The longest spacewalk in history was in 2001 and it lasted eight hours and 56 minutes.
What's A Spacewalk, Anyway?
A spacewalk is also called an extravehicular activity (EVA). During an EVA, astronauts exit the spacecraft to work on its exterior. The longest spacewalk in history was conducted on March 11, 2001, by astronauts Susan Helms and Jim Voss. During the STS-102 mission of the shuttle Discovery, Helms and Voss set out to relocate a component on the ISS exterior and install a fixture on top of the station's U.S. Destiny laboratory. However, they encountered several difficulties, including tools that floated away into space and stubborn connectors that wouldn't come loose from the station's surface. The EVA clocked in at 8 hours and 56 minutes, 30 minutes longer than the previous record holder.
NASA has its eyes on getting humans to Mars, and a trip there could last up to 1,100 days, which means it's vital to understand how "humans respond to prolonged low gravity, cosmic radiation, and confined quarters (among other things)," as National Geographic explains. "Right now, our best proxy is to look at how seasoned astronauts are faring after long hours in Earth's orbit." That includes Voss and Helms' epic spacewalk. Specifically, how they fared in those bulky spacesuits. "Crews on Mars will also need to roam outside the relative safety of a habitat module for prolonged periods, so NASA is working on various ways to improve spacesuit designs, such as making them more flexible and easier to get on and off."