Gas-Phase Abundance Variations from Dust Grain Sputtering in an SNR Shock

Sputtering in an SNR shock erodes dust grains, returning elements such as Fe,Si, and Mg to the gas phase. Since these elements are thought to besignificantly depleted onto grains, the gas phase abundances in the postshockregion of an SNR shock should be a function of the time since the gas wasshocked. This has never been directly observed, as doing so would require alarge, wellresolved, edgeon shock from an SNR, detailed infrared modeling ofthe emission from warm dust in the post shock region, and sufficient counts inthe Xray spectra to place tight constraints on the abundances. The P7..region in the northeast Cygnus Loop satisfies all these criteria, and we proposea deep observation of this nonradiative shock region. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]