Ammonia hydrates and crystalline ice were two items I thought I could use to potentially narrow down or identify the age of the event that created Charon's smooth southern hemisphere. Turns out neither is a reasonable age dating method for this event. Crystalline ice is found on other Kuiper Belts Objects (KBO) of similar size to Charon and the ammonia hydrates are spread across Charon's northern and southern surfaces but not around its trailing hemisphere. If the ammonia was predominately on the southern hemisphere it would suggest the event created the ammonia hydrates. If crystalline water ice were only on Charon it might also point to the event as a cause but neither is correct. Instead the leading hemisphere displaying ammonia indicates Charon's rotational orbit around Pluto is the key factor is the placement of the ammonia.

Zones - Rocky Planets, Main Asteroid Belt, Gas Giants, Kuiper Belt Objects, Transneptunian Objects
Rocky Planets - temperature from Sun evaporates away volatiles
Main Belt - Frost line, Albedo shift
Gas Giants - Centaurs, Trojans
Kuiper Belt - Cold Classical Red KBO, Neptune Perturbed (resonant) Multicolored Scattered Disk Objects, Plutinos
Transneptunian Objects,

http://www.johnstonsarchive.net/astro/astalbedo.html

NASA's NeoWISE spacecraft has identified 29,375 solar system objects, including 788 near-Earth comets and asteroids. https://www.jpl.nasa.gov/news/news.php?release=2018-078

https://www.nasa.gov/mission_pages/WISE/multimedia/neowise20130725i.html

Lonar Lake is a saline soda lake located at Lonar in Buldhana district, Maharashtra, India, which was created by a meteor impact during the Pleistocene Epoch