Video: Soyuz MS-01 leaves the space station for landing

Astronaut Scott Kelly and cosmonaut Mikhail Kornienko ended a record-setting 340-day stay in orbit with a fiery plunge to Earth Tuesday, settling to a jarring rocket-assisted touchdown in Kazakhstan to close out a medical research voyage that may help pave the way for flights to Mars.

SpaceX was already tasked with returning NASA astronauts Butch Wilmore and Suni Williams as part of the Crew-9 mission. That departure was delayed by NASA due to unresolved issues with the fifth Crew Dragon capsule that will launch the Crew-10 flight.

SpaceX’s first upgraded Cargo Dragon spaceship departed the International Space Station Tuesday morning with more than 4,400 pounds of research specimens and other equipment, heading for splashdown Wednesday night in the Gulf of Mexico off the west coast of Florida.