Two Rocks, One Snowman: Hayabusa2's Daring Flyby Reveals Asteroid Torifune's Secret
On the evening of July 5, 2026, a spacecraft the size of a small car hurtled past an asteroid at 18,000 kilometers per hour, aiming to miss it by less than a kilometer. Some of the scientists who wanted the data had been told the attempt was too dangerous. The engineers proposed it anyway, the debate ran for months, and on July 6, Japan time, the images arrived — bigger, sharper, and stranger than anyone had dared to hope. The asteroid Torifune, a 450-meter rock drifting some 100 million kilometers from Earth, turned out to be a snowman: two roughly equal lobes fused at a neck, covered in boulders, glowing in the infrared like a world with secrets.
The Japan Aerospace Exploration Agency announced the successful flyby on July 6, calling it the first asteroid exploration of the Hayabusa2 Extended Mission — known to its team as Hayabusa2 Sharp, or Hayabusa2♯. It was a precision shot from 100 million kilometers away, executed by a spacecraft that completed its original mission nearly six years ago, and it is a preview of how veteran probes can keep delivering science long after their primary objectives are done.
The Daring Plan
Flying past Torifune was never part of Hayabusa2’s original mission. The spacecraft launched in December 2014 on a mission to the asteroid Ryugu, arriving in 2018, collecting samples — including a dramatic artificial-crater experiment — and delivering its sample capsule to Earth in December 2020. Mission accomplished. But the spacecraft itself was healthy, with fuel to spare and instruments still working. So JAXA designed an extended mission: a flyby of the asteroid Torifune in 2026, followed by a long cruise to rendezvous with the tiny asteroid 1998 KY26 — just 11 meters across — in 2031.
The Torifune flyby was the first test of that second life, and it was, by the team’s own admission, risky. The asteroid’s dimensions were uncertain. The spacecraft would streak past at a relative speed of about 5 kilometers per second. And the aim point was extraordinarily tight: the team targeted a pass coming as close as 800 meters from the asteroid’s center — a bullseye on a 450-meter rock at interplanetary distance.
That is why the plan sparked months of debate between the science and engineering teams. The scientists wanted the close approach for the best possible images and data; some worried the maneuver was too dangerous for the aging spacecraft. One member of the science team had previously described the flyby as a risky operation, given the unknowns surrounding the asteroid. In the end, a last-minute proposal pushed the attempt to the very edge of what Hayabusa2 was designed to do — and the team signed off.
The payoff arrived on the morning of July 6, Japan time. “We did not imagine such a contact binary,” Makoto Yoshikawa, the former mission manager of Hayabusa2, told scientists gathered at the Asteroids, Comets and Meteors conference in Poznań, Poland, on July 10. “Originally, we didn’t think we could have such a very big image. Maybe we will take a very small one, but the image was much larger than we expected.”
What Hayabusa2 Saw
The headline image came from Hayabusa2’s Optical Navigation Camera – Telescopic (ONC-T), captured at 18:29:59 JST on July 5 — moments before the spacecraft’s closest approach was confirmed from ground communications at 18:35 JST. It shows Torifune in crisp detail: two similar-sized lobes joined at a narrow neck, the surfaces of both lobes scattered with boulders of varying sizes.
Astronomers call this shape a contact binary. It forms when two separate objects collide gently — at speeds of just meters per second, slow enough that gravity welds them together rather than shattering them — and remain attached. The result is the peanut or snowman shape seen in the ONC-T image. Ground-based photometry had previously suggested that Torifune might be a contact binary, but the flyby images are the first direct visual confirmation.
The image was also, as Yoshikawa noted, unexpectedly large. Before the flyby, the team had braced for a small, distant snapshot. Instead, the navigation and timing worked so well that Torifune filled the frame far more generously than planned — a two-lobed world with real texture, real topography, and boulders strewn across both lobes like debris from the collision that made it.
Earlier, between June 20 and 21, Hayabusa2 had also captured a long-range view of Torifune — a composite of ONC-T exposures showing the asteroid as a small celestial body drifting against the stars, moving in the direction of its travel. That image, released by the German Aerospace Center (DLR), which is scientifically involved in the Hayabusa2♯ mission, shows the approach phase: the spacecraft homing in on its tiny target across millions of kilometers.
Reading the Heat
Hayabusa2 did far more than take pictures. During the flyby, the spacecraft also observed Torifune with its Thermal InfraRed Imager (TIR), captured at 18:29:58 JST from a distance of approximately 10 kilometers. The mid-infrared image reveals Torifune’s temperature landscape in false color: the asteroid is much cooler in the shadowed regions — including the crevices near the neck between the lobes — and much warmer where the surface faces the Sun.
