Video: Alice Bowman, New Horizons mission operations manager, previews Ultima Thule flyby (members only)

A Russian cosmonaut and his two NASA crewmates undocked from the International Space Station and landed in Kazakhstan early Friday, returning to an unfamiliar world in the grip of a pandemic that will force them to extend the social isolation they were hoping to end.

A NASA post advertising an opening for a new Planetary Protection Officer provided a field day for headline writers who apparently couldn’t resist having a bit of fun at the agency’s expense by suggesting, in large type, that whoever filled the post would be defending Earth from aliens. And making good money to boot.

Engineers have spotted two small breaks in the treading on the left middle wheel on NASA’s Curiosity rover, one of six wheels that have moved the robot nearly 10 miles across the Martian surface since landing in August 2012.