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Is Anyone Out There? The Search for Extra Terrestrial Life By Ulrike Lahaise Georgia Perimeter College November 2012.

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Presentation on theme: "Is Anyone Out There? The Search for Extra Terrestrial Life By Ulrike Lahaise Georgia Perimeter College November 2012."— Presentation transcript:

1 Is Anyone Out There? The Search for Extra Terrestrial Life By Ulrike Lahaise Georgia Perimeter College November 2012

2 Overview Necessities for Life as We Know It Necessities for Life as We Know It Search For Extra Terrestrial Life In Our Solar System Search For Extra Terrestrial Life In Our Solar System Extreme Life On Earth Extreme Life On Earth Search For Extra-solar Planets, aka Exoplanets Search For Extra-solar Planets, aka Exoplanets Search For Life on Exoplanets Search For Life on Exoplanets How You Can Get Involved With Exoplanets How You Can Get Involved With Exoplanets

3 What’s essential for life? Deprived of ___________, you would die in a 1. few weeks. 2. few days. 2. few days. 3. few minutes. A. FoodB. AirC. Water

4 Planet Atmospheres Which “Planets” have 5. no significant atmosphere? 5. no significant atmosphere? 6. a very thick outer gas layer? 6. a very thick outer gas layer? 7. a relatively thin but significant atmosphere? 7. a relatively thin but significant atmosphere? A. Earth, Venus, Mars B. Mercury, Pluto, the Moon C. Jupiter, Saturn, Neptune

5 Planet Sizes Which “planets” below are 7. medium-sized (1/2 to 2x Earth’s diameter)? 8. large-sized (over 3 times Earth’s diameter)? 9. small-sized (less than 1/3 Earth’s diameter)? A. Jupiter, Saturn, Neptune B. Mercury, Pluto, the Moon C. Earth, Venus, Mars

6 Water Based Lifeforms 10. Which choice below is the percentage of liquid water in the bodies of most animals (there are exceptions)? A. 464 to 470D to 427 B to 27E. 0 to 100 C. 50 to 70

7 Surface Temperatures Which choice below is the temperature range 12. on Venus in Celsius? 13. on Mercury in Celsius? 14. on Mars in Celsius? A. 464 to 470D to 427 B to 27E. 0 to 100 C. 50 to 70

8 Question: Is There Extra Terrestrial Life Similar To Us? Need to look for planets/moons that have Need to look for planets/moons that have Medium size Medium size Temperature range allowing liquid water at surface Temperature range allowing liquid water at surface Atmosphere, not too thick or thin Atmosphere, not too thick or thin Surface conditions that don’t vary too much Surface conditions that don’t vary too much Most obvious place to look: Our Solar System Most obvious place to look: Our Solar System

9 Water-Based Life In Solar System? (1) Look at Classical Earthlike Planets Look at Classical Earthlike Planets Mercury? NO Mercury? NO No atmosphere, no water, day too hot, night too cold No atmosphere, no water, day too hot, night too cold Venus? NO Venus? NO Fairly thick atmosphere, no liquid water, day- and night way too hot (would melt lead!) Fairly thick atmosphere, no liquid water, day- and night way too hot (would melt lead!) Earth? YES Earth? YES Perfect! Let’s not mess it up! Perfect! Let’s not mess it up! Mars? NOT TODAY BUT MAYBE IN PAST! Mars? NOT TODAY BUT MAYBE IN PAST! Thin atmosphere, too cold for liquid water to persist but temperatures can get above freezing Thin atmosphere, too cold for liquid water to persist but temperatures can get above freezing BUT: Mars’ landscape shows dried up rivers!!! BUT: Mars’ landscape shows dried up rivers!!!

