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Charged Dust Odysseys -and- Dating Old Earth Rocks

Wednesday, February 1, 2012
Amara
Graps (Applicant)
Abstract [1]: Charged Dust Odysseys

Charged Dust:
1. Intrinsic property of matter that occurs in two forms:
positive or negative, dependent on the deficiency or surplus
of electrons carried by fine particles of matter
2. Obligated Trash
3. Loaded Confusion
3. Excited Lint

Odyssey:
1.  An extended adventurous voyage or trip.
2.  An intellectual quest

The charging of cosmic dust as a topic of study provides nonintuitive details of the important charge parameter in the electrodynamics force, which plays a dominant role over the gravitational force for the Universe's tiny cosmic dust particles. Cosmic dust particles are rarely electrically neutral because they are immersed in space plasmas, collecting ions, electrons, residual high-energy particles, and receiving ultraviolet radiation from nearby stars. The tiny particles electrically and dynamically respond to their environment with surface charge potentials which closely follow the surrounding plasma and magnetic field conditions. At the same time that the particle charges up, it is responding to its environment dynamically via the Lorentz electromagnetic force. Therefore, small cosmic dust particles are ideal tracers of their astrophysical environments.

A variety of charged cosmic dust populations exist in our solar system, and in this talk, I will present two. I will present cirumplanetary dust streams, the Saturnian dust streams in particular, and describe their possible link to Saturn's E-Ring. Another population of charged dust is that on the surfaces of airless bodies such as the Moon and asteroids. What makes an asteroid an especially attractive dust laboratory, is its fine regolith embedded in the interplanetary plasma and illuminated by solar photons. Electrostatic forces have been specifically invoked as one means by which small grains can be transported across an airless body's surface in what is known as electrostatic levitation. To finish the charged dust topic, I will present what are the necessary inputs for determining an asteroid's dusty electrostatic environment and what one, such as Lutetia, might look like.

Abstract [2]: Dating Old Earth Rocks

In the geologic time-span from accretion from the solar nebula (4.54 Ga), through to the beginning of the Archean eon (3.8 Ga), the planet Earth formed and  differentiated. Chemical and physical processes such as mantle convection, tectonic-plate recycling and magma generation through partial melting should have scrambled, if not erased, any coherent geochemical signature of the primordial material [D. Graham, 2010]. Even if a vestige of such material remained, it seems unlikely that it would be found in any samples from Earth's surface or the shallow subsurface that are available to geologists. Or so it was generally thought.

One such location on the Earth's surface is Baffin Island, Canada. On the basis of a trace-element and isotopic study, Jackson et al., 2010 proposed that lavas from this region were derived from a deep-Earth reservoir that has remained isolated since the earliest days of planetary accretion some 4.5 billion years ago. Their work relies on combined analyses of the isotopes of helium, lead, neodymium and hafnium. Collectively, the results are the first of their kind for terrestrial volcanic rocks. Another such location on Earth's surface is the Dresser Formation, Western Australia. While one billion years younger (say) than Baffin Island, it provides a more intriguing glimpse of our Earth's history. It includes rocks with chemical signatures indicative of life, and is now thought to possibly have ancient atmosphere trapped in quartz fluid inclusions from the Archean period. As one of the oldest sedimentary-volcanic units, accurate ages of specific rocks from this region can help refute or support new solar system dynamical model revisions of the timing and source regions for a period known as the Late Heavy Bombardment (LHB).

The Late Heavy Bombardment (LHB) is thought to be a solar system-wide barrage of comets and asteroids that produced many young lunar basins; showing a spike in the size-frequency-distribution of craters that started about 3.9 Ga and which lasted about 200 My. Meanwhile, on the Earth, it was thought that large-scale LHB impact
signs were erased due to the resurfacing processes of plate tectonics. Many lines of evidence are pointing to a revised view of the LHB that these timing and erasing assumptions are probably wrong. A new modification of the LHB has been proposed by Bottke, W. et al, 2011, which proposes an "E-belt", which is a hypothesized
extension of the primordial asteroid belt between 1.7-.1 AU. The E-belt could have produced an extended LHB-era. Dating our Baffin Island and Dresser Formation rock samples using an alternate geochronology system would not only calibrate our system, built by F.S. Anderson (SwRI) and up-and-running, but provide another set of
data to apply to the new modified LHB concept.

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