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Geoneutrino collaborators : - John Learned : University of Hawaii

Antineutrino, geoneutrinos and heat production in the Earth. Geophysics tells us where we are at today Geochemistry tells us how we got there…. Geochemistry collaborator : - Ricardo Arevalo : University of Maryland. Geoneutrino collaborators : - John Learned : University of Hawaii

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Geoneutrino collaborators : - John Learned : University of Hawaii

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  1. Antineutrino, geoneutrinos and heat production in the Earth Geophysics tells us where we are at today Geochemistry tells us how we got there… Geochemistry collaborator: - Ricardo Arevalo : University of Maryland Geoneutrino collaborators: - John Learned : University of Hawaii - Steve Dye: Hawaii Pacific University

  2. 5 Big Questions: • What is the Planetary K/U ratio? • Radiogenic contribution to heat flow? • Distribution of reservoirs in mantle? • Radiogenic elements in the core?? • Nature of the Core-Mantle Boundary? planetary volatility curve secular cooling whole vs layered convection Earth energy budget hidden reservoirs

  3. d = √pkt d AGE OF THE EARTH thermal evolution Heat loss depends on thermal boundary layer thickness d John Perry Lord Kelvin 1895 1862 Conductive cooling of a planet with a convecting interior Conductive cooling of a solid planet Age of Earth ~100 My k =35 km2/My Age of Earth ~1 Gy radioactivity “… Kelvin had limited the age of the earth provided that no new source of heat was discovered. … what we are considering tonight, radium!" Rutherford fondly recalled, "Behold! the old boy beamed upon me.” (Kelvin was in the audience) Ernest Rutherford 1904

  4. Time Line 1st order Structure of Earth Rock surrounding metal 1897 Emil Wiechert 1915 CORE-MANTLE 1925 UPPER-LOWER MANTLE INNER-OUTER CORE 1935 PLATE TECTONICS 1970 1995

  5. “Standard” Planetary Model • Chondrites, primitive meteorites, are key • So too, the composition of the solar photosphere • Refractory elements (RE) in chondritic proportions • Absolute abundances of RE – model dependent • Mg, Fe & Si are non-refractory elements • Chemical gradient in solar system • Non-refractory elements – model dependent • U & Th are RE, whereas K is moderately volatile

  6. Meteorites chondrites Achondrite, Ca-poor, Diogenite Allende Mantle-crust pieces (?) undifferentiated planets (?) Johnstown Carbonaceous chondrite (CV3) Imilac Henbury IIIAB Pallasite: olivine and iron mixtures (CMB?) Irons: pieces of core

  7. “Standard” Planetary Model • Chondrites, primitive meteorites, are key • So too, the composition of the solar photosphere • Refractory elements (RE) in chondritic proportions • Absolute abundances of RE – model dependent • Mg, Fe & Si are non-refractory elements • Chemical gradient in solar system • Non-refractory elements – model dependent • U & Th are RE, whereas K is moderately volatile

  8. H O C N Solar photosphere (atoms Si = 1E6) B Li C1 carbonaceous chondrite (atoms Si = 1E6)

  9. “Standard” Planetary Model • Chondrites, primitive meteorites, are key • So too, the composition of the solar photosphere • Refractory elements (RE) in chondritic proportions • Absolute abundances of RE – model dependent • Mg, Fe & Si are non-refractory elements • Chemical gradient in solar system • Non-refractory elements – model dependent • U & Th are RE, whereas K is moderately volatile

  10. Th & U Volatility trend @ 1AU from Sun

  11. Detecting Geoneutrino in the Earth b- decay REFRACTORY ELEMENTS Detecting Electron Antineutrinos from inverse beta -decay 2 flashes close in space and time Rejects most backgrounds Nature436, 499-503 (28 July 2005)

  12. MeV-Scale Electron Anti-Neutrino Detection Key: 2 flashes, close in space and time, 2nd of known energy, eliminate background Production in reactors and natural decays Detection Evis=Eν-0.8 MeV prompt delayed Evis=2.2 MeV • Standard inverse β-decay coincidence • Eν > 1.8 MeV • Rate and spectrum - no direction Reines & Cowan

