Here we have investigated the degree to which energetic electrons cause structural changes in microporous H2O ice using infrared and ultraviolet–visible spectroscopy as analytical tools. In these studies, we found that energetic electrons destroy both the dangling bond (DB) absorption bands, indicative of internal surface area, and the internal porosity of our samples. In addition, we find it takes about a factor of 3 higher fluence to decrease the internal pore volume by 63.2% than it does the internal surface area, which is likely because the surface area decreases by both destruction of the internal pores and also by smaller pores coalescing into large ones. Extrapolating our results to the interstellar medium (ISM), we estimate that the time needed for these processes to occur is significantly shorter than the expected lifetime of a molecular cloud, leading us to speculate that future detections of the DB absorption bands or other indicators of porosity in the ISM will be relatively rare.

We present a stacking analysis of 2.61 Msec of archival Chandra observations of stellar wind bow shocks. We place an upper limit on the X-ray luminosity of IR-detected bow shocks of < 2 × 10 29 erg s −1 , a more stringent constraint than has been found in previous archival studies and dedicated observing campaigns of nearby bow shocks. We compare the X-ray luminosities and L X /L bol ratios of bow shock driving stars to those of other OB stars within the Chandra field of view. Driving stars are, on average, of later spectral type than the "field of view" OB stars, and we do not observe any unambiguously high L X /L bol ratios indicative of magnetic stars in our sample. We additionally asses the feasibility of detecting X-rays from stellar wind bow shocks with the proposed Lynx X-ray Observatory. If the X-ray flux originating from the bow shocks is just below our Chandra detection limit, the nearest bow shock in our sample (at ∼0.4 kpc with an absorbing column of ∼ 10 21 cm −2 ) should be observable with Lynx in exposure times on the order of ∼100 kiloseconds.