First story in my Unified Fiction universe. Crossover between My Little Pony and Serenity/Firefly

Several years back, a spaceship landed on Equestria, changing the lives of its inhabitants, and probably not for the better. In current day, a medical researcher gives his life to send an ex-colleague a message about the material he was researching, prompting a few questions from the crew of the Serenity.

What is the main ingredient in the G-23 Paxilon Hydrochlorate? Why has there been no attempts to colonize outside of this solar system? What is the average flight speed of an unladen swallow? Oh, wait...