NASA will return four astronauts to Earth early from the International Space Station due to a medical concern with one of the Crew-11 astronauts. Here's the latest news.
The closest planet to the Sun is Mercury. It's a tiny world, even smaller than Saturn's moon Titan and Jupiter's moon Ganymede. That's unusual for a planetary system. Most star systems have a large world between the size of Earth and Neptune orbiting much closer than Mercury. A new study has figured out how these close-orbiting super-Earths form and clues about why they are so common.

