[8] On February 7, the fourth day of the mission, astronauts McCandless and Stewart performed the first untethered spacewalk, operating the Manned Maneuvering Unit (MMU) for the first time.

[5][9] At 8:25 a.m. EST, pulsing the MMU's thrusters, McCandless ventured out of Challenger's payload bay, and reached 98 m (322 ft) from the orbiter.

[10] Stewart tested the "work station" foot restraint at the end of the Remote Manipulator System (Canadarm).

[11] Included in one of the GAS canisters was the first experiment designed and built by a high school team to fly in space.

[12][13]: 6  During re-entry, ice from the dump valves broke off their nozzles situated near the nose of the orbiter and struck the left Orbital Maneuvering System (OMS) pod, damaging three Thermal Protection System (TPS) tiles and leading to a burn-through,[13]: 4  but the damage was minimal enough that Challenger and its crew were unharmed.

[14] Astronaut Bruce McCandless II sued singer Dido in 2010 over the use of a public domain photo of him in space on this mission on her 2008 album Safe Trip Home.