Watch a live view of the Atlas 5 launch pad with countdown audio (members only)

After a six-month voyage from Earth, NASA’s InSight Mars lander, streaking through space at at some 12,300 mph, will slam into the thin martian atmosphere Monday afternoon to begin a nail-biting six-and-a-half-minute descent to the surface, kicking off a billion-dollar mission to probe the red planet’s hidden interior.

A day-and-a-half before its liftoff with a U.S. Air Force communications satellite, a United Launch Alliance Atlas 5 rocket rolled out to its launch pad at Cape Canaveral on Monday morning.

The next Atlas 5 rocket launch from Cape Canaveral will be delayed two weeks to resolve an undisclosed issue with the payload, United Launch Alliance officials announced Friday.