For decades, scientists have had better maps of the Moon and Mars than of Earth’s own ocean floor. But thanks to NASA’s Surface Water and Ocean Topography (SWOT) satellite, a groundbreaking new space-based map of the seafloor is changing that.

After nine months on the International Space Station, NASA astronauts Sunita Williams and Barry “Butch” Wilmore splashed down in the Gulf of Mexico on March 18.

The astronauts will be checked out by flight surgeons as they adjust to gravity, officials said, and should be allowed to go home after a day or two. However, their condition will be monitored for long after that.