10 Water-Based Life In Solar System? (2) Look at Classical Jupiter-like Planets Look at Classical Jupiter-like Planets Jupiter and Saturn? NO Jupiter and Saturn? NO Very large planet with large gravity Very large planet with large gravity Very thick hydrogen/helium atmosphere that becomes denser and denser, eventually liquid, large pressures Very thick hydrogen/helium atmosphere that becomes denser and denser, eventually liquid, large pressures Uranus and Neptune? NO Uranus and Neptune? NO Still pretty large planet with larger gravity Still pretty large planet with larger gravity Thick hydrogen/helium atmosphere that becomes denser, eventually high pressure watery slush Thick hydrogen/helium atmosphere that becomes denser, eventually high pressure watery slush Some Jupiter-like Planets have pretty large moons… need to look at those! Some Jupiter-like Planets have pretty large moons… need to look at those!

11 Life in Our Solar System? Best Candidates (1) Follow the liquid water !!! Jupiter’s moon Europa Jupiter’s moon Europa Saturn’s moon Enceladus Saturn’s moon Enceladus Mars (maybe not today but in the past) Mars (maybe not today but in the past)

12 Life in Our Solar System? Best Candidates (2) Mars Today: frozen, dry, no life! Today: frozen, dry, no life! Past: Thicker, warmer air, evidence of long periods with liquid water! Past: Thicker, warmer air, evidence of long periods with liquid water! Nirgal Vallis, MarsAres Vallis, Mars Ancient flood plains Dried up river beds Craters with muddy splashes

13 Best Candidates For Life (3) Curiosity searches for a habitable environment (but cannot search for actual life) Landed in Mars’ Gale Crater on August 5, 2012 Landed in Mars’ Gale Crater on August 5, 2012 Can verify three conditions needed for life Can verify three conditions needed for life Necessary chemical ingredients (organics) Necessary chemical ingredients (organics) Liquid water Liquid water Energy source Energy source

14 Best Candidates For Life? (4) Jupiter’s icy moon Europa Far from Sun Far from Sun Surface covered by very cold ice sheets possibly over 100 miles thick Surface covered by very cold ice sheets possibly over 100 miles thick But: heated by Jupiter’s and other moons’ tidal forces But: heated by Jupiter’s and other moons’ tidal forces Analogy: like heat stress on racquet ball being hit repeatedly Analogy: like heat stress on racquet ball being hit repeatedly NASA Fracturing is evidence of Motion below due to heat

15 Best Candidates For Life? (5) Current model of Europa Convecting ice layer beneath ice sheets! Convecting ice layer beneath ice sheets! Cause variety of surface features Cause variety of surface features Liquid watery ocean below ice, then rocky interior and metallic core Liquid watery ocean below ice, then rocky interior and metallic core NASA lpi.usra.edu

16 Best Candidates For Life? (6) Enceladus (as tiny as Scotland) experiences tidal heating due to Saturn and its other major moons Enceladus (as tiny as Scotland) experiences tidal heating due to Saturn and its other major moons Space probe Cassini saw icy geyser-like plumes: Evidence for sub-surface liquid water in south polar region Space probe Cassini saw icy geyser-like plumes: Evidence for sub-surface liquid water in south polar region Possibly salty (NaCl found in Saturn’s E-ring) Possibly salty (NaCl found in Saturn’s E-ring) Univ. of Idaho

17 Best Candidates For Life? (7) Europa’s and Enceladus’ sub-ice liquid/slushy oceans are extremely cold Europa’s and Enceladus’ sub-ice liquid/slushy oceans are extremely cold What, if any, life could there be? What, if any, life could there be? Example from Earth: cold loving bacteria like archaea or “methane worms”? Example from Earth: cold loving bacteria like archaea or “methane worms”?

