Asteroids are compromised. Billions of years of impacts and solar radiation have baked and battered every one we've sampled. Comets haven't.
image from grok
JAXA is proposing the Next Generation Small-Body Return (NGSR) mission, targeting launch in the 2030s as a large-class strategic mission to land on and return samples from comet 289P/Blanpain, a 160-meter Jupiter-family comet with unusually low outgassing that has been stored at cryogenic temperatures since before the planets formed. Unlike asteroids, which have been thermally altered by 4.6 billion years of impacts and solar radiation, cometary interiors preserve the original presolar building blocks of the solar system in their pristine state, offering the first direct sampling of unaltered material from the solar nebula. The mission's two primary science objectives are recovering original presolar grains for compositional analysis and studying the intact record of planetesimal formation mechanisms.
JAXA Wants to Land on a Comet Nobody Has Touched in 4.6 Billion Years
JAXA has spent two decades getting very good at bringing back pieces of the solar system. First Itokawa, then Ryugu. Now the agency wants the hard one.
The Next Generation Small-Body Return, or NGSR, is a proposed JAXA mission designed to land on a comet and extract material that has been frozen since before the planets formed. The target is 289P/Blanpain, a Jupiter-family comet roughly 160 meters in radius that was lost to astronomy for nearly two centuries, rediscovered in 2003, and confirmed as a living comet after an unexpected outburst in 2013, per Universe Today.
The mission concept was detailed in a paper presented at the 2025 Lunar and Planetary Science Conference, led by JAXA researcher Naoya Sakatani, with co-authors from JAXA, the University of Tokyo, Osaka University, Purdue, and others. JAXA is assessing NGSR as a large-class strategic mission targeting launch in the 2030s, according to the LPSC 2025 conference paper.
Why a comet instead of another asteroid? Because asteroids are compromised. Four billion years of impacts, solar radiation, and space weathering have baked and battered every one we have sampled. Hayabusa2's Ryugu material told us about asteroid composition, but the heat of formation destroyed anything older. Comets, spending most of their time far from the Sun, have been stored at cryogenic temperatures since the solar system assembled. What they hold is what the solar system was actually made from.
The choice of 289P/Blanpain over a more spectacular comet is deliberate. Most comets are active — erupting gas and dust as they approach the Sun, which makes landing hazardous and sample collection messy. 289P/Blanpain has unusually low outgassing, as detailed in the mission concept study. At its orbital distance it produces minimal jets, creating a safer environment for a spacecraft to perform proximity operations and excavate subsurface material.
The science case breaks into two parts. The first is presolar material: the raw stock from which the Sun and planets formed. Carbonaceous meteorites contain organic matter, including amino acids, but the thermal history of asteroids has altered it. Pristine comet interior, never heated above a few hundred degrees, should contain original presolar grains in their original state. Finding them would be the first direct look at what the solar system's building blocks actually were when they formed.
The second goal is planet formation itself. The exact mechanism by which microscopic dust grains overcame gas drag and other barriers to form kilometer-sized planetesimals remains one of the fundamental unsolved problems in planetary science. The interior of a comet contains the earliest formed aggregates in their original configuration, unlike asteroids which have been reworked by impact and heating.
The timeline matters. JAXA's Martian Moons eXploration mission, MMX, was delivered to the Tanegashima Space Center in late March 2026 and remains on schedule for launch before the end of the year, per JAXA ISAS announcements. MMX will return samples from Phobos and Deimos. NGSR would follow in the 2030s. The sequence matters because JAXA is building expertise in small-body operations toward increasingly difficult targets. Asteroids are forgiving. Comets are not.
NGSR is not yet approved. It is under assessment as a strategic-class mission, which means it has cleared the first filter but has not received final funding or launch assignment. The 2030s timeline is an estimate, not a commitment. The mission concept needs to survive review, survive budget cycles, and survive the MMX results before anything is certain.
The thing that makes this story worth telling now is not the launch date. It is the target. 289P/Blanpain, per Wikipedia, is one of the most unmodified objects in the solar system, a piece of the original solar nebula that has been stored at roughly 40 Kelvin for 4.6 billion years in the outer solar system and occasionally drifts close enough to study. The last mission to return comet material was Stardust in 2006, which grabbed interplanetary dust from the coma of Wild 2, not subsurface material from the interior of a comet. NGSR, if it flies, would be in a different category entirely.
What JAXA is proposing is the difference between scraping something off the surface of a museum exhibit and actually taking the exhibit apart. The question is whether the agency can afford the museum admission fee.
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Research completed — 4 sources registered. NGSR targets 289P/Blanpain, a lost comet rediscovered 2003, confirmed after 2013 outburst. Two goals: presolar material and planet formation. Low outg
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