This is how Dimorphos changed after the impact of the DART ship

he The first controlled crash The story of a spacecraft against an asteroid to voluntarily divert its course was not only a milestone for making so-called planetary defense a reality and had any chance of protecting Earth from a future collision with one of these space rocks. impact dart probe NASA against the asteroid DimorphicOn September 26, it was a golden opportunity for astronomers to investigate the formation of these celestial bodies, whose materials they believe are the key to the origin of life on Earth.

The collision occurred at a speed of 22,530 kilometers per hour at a distance of 11 million kilometers from Earth, which is a great distance, but a very reasonable distance not only for space telescopes. James Webb And Hubblewhich Caught the momentbut also to the most powerful ground-based telescopes such as the VLT (Very Large Telescope or Telescopio Muy grande) owned by the European Southern Observatory (ESO) in the Atacama Desert, in Chile.

Preparing for this astronomical feat, four 8.2-meter telescopes that make up the VTL pointed at the asteroid system made up of the small (160-meter diameter) Dimorphos, the ship’s target, and Didymos, a 700-meter asteroid orbiting the smaller one. Neither of these objects posed a danger to Earth, and they were chosen to test a controlled deflection technique, NASA announced two weeks later, It was successful Because it was possible to change the orbit of the asteroid Dimorphos around Didymos in 32 minutes, more than expected.

Thus, astronomers were able to watch the crash of the DART spacecraft (short for Double asteroid reorientation test Which is also mean Arrow in English) and keep an eye on it for the next month. This past Tuesday, two of the two teams using data from ESO’s Chilean telescope presented the results of their observations of the system made up of these two asteroids.

“Inter-asteroid impacts happen naturally, but we can never know in advance,” says Cyril Opetom, an astronomer at the University of Edinburgh and lead author of one of the research papers. In his view, the DART mission was ” A great opportunity to study a controlled effect, almost like doing it in a laboratory. “

debris cloud

The team led by Opitom has been following the evolution of the debris cloud generated after the spacecraft’s impact with the asteroid for a month using the Multi Unit Spectroscopic Explorer (MUSE) instrument on the VLT, the results of which are shown in the collection Pictures were taken between September 26th and October 25th. Scientists saw that the ejected cloud of material was bluer than the asteroid itself before impact, indicating that the cloud could be composed of very fine particles. In the hours and days that followed, other structures developed, including cumulonimbus clouds, spirals, and a long tail powered by solar radiation. The spirals and tail were much redder than the primary cloud, so it could have been composed of larger particles, according to his hypothesis.

The MUSE instrument allowed them to separate the light from the cloud to look for chemical signatures of the different gases present. particularly, They looked for oxygen and water from the ice that had been exposed by the impact, but found nothing. “Asteroids are not expected to contain large amounts of ice, so discovering any trace of water would have been a real surprise,” says Obitum, who also found no residual DART propellant, a possibility they considered remote because “the amount of gasoline left In powertrain tanks it wouldn’t be huge. Also, some of it would have traveled too far to detect with MUSE by the time we started looking.”

A second DART investigation published Tuesday focused on How has the asteroid surface changed?. “When we look at objects in our solar system, we’re looking at sunlight scattered by their surface or by their atmosphere, which becomes partially polarized. We track how the polarization changes with the asteroid’s orientation relative to us,” said Stefano Bagnolo, an astronomer at the Armagh Observatory and Planetarium in UK and Work Leader, “The Sun Reveals the Structure and Composition of Its Surface.”

Using the FOcal Reducer / Spectrograph 2 (FORS2) instrument on the VLT, they discovered that the level of polarization suddenly decreased after the impact. At the same time, the overall brightness of the system increased. One possible explanation is that the impact revealed more pure material from within the asteroid. “Maybe the material brought to the surface by the impact was brighter and less polarized than the material at the surface, because it was never exposed to the solar wind or solar radiation,” Bagnolo suggests, pointing to another possibility: destroyed particles at the surface, thus expelling much smaller ones into the debris cloud. .