These thermal measurements are science, not decoration. Surface temperature differences help researchers understand the asteroid’s surface composition, the distribution of rock and dust, the thermal properties of the regolith, surface roughness, and how the asteroid responds to sunlight. A boulder and a patch of fine dust heat up and cool down at different rates; by watching Torifune’s thermal behavior, scientists can infer what its surface is made of and how it is put together. Together with the optical images, these observations will help researchers characterize Torifune’s physical properties in detail once the rest of the scientific data captured during the flyby is downloaded and analyzed — JAXA noted that the remaining data will reach Earth at a later date.
Meet Torifune
Asteroid (98943) Torifune — its name means “flying boat” in Japanese — is a member of the Apollo group, a classification of near-Earth asteroids whose orbits cross Earth’s path around the Sun. It circles the Sun every 383 days and spins on its axis every 5 hours. At roughly 450 meters across, it is a respectable size for a near-Earth object: big enough to be interesting, small enough that its shape was uncertain until a spacecraft got close.
At the time of the flyby, Torifune was about 100 million kilometers (62 million miles) from Earth. The encounter was, by the accounts of those who followed it, one of the closest-ever high-speed passes a spacecraft has made with an asteroid — a deliberate near-miss engineered for science.
The contact-binary shape puts Torifune in fascinating company. Many of the small bodies visited by spacecraft in recent years have turned out to be contact binaries or similarly complex shapes: the comet 67P/Churyumov–Gerasimenko visited by ESA’s Rosetta is a duck-shaped contact binary; the Kuiper Belt object Arrokoth, visited by NASA’s New Horizons, is a flattened snowman; the asteroid Itokawa, visited by the original Hayabusa mission, has a two-lobed “sea otter” shape. Torifune’s crisp snowman profile adds another data point to a growing realization: small bodies in the solar system are rarely simple spheres, and their shapes record their violent and gentle histories alike.
The Science of Contact Binaries
Why do astronomers care whether an asteroid looks like a snowman? Because the shape is a fossil. A contact binary forms when two bodies that were once separate drift together at very low relative speed and merge. That gentle merger preserves information about the environment where it happened — the density of the early solar nebula, the dynamics of the asteroid belt or the near-Earth population, the slow gravitational dances that bring rocks together without smashing them apart.
The two lobes of Torifune are similar in size, which suggests the merger was between two comparable bodies rather than a small moonlet accreting onto a larger one. The neck between them — the contact zone — is where the most interesting geology may lie: material from both bodies mixed and compacted, possibly with distinct thermal and mechanical properties. The TIR data showing cooler temperatures in the shadowed crevices near the neck is a first hint of what that zone looks like thermally; the full dataset may reveal whether the neck’s material differs from the lobes’.
Boulder distribution matters too. The ONC-T image shows boulders of varying sizes scattered across both lobes. On Ryugu, Hayabusa2 found a surface covered in boulders with surprisingly little fine dust — a finding that reshaped ideas about how rubble-pile asteroids evolve. Comparing Torifune’s boulder populations, lobe by lobe, with Ryugu’s may reveal whether contact binaries weather differently from single rubble piles, and how the merger event itself redistributed material.
There is also the planetary-defense angle. Near-Earth asteroids like Torifune are the population that matters for impact hazard assessment, and contact binaries may respond differently to deflection attempts than monolithic rocks. Understanding their internal structure — whether the two lobes are loosely bound or deeply merged — is directly relevant to any future effort to nudge one off a collision course.
From Ryugu to 1998 KY26: A Second Life
The Torifune flyby is a milestone in what is becoming a new era of space exploration: the extended mission. Hayabusa2 completed its primary objectives in 2020, but JAXA recognized that a healthy spacecraft with working instruments and remaining fuel is too valuable to waste. The extended mission — Hayabusa2♯, the “Sharp” — was designed to squeeze more science from the veteran probe.
The plan has two acts. Act one was Torifune: a high-speed flyby of a 450-meter Apollo asteroid, demonstrating precision navigation and gathering comparative data on a very different body from Ryugu. Act two is the long game: a cruise to asteroid 1998 KY26, a rock thought to measure just 11 meters across, with arrival scheduled for 2031. If Torifune was a needle-threading exercise, 1998 KY26 will be something else entirely — a rendezvous with an object barely larger than the spacecraft’s own solar panels, a fast-spinning pebble that will test every capability the extended mission has.