  13. 20% Detectable >1.8 MeV 31% 1% 46% n p + e- + ne Radiogenic heat & “geo-neutrino” K-decay chain 238U, 232Th and 40K generate 8TW, 8TW, and 3TW of radiogenic heat in the Earth Th-decay chain Beta decays produce electron antineutrinos (aka “geo-neutrinos”) U-decay chain

  14. Silicate Earth REFRACTORY ELEMENTS VOLATILE ELEMENTS Allegre et al (1995), McD & Sun (’95) Palme & O’Neill (2003) ? Lyubetskaya & Korenaga (2007) Normalized concentration Potassium in the core Half-mass Condensation Temperature

  15. U in the Earth: ~13 ng/g U in the Earth Metallic sphere (core) <<<1 ng/g U Silicate sphere 20 ng/g U Continental Crust 1000 ng/g U Mantle 10 ng/g U “Differentiation” Chromatographic separation Mantle melting & crust formation

  16. Oceanic crust <<200 million years old

  17. Continents up to 3500 million years old ages (Ga) <0.6 06.-2.6 >2.6

  18. Earth’s Total Surface Heat Flow • Conductive heat flow measured from bore-hole temperature gradient and conductivity Data sources Total heat flow Conventional view 463 TW Challenged recently 311 TW Source: International Heat Flow Commission web-site

  19. after Jaupart et al 2008 Treatise of Geophysics

  20. Urey Ratio and Mantle Convection Models • Mantle convection models typically assume: mantleUrey ratio: 0.4 to 1.0, generally ~0.7 • Geochemical models predict: mantleUrey ratio 0.3 to 0.5 radioactive heat production Urey ratio = heat loss

  21. Discrepancy? • Est. total heat flow, 46 or 31TW est. radiogenic heat production 20TW or 31TW give Urey ratio ~0.3 to ~1 • Where are the problems? • Mantle convection models? • Total heat flow estimates? • Estimates of radiogenic heat production rate? • Geoneutrino measurements can constrain the planetary radiogenic heat production.

  22. Mantle is depleted in some elements (e.g., Th & U) that are enriched in the continents. -- models of mantle convection and element distribution Th & U poor Th & U rich

  23. Predicted Geoneutrino Flux Reactor Flux - irreducible background Geoneutrino flux determinations -continental (KamLAND, Borexino, SNO+) -oceanic (Hanohano)

  24. Geoneutrinos Reactor Background with oscillation Reactor Background • KamLAND was designed to measure reactor antineutrinos. • Reactor antineutrinos are the most significant background. KamLAND

  25. Continental Heat Flow : example from Canadian Shield SNO+ Perry et al (2006)

  26. Large liquid scintillation detectors used for measuring the Earth antineutrino flux Borexino, Italy (0.6kt) KamLAND, Japan (1kt) SNO+, Canada (1kt) Hanohano, US ocean-based (10kt)

  27. Hanohano An experiment with joint interests in Physics, Geology, and Security • multiple deployments • deep water cosmic shield • control-able L/E detection A Deep Ocean e Electron Anti-Neutrino Observatory Deployment Sketch Descent/ascent 39 min

  28. Summary of Expected ResultsHanohano- 10 kt-yr Exposure • Neutrino Geophysics- near Hawaii • Mantle flux U geoneutrinos to ~10% • Heat flux ~15% • Measure Th/U ratio to ~20% • Rule out geo-reactor if P>0.3 TW • There is also plenty of Neutrino Physics.. • And much astrophysics and nucleon decay too….

  29. Published May 2008 Based on: R. de Meijer & W. van Westrenen South African Journal of Science (2008)

  30. Paramount Request Detecting Potassium (K) e • Significant for the Planetary budget of volatile element -- What did we inherit from our accretion disk? • Fundamental to unraveling Mantle structure -- 40K controls mantle Ar inventory 40K 40Ar (EC) • Geophysics want K in core to power the Geodynamo? -- We don’t understand the energy source…

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