18 Extreme Life On Earth (1) Life similar to Earth’s “extremophiles” might thrive on other worlds Microbes that thrive in extreme conditions Microbes that thrive in extreme conditions Bone dry, freezing cold, super hot, very acidic or basic Bone dry, freezing cold, super hot, very acidic or basic Two miles deep in rock, live on radioactivity (left) or metal (right)! Two miles deep in rock, live on radioactivity (left) or metal (right)! Check out PlanetQuest’s Alien Safari: Check out PlanetQuest’s Alien Safari:

19 Extreme Life on Earth (2) What other worlds might extremophiles exist on? Mars: cold/dry, Europa and Enceladus: cold/icy-watery Mars: cold/dry, Europa and Enceladus: cold/icy-watery There could be many planets and moons orbiting other stars that are like them (called “exoplanets”/”exomoons”) There could be many planets and moons orbiting other stars that are like them (called “exoplanets”/”exomoons”) Hot super-earths that are hot and possibly dry or rocky or acidic/basic, or ocean covered super-earths that are like our ocean floors? Hot super-earths that are hot and possibly dry or rocky or acidic/basic, or ocean covered super-earths that are like our ocean floors? Let’s see what’s OUT THERE!!!

20 Search for Exoplanets (1) “Exoplanet” A planet that orbits a star other than the Sun A planet that orbits a star other than the Sun Wikipedia: Wikipedia: “Exomoon” A moon that orbits an exoplanet A moon that orbits an exoplanet Why are they so hard to find? Planets don’t have own light Planets don’t have own light They are far, far, far away (tens or more light years) They are far, far, far away (tens or more light years) The closest neighbor star, Alpha Centauri, is 4.3 ly away! The closest neighbor star, Alpha Centauri, is 4.3 ly away! Blinding glare of their parent stars Blinding glare of their parent stars Analogy: Looking for a planet orbiting Alpha Centauri is like observing a moth near a spotlight in San Diego from Boston! Analogy: Looking for a planet orbiting Alpha Centauri is like observing a moth near a spotlight in San Diego from Boston!

21 Search For Exoplanets (2) Direct Imaging Coronography: blocks light of star with masking device Coronography: blocks light of star with masking device See orbiting planets better See orbiting planets better Interferometry: combines light from several telescopes to cancel star’s light Interferometry: combines light from several telescopes to cancel star’s light Planet’s light stays Planet’s light stays Ground based telescope and image processing technology started being sensitive enough around 2003 Ground based telescope and image processing technology started being sensitive enough around 2003 Adaptive optics to counteract atmospheric distortions Adaptive optics to counteract atmospheric distortions Hubble Space Telescope

22 Search For Exoplanets (3) Gravitational Microlensing: Measure relativistic light bending effect of exoplanet on light from much more distant star Gravitational Microlensing: Measure relativistic light bending effect of exoplanet on light from much more distant star Planet’s gravity acts like lens: focuses star light Planet’s gravity acts like lens: focuses star light Distant star will appear brighter and at a slightly different place Distant star will appear brighter and at a slightly different place

23 Search For Exoplanets (4) Motion of Exoplanet around its star: Motion of Exoplanet around its star: Gravitational tug of planet makes star “wobble” Gravitational tug of planet makes star “wobble” System’s center of mass: not exactly in star’s center System’s center of mass: not exactly in star’s center All objects, including star, orbit center of mass All objects, including star, orbit center of mass Star “wobbles” around a point not exactly in its center Star “wobbles” around a point not exactly in its center Analogy: balancing a mobile with items of different masses Analogy: balancing a mobile with items of different masses

24 Search For Exoplanets (5) Radial Velocity Method - uses Doppler Shift of star light to measure its wobble Analogy: sound of ambulance Analogy: sound of ambulance Toward us: higher pitch Toward us: higher pitch Away from us: lower pitch Away from us: lower pitch Change in level of sound Not change in loudness Change in level of sound Not change in loudness When star moves When star moves toward us: higher pitch in light makes wavelengths shorter toward us: higher pitch in light makes wavelengths shorter Away from us: lower pitch in light makes wavelengths longer Away from us: lower pitch in light makes wavelengths longer The larger and closer the planet, the faster the wobble and the greater the shift: earliest discoveries were of Jupiter-sized planets The larger and closer the planet, the faster the wobble and the greater the shift: earliest discoveries were of Jupiter-sized planets

