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As millions of people on Earth celebrate Christmas with their families and friends today (Dec. 25), exchanging gifts and sharing elaborate meals, astronauts at the International Space Station (ISS) will do much of the same — while floating weightlessly some 250 miles (400 kilometers) above the Earth. 

The three NASA astronauts currently aboard the ISS (Joe Acaba, Mark Vande Hei and Scott Tingle) will have the day off this Christmas, NASA spokesman Dan Huot told Space.com. Because the crew are typically off-duty on the weekends, too, they'll get to enjoy a special long weekend in space. Instead of doing research or working on science experiments, they will spend the day relaxing, calling their families and opening gifts. 

Santa Claus might have a hard time delivering gifts to the ISS — his reindeer would have to fly as fast as 17,500 mph (28,000 km/h) without any air to breathe — but there will still be gifts for the crew to open Christmas morning. Some gifts traveled with the most recent crew of three, who arrived at the ISS on Dec. 19. A Cygnus cargo spacecraft that arrived in November also brought some gifts from the astronauts' families. [Holidays in Space: An Astronaut Photo Album]

"We have packages and gifts from our families and friends, and packages on board the ISS labeled to open on Dec. 25 for U.S. crewmembers and Dec. 31 for us from Russia," Russian cosmonaut Anton Shkaplerov told reporters Dec. 16, one day before he launched to the ISS with Tingle and Japanese astronaut Norishige Kanai. (Russia celebrates Eastern Orthodox Christmas on Jan. 7, but Russians traditionally open gifts on New Year's Eve.)

There's even at least one small artificial Christmas tree aboard the space station. "We [already] have a Christmas tree aboard, and there is a new Christmas tree arriving soon," Shkaplerov said during the prelaunch briefing. 

But because there's effectively no gravity at the ISS, the gifts won't exactly be waiting under the tree. In fact, there is no real concept of "up" or "down" at the ISS, where the differences between floors, walls and ceilings becomes pretty vague. Whether the gifts are beneath, above or beside the tree is only a matter of perspective. 

After opening their gifts, the astronauts will likely share a special holiday meal together, although the Christmas dinner menu has not yet been disclosed, Huot said. For last year's space station feast, the Expedition 50 crew enjoyed turkey, corn-bread stuffing, gingerbread cookies and hot cocoa. 

Expedition 30 crewmembers celebrate Christmas on the International Space Station in 2011. The Expedition 54 crew will do the same on Dec. 25, 2017.
Expedition 30 crewmembers celebrate Christmas on the International Space Station in 2011. The Expedition 54 crew will do the same on Dec. 25, 2017.
Credit: NASA

Email Hanneke Weitering at hweitering@space.com or follow her @hannekescience. Follow us @Spacedotcom, Facebook and Google+. Original article on Space.com.