The Moon s Journey Through Time (Abridged)

Transcription

1 LIVE INTERACTIVE YOUR DESKTOP The Moon s Journey Through Time (Abridged) Presented By: Brad Bailey and Brian Day November 30, 2010

2 The Moon s Journey Through Time (Abridged) Brad Bailey NASA Lunar Science Institute NASA Ames Research Center

3 Chapter 1: In the Beginning of Things a very, very good place to start.

4 In the Beginning there was Darkness. And then God said unto the Universe: And there was light.

5 Evolution of the Universe via the Highly Redshifted 21 cm Line Loeb, A. 2006, Scientific American, 295, 46.

6 History of the Universe

7 Planet Formation in the Inner Solar System The planet formation population was originally made up of planetesimals and Moon- to Mars-sized planetary embryos.

8 Three Theories on The Formation of the Moon Accretion: The Moon formed jointly with the Earth during solar system formation. Capture: The Moon formed separate from the Earth and was gravitationally captured (Phobos and Deimos). Impact: The Moon originated as a large planetessimal and collided with the proto-earth

9 Challenge Question #1: How do YOU think the Moon was created? A: Accretion B: Capture C: Impact

10 Giant Impact Theory Theia

11 Evidence for the Giant Impact Similar Oxygen Isotopes to the Earth Evidence from abundances of KREEP and a highly anorthositic crust that there was once a molten magma ocean Relatively small core of the Moon (~25% of the radius compared to ~50% of other inner planets) Similar warm, Silica dust and SiO gas rings found around other similar stars

12 Let s pause for questions from the audience

13 Chapter 2: What is the Lunar Late Heavy Bombardment?

14 Craters Craters are found on nearly every solid body in the solar system. If properly interpreted, craters can help us understand how these bodies have evolved over the last 4.5 Gy.

15 Impact History of the Moon The Moon has the most complete and clear impact history available of the last 4.5 Gy of Solar System evolution.

16 The Lunar Impact Rate Lunar impact rate has been variable with time. Hartmann et al. (1981); Horz et al. (1991)

17 Motivation: The Lunar Impact Rate Lunar impact rate has been variable with time. Crater production rates >100 times higher >3.8 Gy ago. Hartmann et al. (1981); Horz et al. (1991)

18 The Lunar Impact Rate Lunar impact rate has been variable with time. Crater production rates >100 times higher >3.8 Gy ago. Relatively constant crater rate since ~3.7 Ga. Hartmann et al. (1981); Horz et al. (1991)

19 Lunar Basins and the Moon s Early History More than 40 basins (D > 300 km) formed on the Moon between ~ Gy ago (Wilhelms 1987).

20 Lunar Basins and the Moon s Early History Imbrium Basin ( Ga) Orientale Basin ( Ga) Stoffler and Ryder (2001); Gnos et al. (2004) The two largest and latest-forming basins with solid age constraints are Imbrium (1160 km) and Orientale (930 km).

21 Lunar Late Heavy Bombardment Koeberl (2003) Were these basins they produced by a declining bombardment of leftover planetesimals from terrestrial planet formation?

22 Lunar Late Heavy Bombardment Koeberl (2003) Or Were these two large basins produced by a spike of impactors near ~ 3.8 Ga, creating a terminal cataclysm?

23 The Nice Model of the Lunar Late Heavy Bombardment Much of this work is found in 3 Nature papers: Tsiganis et al. (2005); Morbidelli et al. (2005); Gomes et al. (2005)

24 New Solar System Formation Model TNOs Old view. Gas giants/tnos formed near present locations and reached current orbits ~4.5 Gy ago.

25 New Solar System Formation Model TNOs Old view. Gas giants/tnos formed near present locations and reached current orbits ~4.5 Gy ago. Primordial TNOs New view. Gas giants formed in a more compact configuration between 5-15 AU. Massive TNO population existed between AU.

26 Destabilizing the Outer Solar System Tsiganis et al. (2005); Morbidelli et al. (2005); Gomes et al. (2005) Watch what happens after 850 My!

27 Destabilizing the Outer Solar System Tsiganis et al. (2005) Jupiter/Saturn enter 1:2 mean motion resonance Gravitational interactions with planetesimals cause migration. Over time, Jupiter/Saturn enter 1:2 MMR. This destabilizes orbits of Uranus and Neptune.

