The European Space Agency (ESA) is Europe’s gateway to space. Its mission is to shape the development of Europe’s space capability and ensure that investment in space continues to deliver benefits to the citizens of Europe and the world.
Find out more about space activities in our 23 Member States, and understand how ESA works together with their national agencies, institutions and organisations.
Exploring our Solar System and unlocking the secrets of the Universe
Go to topicProtecting life and infrastructure on Earth and in orbit
Go to topicUsing space to benefit citizens and meet future challenges on Earth
Go to topicMaking space accessible and developing the technologies for the future
Go to topicThe potassium to thorium ratio in the surface of planets is believed to depend on the temperature at which the planets formed. The volatile potassium evaporates at high temperatures while thorium remains. Mercury, however, appears to have too much potassium. About as much as if it formed much farther away from the Sun, about as far as Mars