DART mission reveals Asteroid Dimorphos is Dry as a Bone

Six months after NASA crashed a spacecraft into an asteroid at high speed, scientists have begun to better understand the mission’s goal.

New results from the European Southern Observatory have shown that careful examination of debris from NASA’s DART mission into Dimorphos did not reveal any evidence of water ice or the remnant of spacecraft thruster fuel.

The data from MUSE (Multi-Unit Spectroscopic Explorer, opens in new tab), an instrument on ESO’s Very Large Telescope, Chile, does show differences in the sizes of the particles and how the polarization from the asteroid changed. Both of these data could reveal information about the nature and origins of the ejecta from the impact.

DART or Double Asteroid Redirection Test was an attempt to push the asteroid Dimorphos (at 580 feet, 177 meters) while it orbited around Didymos (at 2,788 feet wide, 850 meters). DART, the Double Asteroid Redirection Test, was launched to demonstrate that it is possible for potentially Earth-threatening asteroids to be moved off their current trajectories. It slammed into Dimorphos on Sept 26, 2022. This altered its orbital period by 33 seconds.

“Before we felt the impact, we weren’t really sure what to expect,” Cyrielle Opitom of the University of Edinburgh said in an interview with Space.com.

Also Read: A new class of medicinal compounds that target RNA

Although asteroids are mostly made of rock and are held together by gravity, the presence of water ice on some asteroids is still a topic of discussion. NASA’s Infrared Telescope Facility (Hawaii) revealed that 24 Themis had water ice on its surface in 2009. However, it is not clear how this ice got there. One theory is that some asteroids have a layer beneath their surface. This could be due to the possibility of an ice-like substance that formed further out from the sun and then moved inwards. Some even speculate that asteroids could have brought water from Earth to our planet.

Opitom commanded a team that used MUSE to search for water on Dimorphos. From the time of the impact up to a month later, they observed the Didymos–Dimorphos system 11 times. MUSE can split the light of the double-asteroid into different colors to search for specific wavelengths that correspond to specific molecules. Opitom’s team looked at the ejecta looking for water molecules and oxygen that might have been formed by the impact. But, there was no evidence of water. Dimorphos appear to be a dry asteroid.

The ejecta also did not contain any trace of DART’s hydrazine fuel or xenon, even though it is not surprising that they were present in small amounts.

MUSE’s observations, however, were able to track the evolution and size distribution of the cloud of debris (ejecta) created by the impact. They also helped to determine the tail that was ejected from the asteroid.

DART crashed into Dimorphos and released an estimated 900,000.00 kilograms of dust into space. VLT-MUSE observations revealed that the ejecta was moving quickly from the impact site. The pressure of sunlight combined with the gravity of nearby Didymos pushed the dust onto the ground, creating a cone-shaped cloud. Over the next weeks, a dust tail developed.

Opitom stated that DART offered a unique opportunity because it allowed us to know the exact time and mass of the impactor. Opitom said that they have amazing images of the impact site and that the aftermath was also observed using a variety of instruments. All this information combined will give us a complete picture of the event and will allow us to interpret observations of impacts on other asteroids.

The research was published on March 21 in the journal Astronomy & Astrophysics (opens in new tab).

Leave a Comment