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Internal Heating: Planets and Moons July 21, 2005 Presented to teachers in TRUST

Internal Heating: Planets and Moons July 21, 2005 Presented to teachers in TRUST by Denton S. Ebel Assistant Curator, Meteorites Department of Earth and Planetary Sciences. Heat Sources of Planetary Bodies Primordial Gravitational potential energy (differentiation)

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Internal Heating: Planets and Moons July 21, 2005 Presented to teachers in TRUST

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  1. Internal Heating:Planets and Moons July 21, 2005 Presented to teachers in TRUST byDenton S. EbelAssistant Curator, MeteoritesDepartment of Earth and Planetary Sciences

  2. Heat Sources of Planetary Bodies Primordial Gravitational potential energy (differentiation) Accretion or collision energy (external source) Contemporary Decay of radioactive elements (all rocky planets) (probably 60-80% of Earth’s heat flow: 40K, 232Th, 235U, 238U) Tidal friction (only in some cases, e.g.-Io) Solar heating (restricted to surfaces)

  3. Complex and Simple Cratering (images taken from published literature have been removed here)

  4. Early Solar System: Collisions of Small Bodies to Make Bigger Bodies and Eventually Planets (image taken from published literature has been removed here)

  5. Chondritic meteorites contain radionuclides

  6. Abundant Isotopes Extinct: 26Al => 26Mg 720 K years Present time: 40K => 40Ar, 40Ca 1.27 G years 238U …. 208Pb 4.47 G years 235U …. 207Pb 704 M years 232Th …. 208Pb 14.0 G years

  7. From The New Solar System, Beatty, Petersen & Chaikin (1999), Cambridge U. Press, ch. 17 fig. 5 Tidal Heating of Io (image taken from published literature has been removed here) Orbital resonance with Europa tugs Io, so Io’s Jupiter-facing side wobbles slightly. These tidal forces generate heat by internal friction.

  8. Io Comparing the orbital radius with the gravity of the primary gives an idea of the tidal forces experienced by a Moon.

  9. Jupiter’s major moons, seen by Galileo in 1610: Io Europa Ganymede Callisto Earth’s moon, Moon Saturn’s major moon, Titan

  10. Voyager missions (1979) showed that each of these moons is a different world. The moons are all ‘tidally locked’, rotate in the same direction in nearly circular orbits in Jupiter’s equatorial plane. They likely formed as a ‘subnebula’ in the solar disk. Io Europa Ganymede Moon orbit density Io 5.9 3.5 Europa 9.4 3.0 Ganymede 15.0 1.9 Callisto 26.4 1.8 (orbits are in Jupiter radii) Callisto

  11. Our Solar System Pluto-Kuiper belt (short period comets) Asteroid belt (meteorites)

  12. Io

  13. Plan Patera plume, 140 km (Galileo spacecraft 1997) Pele’s plume, 300 km high (Voyager 1, 1979) Prometheus plume (Galileo spacecraft 1997)

  14. Pele volcano on Io (Galileo spacecraft image, 1997)

  15. Io

  16. April 1997 September 1997 400 km Pillan Patera volcano outflow on Io, imaged by Galileo spacecraft, 1997

  17. Inside Io (maybe) Io Silicate - sulfur crust Silicate Mantle FeS? Core

  18. Europa

  19. Crater on Europa

  20. Streaks on Europa Streaks -fractures filled with ice.

  21. Streaks on Europa

  22. Ice Rafts on Europa Great rafts of ice in re-frozen surface (view width ~70 km)

  23. Deformation of Europa Four possible processes: 1 - upwarping 2 - surface fractures 3 - upwelling & fluid flow 4 - collapse to chaotic terrain

  24. Silicate + ice Crater on Europa Europa inside (maybe) silicate FeS? Core water ice crust

  25. The Moon Photo #:    IV-121-M Mission:    Lunar Orbiter IV Date:    1967 Photo #:    IV-138-M

  26. Galileo Galilei (1564-1642) - observed the moon through a telescope and called the dark smooth areas maria (latin for seas) and the lighter colored, rugged terrain, he called terrae (latin for lands). Aside from the Earth the moon is the best understood planetary body in the solar system. Many of our current theories and hypotheses of how the Earth and other planets formed were developed and tested by studying the moon. The Moon

  27. Dr. Harrison Schmitt, astronaut on Apollo 17 Large split boulder at Taurus-Littrow landing site

  28. Moon Formation Theories 1) Co-accretion in orbit while Earth formed. 2) Capture - Moon formed elsewhere in the nebula but was captured by Earth’s gravity. 3) Giant Impact. • Observations that need to be explained • Chemically the moon is similar to Earth’s mantle • The moon lacks the more volatile elements • Moon’s metal core, if present< is relatively small • Oxygen isotopes are similar to the earth.

  29. Schematic of Moon Forming Impact (image taken from published literature has been removed here)

  30. Radiometric Dates for the Moon • Absolute ages determined by radiometric dating of rocks from the moon. • Basaltic lavas are 3.65 to 4.0 billion years old. • Lunar highlands are more than 4.5 billion years old. • Indicates that the terrae formed shortly after accretion of the moon. • Some ray material from Copernicus is less than 1 billion years old. • Integrating these ages into the relative scale allows the development of an absolute scale.

  31. Rate of Cratering and Volcanism with Time • Rate of cratering was much more intense in the earlier periods of lunar history. • The decline in the amount of impact events was rapid after about 3 billion years ago. • It is assumed that this is representative of the cratering history of all planets including the Earth. • Based on radiometric ages, volcanism lasted about one billion years between 4.0 and 3.2 billion years ago. • Some lavas are 2.5 billion years old but may be melt generated by impact.

  32. Lunar chronology of Crater Copernicus region. Shoemaker and Hackman (1962)

  33. Mare Imbrium Erastothenes Copernicus Kepler

  34. Crater Copernicus • Copernicus • Bright rays extend over 300 km. • Rays extend across Procellarum and Mare Imbrium. • Rays cut across the floor of Erastothenes. • Craters Kepler and Aristarchus have similar patterns of rays to those of Copernicus. • Therefore Copernicus ( and Kepler and Aristarchus) are younger than Erastothenes and the basalts of Mare Imbrium).

  35. Crater Erastothenes • Erastothenes • Found on the lunar maria • Terraced walls • Circular floor • Central peak • Small secondary craters • No visible rays • Therefore, Erastothenes is younger than the maria and older than the rayed craters.

  36. Imbrium Basin • Imbrium Basin • Large multi-ring basin • Filled by lunar maria • Craters like the Imbrium Basin are older than the lunar maria and craters like Erostathenes • This period of muilti-ring craters and extrusions of the lunar maria is known as the Imbrium Period Ejecta from the Imbrium Basin overlap craters like the Nectarian Basin in the lunar highlands.

  37. Titan

  38. N2 CH4 Ar surface T: 93.8 K (-180 C) Artist rendering of Huygens probe descending into Titan

  39. Saturn A Ring UV Imaging Spectrograph dirty = red; icy = turquoise res = 60 miles (97km) Photo # PIA05075 The End

  40. PIA05076 C+B rings

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