25 Search For Exoplanets (6) Astrometry: measure tiny change in star’s position due to planet’s tug Astrometry: measure tiny change in star’s position due to planet’s tug The smaller and further the planet the smaller the effect The smaller and further the planet the smaller the effect Transit Method: measure change in brightness of star’s light when planet passes in front of star Transit Method: measure change in brightness of star’s light when planet passes in front of star The smaller the planet the smaller the dip The smaller the planet the smaller the dip NASA

26 Search For Exoplanets (7) Kepler Space Telescope First instrument to detect Earth sized exoplanets First instrument to detect Earth sized exoplanets Started operating May 12, 2009 Started operating May 12, 2009 Uses transit method Uses transit method Images from NASA/JPL

27 Search For Exoplanets (8) NASA Exoplanet Archive (current tally) confirmed, 2,320 exoplanet candidates 809 confirmed, 2,320 exoplanet candidates

28 Closest Exoplanet: Alpha Centauri Bb Orbits host star Alpha Centauri B (discovered Oct. 16, 2012) Wikipedia Entry: Wikipedia Entry: At 4.37 light years At 4.37 light years Solar-type star Solar-type star Part of triple star system Part of triple star system Discovered by European Southern Observatory (ESO) Discovered by European Southern Observatory (ESO) By Doppler Shift method By Doppler Shift method Only 1.13 Earth masses BUT orbits star in 3 days! Only 1.13 Earth masses BUT orbits star in 3 days! ESO

29 Life On Exoplanets? (1) What makes a planet or natural satellite (moon) habitable? NASA’s criteria NASA’s criteria Extended regions of liquid water Extended regions of liquid water Favorable conditions to form organic molecules Favorable conditions to form organic molecules Energy sources to sustain a metabolism Energy sources to sustain a metabolism Need the right type of star Need the right type of star Need to be at the right distance from the star Need to be at the right distance from the star In Habitable Zone (HZ) or “Goldilocks Zone” In Habitable Zone (HZ) or “Goldilocks Zone” Need the right type of planet Need the right type of planet

30 Life On Exoplanets: Right Distance If we look for life similar Earth If we look for life similar Earth Then look in “Habitable Zone” – distance from a star where liquid water can exist Then look in “Habitable Zone” – distance from a star where liquid water can exist Too close: water will be a gas Too close: water will be a gas Too far: water will be frozen Too far: water will be frozen

31 Life On Exoplanets: Right Star (1) Habitable Zones (HZs) around different stars Cool red dwarfs: close and narrow Cool red dwarfs: close and narrow Sunlike stars: medium distance and width Sunlike stars: medium distance and width Hot blue giants: far and wide Hot blue giants: far and wide Would this planet be in star’s habitable zone?

32 Life On Exoplanets: Right Star (2) Which type of stars are best? Which type of stars are best? Cool red dwarf: planet so close that same side always faces star (tidally locked like the Moon around Earth) Cool red dwarf: planet so close that same side always faces star (tidally locked like the Moon around Earth) Very slow spin, extreme day and night temperatures Very slow spin, extreme day and night temperatures Atmosphere not protected by a magnetic field Atmosphere not protected by a magnetic field

33 Life On Exoplanets: Right Star (3) Hot blue giant: star doesn’t last very long, burns out after less than 1 billion years Hot blue giant: star doesn’t last very long, burns out after less than 1 billion years Not enough time for complex, intelligent life to evolve Not enough time for complex, intelligent life to evolve Medium yellow or even slightly cooler orange star Medium yellow or even slightly cooler orange star Just right! Life needs enough time to develop and enough protection from harsh radiation and solar wind Just right! Life needs enough time to develop and enough protection from harsh radiation and solar wind

