Exploration Mission 2 or EM-2 is scheduled to be the first manned mission of NASA's Orion project, which is to restart manned exploration of the Solar System. It is to be launched as early as 2021 and will take a 2 person crew, for the first time, to a captured asteroid in lunar orbit.
In the event this mission does in fact go ahead it will (barring earlier flights by other Agencies in the interim) be the first time humans have left low earth orbit since Apollo 17 in December 1972.
EM-2 is a single launch mission of a Block I SLS with ICPS and lunar Block 1 Orion Multi-Purpose Crew Vehicle (MPCV) with a liftoff mass around 68.8 t with SLS’ Payload Insertion of 50.7 t, which would be a ten to fourteen day mission with a crew of four astronauts who would spend four days in lunar orbit. Its current description is “Crewed mission to enter lunar orbit, test critical mission events, and perform operations in relevant environments”. The destination for EM-2, as of 2013, is regarded to be a captured asteroid, in lunar orbit, to be conducted by no later than 2021. The destination could possibly be 2000 SG344 although there are a number of other options.