(a) Tube with synthesized HP material (tan and red regions) before collection. The origin of the color difference is unclear, but it is thought to be due to a difference in the thickness/amount of deposited material in each region. Black markings (around 10.7 and 12 cm) are from highly localized arc discharging where the RF plasma electrodes are located, and only affect the glass tube itself. Significant arcing has not been witnessed and is not expected to occur or affect resulting tholin. The runtime of this experiment is 180 hr. (b) Powder samples obtained after manual scraping of the red and tan regions in subfigure a. Scraped powders achieve a uniform color with no clear tan or red differences after collection. (c) Fused silica standard (top) and tholin thin film on glass (bottom), ready for nanoindentation measurements.