UCL: Comet chaser mission moves from blueprint to reality

The Comet Interceptor mission was formally adopted by ESA at a meeting in Madrid, with the next step to select a contractor to build the spacecraft and a robotic probe.​

Due for launch in 2029 it will see one main spacecraft and two robotic probes – the other built by the Japanese Space Agency – travel to an as-yet unidentified comet and map it in three dimensions.

The mission was first proposed by an international team from Europe, Japan, and the US led by UCL’s Professor Geraint Jones and Professor Colin Snodgrass of the University of Edinburgh.

Professor Geraint Jones (UCL Mullard Space Science Laboratory) said: “This mission should give us our first glimpse of a truly pristine body – an invaluable example of the objects that came together to form the Earth and other planets. The comet’s surface will be largely unchanged since the time of the Solar System’s formation several billion years ago, and I can’t wait to see that uncharted territory sometime in the 2030s.

“It’s fantastic to get the green light for the mission after almost four years of hard work since the European Space Agency’s invitation to propose came out. The international team of scientists and engineers, working with colleagues at ESA, kept mission development on track despite the many complications raised by Covid-19.”

Instruments on the mission will return high resolution images of the comet’s nucleus, measure its composition directly and indirectly, and study how the comet interacts with the interplanetary magnetic field and the flow of charged particles from the Sun.

Comet Interceptor will share a ride into space in 2029 with another ESA mission in which UCL plays a leading role: the Ariel exoplanet mission, whose principal investigator is Professor Giovanna Tinetti (UCL Physics & Astronomy).

Caroline Harper, Head of Space Science at the UK Space Agency, said: “This is a huge milestone for the Comet Interceptor mission. After an intensive period working on the mission design feasibility and definition, we are ready to move forward to the full implementation stage.

“Comet Interceptor will not only further our understanding of the evolution of comets but help unlock the mysteries of the Universe.”

Comets are what is left over when a planetary system forms and in each ancient object is preserved information about the formation of the Solar System 4.6 billion years ago.

Comet Interceptor would be the first mission to travel to a comet which has never previously encountered the inner Solar System.

To do this, it will need to launch and reach a holding position around 1 million miles away from Earth. There it will lie in wait – possibly for years – until astronomers on the ground spot a suitable comet for it to intercept. The two probes will make closer passes of the comet’s nucleus and beam their data back to the main craft.

This new ambush tactic is the first of its kind. The fly-by of the three spacecraft, including the two probes, which measure less than a meter across, is likely to take just a few hours but could illuminate conditions that prevailed more than 4 billion years ago.

Previous missions have studied comets trapped in short-period orbits around the Sun, meaning they have been significantly altered by our star’s light and heat. Breaking from that mould, Comet Interceptor will target a pristine comet on its first approach to the Sun.

The scientists are likely to target a comet travelling from the Oort Cloud — a band of icy debris that lies about halfway between the Sun and the next nearest star.

This debris was formed during the conception of the Solar System but was rapidly ejected to its outermost edge. Unlike more familiar comets, their surface will not have been vaporised by the Sun’s energy — a process that leads to dust building up on a comet, obscuring its original state.

Once the probes reach a pristine comet, they will study and scrutinise the chemical composition of it, with one aim being to evaluate whether similar objects may have brought water to planet Earth in the past.

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