Why visit a comet?

The Rosetta Mission has been a long and complex mission to land a probe on a comet. What exactly is a comet and why land a probe on one? Avionics engineer Warwick Holmes explains how comets may offer insights into big questions such as how did life come about on Planet Earth?

Transcript

WARWICK HOLMES

What is a comet and why do you want to visit one? Well, a comet is a planetary body of our Solar System. It’s gravitationally bound to the Sun. But it’s extremely different than all other planetary bodies which have been visited by all other missions during space exploration, and that includes all the planets and even the Sun itself.

The planets and the Sun have been heated by the process of gravitational collapse and by, obviously, the fusion of the nuclear reaction of the Sun. Comets were the original primordial material that first formed when the Solar System was forming 4.5 billion years ago, and it was material that was slowly condensing and collapsing under gravity before the Sun and the planets existed. So there was no light, there was very little gravity, and it was just this process of elements slowly coming together and making molecules we’ve never seen before.

The best analogy I can give, it’s like burning a piece of paper and never seeing the white piece of paper. So the terrestrial planets we live on and the Sun have all been burnt, so the chemistry has been completely changed by heat. As of this mission, we have never seen a white piece of paper, and that’s what this mission is all about is trying to understand the chemistry of the white piece of paper, the cake mix of our Solar System, and trying to visit and land on there to find out what chemistry, what physical processes, what makes a comet.

So the fundamental question is, how do we get from this? This ball of dust, which is from a supernova explosion – another star which has already exploded, generated lots of dust and new elements whizzing through space and collapsing to form a new star, a new Solar System. How did we get from that gas and dust to Planet Earth with water to intelligent human life? Every single one of you is made of cometary dust from the elements of a supernova explosion more than 4.5 billion years ago. How did we all get here?

Acknowledgements
The Science Learning Hub would like to acknowledge the following for their contribution to this resource:
Warwick Holmes
Lecture video footage courtesy of the University of Waikato
Footage of comet in sky and animated 3D image of Comet 67P courtesy of ESA – European Space Agency and NASA Jet Propulsion Laboratory
Image of Comet 67P courtesy of ESA/Rosetta/NavCam and licensed under Creative Commons licence 3.0
Image of exploded supernova courtesy of European Southern Observatory (ESO) and licensed under Creative Commons Licence 4.0