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What a comet can tell us about life on Earth

This week the robot probe Philae made a historic landing on a comet. So what do scientists hope to learn from the probe, and what does this mean for manned space missions?

How it got there

Philae was carried on a 10 year journey by the Rosetta satellite, to rendezvous with Comet 67P/Churyumov-Gerasimenko. After reaching its target, the probe, about the size of a washing machine, was dropped from the satellite for its seven hour journey to the comet’s surface, landing at about 1600 GMT on Wednesday.

It is the first spacecraft ever to land on a comet, although there are concerns about its long-term stability as the harpoons that were supposed to attach to the surface failed to fire.

What does it hope to achieve?

Even aside from the landmark significance of landing a mission on an object that is moving through space at speeds of up to 40,000 kilometres an hour, scientists hope Philae will help answer important questions.

Comets are the remnants of the formation of the solar system, the bits left over when planets were being created, and the mission could shed light on how that happened. Philae will spend several months on the comet, taking pictures and analysing the chemical composition of its surface.

Previous work has shown that comets contain a large proportion of water-ice, and among the hypotheses being tested are whether a bombardment from comets brought water and other organic molecules to Earth billions of years ago. This could mean that comets played a role in creating life on Earth.

The comet’s interior is believed to be composed of the same material involved in the creation of the solar system 4.5 billion years ago and analysis could help us understand how planets are formed.

The facts about the mission

Planning for the journey began 25 years ago, with Rosetta taking 10 years to travel to the comet. The comet is more than four billion years old, weighs 10 billion tonnes and is shaped like a rubber duck.

The 10 year journey covered four billion miles, the equivalent of 8,000 return trips to the moon, and involved passing Mars once and Earth three times in order to benefit from its gravitational pull. It also involved a two-and-a-half-year hibernation period to conserve energy.

The mission was carried out by the European Space Agency, with some support from NASA, and is estimated to have cost almost £1bn.

Questions for debate and discussion

  • How will we benefit from knowing how our planet was formed?
  • How can we justify spending that much money on a space mission?
  • Will manned spaceflights over such large distances ever be feasible?
  • How could the ability to rendezvous with a comet help us in the future?

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