A cosmic ice cream cone is drifting through our solar system
On April 20, 2025, NASA’s Lucy spacecraft will perform a high-stakes flyby of asteroid 52246 Donaldjohanson. This carbon-rich fragment, shaped like two nested ice cream cones, offers a rare, relatively recent glimpse into the violent collisions that shaped our planetary neighborhood.
The asteroid Donaldjohanson is a fragment of the Erigone family, born roughly 150 million years ago when a massive collision struck the asteroid 163 Erigone. Because of this relatively recent origin, it is among the youngest main belt asteroids ever approached by a spacecraft. Earth-based data previously suggested the body had an average diameter of about 4 kilometers and a very slow rotation, resulting in a 251-hour day. However, early images from Lucy’s L’LORRI imager suggest a much larger structure, measuring approximately 8 kilometers long and 3.5 kilometers wide at its widest point.
The encounter itself presented significant technical hurdles. To protect sensitive instruments like the L’Ralph color imager and L’TES infrared spectrometer from intense sunlight, the spacecraft had to stop tracking the asteroid 40 seconds before its closest approach. At 1:51pm EDT, Lucy passed within 960 kilometers of the surface. This specific geometry was uniquely challenging; unlike the mission's first encounter with Dinkinesh, the spacecraft had to manage extreme glare that could have damaged cameras designed to observe light 25 times dimmer than what we see on Earth.
The morphology of Donaldjohanson has surprised researchers. While scientists expected an elongated contact binary, the narrow neck connecting its two lobes is unexpectedly complex. This discovery, alongside the asteroid's carbon-rich composition, provides vital clues about the building blocks of the solar system. As the mission continues toward its primary targets, the Jupiter Trojans, the data retrieved from this 'dress rehearsal' will help engineers refine the complex observing sequences required for the decade-long exploration ahead.
Source: NASA’s Lucy Mission Will Explore Asteroid Donaldjohanson
