Astronaut Richard Arnold, STS-119 mission specialist, participates in the mission's first scheduled session of extravehicular activity (EVA) as construction and maintenance continue on the ISS on March 19, 2009.
The smell of space will linger for the seven astronauts aboard the space shuttle Discovery long after they return to Earth on Saturday.
"One thing I've heard people say before, but it wasn't so obvious, was the smell right when you open up that hatch," Discovery pilot Dominic "Tony" Antonelli said after a March 21 spacewalk. "Space definitely has a smell that's different than anything else."
The odor, Antonelli said, could be smelled once spacewalkers locked the station airlock's outer hatch and reopened the inner door.
Discovery is set to land at 1:39 p.m. EDT (1739 GMT) tomorrow at NASA's Kennedy Space Center in Florida after a 13-day mission that delivered a new crewmember and the final set of U.S. solar wings to the International Space Station. It was after each of the three spacewalks performed by the shuttle crew that the spaceflyers detected the distinctive odor of space.
Like ozone, or gunpowder
Japanese astronaut Koichi Wakata, who launched to the station aboard Discovery and stayed behind when it left to join the outpost's crew, said he also could smell the odd odor that wafted in from outside the station. But both Antonelli and Wakata, who helped Discovery's spacewalkers climb in and out of their spacesuits, could not put words to the distinctive out-of-this-world scent.
Former NASA astronaut Thomas Jones, a veteran of three spacewalks before retiring from spaceflying in 2001, thinks the odor could stem from atomic oxygen that clings to spacesuit fabric.
"When you repressurize the airlock and get out of your suit, there is a distinct odor of ozone, a faint acrid smell," Jones told SPACE.com, adding that the smell is also similar to burnt gunpowder or the ozone smell of electrical equipment. "It's not noticeable inside the suit. The suit smells like plastic inside."
The smell, he adds, only occurs on a shuttle or the space station after a spacewalk and is unmistakable to astronauts working with the spacesuits and equipment that was used in the vacuum of space.
"In those tight spaces, your nose gets right next to the fabric," Jones said. "I like to think of it as getting a whiff of vacuum!"
The three spacewalks performed by Discovery's crew occurred between March 19 and Monday as the astronauts installed the space station's final set of solar arrays to boost the orbiting laboratory to full power.
The shuttle ferried Wakata Japan's first long-term resident to the space station, where he replaced NASA astronaut Sandra Magnus as a member of the outpost's three-person crew. Magnus is returning home aboard Discovery to complete a 4 1/2-month mission to the space station. The shuttle undocked from the space station on Wednesday.
Discovery astronauts spent Friday checking the shuttle's systems for its planned landing tomorrow and speaking with students at Punahou School in Honolulu, Hawaii, President Barack Obama's high school alma mater. The spaceflyers spoke with President Obama before departing the space station.
SPACE.com is providing continuous coverage of Discovery's STS-119 mission with reporter Clara Moskowitz and senior editor Tariq Malik in New York. Click here for mission updates and SPACE.com's live NASA TV video feed.
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