This is the quiet revolution in planetary science: spacecraft that were supposed to die are living second lives. New Horizons flew past Arrokoth years after Pluto. The Mars rovers outlived their warranties by decades. Hayabusa2 is now writing its own second chapter, and the Torifune flyby proves the pen still works.
The Team Behind the Shot
The flyby was a team effort spanning continents. JAXA led the operation, with the ONC-T image credited to JAXA, the University of Tokyo, Chiba Institute of Technology, the Institute of Science Tokyo, AIST, the Paris Observatory, and the Instituto de Astrofísica de Canarias. The TIR thermal image credits JAXA with the Maebashi Institute of Technology, Chiba Institute of Technology, the University of Aizu, the Hokkaido University of Education, and AIST.
The German Aerospace Center, DLR, is scientifically involved in Hayabusa2♯ — a continuation of a partnership that goes back to the original mission, when DLR (with France’s CNES) built and deployed the MASCOT lander onto Ryugu in 2018. The extended mission’s science team includes researchers like Patrick Michel, who had flagged the flyby’s risks, and the broader community that debated, refined, and ultimately approved the daring close approach.
And then there is Makoto Yoshikawa, the former mission manager who stood before the Asteroids, Comets and Meteors conference in Poznań on July 10 with two surprises to report: the contact binary nobody had quite imagined, and an image far larger than the team had expected. In planetary science, as in life, the best results are often the ones you didn’t plan for.
What Comes Next
The images released on July 6 are only the beginning. JAXA has said that the rest of the scientific data captured during the flyby will be transmitted to Earth at a later date — the full dataset from the optical and thermal cameras, plus whatever the spacecraft’s other instruments recorded during the encounter. Analysis will take months: measuring the lobes’ dimensions, mapping boulder distributions, modeling the thermal inertia of the surface, and reconstructing the merger that made Torifune a snowman.
The results will feed into the broader comparative study of small bodies that missions like Hayabusa2, OSIRIS-REx, DART, and the upcoming generation of asteroid missions are building. Each asteroid visited is a new world with its own history; together, they are teaching us how the solar system’s smallest bodies form, evolve, and occasionally come together.
And Hayabusa2 itself is already moving on. The spacecraft is on its long cruise toward 1998 KY26, with arrival in 2031. Along the way, there will be more observations, more calibrations, more of the quiet engineering that keeps a decade-old spacecraft alive and on course. The Torifune flyby was the first proof that the extended mission can deliver — a super-close pass, a snowman asteroid, and images larger than anyone expected.
Why Flybys Still Matter
In an era of flagship orbiters and sample-return missions, it is easy to overlook the humble flyby. But flybys are how we build the census of small worlds. Rendezvous missions like Hayabusa2’s visit to Ryugu or OSIRIS-REx’s stay at Bennu deliver extraordinary detail — but each one takes years and hundreds of millions of dollars, and can only ever visit a single target. A flyby, by contrast, is comparatively cheap and fast: a spacecraft already going somewhere threads its trajectory past a rock, grabs what data it can in a few frantic hours, and moves on.
The Torifune encounter shows how much a well-executed flyby can deliver. In a single pass, Hayabusa2 confirmed the asteroid’s contact-binary structure, mapped its boulder-strewn surface, and measured its thermal landscape — data that will keep scientists busy for years. It did so with a spacecraft that was already paid for, already in space, and already on its way elsewhere. That is the economic logic of extended missions: the marginal cost of a flyby is a fraction of a dedicated mission, while the scientific return can be transformative.
There is also a strategic dimension. The population of near-Earth asteroids numbers in the tens of thousands, and we have visited only a tiny fraction up close. Flybys are the only practical way to sample the diversity of that population — the contact binaries, the fast rotators, the metal-rich oddballs — before we commit flagship resources to the most interesting ones. Torifune was chosen partly because it was reachable, and partly because it was unknown. It turned out to be a snowman. The next unknown rock might be stranger still.
Twelve years after launch, six years after its sample capsule parachuted into the Australian outback, Hayabusa2 is still exploring. On July 5, 2026, it threaded a needle past a two-headed rock at 18,000 kilometers per hour and sent home the pictures to prove it. The scientists who said it was too dangerous got their data anyway. The engineers who proposed it got their vindication. And the rest of us got a snowman, floating in the dark, 100 million kilometers away — two rocks that found each other, and held on.
