Japan’s Hayabusa2 spacecraft, best known for hauling samples of asteroid Ryugu back to Earth, has begun the science phase of its extended mission with a fast, close pass of a small near-Earth asteroid. When the probe swept past the object earlier in July 2026, its cameras revealed something that ground telescopes had missed: the asteroid is not a single elongated rock but two rounded bodies joined at a narrow neck. The discovery adds another example to a growing catalog of so-called contact binaries, objects that record how the solar system’s smallest worlds came together.
The target, formally designated 98943 Torifune and previously catalogued as 2001 CC21, orbits the Sun on a path that repeatedly brings it near Earth’s neighborhood, though it poses no danger. Distant observations had suggested only that it was oblong. The flyby replaced that blurry picture with sharp images that changed how planetary scientists describe the object.
Hayabusa2’s extended mission and the Torifune flyby
After delivering its Ryugu capsule in 2020, the Japan Aerospace Exploration Agency kept Hayabusa2 flying, assigning it new targets to visit on the way to a later rendezvous. Torifune was the first of those encounters. According to an account of the encounter published by The Planetary Society, the spacecraft threaded past the asteroid at extremely high relative speed, capturing both visible-light and thermal images during a window that lasted only minutes. Because the probe was moving so quickly, mission planners had to point its instruments precisely to catch the body as it flashed by roughly 100 million kilometers from Earth.
The maneuver was demanding. A slow orbital survey, like the one Hayabusa2 conducted at Ryugu, was never on the table for this leg of the mission; the geometry allowed only a single high-velocity pass. That constraint makes the returned imagery all the more valuable, because it is the only close look at Torifune that this mission will provide before the spacecraft moves on.
Two lobes stuck together
The most striking result is structural. NASA’s Astronomy Picture of the Day feature on the encounter notes that although earlier measurements from Earth indicated an oblong shape, the close-up views show that Torifune actually consists of two joined lobes. In other words, it is a contact binary: two separate pieces that formed independently and later drifted together gently enough to stick rather than shatter. The connecting region between the lobes appears as a distinct waist, the signature feature astronomers look for when classifying such objects.
The asteroid is not large. Descriptions of the imagery put its length at roughly four soccer fields laid end to end, small enough that its own gravity is weak but large enough to hold a jumble of material together. Scientists studying the pictures also noted an abundance of large boulders strewn across the surface, a texture consistent with a body assembled from loose debris rather than carved from a single solid slab.
A rubble pile with boulders but no obvious craters
One surprise stood out in the data: the surface shows few if any clear impact craters. On many airless worlds, craters accumulate over hundreds of millions of years and serve as a rough clock for a surface’s age. Their apparent absence on Torifune points to a body whose surface is a loosely bound pile of rubble. On such surfaces, incoming impacts tend to compress and rearrange the debris instead of blasting out sharp, lasting bowls, and ongoing seismic shaking as the object tumbles can erase older features over time.
That interpretation fits the boulder-strewn appearance. A rubble-pile structure implies that Torifune is more a swarm of gravel, rocks, and boulders held together by feeble gravity than a monolithic stone. Understanding how such bodies hold their shape, and how they respond to being nudged, matters for planetary defense as well as for basic science, because rubble piles behave very differently from solid rock when struck.
Echoes of Arrokoth and the path to 1998 KY26
Torifune joins a short but influential list of contact binaries visited by spacecraft. The most famous is Arrokoth, the distant Kuiper Belt object that NASA’s New Horizons mission flew past in 2019 and that also proved to be two lobes fused at a neck. The NASA overview of the Hayabusa2 mission underscores why these gentle mergers interest researchers: they preserve a record of the low-speed collisions that built up larger bodies in the early solar system, before violent impacts began tearing worlds apart. Each new example helps scientists test whether that assembly process was common across very different regions of the solar system.
The comparison is instructive because Arrokoth and Torifune occupy wildly different environments, one in the frigid outer solar system and the other on a near-Earth orbit, yet share the same basic architecture. That similarity suggests contact binaries are a widespread outcome of how small bodies form, and that the gentle mergers behind them were not confined to a single corner of the early solar system. Each additional example also lets scientists compare how such bodies weather over time in very different thermal and radiation conditions.
For Hayabusa2, Torifune is a waypoint rather than a destination. The spacecraft is continuing toward a planned 2031 encounter with 1998 KY26, a much smaller asteroid that spins unusually fast and may harbor reservoirs of ice. Reaching that target will require years of careful cruising and additional gravity assists, and the Torifune pass doubled as a chance to exercise the probe’s aging instruments under real observing conditions. The flyby therefore serves as both a scientific bonus and a rehearsal for that harder, farther meeting still to come.
This article was produced with AI assistance and reviewed by Morning Overview editors.
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