34 Life On Exoplanets: Right Planet (1) Look for Earthlike (terrestrial) planets Made of silicate rocks without hydrogen/helium outer gas layers Made of silicate rocks without hydrogen/helium outer gas layers Should have about Earth’s mass up to a few times more Should have about Earth’s mass up to a few times more Jupiterlike (jovian) planets may not be habitable but their terrestrial moons can be Jupiterlike (jovian) planets may not be habitable but their terrestrial moons can be Could be much smaller than Earth, tidal heating from their planet and fellow moons keeps them geologically active Could be much smaller than Earth, tidal heating from their planet and fellow moons keeps them geologically active NASA’s habitability conditions are basic necessities for single cell life such as bacteria, archaea NASA’s habitability conditions are basic necessities for single cell life such as bacteria, archaea More complex necessities (more stringent conditions) for multicellular life, such as animals and plants More complex necessities (more stringent conditions) for multicellular life, such as animals and plants

35 Life On Exoplanets: Right Planet (2) Need the right orbit and rotation: stable, no variations Earth has almost circular orbit Earth has almost circular orbit Almost always the same distance from the Sun Almost always the same distance from the Sun Earth has the right axis tilt for moderate seasons Earth has the right axis tilt for moderate seasons Quick enough rotation Quick enough rotation Moderate day/night temperature differences Moderate day/night temperature differences Maintain magnetic dynamo Maintain magnetic dynamo Presence of Earth’s large Moon stabilizes tilt of axis Still controversial among astronomers Still controversial among astronomers Jatakacs.edublog.org

36 Life On Exoplanets: Right Planet (3) Need the right chemical elements Four elements most vital for life: carbon, hydrogen, oxygen, and nitrogen Four elements most vital for life: carbon, hydrogen, oxygen, and nitrogen React and form molecules most easily (e.g. amino acids) React and form molecules most easily (e.g. amino acids) Amino acids have even been found in meteorites Amino acids have even been found in meteorites They are the building blocks of proteins They are the building blocks of proteins Add common elements sulfur and phosphorus Add common elements sulfur and phosphorus Now you can build proteins, DNA, RNA, and molecules for our metabolism Now you can build proteins, DNA, RNA, and molecules for our metabolism Gasses from volcanoes when crust first formed plus energy can lead to amino acids Gasses from volcanoes when crust first formed plus energy can lead to amino acids BUT: cannot account for huge amounts of water! BUT: cannot account for huge amounts of water! Popsci.com

37 Life On Exoplanets: Right Planet (4) Need the right solar system companions Icy comets from outer solar system with other compounds like amino acids impacted on Earth right after it formed Icy comets from outer solar system with other compounds like amino acids impacted on Earth right after it formed Comet reservoir is far enough away from Sun that water/other compounds could remain solid Comet reservoir is far enough away from Sun that water/other compounds could remain solid Lynette Cook, Science Photo Library

38 Life On Exoplanets: Best Candidates (1) Gliese 581 (in Libra) – red dwarf star, 22 ly away 3 confirmed planets (radial velocity): e, b, c; one probable: d 3 confirmed planets (radial velocity): e, b, c; one probable: d 2 disputed: f, g 2 disputed: f, g c: more like Venus c: more like Venus d: more like Mars d: more like Mars g: disc. Sept middle of HZ, most likely for liquid water, 37 day orbit, ~ 1.7 R earth, tidally locked, nearside always lit, farside always dark! Dense enough atmosphere moderates. g: disc. Sept middle of HZ, most likely for liquid water, 37 day orbit, ~ 1.7 R earth, tidally locked, nearside always lit, farside always dark! Dense enough atmosphere moderates. Henrykus, European Southern Observatory

39 Life On Exoplanets: Best Candidates (2) Kepler-22b: Wikipedia Discovered by NASA’s Kepler Space Telescope using transition method Discovered by NASA’s Kepler Space Telescope using transition method On May 12, 2009 On May 12, 2009 Confirmed Dec. 5, 2011 Confirmed Dec. 5, 2011 Host star: Kepler-22 Host star: Kepler-22 Sunlike, tad smaller Sunlike, tad smaller 289 day orbit 289 day orbit 2.4 times Earth size 2.4 times Earth size 6.36 times Earth mass 6.36 times Earth mass About 600 light years away from Earth! About 600 light years away from Earth! No info yet on orbit shape and atmosphere No info yet on orbit shape and atmosphere NASA

