Glimpses of Hera's Target Asteroids Inspire New Science
Glimpses of Hera's Target Asteroids Inspire New Science
DART Collects Nearly Six Minutes of Close-Range Video
As ESA’s Hera mission for planetary defense completes its pre-launch testing, its target asteroids have come into focus as tiny worldlets of their own. A special issue of Nature Communications published last week presents studies of the Didymos asteroid and its Dimorphos moon, based on the roughly five and a half minutes of close-range footage returned by NASA’s DART spacecraft before it impacted the latter body – along with post-impact images from the Italian Space Agency’s LICIACube.
“The amount of knowledge gained out of the brief few minutes of images returned by DART and LICIACube has turned out to be extraordinary.” Hera Principal Investigator Patrick Michel
On 26 September 2022 NASA’s approximately half-metric ton Double Asteroid Redirect Test, DART, spacecraft impacted the boulder covered Dimorphos asteroid at a speed of 6.1 km/s.
Humankind’s first experiment in the kinetic impact method of asteroid deflection was successful to a surprising degree: the orbit of Dimorphos around Didymos was shortened by more than half an hour - at the upper end of predictions – observed from Earth as well as from DART’s accompanying LICIACube.
Scientists are still not sure why the impact occurred the way it did, so have been busy studying all available data, in a bid to better understand the process of kinetic impact for planetary defense, as well as the underlying nature of asteroids.
The images from DART’s DRACO camera plus LICIACube represent one of the most important data sources – until ESA’s Hera mission, which lifts off this October, reaches Didymos for its own close-up study in late 2026 to fill the remaining gaps in information, to provide a full picture of the DART impact.
“The amount of knowledge gained out of the brief few minutes of images returned by DART and LICIACube has turned out to be extraordinary,” said Hera Principal Investigator Patrick Michel, Director of Research at CNRS at Observatoire de la Côte d'Azur, “This imagery contributed to more than 80 published scientific papers to date.”
The papers in this special edition of Nature Communications were a collaboration between the Johns Hopkins Applied Physics Laboratory (APL) in Maryland, USA – which developed and led DART for NASA – together with several European research bodies including Italy’s National Institute for Astrophysics, INAF and France’s Institut Supérieur de l'Aéronautique et de l'Espace, ISAE-Supaero, part of the University of Toulouse.
Through painstaking analysis of DART and LICIACube imagery, the five papers chart key surface characteristics of the two bodies to make various findings about the nature and likely origins of the asteroid pair.
One APL-led paper uses these inputs to model the age and origin of the two bodies: the mountain-sized Dimorphos asteroid has a surface age 40–130 times older than its Great Pyramid-sized Dimorphos moon, with the former estimated to be 12.5 million years, which corresponds to the mean lifetime of Near-Earth objects, and the latter less than 300 000 years old (making it roughly the same age as Homo sapiens here on Earth).
This suggests that the formation of Dimorphos is very recent in the history of the asteroid system, unless some re-surfacing occurred that erased former craters and reset the clock used to estimate its age.
Once it reaches the Didymos system in late 2026, Hera will perform a close-up survey of the post-impact Dimorphos while also acquiring data on Didymos. The spacecraft will also release a pair of shoebox-sized CubeSats for complementary observations, including the first radar survey within an asteroid. Hera will therefore enable improved versions of the analyses performed in these papers
“Hera will document fully all required characteristics of the binary system as well as the DART impact outcome," Michel said. "So Hera and DART together will deliver the first fully documented asteroid deflection test. This is fundamental for the validation of numerical impact models at actual asteroid scale and their application to other scenarios as well as for the assessment of the efficiency of the kinetic impactor technique.”
The mission is being supported by the international Hera Science Working Groups.
Hera is currently completing its test campaign at ESA’s ESTEC Test Center in the Netherlands, in preparation for transport to Cape Canaveral at the beginning of September for launch by SpaceX Falcon 9 the following month.