Experimental constraints on the ordinary chondrite shock darkening caused by asteroid collisions. (arXiv:2004.00625v1 [astro-ph.EP])

Experimental constraints on the ordinary chondrite shock darkening caused by asteroid collisions. (arXiv:2004.00625v1 [astro-ph.EP])
<a href="http://arxiv.org/find/astro-ph/1/au:+Kohout_T/0/1/0/all/0/1">T. Kohout</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Petrova_E/0/1/0/all/0/1">E. V. Petrova</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Yakovlev_G/0/1/0/all/0/1">G. A. Yakovlev</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Grokhovsky_V/0/1/0/all/0/1">V. I. Grokhovsky</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Penttila_A/0/1/0/all/0/1">A. Penttil&#xe4;</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Maturilli_A/0/1/0/all/0/1">A. Maturilli</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Moreau_J/0/1/0/all/0/1">J.-G. Moreau</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Berzin_S/0/1/0/all/0/1">S. V. Berzin</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Wasiljeff_J/0/1/0/all/0/1">J. Wasiljeff</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Danilenko_I/0/1/0/all/0/1">I. A. Danilenko</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Zamyatin_D/0/1/0/all/0/1">D. A. Zamyatin</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Muftakhetdinova_R/0/1/0/all/0/1">R. F. Muftakhetdinova</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Heikkila_M/0/1/0/all/0/1">M. Heikkil&#xe4;</a>

Shock-induced changes in ordinary chondrite meteorites related to impacts or
planetary collisions are known to be capable of altering their optical
properties. Thus, one can hypothesize that a significant portion of the
ordinary chondrite material may be hidden within the observed dark C/X asteroid
population. The exact pressure-temperature conditions of the shock-induced
darkening are not well constrained. Thus, we experimentally investigate the
gradual changes in the chondrite material optical properties as a function of
the shock pressure. A spherical shock experiment with Chelyabinsk LL5 was
performed in order to study the changes in its optical properties. The
spherical shock experiment geometry allows for a gradual increase of shock
pressure from $sim$15 GPa at a rim toward hundreds of gigapascals in the
center. Four distinct zones were observed with an increasing shock load. The
optical changes are minimal up to $sim$50 GPa. In the region of $sim$50–60
GPa, shock darkening occurs due to the troilite melt infusion into silicates.
This process abruptly ceases at pressures of $sim$60 GPa due to an onset of
silicate melting. At pressures higher than $sim$150 GPa, recrystallization
occurs and is associated with a second-stage shock darkening due to fine
troilite-metal eutectic grains. The shock darkening affects the ultraviolet,
visible, and near-infrared (UV, VIS, and NIR) region while changes to the MIR
spectrum are minimal. Shock darkening is caused by two distinct mechanisms with
characteristic pressure regions, which are separated by an interval where the
darkening ceases. This implies a reduced amount of shock-darkened material
produced during the asteroid collisions.

Shock-induced changes in ordinary chondrite meteorites related to impacts or
planetary collisions are known to be capable of altering their optical
properties. Thus, one can hypothesize that a significant portion of the
ordinary chondrite material may be hidden within the observed dark C/X asteroid
population. The exact pressure-temperature conditions of the shock-induced
darkening are not well constrained. Thus, we experimentally investigate the
gradual changes in the chondrite material optical properties as a function of
the shock pressure. A spherical shock experiment with Chelyabinsk LL5 was
performed in order to study the changes in its optical properties. The
spherical shock experiment geometry allows for a gradual increase of shock
pressure from $sim$15 GPa at a rim toward hundreds of gigapascals in the
center. Four distinct zones were observed with an increasing shock load. The
optical changes are minimal up to $sim$50 GPa. In the region of $sim$50–60
GPa, shock darkening occurs due to the troilite melt infusion into silicates.
This process abruptly ceases at pressures of $sim$60 GPa due to an onset of
silicate melting. At pressures higher than $sim$150 GPa, recrystallization
occurs and is associated with a second-stage shock darkening due to fine
troilite-metal eutectic grains. The shock darkening affects the ultraviolet,
visible, and near-infrared (UV, VIS, and NIR) region while changes to the MIR
spectrum are minimal. Shock darkening is caused by two distinct mechanisms with
characteristic pressure regions, which are separated by an interval where the
darkening ceases. This implies a reduced amount of shock-darkened material
produced during the asteroid collisions.

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