Spacecraft collision with asteroid impact analysed

The aftermath of a deliberate collision between a spacecraft and an asteroid, 11 million kilometers from Earth, has been studied by a team that includes Edinburgh scientists.

The NASA led mission, known as the Double Asteroid Redirection Test (DART), aimed to change the trajectory of a harmless asteroid. The mission was successful in changing the orbit of a small asteroid around a larger one, proving that it could be possible if an asteroid was to head towards Earth.

This first test of planetary defence technology also gave astronomers a unique insight into the asteroid named Dimorphos’s composition – through analysis of the cloud of debris expelled during and after the collision.

Scientists from the School of Physics and Astronomy used the European Southern Observatory’s Very Large Telescope to follow the evolution of the expelled material for a month after the spacecraft’s initial impact with Dimorphos.

The results, published in Astronomy & Astrophysics, found that the ejected cloud of material was bluer than the asteroid before the collision, indicating that it could be made up of very fine dust particles. Days after the collision, the research team found other structures developing from the cloud – clumps, spirals and a long tail of dust pushed away by the Sun’s radiation. The spirals and tail were redder than the initial cloud, and could be made of larger dust particles, experts say.

Spectroscopic instruments – used to spread visible light into its different components – enabled the team to break up the light from the cloud into a rainbow-like pattern and to look for the chemical fingerprints of different gases.

A search for oxygen and water coming from the ice exposed by the impact revealed nothing. The team also looked for traces of the propellant of the DART spacecraft, but found none.

Lead author, Dr Cyrielle Opitom, Chancellor’s Fellow, Institute for Astronomy, University of Edinburgh, said:

Impacts between asteroids happen naturally, but you never know it in advance. DART is a really great opportunity to study a controlled impact, almost as in a laboratory. Asteroids are not expected to contain significant amounts of ice, so detecting any trace of water would have been a real surprise.

Co-lead author, Professor Colin Snodgrass, Personal Chair of Planetary Astronomy, Institute for Astronomy, said:

The impact of the DART spacecraft on asteroid Dimorphos lasted only a fraction of a second but the impact this will have on the study of asteroids will be felt for years. There are many more exciting results to come.

Co-author, Brian Murphy, a PhD student from The Institute for Astronomy, University of Edinburgh, said:

Asteroids are some of the most basic relics of what all the planets and moons in our Solar System were created from so studying the cloud of material ejected after DART’s impact can therefore tell us more about how our Solar System formed.

Johns Hopkins Applied Physics Lab built and operated the DART spacecraft and manages the DART mission for NASA’s Planetary Defense Coordination Office as a project of the agency’s Planetary Missions Program Office. LICIACube, which was part of the DART mission, is a project of the Italian Space Agency (ASI), carried out by Argotec.