Scientists used images collected by NASA’s DART asteroid impact mission to paint a more detailed picture of its asteroid targets Didymos and Dimorphos. The research could help 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 double asteroid binary system, the moon Dimorphos, which orbits the larger space rock Didymos. However, the aim was to find out 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 on a collision course with Earth.
Before impacting Dimorphos on September 26, 2023, DART was able to take images of two near-Earth asteroids. By matching data from the Light Italian Cubesat for Imaging of Asteroids (LICIACube) mission, scientists were able to determine some geological features and physical properties of Didymos and Dimorphos.
A team led by Olivier Barnouin of the Johns Hopkins University Applied Physics Laboratory studied the surface of Didymos, the larger of the two asteroids. Scientists found that at high altitudes, Didymos is rugged, hosting large boulders 33 to 525 feet (10–160 meters) long and several craters. At low altitudes, the surface of this asteroid becomes smoother, with fewer large rocks and craters.
Its smaller moon companion Dimorphos has rocks on its surface that have a wider range of sizes. While the surface of Dimorphos is mostly free of craters, it is dotted with a few cracks or “flaws”.
The findings helped Barnouin and colleagues determine that Dimorphos likely formed from material ejected from Didymos and then clumped together under the influence of gravity.
The team used the number of craters on both asteroids to measure the age of both asteroids. they found that Didymos’ parent body is 12.5 million years old, which is 40 to 130 times older than Dimorphos. They estimated the age of the Moon at 0.3 million years.
Related: NASA’s asteroid impact DART mission completely changed the shape of its target
Looking at the size of the boulders and their distribution in Dimorphos, a separate team of scientists led by Maurizio Pajola from the INAF – Astronomical Observatory of Padua found that they formed at different times, not all at once.
This means that the rocks on the surface of Dimorphos are directly inherited from Didymos, further supporting the idea that moons in binary asteroid systems form from material released by their larger partners. This process would also explain the prominent ridge on the equator of the parent body, Didymos.
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Another team of researchers led by Naomi Murdoch of the Université de Toulouse looked at the boulder tracks on the surface of Didymos. They found that the surface of Didymos is composed of very loose material that is able to support much less weight than dry sand on Earth or lunar soil on the Moon.
Meanwhile, Alice Lucchetti of the INAF-Astronomical Observatory in Padua and colleagues also found that the boulders on the surface of Dimorphos have been breaking for about 100,000 years through a process called “thermal fatigue”, which is the result of changing temperatures causing micro-fractures in the rock.
While 100,000 years may seem like an incredibly long time to us, it is a short time in geological terms, especially in a solar system that is about 4.6 billion years old. This means that the heat exhaustion experienced by Dimorphos is rapid. This is the first time rapid thermal fatigue has been observed on a rocky asteroid made up of silicate materials and nickel-iron.
A third team, led by Université de Toulouse researcher Colas Robin, compared 34 boulders on the surface of Dimorphos that ranged from 5.5 feet (1.67 meters) to 22 feet (6.7 meters) to stones found on loose “pile debris’ of the Itokawa asteroids. , Ryuga and Bennu.
They found similarities between the rock morphologies of all these asteroids and suggested to Robin and colleagues a common mechanism of formation and evolution.
The teams’ results create a detailed picture of the Didymos system as it was before DART hit Dimorphos. The findings could help inform the European Space Agency’s (ESA) upcoming Hera mission.
Due to launch in October of this year, Hera will rendezvous with Didymos and Dimorphos in September 2026. One in the Didymous binary, Hera, will capture higher-resolution data that will enable a more comprehensive exploration of the system as it is after the DART impact. This should help scientists better determine the consequences of DART’s collision with Dimorphos.
The three teams’ research was published Tuesday (July 30) in the journal Nature.