A key component of putting humans on Mars is being able to reuse the rockets that have launched spacecraft into orbit, and private space firm SpaceX has just taken another step towards making this a reality.
Earlier today, Elon Musk's company successfully launched a rocket before landing it on the ground for the second time.
The CRS-9 mission, which was sending a Dragon spacecraft to the International Space Station with supplies for astronauts, successfully launched on July 18.
As part of the mission the Falcon 9 rocket completed an "experimental landing" at Cape Canaveral Air Force Station, Florida, US.
"We just completed the post-landing inspection and all systems look good.
Ready to fly again," Elon Musk, the founder of SpaceX said in a tweet after the rocket had touched down.