SpaceProbe set to become Mercury's first artificial satellite NASA's Messenger probe will attempt to go into orbit around the sun-baked planet on Friday – it could help reveal why Mercury is so dense ¿ìè¶ÌÊÓÆµ
EarthWhat if the Earth stopped spinning? Or what if our home planet had two moons, or none, or was a moon itself? Hazel Muir explores the science of six alternate Earths Features