announcements ● assignments were very good this week! ● let me know this week if you’re...

AnnouncementsAnnouncements

● Assignments were very good this week!Assignments were very good this week!

● Let me know this week if you’re planning to do a Let me know this week if you’re planning to do a presentation rather than a reportpresentation rather than a report

The SearchThe Search● An overview of the Mars Rover MissionAn overview of the Mars Rover Mission● Gas Giant PlanetsGas Giant Planets

– Sketch of a Gas GiantSketch of a Gas Giant– Who's who in the Outer Solar SystemWho's who in the Outer Solar System– Formation of Gas GiantsFormation of Gas Giants– Formation of GG moonsFormation of GG moons– Tidal ForcesTidal Forces– Visits to the PlanetsVisits to the Planets

● How Unique is Earth?How Unique is Earth?

The Mars RoversThe Mars Rovers

● Identical pairs of rovers sent to opposite Identical pairs of rovers sent to opposite sides of Marssides of Mars

● Spirit and OpportunitySpirit and Opportunity● Each has a 12:20 `day' (sol) ; since on Each has a 12:20 `day' (sol) ; since on

opposite sides of Mars, it is always day opposite sides of Mars, it is always day for one of the twofor one of the two

● Primarily geology mission. Primarily geology mission.


● Launched in June/July 2003Launched in June/July 2003● 3 Stages:3 Stages:

– Get off out Earth's surfaceGet off out Earth's surface– Get out out Earth's orbitGet out out Earth's orbit– Head towards MarsHead towards Mars


● Began landing in Jan 2004Began landing in Jan 2004● Entered atmosphere at 12,000 mph Entered atmosphere at 12,000 mph

(Chicago -> San Francisco in 9 minutes)(Chicago -> San Francisco in 9 minutes)● Broke using heat shield, parachute.Broke using heat shield, parachute.● Took pictures on decent to gauge Took pictures on decent to gauge

horizontal velocityhorizontal velocity● Deployed airbagsDeployed airbags● Fired retro-rocketsFired retro-rockets● Bounced a lotBounced a lot


● Once landed and stable, base unfurled Once landed and stable, base unfurled ● Rover, which was also folded up, Rover, which was also folded up,

unfurledunfurled


● Four Science Goals:Four Science Goals:

– Determine whether Life ever arose Determine whether Life ever arose on Marson Mars

– Characterize the Climate of MarsCharacterize the Climate of Mars– Characterize the Geology of MarsCharacterize the Geology of Mars– Prepare for Human ExplorationPrepare for Human Exploration


● Search, characterize rocks & soils that hold Search, characterize rocks & soils that hold clues to clues to past water activity and geologic processpast water activity and geologic process

● Determine Determine distributiondistribution, composition of minerals, , composition of minerals, rocks, and soils surrounding the landing sites.rocks, and soils surrounding the landing sites.

● Perform "ground truth" of surface observations made Perform "ground truth" of surface observations made by orbitersby orbiters

● Search for iron-containing minerals that indicate Search for iron-containing minerals that indicate waterwater

● Geological clues to the Geological clues to the environmental conditionsenvironmental conditions that existed when liquid water was present. Assess that existed when liquid water was present. Assess whether those environments were conducive to life.whether those environments were conducive to life.


● CamerasCameras

– Panoramic Camera (Pancam)Panoramic Camera (Pancam)– Microscopic Imager (MI)Microscopic Imager (MI)– Engineering cameras: Hazcams and NavcamsEngineering cameras: Hazcams and Navcams

● SpectrometersSpectrometers

– Miniature Thermal Emission Spectrometer Miniature Thermal Emission Spectrometer (Mini-TES)(Mini-TES)

– Mössbauer Spectrometer (MB)Mössbauer Spectrometer (MB)– Alpha Particle X-Ray Spectrometer (APXS)Alpha Particle X-Ray Spectrometer (APXS)

● Rock Abrasion Tool (RAT)Rock Abrasion Tool (RAT)● Magnet ArrayMagnet Array

Gas Giant PlanetsGas Giant Planets

● OverviewOverview● Who's WhoWho's Who● FormationFormation● MoonsMoons● Tidal ForcesTidal Forces

Our Solar SystemOur Solar System

● Almost all of mass of planets are in the 4 giant Almost all of mass of planets are in the 4 giant planetsplanets

The GiantsThe Giants

● The Giants are sometimes all The Giants are sometimes all called `Jovian' planets after called `Jovian' planets after JupiterJupiter

● After more exploration After more exploration showed their diversity, this showed their diversity, this term lost favorterm lost favor


● The giant planets inhabit the The giant planets inhabit the outer solar system (5-30 AU)outer solar system (5-30 AU)

● This means they get less This means they get less energy from the Sun (4% - energy from the Sun (4% - 0.1%) per area0.1%) per area

● Top of cloud cover of planets Top of cloud cover of planets is very cold (-170is very cold (-170ooF --- F --- 350350ooF)F)


● The giant planets can be The giant planets can be weighed very accurately by weighed very accurately by measuring the speed of their measuring the speed of their moons.moons.

