The US military has had a robotic space plane in orbit around Earth since December - and no one knows what it's doing.
The US Air Force's X-37B space craft is a reusable, currently unmanned vehicle similar - though smaller - than the retired Space Shuttle.
The Boeing-built X-37B is about 30 feet long, 15 feet wide, weighs 11,000 pounds and can carry about the same load as a delivery van.
It took off from Cape Canaveral on 11 December, carried by an Atlas V rocket.
It has now been in space for more than two months, and shows no signs of returning.
It is the same vehicle which spent 225 mysterious days in space in 2010 before landing automatically in California - and as such marks the first time the US Navy has successfully reused space hardware.
Officially named USA-240, the current mission is also known as Orbital Test Vehicle-3 since it is the third time the craft has flown.
A report by Space.com did not turn up details about what the space plane is doing - but still makes for fascinating reading.
Among the choice quotes is this by Air Force Maj. Eric Badget, who says simply: "The mission is ongoing".
In a fact sheet, the Air Force says simple that the X-37B is developed "to demonstrate a reliable, reusable, unmanned space test platform for the United States Air Force".
It is commanded by the 3rd Space Experimentation Squadron, 21st Space Wing, of the Air Force Space Command in Colorado.
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