Incredible images have been revealed of the swirling clouds of dust produced when NASA’s Double Asteroid Redirection Test (DART) spacecraft hit an asteroid.
The refrigerator-sized spacecraft collided with the 160-meter-wide space rock known as Dimorphos on Sept. 26 last year.
The purpose of the mission was to demonstrate that the technology would be capable of deflecting asteroids that could pose a threat to Earth in the future.
This month it was revealed that DART removed 33 minutes from Dimorphos’ orbit – nearly five times more than predicted – and it was deemed a success.
Scientists from the University of Edinburgh studied the aftermath of the collision, including what was in the debris it left behind and how it clumped together over time.
Evolution of debris cloud ejected when DART spacecraft collided with Dimorphos. The first photo was taken just before impact and the last almost a month later. The white arrow indicates the direction of the sun. The stripes in the background are stars. The images were taken with the MUSE instrument of the Very Large Telescope
The refrigerator-sized DART satellite collided with the 160-meter-wide space rock Dimorphos on September 26 last year. The purpose of the mission was to demonstrate that the technology would be capable of deflecting asteroids that could pose a threat to Earth in the future.
“Asteroids are some of the most basic remnants from which all the planets and moons in our solar system formed,” says PhD student Brian Murphy.
WHAT WAS DART?
DART was the world’s first planetary defense test mission, launched in November 2021.
It involved a spacecraft crashing into the small lunar asteroid Dimorphos, which orbits a larger companion asteroid called Didymos.
This was done to slightly alter Dimorphos’ orbit.
The moon has a diameter of about 165 meters and although it poses no threat to Earth, NASA wanted to measure the asteroid’s changed trajectory as a result of the collision.
Post-impact observations from Earth-based optical telescopes and planetary radars measured the change in Dimorphos’ orbit around Didymos.
Before the collision, the time it took the moonlet to complete one circuit of its sibling was 11 hours and 55 minutes, but now it takes 11 hours and 22 minutes.
This demonstration of planetary defense will inform future missions that could one day save Earth from a deadly asteroid impact.
The dust cloud left after DART entered Dimorphos at 14,000 mph could tell us what happened when our solar system formed.
It could also provide more information about the chemical composition of these asteroids.
Astronomer Dr Cyrielle Opitom added: ‘Impacts between asteroids happen naturally, but you never know in advance.
“DART is a really great opportunity to study a controlled impact, almost like in a lab.”
The team used the European Southern Observatory’s Very Large Telescope (VLT) to observe the DART mission as it took place 7 million miles away.
For their study, published in Astronomy & Astrophysicsthey observed the resulting debris for a month using the Multi Unit Spectroscopic Explorer (MUSE) instrument on the VLT in Chile.
They found that the dust appeared blue in color immediately after impact, indicating it was made up of very fine particles.
But as time went on, the particles began to come together to form clumps, spirals and a long tail that stretched away from the sun’s radiation.
The tail and spirals appeared redder than the original dust cloud, suggesting they were made up of larger particles.
MUSE also enabled the scientists to study the chemical composition of Dimorphos based on the dust emitted.
This is because certain wavelengths of sunlight are reflected from specific molecules, such as water (H₂O) and oxygen (O₂), allowing them to be identified.
This artist’s illustration shows the ejection of a cloud of debris after NASA’s DART spacecraft collided with the asteroid Dimorphos
These two molecules in particular would be indicative of the presence of ice in the asteroid, but none could be found.
“Asteroids are not expected to contain significant amounts of ice, so it would have been a real surprise to detect any trace of water,” said Dr Opitom.
They also looked for traces of propellant from the DART spacecraft, but that too could not be found.
Dr. Opitom added: ‘We knew it was a gamble because the amount of gas left in the tanks by the propulsion system wouldn’t be huge.
“Plus, some of it would have traveled too far for MUSE to detect it by the time we started observing.”
The researchers found that the dust ejected by Dimorphos appeared blue in color immediately after impact, indicating that it was made up of very fine particles.
Light reflected from the surface of the Dimorphos (pictured) became less polarized immediately after impact, thus more randomly oriented. Researchers suggest this is because it revealed untouched matter with a more symmetrical molecular structure, which is less polarizing
Another team from the Armagh Observatory and Planetarium used another VLT instrument to study what the impact did to the asteroid’s surface.
When objects in space reflect sunlight, it partially polarizes it, meaning the waves change from oscillating in many different directions to just one direction.
For their study, published in Astrophysical Journal Lettersthe researchers used the FOcal Reducer/low dispersion Spectrograph 2 (FORS2) to observe the polarization of the light reflected from Dimorphos.
“Tracking how the polarization changes with the orientation of the asteroid relative to us and the sun reveals the structure and composition of the surface,” said study co-author Dr Stefano Bagnulo.
They found that the light reflected from the asteroid’s surface became less polarized immediately after impact, thus more randomly oriented.
They suggest this is because it revealed untouched matter with a more symmetrical molecular structure, which is less polarizing.
The asteroid also reflected more light after impact, suggesting that this inner material is smoother than its rough exterior.
The fact that the inside has a smoother texture and a more regular molecular structure than the outside may be the reason it was not exposed to solar wind and radiation.
Another possibility is that DART completely destroyed the top layer of Dimorphos, creating fine dust particles.
‘We know that under certain circumstances smaller fragments are more efficient at reflecting light and less efficient at polarizing it,’ says PhD student Zuri Gray.
Dr. Optiom added: ‘This research took advantage of a unique opportunity when NASA struck an asteroid, so it cannot be repeated by any future facility.
“This makes the data obtained with the VLT around the time of impact extremely valuable when it comes to better understanding the nature of asteroids.”
NASA’s interactive tool lets users track the asteroids racing toward Earth
Earlier this month, NASA warned that a city-destroying asteroid the size of the Leaning Tower of Pisa could slam into Earth in just over 20 years.
It came just two months after another space rock — the size of a London bus — made the fourth closest approach to our planet ever.
The good news is that the US space agency, along with scientists from around the world, is monitoring potential asteroids – and the even better news is that you can do this too interactive tool.
It shows the next five closest approaches to Earth, starting with 2020 FV4 in three days.
The 100-foot-wide object is expected to race past our planet at a distance of about 4.1 million miles (6.7 million km).
Read more here