40 Life On Exoplanets: Best Candidates (3) HD 40307g in constellation of Pictor, at 43 ly, orange host star 0.75 Sun’s mass HD 40307g in constellation of Pictor, at 43 ly, orange host star 0.75 Sun’s mass 200 day orbit at 0.6AU, ~ 7 Earth masses, e ~ 0.2, gets 62% of Earth’s solar radiation 200 day orbit at 0.6AU, ~ 7 Earth masses, e ~ 0.2, gets 62% of Earth’s solar radiation Far enough from star to not be tidally locked Far enough from star to not be tidally locked 5 other Super-Earths (a – f) orbit much closer 5 other Super-Earths (a – f) orbit much closer No atmospheric info yet! No atmospheric info yet! Discovered by European Southern Observatory Team with radial velocity method, Nov Wikipedia:

41 Life On Exoplanets: ESI (1) Earth Similarity Index (ESI) (Developed by Schulz-Makuch et. al., Planetary Habitability Laboratory, Arecibo, similarity-index-esi) similarity-index-esihttp://phl.upr.edu/projects/earth- similarity-index-esi Multiparameter statistical assessment of Earth-likeness for solar - and exoplanets Multiparameter statistical assessment of Earth-likeness for solar - and exoplanets 0 (no similarity) <= ESI <= 1 (identical to Earth) 0 (no similarity) <= ESI <= 1 (identical to Earth) A product with weighted factors A product with weighted factors x i can be any planetary property (i.e. T surface in Kelvin) x i can be any planetary property (i.e. T surface in Kelvin) x io is the corresponding Earth value (i.e. 288K) x io is the corresponding Earth value (i.e. 288K) n is the number of properties n is the number of properties w i is the weighting exponent (sensitivity of property) w i is the weighting exponent (sensitivity of property)

42 Life On Exoplanets: ESI (2) Definition of Earth-like planet Properties: mean radius, bulk density, escape velocity, T surface Properties: mean radius, bulk density, escape velocity, T surface Interior ESI: R mean, D bulk Interior ESI: R mean, D bulk Surface ESI: v escape, T surface Surface ESI: v escape, T surface ESI > 0.8: similar terrestrial composition and an atmosphere suitable for most terrestrial vegetation ESI > 0.8: similar terrestrial composition and an atmosphere suitable for most terrestrial vegetation 0.6 < ESI < 0.8: barely habitable, too hot or too cold, suitable only for terrestrial extremophiles (i.e. Mars) 0.6 < ESI < 0.8: barely habitable, too hot or too cold, suitable only for terrestrial extremophiles (i.e. Mars)

43 Life On Exoplanets: ESI (3) ESI plot Orange: Sol. Sys. objects > 100 km Orange: Sol. Sys. objects > 100 km Blue: 258 known exoplanets Blue: 258 known exoplanets Red shading: rocky interior Red shading: rocky interior Blue shading: temperate surface Blue shading: temperate surface GREEN SHADING: Earth-like GREEN SHADING: Earth-like Dashed lines: constant ESI Dashed lines: constant ESI HD 40307g, Kepler 22b not included yet HD 40307g, Kepler 22b not included yet

44 Life On Exoplanets: ESI (4) ESI plot with 1235 Kepler candidates ESI was estimated with mass-radius relationships for gas, ocean, and rocky planets ESI was estimated with mass-radius relationships for gas, ocean, and rocky planets Potential abundance of rocky planets Potential abundance of rocky planets Two candidates in Earth-like zone! Two candidates in Earth-like zone!

