TERRAPUB Earth, Planets and Space

Earth Planets Space, Vol. 65 (No. 10), pp. 1159-1166, 2013

Organic grain coatings in primitive interplanetary dust particles: Implications for grain sticking in the Solar Nebula

George J. Flynn1, Sue Wirick2, and Lindsay P. Keller3

1Dept. of Physics, SUNY-Plattsburgh, 101 Broad St., Plattsburgh, NY 12901
2CARS, The University of Chicago, Chicago, IL 60637
3NASA Johnson Space Center, NASA Highway 1, Houston, TX 77058

(Received October 31, 2012; Revised April 18, 2013; Accepted May 9, 2013; Online published October 24, 2013)

Abstract: The chondritic porous interplanetary dust particles (CP IDPs), fragments of asteroids and comets collected by NASA high-altitude research aircraft from the Earth's stratosphere, are recognized as the least altered samples of the original dust of the Solar Nebula available for laboratory examination. We performed high-resolution, ∼25 nm/pixel, x-ray imaging and spectroscopy on ultramicrotome sections of CP IDPs, which are aggregates of ≥104 grains, and identified and characterized ∼100 nm thick coatings of organic matter on the surfaces of the individual grains. We estimated the minimum tensile strength of this organic glue to be ∼150 to 325 N/m2, comparable to the strength of the weakest cometary meteors, based on the observation that the individual grains of ∼5 μm diameter aggregate CP IDPs are not ejected from the particle by electrostatic repulsion due to charging of these IDPs to 10 to 15 volts at 1 A.U. in space. Since organic coatings can increase the sticking coefficient over that of bare mineral grains, these organic grain coatings are likely to have been a significant aid in grain sticking in the Solar Nebula, allowing the first dust particles to aggregate over a much wider range of collision speeds than for bare mineral grains.
Key words: Interplanetary dust particles, grain sticking, grain aggregation, organic matter.

Corresponding author E-mail: george.flynn@plattsburgh.edu

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