Wayne Roberge, Ray Menzel

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Asteroids, Amino Acids and the Origin of Life
Wayne Roberge, Ray Menzel Glenn Ciolek School
of Science Brown Bag Lunch October 28, 2009
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New York Center for AstrobiologyMember, NASA
Astrobiology Institute
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Setting the stage for life
Interdisciplinary research combines observational
and computational astrophysics, Earth and
planetary sciences, and prebiotic chemistry in a
common quest to understand the origins of
life-bearing planets and environments. Our
research also supports several current and
upcoming NASA space missions Spitzer, Dawn, JWST
and Mars Sample Returns.
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Origin of Terrestrial Amino Acids
At least some amino acids were made on asteroids!
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The Inner Solar System
Mars (1.5 AU)
Jupiter (5 AU)
Image NASA/Hubble Space Science Institute
(STScI).
Asphaugm Ann. Rev. Earth Planetary Science, 37,
413 (2009)
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Asteroid Composition Types
Igneous (SME) - melting partially or completely
exposed metallic cores. Metamorphic (CBGF) -
aqueous alteration at 25-150 oC hydrated
minerals. Primitive (PD) no heating primitive
solar system materials (?).
Image NASA/Hubble Space Science Institute
(STScI).
W.B. McKinnon, Nature, 340, 343 (1989)
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Induction Heating of Asteroids Sonnet et al.
1970
Solar Wind Plasma E0, B 0
plasma current
V 400 km/s
asteroid

• Nonzero electric field appears in asteroid
  frame.
• Asteroid material becomes electrically
  polarized.
• Currents in plasma (yellow) flow from to - .
• Currents inside asteroid (green) close circuit.
• Heating rate P J E sE2 10-8 W/kg (?)

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Radioactive Heating of Asteroids Urey 1955

• 26Al 26Mg energy
• Half life t1/2 0.7 Myr
• 26Mg in meteorite Allende implies live 26Al was
  present.
• 26Al/27Al 6 x 10-5 in Allende, enough to melt
  asteroids.
• But how did 26Al arrive at the party live?
• Unknown but 26Al DID get here!
• Why did heating decrease with heliocentric
  distance?
• Grimm McSween (1993) accretion time increases
  with distance.
• Why did some asteroids see B10G precisely when
  they were melted???

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Solar Wind and B Field Gradients
Solar wind compresses B field near planets. Large
field gradients exist. Excluded from solid by
magnetosphere. But asteroids did not(?) have
magnetospheres!
Image NASA
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L
B
DB
x
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