After his return from nearly a year in space, NASA astronaut Scott Kelly gave Microsoft’s HoloLens headset a big thumbs-up for work on the International Space Station – and for shooting down aliens in his spare time.

“It worked great,” he said today during a news briefing at NASA’s Johnson Space Center in Texas. “I was really surprised. We messed around with it for about two hours, and immediately I sensed this is a capability we could use right now.”

The orbital test was part of Project Sidekick, a Microsoft-NASA collaboration to see how augmented-reality tools like HoloLens could facilitate operations on the space station. The HoloLens glasses can superimpose computer-generated graphics on the wearer’s field of view, and show someone else what the wearer is looking at. Both functions were put to the test in orbit.

“It had some cameras on it, and we could also see a display that’s in your field of view, The person on the ground could be drawing things in your field of view, and pointing to things, and I could be doing the same thing,” Kelly explained.

For example, ground controllers could monitor Kelly’s HoloLens view during a maintenance procedure. “I could say, ‘Hey, is this the bolt or connector you’re talking about?’ And the person [at Mission Control] could just write an arrow in your field of view,” Kelly said.

The glasses also make it possible to display a checklist off to the side of the frame, which could come in handy during a complex task. “Looking through it, you can change the opacity of the procedure so it’s right in front of your field of view,” Kelly said.

It wasn’t all work and no play for the astronauts. Kelly said he played RoboRaid, one of the games that Microsoft developed for the HoloLens, and didn’t experience any of the disorientation or nausea that’s sometimes associated with virtual-reality applications. The astronauts’ main concern was fighting off the alien invaders.

“It has alien spaceships coming inside the space station, and there’s these aliens attacking you,” Kelly said of the game. “You’ve got to shoot them with your finger. … It was kinda fun.”

Kelly came back down to Earth on Tuesday after spending 340 days in space, which marks a U.S. record for continuous spaceflight. But the HoloLens headsets are still onboard and available for testing.

“The technology in general has great potential for applications, not only in space but of course on Earth as well.” he said.

Today’s briefing gave journalists their first good chance to ask about Kelly’s record-setting experience. After landing in Kazakhstan on Tuesday, the 52-year-old veteran astronaut was whisked off to Norway, went through a battery of medical tests, and then flew via Newfoundland to Houston early Thursday. The first thing he did when he got back home was throw himself into his swimming pool.

“We make do with not having a shower on board [the space station], and it’s not like you feel dirty, but you definitely feel like you would like to jump in a pool. So I did,” Kelly said.

Kelly said he added about an inch and a half to his height while he was on the space station. That’s typical for long-term stays on the space station, where zero-G causes the vertebrae in a spaceflier’s spine to space themselves out. Mark Kelly, Scott’s twin and a retired astronaut himself, said it took only a day for his brother to be “squished back to normal height.”

Over the past year, Scott and Mark Kelly have undergone a wide range of medical tests – ranging from blood, urine and saliva samples to MRI scans, ultrasound readings and genetic analyses. NASA medical researcher John Charles said the Kellys would undergo nine more months of on-the-ground tests. “We’ve got lots of other surprises to spring on Scott and Mark,” he told journalists.

Comparisons of the Kellys’ medical status and genetic profiles are expected to provide insights into what would be required to keep astronauts healthy and productive during the even longer journeys to Mars and other deep-space destinations in the 2020s and 2030s. One of Kelly’s Russian crewmates, Mikhail Kornienko, also spent 340 days in orbit and will be studied by researchers in Russia.

Although the medical findings will be kept confidential until the scientific studies are published, Kelly provided some personal observations on his year in space and its aftermath:

Kelly’s 340-day tour of duty was actually his second long-term stint on the space station. The first was a 159-day orbital visit in 2011. “Initially, this time, coming out of the capsule, I felt better than I did last time,” Kelly said. “But at some point those two lines have crossed, and my level of muscle soreness and fatigue is a lot higher than it was last time.” He also said his skin felt surprisingly sensitive. “It’s almost like a burning feeling wherever I sit or lie or walk.” He said thick-soled running shoes are making his feet feel better.

Kelly said he’s not letting go of things and expecting them to float in the air, as some freshly returned astronauts have done. But he’s become an even lousier basketball shooter. “Definitely throwing things, you tend to underestimate the effects of gravity,” he said.

Kelly had planned to have a slice of pizza as his first earthly treat, but as he was flying back home, a banana that was sitting out looked so good that he took a bite. It wasn’t until he was halfway through the banana that he realized the irony: Before he left the space station, he received a gorilla suit as a gag gift from his brother and used it to play a prank on his crewmates.

There was one big news story that held Kelly’s attention while he was in space: the presidential campaign. Super Tuesday’s outcome was one of the first things he asked about after he climbed out of the Soyuz capsule in Kazakhstan. He declined to say what he thought of the results. “As a government employee, I’m subject to the Hatch Act, so I can’t say what I think,” Kelly told reporters.

Kelly said he missed his family while he was in orbit, but he wouldn’t characterize it as “having the blues.” And he repeated his view that he could have stayed in space much longer if there was a good reason to do so – like going to Mars.

“I personally think, going to Mars, if it takes two years or two and a half years, that’s doable,” he said. “Certainly for the first people that go there, that’s going to be a big motivator, going first. … I think we know enough and I think we’re close enough that if we made the choice, ‘Hey, we’re going to do this, we’re going to set a goal, we’re going to set a time’ … yeah, I think we could do it.”