Europe’s mission to land the first-ever probe on a comet was on track Wednesday with one final “go” pending for the robot lab to eject from its mothership and start a nail-biting seven-hour descent.

European scientists were hoping for a stream of data Thursday after a robot lab made the first-ever landing on a comet, a key step in a marathon mission to probe the mysteries of space. Operation ...

The Stardust mission ended early Sunday when the 100-pound capsule landed at the U.S. Air Force Utah Test and Training range two minutes ahead of schedule at 3:10 a.m. “We visited a comet, grabbed a ...