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Scientists have used images collected by NASA’s DART asteroid impactor mission to paint a more detailed picture of the asteroid targets Didymos and Dimorphos. The research could help better understand the formation and evolution of such binary asteroids.
DART, which stands for “Double Asteroid Redirection Test,” only hit the smaller body in this binary asteroid system, tiny Dimorphos, which orbits the larger space rock Didymos. The goal, though, was to see what effect such an impact would have on both bodies. Data collected during this successful mission could help scientists better plan a planetary defense mission to redirect an asteroid on a collision course with Earth.
DART was able to capture images of two near-Earth asteroids before they collided with Dimorphos on September 26, 2023. In conjunction with data from the Light Italian Cubesat for Imaging of Asteroids (LICIACube) mission, researchers were able to determine some geological and physical characteristics of Didymos and Dimorphos.
The team, led by Olivier Barnouin of the Johns Hopkins University Applied Physics Laboratory, studied the surface of Didymos, the larger of the two asteroids. The researchers found that at higher altitudes, Didymos is rugged and contains large boulders measuring 33 to 525 feet (10–160 meters) and several craters. At lower altitudes, the asteroid’s surface becomes smoother and has fewer large boulders and craters.
The smaller moon, Dimorphos, has a wider range of rocks on its surface. The surface of Dimorphos is mostly crater-free, but is broken by a few cracks or “faults”.
The findings helped Barnouin and his colleagues determine that Dimorphos is likely composed of material ejected from Didymos and then brought together by gravity.
The team used the number of craters on both asteroids to measure their ages. They determined that the parent body, Didymos, was 12.5 million years old, 40 to 130 times older than Dimorphos. They estimated the moonlet to be about 0.3 million years old.
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A separate team of scientists, led by Maurizio Pajola of the INAF Astronomical Observatory in Padova, studied the size of the rocks and their distribution in Dimorphos, finding that they were not formed simultaneously but at different times.
This means that the rocks on Dimorphos’ surface were inherited directly from Didymos, further supporting the idea that moonlets in binary asteroid systems formed from material shed by their larger partners. This process also explains the prominent ridge on the equator of parent body Didymos.
Another research team, led by Naomi Murdoch from the University of Toulouse, looked at rock impressions on the surface of Didymos. They found that the surface of Didymos is made up of very loose material that can support much less weight than dry sand on Earth or lunar soil on the Moon.
Meanwhile, Alice Lucchetti from INAF-Padova Astronomical Observatory and her colleagues also found that rocks on the surface of Dimorphos have fractured over a period of about 100,000 years by a process called “thermal fatigue” caused by temperature changes that cause microcracks in the rocks.
While 100,000 years may seem like an incredibly long time to us, it is actually a short time in geological terms, especially in a solar system that is about 4.6 billion years old. This means that the thermal fatigue experienced by Dimorphos was rapid. This is the first time that rapid thermal fatigue has been seen in a rocky asteroid composed of silicate materials and nickel-iron.
A third team, led by University of Toulouse researcher Colas Robin, compared 34 rocks from the surface of Dimorphos, ranging from 1.67 meters (5.5 feet) to 6.7 meters (22 feet), with rocks found on the loose “rubble pile” asteroids Itokawa, Ryugu and Bennu.
They found similarities between the rock morphologies of all these asteroids, leading Robin and colleagues to propose a common formation and evolution mechanism.
Related Stories:
— Asteroid impact: This is the last thing NASA’s DART spacecraft saw before it hit
— DART asteroid impact seen by James Webb and Hubble space telescopes (photos)
— DART impact leaves a debris trail thousands of miles long on asteroid Dimorphos (breathtaking photo)
The teams’ results provide a detailed picture of the Didymos system before DART’s impact with Dimorphos, and the findings could help inform the European Space Agency’s (ESA) upcoming Hera mission.
Scheduled to launch in October of this year, Hera will rendezvous with Didymos and Dimorphos in September 2026. Hera, in the binary system Didymos, will capture higher-resolution data from the DART collision, allowing for a more comprehensive study of the system. This should help scientists better determine the aftermath of DART’s collision with Dimorphos.
The three teams’ research papers were published in the journal Nature on Tuesday (July 30).