Systen

– History of Outer Solar System ExplorationHistory of Outer Solar System Exploration– The Nature of Gas GiantsThe Nature of Gas Giants

● AtmosphereAtmosphere● ChemistryChemistry

– The Moons of Jupiter, Saturn, Uranus, The Moons of Jupiter, Saturn, Uranus, NeptuneNeptune

● Chapter 16: How Unique is Earth?Chapter 16: How Unique is Earth?

– Necessary ResourcesNecessary Resources– On Having a Large MoonOn Having a Large Moon– Staying alive by accidentStaying alive by accident