45 Life On Exoplanets: ESI (5)

46 Life On Exoplanets: Atmospheric Analysis (1) Spitzer Space Telescope (observes in infra red) Looks at light from planet by subtracting out light of star Looks at light from planet by subtracting out light of star Can detect gases in atmosphere Can detect gases in atmosphere For transit method only For transit method only If there is water, oxygen, carbon dioxide  could indicate life If there is water, oxygen, carbon dioxide  could indicate life As simple as algae or a complex civilization As simple as algae or a complex civilization Need to eliminate non living causes of these gases Need to eliminate non living causes of these gases Spitzer Space Telescope

47 Life On Exoplanets: Atmospheric Analysis (2) Diffraction spectra of star and planet by ESO’s VLT Diffraction spectra of star and planet by ESO’s VLT Spectra were obtained by an infrared instrument mounted on the VLT (Very Large Telescope) (independent of planet Spectra were obtained by an infrared instrument mounted on the VLT (Very Large Telescope) (independent of planet orientation) orientation) Planet Planet Star Star HR 8799 is a young, 1.5 solar mass star, 130 ly away HR 8799 is a young, 1.5 solar mass star, 130 ly away 3 giant companion planets, the middle one was measured 3 giant companion planets, the middle one was measured 10 Jupiter masses, 800 C hot 10 Jupiter masses, 800 C hot

48 Get Involved With Real Exoplanets Jet Propulsion Laboratory’s PlanetQuest, The Search For Another Earth: Jet Propulsion Laboratory’s PlanetQuest, The Search For Another Earth: Science/technology info, images/video and interactives Science/technology info, images/video and interactives With Planet Hunters you can help discover real exoplanets: With Planet Hunters you can help discover real exoplanets: Volunteers discovered exoplanet Oct. 15, 2012! Volunteers discovered exoplanet Oct. 15, 2012! With Agent Exoplanet you can help study properties of known exoplanets: With Agent Exoplanet you can help study properties of known exoplanets: Planet Hunters

49 Resources Habitable Planet Questions, GEMS (Great Explorations in Math and Science) Activity developed with NASA’s Kepler Mission Habitable Planet Questions, GEMS (Great Explorations in Math and Science) Activity developed with NASA’s Kepler Mission Michelle Thaller, Spitzer Space Center, “Probing Extrasolar Planets with the Spitzer Space Telescope”, Astronomical Society of the Pacific, No. 75, Spring Michelle Thaller, Spitzer Space Center, “Probing Extrasolar Planets with the Spitzer Space Telescope”, Astronomical Society of the Pacific, No. 75, Spring Nancy Neal-Jones, Cynthia O’Carroll, “Earthlike Planets May Be Common in Known Planetary Systems”, Goddard Space Flight Center, 2006: Nancy Neal-Jones, Cynthia O’Carroll, “Earthlike Planets May Be Common in Known Planetary Systems”, Goddard Space Flight Center, 2006: NASA, JPL Planetquest: NASA, JPL Planetquest: Alien Earths, traveling exhibition: Alien Earths, traveling exhibition: Cool Cosmos from Caltech (IPAC, NASA): Cool Cosmos from Caltech (IPAC, NASA): Kepler Mission: Kepler Mission: Wikipedia: Wikipedia: Neil DeGrasse Tyson, Goldilocks and the Three Planets, Neil DeGrasse Tyson, Goldilocks and the Three Planets, Jason Major, Universetoday.com, tantalizing-hints-of-a-potentially-habitable-exoplanet/ Jason Major, Universetoday.com, tantalizing-hints-of-a-potentially-habitable-exoplanet/http://www.universetoday.com/98379/astronomers-find- tantalizing-hints-of-a-potentially-habitable-exoplanet/http://www.universetoday.com/98379/astronomers-find- tantalizing-hints-of-a-potentially-habitable-exoplanet/ Joshua Rodriguez/PlanetQuest “Earth on Steroids? Unraveling the Mystery of Super-Earths”: Joshua Rodriguez/PlanetQuest “Earth on Steroids? Unraveling the Mystery of Super-Earths”: Discovery Channel News web site: Discovery Channel News web site: National Science Foundation “Special Report: Extreme Microbes”: National Science Foundation “Special Report: Extreme Microbes”: Space.com’s articles on Curiosity and its capability to search for traces of life: Space.com’s articles on Curiosity and its capability to search for traces of life:


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