An unidentified instrument is visible on Progress MS-07 spacecraft scheduled for launch to ISS on Oct. 12, 2017. Anatoly Zak

Thursday's early morning launch at the Baikonur Cosmodrome in Kazakstan is a routine one, delivering fuel, water, and food for the six astronauts currently on board the International Space Station. But there's one thing that's definitely not routine. Russia's seven-ton Progress MS-07 tanker will be carrying a secret, a previously unseen instrument attached to the exterior front section of the spacecraft. NASA has no idea what it is.

NASA specialists spotted the unknown gizmo in official photographs of the Progress ship released during mission preparation. Since then, a number of pictures documenting the work on Progress MS-07 in Baikonur also showed the unidentified device, indicating that Russian authorities aren't reallykeeping it secret. But when NASA asked about the hardware, Russian officials said only that it would be a scientific payload intended for a one-time trip aboard the cargo ship. They provided no further details.

Anatoly Zak

The brush-off response puzzled U.S. officials because all five space agencies involved in the ISS have shared information about all the hardware flying to or near the outpost. This is probably the first time in the nearly 19-year history of joint operations on board the ISS that one of the partners is delivering unexplained cargo to the station. (It's not the first time a partner has ran afoul of usual standards and practices. In June, a classified U.S. satellite reportedly made unexplained passes in the proximity of the station and no one is