28 Hadean Zircons Trail et al. (2005) Zircons (ZiSiO 4 ) are diamond-like objects found in Earth s crust. Some are the oldest minerals on Earth, with one formed 4.4 Ga. Hadean zircons are the only dated material on Earth to have gone through the LHB. Most found in Jack Hills, Western Australia. The cores are igneous. The overgrowths record high temperature events taking place all over the Earth.

29 What does this all mean? The Moon is the best place in the whole solar system to explain early planetary formation and evolution Imbrium and Orientale Basins may be the result of this large scale heavy-bombardment of the inner planets The South Pole-Aitken Basin is thought to be around 3.9 Gy old and is the largest impact basin in the solar system.

30 Challenge Question #2: How big was the impactor and resultant crater that killed the dinosaurs and began the mass extinction of ~95% of species on Earth?? A: 10 km impactor and 180 km crater B: 25 km impactor and 500 km crater C: 50 km impactor and 1000 km crater D: 100 km impactor and 2000 km crater Hint: The South Pole-Aitken Basin shown here was created by ~150 km impactor and is 2500 km across.

31 Challenge Question #2: How big was the impactor and resultant crater that killed the dinosaurs and began the mass extinction of ~95% of species on Earth?? A: 10 km impactor and 180 km crater B: 25 km impactor and 500 km crater C: 50 km impactor and 1000 km crater D: 100 km impactor and 2000 km crater Hint: The South Pole-Aitken Basin shown here was created by ~150 km impactor and is 2500 km across. Nugget: A good rule of thumb is that an impactor makes a crater about ~20x as large as its diameter.

32 Let s pause for questions from the audience

33 Chapter 3: Current State of the Moon

34 Lunar Topography Image courtesy of Mark Wieczorek

35 Mare and the Highlands Highlands = Anorthosite Mare = Basalt

36 Lunar Dusty Atmosphere Yes, but very thin! A cubic centimeter of Earth's atmosphere at sea level contains about molecules. That same volume just above the Moon's surface contains only about 100,000 molecules. It glows most strongly from atoms of sodium. However, that is probably a minor constituent. We still do not know its composition.

37 Lunar Dust Movement Surveyor 6 Image McCoy, 1976

38 Earth Tides and Lunar Recession Tidal friction on the Earth is acting as brake pads As a consequence, the Earth s days are getting longer by secs/century The Moon is receding away from the Earth at ~3.8 cm/year

39 Challenge Question #3: How long was an Earth day back when the Moon was newly formed? A: 2 Hours B: 5 Hours C: 12 Hours D: 18 Hours E: 24 Hours

40 Challenge Question #4: Where is the coldest place in the whole solar system. A: Pluto B: Europa C: The Moon D: Your significant other s shoulder after you ve said something stupid.

41 Challenge Question #4: Where is the coldest place in the whole solar system. A: Pluto B: Europa C: The Moon D: Your significant other s shoulder after you ve said something stupid. Permanently Shadowed regions can Get down to 25K!! (-425 F or -248 C)

42 Permanently Shadowed Regions

43 PSRs Continued

44 Water on the Moon!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! M^3 Deep Impact Data published in Science, Oct 23, 2009

45 Water on the Moon!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! M^3 Deep Impact Data published in Science, Oct 23, 2009

46 Challenge Question #5: How did the water get onto the Moon?! A: Cometary Impacts B: Subsurface cold chemistry C: Creation by the Solar Wind Examiner.com D: Always been there from time of Moon formation

47 Let s Pause for Questions on the Current Moon?

48 Chapter 4: To the Moon, Alice! (a.k.a. Missions to the Moon)

49 Recent Lunar Missions 1994: Clementine (USA) 1999: Lunar Prospector (USA) 2004: SMART-1 (ESA) 2007: Chang E 1 (China), Kaguya (Japan) 2008: Chandrayaan 1 (India) 2009: LRO and LCROSS (USA) 2010: Chang E 2 (China)

50 Clementine bistatic radar Circular polarization ratio (CPR) consistent with ice crystals in the south polar regolith. Later ground-based studies confirmed high-cpr in some permanently-shadowed craters. However, Arecibo scans have also found high-cpr in some areas that are illuminated, probably due to surface roughness. Are we seeing ice or rough terrain in dark polar craters?