● Much heavier than Earth, but Much heavier than Earth, but not so heavy considering their not so heavy considering their sizesize

● Densities 600 – 1600 kg/mDensities 600 – 1600 kg/m33, , compared with Earth's 5700 compared with Earth's 5700 kg/mkg/m33

● Mostly made of gas/liquids?Mostly made of gas/liquids?

The Birth of GiantsThe Birth of Giants

● In outer solar system, coolerIn outer solar system, cooler● Less evaporative stripping of Less evaporative stripping of

volatile gassesvolatile gasses● If sufficiently massive cores If sufficiently massive cores

form, can keep even volatile form, can keep even volatile gasses gasses

● These gasses will be These gasses will be representative of the very representative of the very early solar systemearly solar system


● Since early solar system is Since early solar system is largely composed of largely composed of Hydrogen, so will gas giantsHydrogen, so will gas giants

● Rocky or Icy or Slushy coreRocky or Icy or Slushy core● High-hydrogen atmosphere High-hydrogen atmosphere

has some similarities to has some similarities to atmosphere in Miller-Urey atmosphere in Miller-Urey experimentexperiment

● Can form lots of organicsCan form lots of organics


● Large rotating liquid metal Large rotating liquid metal region means large magnetic region means large magnetic fieldfield

● Jupiter: Significant field Jupiter: Significant field extends out size of the Sun!extends out size of the Sun!

● Can seriously effect nearby Can seriously effect nearby objects.objects.


● Large mass -> high pressure, Large mass -> high pressure, temperature at centertemperature at center

● Temperature at center of Temperature at center of Jupiter ~ 4 times surface of Jupiter ~ 4 times surface of Sun!Sun!

● Collapse from origin of planet Collapse from origin of planet still slowly continuingstill slowly continuing

● Releases heat energyReleases heat energy● These planets have a source of These planets have a source of

heatheatJupiter in Infrared


● Gas giants emit more heat Gas giants emit more heat than they absorb from Sunthan they absorb from Sun

● At earlier times, would have At earlier times, would have been much hotterbeen much hotter

● Moons, which are nearby, Moons, which are nearby, heated by their nearby planetheated by their nearby planet

● Many of these moons are Many of these moons are large (planet-sized)large (planet-sized)

● Moons might be interesting Moons might be interesting for life?for life?

Jupiter in Infrared

The Composition of GiantsThe Composition of Giants

● Structure of gas giant Structure of gas giant atmospheres depends on mass atmospheres depends on mass of planetof planet

● Lower planet mass -> lower Lower planet mass -> lower interior pressure -> may not interior pressure -> may not be high-pressure enough to be high-pressure enough to make hydrogen into a liquid make hydrogen into a liquid metal.metal.

● Rock/Ice cores surrounded by Rock/Ice cores surrounded by Hydrogen/Helium gasHydrogen/Helium gas

The Moons of GiantsThe Moons of Giants

● Planets large enough that many Planets large enough that many moons were also formedmoons were also formed

● Many of them planet sized in their Many of them planet sized in their own rightown right

● Get heat from planetGet heat from planet● Some (Io/Jupiter) effected by planets Some (Io/Jupiter) effected by planets

magnetic fieldmagnetic field● Atmosphere? (Titan, Saturn)Atmosphere? (Titan, Saturn)● Water? (Europa, Jupiter) Water? (Europa, Jupiter)

The Moons of GiantsThe Moons of Giants

● Formation: like planets around sunFormation: like planets around sun● Rotating body, disk formsRotating body, disk forms● Moons generally along plane of Moons generally along plane of

rotation of planet rotation of planet

Tidal ForcesTidal Forces

● Tidal forces familiar from EarthTidal forces familiar from Earth● Not due simply to gravitational Not due simply to gravitational

attraction (that would just move attraction (that would just move the whole body) but the the whole body) but the difference in gravitational force difference in gravitational force across the bodyacross the body

● Gravity: inverse squareGravity: inverse square● Tidal forces: inverse cubeTidal forces: inverse cube● REALLY matters how close the REALLY matters how close the

object isobject is

RingsRings

● Most of the gas giants have Most of the gas giants have ringsrings

● Jupiters are very small, Jupiters are very small, probably transient, and made probably transient, and made largely of dustlargely of dust

● Too close to planet, tidal forces Too close to planet, tidal forces are strong enough to disrupt are strong enough to disrupt moons or prevent them from moons or prevent them from formingforming

● Result is material scattered in Result is material scattered in orbit around planetorbit around planet

Visiting the outer Solar SystemVisiting the outer Solar System

● PioneerPioneer● Voyager I/IIVoyager I/II● GalileoGalileo● UlyssesUlysses● Cassini-HuygensCassini-Huygens

Pioneer 10,11Pioneer 10,11

● Launched in 1972Launched in 1972● Camera, equipment for Camera, equipment for

measuring gas/magnetic fields measuring gas/magnetic fields in the solar system, radiationin the solar system, radiation

● Now ghost shipsNow ghost ships● Carry plaque in case ever Carry plaque in case ever

discovereddiscovered● Plaque designed by Carl SaganPlaque designed by Carl Sagan

Voyager I/IIVoyager I/II

● Launched in 1977Launched in 1977● Carry cameras, equipment for Carry cameras, equipment for

measuring gas/magnetic fields measuring gas/magnetic fields in the solar systemin the solar system

● Now at 90 AU (8.4 billion Now at 90 AU (8.4 billion miles)miles)

● Still send trickle of dataStill send trickle of data● Will continue transmitting until Will continue transmitting until

~2020 (not enough sunlight to ~2020 (not enough sunlight to power equipment)power equipment)


● Carries a golden recordCarries a golden record● Has needle, instructions on how Has needle, instructions on how

to play it on coverto play it on cover● Contents assembled by Carl Contents assembled by Carl

SaganSagan● Contains music, greetings in 55 Contains music, greetings in 55

langaguges, langaguges, natural/atmospheric sounds, natural/atmospheric sounds, written greetingswritten greetings

http://www.jpl.nasa.gov/flash/voyager_record/index.htm


● Travelled past Jupiter, SaturnTravelled past Jupiter, Saturn● Voyager II then flew by Uranus Voyager II then flew by Uranus

and Neptune; Voyager I stopped and Neptune; Voyager I stopped by Titan (largest moon of Saturn), by Titan (largest moon of Saturn), trajectory then sent it out of plane trajectory then sent it out of plane of galaxyof galaxy

UlyssesUlysses

● Sent to examine magnetic field, Sent to examine magnetic field, radiation from Sun, esp. polesradiation from Sun, esp. poles

● Sent to Jupiter for slingshot out of Sent to Jupiter for slingshot out of plane of eclipticplane of ecliptic

● Also obtained magnetic field data Also obtained magnetic field data from Jupiterfrom Jupiter

GalileoGalileo● Launched 1993Launched 1993● Study Jupiter's atmosphere, Study Jupiter's atmosphere,

satellites, magnetosphere for 2 satellites, magnetosphere for 2 years.years.

● Made encounters with asteroidsMade encounters with asteroids● Arrived at Jupiter, Dec 1995Arrived at Jupiter, Dec 1995● Significantly advanced our Significantly advanced our

knowledge of the Galilean moonsknowledge of the Galilean moons● At end of mission was burned up At end of mission was burned up

in Jupiter's atmosphere to avoid in Jupiter's atmosphere to avoid contaminating moonscontaminating moons

http://www.jpl.nasa.gov/videos/quicktime/galileo.qtl

GalileoGalileo

● Took pictures of direct impact of Took pictures of direct impact of comet into Jupiter in 1994comet into Jupiter in 1994

Cassini-HuygensCassini-Huygens

● Will arrive at Saturn later this Will arrive at Saturn later this year (July)year (July)

● Already taking picturesAlready taking pictures● Will send a probe (Huygens) to Will send a probe (Huygens) to

TitanTitan

Planets of InterestPlanets of Interest

● Where might life be?Where might life be?

– Gas Giants?Gas Giants?– Moons?Moons?

● EuropaEuropa● TitanTitan● IapetusIapetus

Gas GiantsGas Giants

● Convection is a fundamental Convection is a fundamental processprocess

– Happens everywhereHappens everywhere● Fluid heated at bottom rises, Fluid heated at bottom rises,

cools, falls back downcools, falls back down● Gas giants have hot centersGas giants have hot centers● Large-scale motionsLarge-scale motions● Mix materialMix material

Gas GiantsGas Giants

● Makes it difficult to imagine Makes it difficult to imagine life forminglife forming

● No real surface to live onNo real surface to live on● Chemicals constantly being Chemicals constantly being

mixed aroundmixed around● No originally contained No originally contained

environment (`protocell')environment (`protocell')

MoonsMoons

● Gas giants have planet-sized Gas giants have planet-sized moonsmoons

● At least one (Titan) has a At least one (Titan) has a significant atmospheresignificant atmosphere

● Another (Europa) very likely Another (Europa) very likely has liquid salty water under a has liquid salty water under a layer of icelayer of ice

EuropaEuropa

● Very suggestive it has a liquid Very suggestive it has a liquid underneathunderneath

– No crateringNo cratering– Many fractures, ridges on Many fractures, ridges on

surfacesurface● What would this mean for life?What would this mean for life?

– If some source of energy If some source of energy on inside (geothermal, on inside (geothermal, chemical), very real chemical), very real possibility of some sort of possibility of some sort of lifelife

TitanTitan

● Very ColdVery Cold● Massive, Cold enough to have Massive, Cold enough to have

an atmosphere (1.5 x as dense an atmosphere (1.5 x as dense as ours!)as ours!)

● No oxygenNo oxygen● No liquid waterNo liquid water● Hydrogen richHydrogen rich● Interesting organic chemistryInteresting organic chemistry● Lakes of hydrocarbons?Lakes of hydrocarbons?● Huygen probe 2005Huygen probe 2005

IapetusIapetus

● Moon of mysteryMoon of mystery● Side facing away from Saturn is Side facing away from Saturn is

very, very darkvery, very dark● Much less light reflected than Much less light reflected than

bright sidebright side● How did this happen?How did this happen?● What is the dark material?What is the dark material?

How Unique is Earth?How Unique is Earth?

● What is special about Earth?What is special about Earth?● How important/rare are those things?How important/rare are those things?● How many such planets are there likely How many such planets are there likely

to be?to be?

EarthEarth

● AtmosphereAtmosphere

– Large surface gravityLarge surface gravity● Reasonable temperatureReasonable temperature● Rocky srfaceRocky srface● Large moonLarge moon● Lots of heavy elementsLots of heavy elements

How Important/Rare are these?How Important/Rare are these?

● Heavy elements;Heavy elements;

– Likely ubiquitous in Likely ubiquitous in planets around Pop I starsplanets around Pop I stars


● Rocky SurfaceRocky Surface

– Can happen if there is Can happen if there is heavy elements (see heavy elements (see above)above)

– Probably true of all Probably true of all planets close enough to planets close enough to have liquid waterhave liquid water

– (But planet migration)(But planet migration)


● AtmosphereAtmosphere

– Requires not too close to Requires not too close to sun sun

– Requires massive enough Requires massive enough planetplanet


● Reasonable TemperatureReasonable Temperature

– `Goldilocks zone’`Goldilocks zone’– Needs to be right distance Needs to be right distance

to starto star


● So we requireSo we require

– Rocky PlanetRocky Planet– Of the right massOf the right mass– At the right distance from At the right distance from

the starthe star

Habitable ZoneHabitable Zone

● Corresponds to further than Corresponds to further than Venus to about Mars distance Venus to about Mars distance for our Sunfor our Sun

● Using inverse-square law, could Using inverse-square law, could calculate for other starscalculate for other stars

● Main requirement: liquid water Main requirement: liquid water in the presence of an in the presence of an atmosphere.atmosphere.

Habitable Zone: Binary StarsHabitable Zone: Binary Stars

● About half of all stars are in About half of all stars are in binary systemsbinary systems

● Stars orbit a common center of Stars orbit a common center of mass (more on that next week)mass (more on that next week)

● Can planets have reasonable Can planets have reasonable orbits in such systems?orbits in such systems?

● Yes, but must orbit one star or Yes, but must orbit one star or be far away from both;be far away from both;

● `Figure 8’ orbits aren’t stable`Figure 8’ orbits aren’t stable

Reading for Next Class (Apr 23)Reading for Next Class (Apr 23)

● Chapter 17: The Discovery of Extra-Solar Chapter 17: The Discovery of Extra-Solar PlanetsPlanets

– Techniques for finding planetsTechniques for finding planets– ResultsResults– Looking closerLooking closer– Atmospheres?Atmospheres?– PlanetQuestPlanetQuest

announcements ● assignments were very good this week! ● let me know this week if you’re...

Documents

mars roverslaunched

lotthe mars roversonce

ofthe giantsthe giant

mass of planets

jovian planets

entered atmosphere

liquid water

rocks soils