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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Artist’s impression of the nucleus of comet 67P/Churyumov–Gerasimenko, portrayed far from the Sun with little to no activity.
Comets are a mix of rock, dust, ice and organic materials, and their surfaces are very dark, typically reflecting only 4% of the light that falls on them. Some parts of the nucleus are smooth and young, while other areas are cratered and old. The smoother, brighter areas of a nucleus are a result of resurfacing processes during active phases of the comet. That is, when its surface is heated up close to the Sun, ices sublimate and gases escape from inside the nucleus, creating a dynamic and unpredictable environment.
Comet 67P/Churyumov–Gerasimenko is thought to be about 4 km wide, but until Rosetta reaches it in 2014, exactly what the nucleus looks like remains a mystery.