Pluto’s icy surface freeze framed
doi:10.1038/nindia.2016.120 Published online 13 September 2016
By simulating the frigid conditions on Pluto’s surface, astrochemists have analysed the absorption spectra of nitrile-bearing molecules that may form on this icy body.
Since cosmic radiation can convert an icy mixture of nitrogen, methane and carbon dioxide into nitrile-bearing molecules on its surface, this spectral analysis could shed light on the complex chemistry of the distant planet.
Images sent by NASA’s New Horizons spacecraft indicated that Pluto’s icy surface might harbour complex molecules. To identify a possible “richer ice chemistry” on Pluto’s mantle, the researchers formed ices of nitrile-bearing molecules such as acetonitrile, propionitrile, butyronitrile, and isobutyronitrile at 10 Kelvins and deposited them on a cooled lithium fluoride substrate inside an ultra-high vacuum chamber. They then measured the molecules’ photoabsorption spectra at vacuum ultraviolet wavelengths.
When warmed the molecules’ morphology changed from amorphous to crystalline, slightly altering their absorption properties. The continuous absorption by the nitrile-bearing molecules at wavelengths between 150 and 175 nm could mirror those on Pluto’s surface.
The researchers posit that it is highly likely that nitrile-bearing molecules could have been incorporated into Pluto’s atmosphere during the formation of the solar system.
1. Sivaraman, B. et al. Vacuum ultraviolet photoabsorption spectra of nitrile ices for their identification on Pluto. Astrophys. J. (2016) doi:10.3847/0004-637X/825/2/141