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
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The main components of a comet – nucleus, coma, hydrogen envelope, dust and plasma tails – indicating their composition, relative sizes and location. Below, the two main reservoirs of comets in the Solar System are shown: the Kuiper Belt and the Oort Cloud. As an example, the orbits of three famous comets are also included: two short-period comets, 67P/Churyumov–Gerasimenko (the target of ESA's Rosetta mission) and 1P/Halley, and a long-period comet, Siding Spring, which will reach its closest approach to the Sun in late 2014.
The diagrams are representative and not to scale.