Thermophysical properties of Almahata Sitta meteorites (asteroid 2008 TC3) for high-fidelity entry modeling

1Stefan Loehle, 2,3Peter Jenniskens, 4Hannah Böhrk, 5Thomas Bauer, 4Henning Elsäβer, 3Derek W. Sears, 6Michael E. Zolensky, 7Muawia H. Shaddad
Meteoritics & Planetary Science (in Press) Link to Article [DOI: 10.1111/maps.12788]
1High Enthalpy Flow Diagnostics Group, Institute of Space Systems, 70569 Stuttgart, Germany
2SETI Institute, Carl Sagan Center, Mountain View, California 94043, USA
3NASA Ames Research Center, Mountain View, California 94035, USA
4DLR, Institute of Structures and Design, 70569 Stuttgart, Germany
5DLR, Institute of Technical Thermodynamics, 51147 Cologne, Germany
6ARES, NASA Johnson Space Center, Houston, Texas 77058, USA
7Physics Department, University of Khartoum, Khartoum, Sudan
Published by arrangement with John Wiley & Sons

Asteroid 2008 TC3 was characterized in a unique manner prior to impacting Earth’s atmosphere, making its October 7, 2008, impact a suitable field test for or validating the application of high-fidelity re-entry modeling to asteroid entry. The accurate modeling of the behavior of 2008 TC3during its entry in Earth’s atmosphere requires detailed information about the thermophysical properties of the asteroid’s meteoritic materials at temperatures ranging from room temperature up to the point of ablation (~ 1400 K). Here, we present measurements of the thermophysical properties up to these temperatures (in a 1 atm. pressure of argon) for two samples of the Almahata Sitta meteorites from asteroid 2008 TC3: a thick flat-faced ureilite suitably shaped for emissivity measurements and a thin flat-faced EL6 enstatite chondrite suitable for diffusivity measurements. Heat capacity was determined from the elemental composition and density from a 3-D laser scan of the sample. We find that the thermal conductivity of the enstatite chondrite material decreases more gradually as a function of temperature than expected, while the emissivity of the ureilitic material decreases at a rate of 9.5 × 10−5 K−1 above 770 K. The entry scenario is the result of the actual flight path being the boundary to the load the meteorite will be affected with when entering. An accurate heat load prediction depends on the thermophysical properties. Finally, based on these data, the breakup can be calculated accurately leading to a risk assessment for ground damage.

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