Charon Relay

The Charon Relay, found encased in ice and orbiting Pluto, was humanity's second greatest discovery after the discovery on Mars. The Prothean ruins found on Mars had given the Systems Alliance a huge leap forward in technology and allowed them to dominate the Sol system. It required the discovery of a mass relay, however, to catapult humans onto the galactic stage.

In 2156, a science team exploring the edge of the solar system near Pluto discovered that Charon was not a moon at all. In fact, it was a gargantuan piece of Prothean technology known as a mass relay station. The discovery was not completely surprising because the alien station on Mars had mentioned such a device. And while they were unable to construct one of their own, scientists were able to activate a dormant relay.

Activating the Charon Relay opened the rest of the galaxy to humanity when a team of brave men and women led by Jon Grissom traveled to the other side, discovering that the mass relay led to Arcturus (and a further three mass relays). Their successful return marked them as heroes for all of Earth and Jon Grissom as the face of Alliance growth and prosperity.

The operation of the Charon Relay has had the side effect of circularising Pluto's elliptical orbit.

Trivia

 * Charon in greek mythology was the ferryman for the dead, ferrying them across the river styx.