July 30, 2024 by admin
Scientists have used images collected by NASA’s DART asteroid impact mission to build a more detailed picture of its asteroid targets Didymos and Dimorphos. The research could help us better understand the formation and evolution of binary asteroids like these.
DART, which stands for Double Asteroid Redirection Test, only hit the smaller body in this two-asteroid binary system, the satellite Dimorphos, which orbits the larger asteroid Didymos. The goal, however, was to see what effect such an impact would have on both bodies. The data collected during this successful mission could help scientists better plan a planetary defense mission to deflect an asteroid heading toward Earth.
Before crashing into Dimorphos on September 26, 2023, DART was able to take images of both near-Earth asteroids. Using data from Italy’s Light Cubesat for Imaging of Asteroids (LICIACube) mission, researchers were able to determine some of the geological features and physical properties 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 high altitudes, Didymos is rough, with large boulders 10 to 160 meters long and several craters. At low altitudes, the asteroid’s surface becomes smoother, with fewer large boulders and craters.
Its companion, a small moon, Dimorphos, is dotted with rocks of more varied sizes. Although Dimorphos’ surface is largely free of craters, it is riddled with several fissures or “faults.”
These results helped Barnouin and his colleagues determine that Dimorphos likely formed from material thrown up by Didymos and then clumped together under the influence of gravity.
The team used the number of craters on the two asteroids to estimate the ages of the two asteroids. They determined that the parent body Didymos is 12.5 million years old, or between 40 and 130 times older than Dimorphos. They estimated the age of the smaller satellite to be about 0.3 million years.
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More pronounced fractures on the surface of Dimorphos captured by DART just before impact (Image credit: A. Lucchetti et al., Nature Communications)
By looking at the size of the rocks and their distribution across Dimorphos, a separate team of scientists led by Maurizio Pajola of INAF – Padua Astronomical Observatory determined that they formed at different times rather than all at once.
This implies that the rocks on the surface of Dimorphos are directly inherited from Didymos, supporting the idea that the satellites of binary asteroid systems form from material shed by their larger partners. This process would also explain a characteristic ridge at the equator of the parent body, Didymos.
Formation of the Didymos Ridge – YouTube
Formation of the Didymos Ridge - YouTube
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Another team of researchers led by Naomi Murdoch of the University of Toulouse studied the traces of rocks on the surface of Didymos. They found that the surface of Didymos is composed of very soft materials, capable of supporting much less weight than dry sand on Earth or lunar soil.
Meanwhile, Alice Lucchetti of INAF-Astronomical Observatory of Padua and her colleagues have also discovered that the rocks on the surface of Dimorphos fracture over a period of about 100,000 years through a process called “thermal fatigue,” which results from temperature changes causing microfractures in the rock.
While 100,000 years may seem like an incredibly long time to us, in geological terms it is a short time, especially in a solar system that is about 4.6 billion years old. This means that the thermal fatigue experienced by Dimorphos is rapid. This is the first time that rapid thermal fatigue has been observed on a rocky asteroid composed of silicate and nickel-iron materials.
Comparison of rocks from Dimorphos, Itokawa, Ryugu and Bennu
A comparison of rocks on Dimorphos, Itokawa, Ryugu and Bennu. (Image credit: A. Duchene and C. Robin (ISAE-SUPAERO).)
A third team, led by researcher Colas Robin of the University of Toulouse, compared 34 boulders on the surface of Dimorphos, measuring between 1.67 and 6.7 meters, to rocks found on the “rubble pile” asteroids Itokawa, Ryugu and Bennu.
They found similarities between the rock morphology of all these asteroids and suggested to Robin and his colleagues a common formation and evolution mechanism.
The results obtained by the teams provide a detailed portrait of the Didymos system as it was before DART’s impact on Dimorphos. These discoveries 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. One of the probes in the Didymos binary system, Hera, will capture higher-resolution data that will allow a more complete examination of the system as it is after DART’s impact. This should help scientists better determine the consequences of DART’s collision with Dimorphos.
The research papers from all three teams were published Tuesday (July 30) in the journal Nature.
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