Comets and how the Solar System formed
The Solar System formed about 4.6 billion years ago when a cloud of gas and dust started to collapse. A disc of material formed around the early Sun, the particles of which collided and joined together, growing increasingly larger and larger, until they formed planets, their moons and millions of asteroids and comets.
Over billions of years the planets have undergone large internal changes due to their own gravity. Comets, however, are so small that they have remained almost unchanged. As they spend most of their time far from the Sun in a 'deep freeze' their matter preserves the original material of the primitive nebula, helping us look back to the very infancy of the Solar System.
In 1986, ESA's Giotto mission achieved the first close encounter of a comet, passing within 600 km of Comet Halley. Giotto, a pioneer in comet science, provided us with the first ever images of a comet's nucleus.
Ground-based observatories and Giotto have shown that comets contain complex organic molecules rich in carbon, hydrogen, oxygen and nitrogen - essential ingredients for life. With Rosetta, scientists expect to be able to answer whether cometary impacts, very common in the early Solar System, brought large quantities of water to Earth, creating the conditions for life to form and evolve.
This panel is available in a print-ready version for the format 70 × 100 cm, which can be downloaded here as a PDF.
These exhibition panels were originally published on ESA's Exhibitions website.