Imma Perfetto
Cosmos science journalist
Observations from NASA’s Double Asteroid Redirection Test (DART) spacecraft, which successfully struck and redirected the asteroid Dimorphos in September 2022, have revealed new insights into the Didymos binary asteroid system.
The findings, which include the estimated ages of the asteroid Didymos and its orbiting moonlet Dimorphos (about 12.5 million years and less than 300 thousand years old, respectively), are published across 5 new studies in the journal Nature Communications.
They provide new understanding into the formation and evolutionary processes of these binary systems, which make up a sizeable fraction of near-Earth asteroids.
A new study by Olivier Barnouin and colleagues found that the surface of Didymos is rough at high elevations, containing craters and large boulders 10–160 metres in length.
In contrast, Dimorphos has boulders of various sizes, several cracks or faults, and only a handful of craters.
“Crater size frequency analyses indicate the surface age of Didymos is 40–130 times older than Dimorphos,” the authors write.
“Solar radiation could have increased Didymos’ spin rate leading to internal deformation and surface mass shedding, which likely created Dimorphos.”
A separate study by Maurizio Pajola and co-authors analysed the surface boulder sizes, shapes, and distribution patterns on both asteroids.
Their findings confirm Didymos and Dimporphos are made up of fragments produced in the catastrophic breakups of their larger parent bodies, which later coalesced under the influence of gravity.
This supports the hypothesis that Dimorphos formed as the result of a mass shedding event from Didymos.
Naomi Murdoch and colleagues’ analysis of boulder tracks determined that Didymos’ bearing capacity – the ability of a surface to support applied loads – is considerably lower than that of lunar soil or dry sand on Earth.
The findings provide a comprehensive overview of the Didymos system just prior to the DART mission’s collision. They help lay the foundation for the upcoming European Space Agency HERA mission, which will provide high-resolution images of the post-impact system.
