"Mass Effect" is set 180 years in the future in the year 2183. According to the back story humans discovered some ancient technology on Mars. This enabled them to build faster than light spacecraft. With this technology humans explored the whole Solar System. Twenty years before the game begins human explorers find that Pluto's moon Charon, is really a Mass Relay. Mass Relays are the only way to travel from one distant end of the galaxy to the other. Mass Relays are ancient technology created by the Protheans, the now exctict race that once ruled the galaxy. This enables spacecraft and people to be sent across the galaxy.