Comet chaser mission moves from blueprint to reality

The Comet Interceptor mission was formally adopted by the European Space Agency (ESA) at a meeting in Madrid today (Wednesday, 8 June 2022), moving from the design phase to implementation, 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 (JAXA) – travel to an as-yet unidentified comet and map it in three dimensions.

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."

The mission was first proposed by an international team led by University College London’s Mullard Space Science Laboratory (MSSL) in Surrey and the University of Edinburgh.

Professor Geraint Jones, from the UCL Mullard Space Science Laboratory, said: "We should get our first glimpse of a truly pristine body with this mission – 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.

Professor Colin Snodgrass, from the University of Edinburgh, added: "It is very exciting to be part of a mission that follows a completely new approach: designing and building the spacecraft before the target is even discovered. This opens up opportunities to visit space objects that were completely inaccessible before, such as comets entering the inner solar system for the very first time, or possibly even interstellar objects that formed around a distant star.

The UK Space Agency has so far provided £2.3 million in funding for two instruments on the mission: The Modular InfraRed Molecules and Ices Sensor (MIRMIS) instrument is led by the University of Oxford. MIRMIS will deliver a unique dataset, providing information such as the comet’s shape, size and rotation state. The Fluxgate Magnetometer (FGM) sensor led by Imperial College London will provide high accuracy and high-time resolution measurements of the comet’s magnetic field size and direction.

Professor Neil Bowles, University of Oxford, said: "Working with our colleagues in Finland, MIRMIS will observe Comet Interceptor’s nucleus at infrared wavelengths that are particularly sensitive to temperature and the composition, mapping out the material in the nucleus on what is possibly the object’s first close encounter with the Sun. Combined with the data from Comet Interceptor’s other instruments and probes, this will provide a unique snapshot of a potentially very ancient object."

By exploring comets, we learn about the origins of our solar system

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 one 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 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 four 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.