51 Hydrogen has been detected at the poles by Lunar Prospector in Is it water ice??? Lunar Prospector neutron spectrometer maps of the lunar poles. These low resolution data indicate elevated concentrations of hydrogen at both poles; it does not tell us the form of the hydrogen. Map courtesy of D. Lawrence, Los Alamos National Laboratory.

52 Lunar Reconnaissance Orbiter LROC image and map the lunar surface in unprecedented detail LOLA provide precise global lunar topographic data through laser altimetry LAMP remotely probe the Moon s permanently shadowed regions CRaTER - characterize the global lunar radiation environment DIVINER measure lunar surface temperatures LEND measure neutron flux to study hydrogen concentrations in lunar soil

53 Centaur-LCROSS-LRO

54 Centaur Impact

55 Centaur Impact Plume

56 LADEE Lunar Atmosphere and Dust Env. Expl. Determine the global density, composition, and time variability of the fragile lunar atmosphere before it is perturbed by further human activity. Determine the size, charge, and spatial distribution of electrostatically transported dust grains Test laser communication capabilities Demonstrate a low-cost lunar mission: Simple multi-mission modular bus design Low-cost launch vehicle

57 Lunar Advantage: No Interference! (z=46) Destination: Moon! RAE (z=13)

58 Let s pause for questions from the audience

59 Hands-On Lunar Education Resources bringing lunar exploration into your classroom Brian Day NASA Lunar Science Institute

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61 Lunar Sample Educational Disk Program Six samples of lunar material (three soils and three rocks) encapsulated in a six inch diameter clear lucite disk are available for you to borrow and bring into your classroom. The disk is accompanied by written and graphic descriptions of each sample in the disk. Mr. Louis Parker JSC Exhibits Manager National Aeronautics and Space Administration Lyndon B. Johnson Space Center Mail Code AP 2101 NASA Parkway Houston, Texas Telephone: FAX: louis.a.parker@nasa.gov

62 Lunar Volcanism: A major force in shaping the surface of the Moon Hortensius Domes Byrgius A lava flow

63 Build a Volcano Lunar and Planetary Institute and Hawaii Space Grant Children make repeated colorful volcanic eruptions using food coloring, vinegar, and baking soda, trace the edges of each lava flow and apply a layer of Play-Doh to record its size and shape. They examine how later flows overlap earlier ones and how earlier flows influence the paths of the subsequent flows. They determine a volcano's history of eruptions based on the layering of different flows and examine images of lava flows on other planets and use their experience with the volcano model to interpret the flow history.

64 Impact Cratering: A major force in shaping the surface of the Moon

65 Cratering the Moon NASA can simulate cratering impacts at the Ames Vertical Gun Range. Allows study of: Different impactor shapes, masses and compositions Different impact velocities and angles Different target compositions and structures

66 In the Cratering the Moon activity, students design their own lunar impact simulator. They conduct a study to determine what role the angle of incidence of an impact plays in determining how effective an impactor is in excavating material from beneath the Moon s surface.

67 Fresno Co. Juvenile Justice Campus Student designed lunar impact simulator 3 teams totaling 60 students creating designs around LCROSS Impact the Moon Challenge. Demonstrates continuous utilization of resources. Successfully engaging a particularly challenging student audience.

68 With Moon Zoo, students and members of the public can assist lunar scientists in analyzing the high resolution images returned by the LROC instrument aboard the Lunar Reconnaissance Orbiter. They perform crater counts, search for boulders, and other interesting landforms.

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70 NASA Meteoroid Environment Office Lunar Impact Monitoring Program Help lunar scientists determine the rate of meteoroid impacts on the Moon. Meteoroid impacts are an important source for the lunar exosphere and dust. Can be done with a telescope as small as 8 inches of aperture.

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72 Selected Online Resources Lunar Samples Program - Exploring the Moon - Lunar and Planetary Institute - My Moon - Explore! - NASA Lunar Science Institute - LRO - LCROSS - Solar System Exploration at JPL - Year of the Solar System - Moon Zoo: Lunar Impact Monitoring - LCROSS Cratering the Moon - Make a Volcano - activities/ makeavolcano.shtml

73 Thank you to the sponsor of tonight's Web Seminar: