OSIRIS-REx,NASA's first asteroid sample return mission, collected samples from the Nightingale site on asteroid Bennu in October, 2020, and returned approximately 121.6 g of asteroid material to Earth on September 24, 2023. Under a Memorandum of Understanding (MOU) between JAXA and NASA, JAXA received bulk samples equivalent to 0.5 wt% (approximately 0.663 g) of the total returned sample mass, as well as TAGSAM contact pads, which were used to collect surface particles from asteroid Bennu.

The samples were received by the Extraterrestrial Sample Curation Center (ESCuC) at the Institute of Space and Astronautical Science (ISAS), JAXA, on August 22, 2024.Currently, JAXA is conducting the initial description of the samples, developing the sample catalog, advancing comparative studies with Ryugu samples, and allocating samples through international Announcement of Opportunity (AO) .　

The Bennu and Ryugu samples are both valuable returned samples from carbonaceous asteroids. At JAXA, comparative studies of between the Bennu and Ryugu samples are being conducted using the same facilities and analytical methods to minimize the effects of differences in analytical conditions. These direct comparisons are rare worldwide and provide important insights into understanding the formation and evolution of asteroids and the origins of water and organic matter.

This sample curation serves as a key technology demonstration toward the future receipt and curation of Phobos samples returned by the Martian Moons eXploration (MMX) mission.

Bennu Sample Receiving Facility

For the receipt of the Bennu samples, JAXA incorporated experience gained from the Hayabusa2 sample curation and developed advanced cleanroom and clean chamber facilities.

Cleanroom

The newly established dedicated cleanroom maintains an ISO Class 6 cleanliness level. The facility incorporates design expertise gained from the Hayabusa and Hayabusa2 missions and has been optimized to enhance operational efficiency.

Clean Chamber

Because the Bennu samples were allocated by NASA under a nitrogen atmosphere, the vacuum container opening system required for the Ryugu samples was not necessary.

Instead, JAXA newly established nitrogen-atmosphere clean chambers, CC5-1 (for processing and storage) and CC5-2 (for analysis), with enhanced analytical capability and improved operability. These clean chambers are directly connected to infrared spectroscopic instruments(MicrOmega and micro-FTIR).

In addition, nitrogen-atmosphere glove boxes (GB8 and GB9) were installed to enable sample processing prior to introduction into the clean chambers and the use of tools that are not compatible with the clean chamber. By making appropriate use of both clean chambers and glove boxes, JAXA has achieved both high cleanliness and flexible sample handling.

Ryugu to Bennu

The technologies developed through the Hayabusa2 mission have been further advanced for Bennu sample curation.

A digital optical microscope (Keyence VHX-8000) has been introduced.By utilizing its automated stage for large-area image acquisition and stitching, depth-composition imaging, and three-dimensional shape measurement, detailed particle documentation and more efficient morphological analysis have been achieved.

A microscopic FTIR spectrometer (JASCO IRT-5200) has been introduced. The instrument covers a broad spectral range from 2.0 to 13.0 μm, enabling measurements extending further into the long-wavelength region compared with the instrument used for the Hayabusa2 mission. It also provides improved spatial resolution. Furthermore, the entire system is enclosed in a nitrogen-purged box, significantly reducing the effects of atmospheric H₂O and CO₂ during measurements.

The near-infrared hyperspectral microscope MicrOmega has been enhanced with a newly added sample stage tilting function (±15°), enabling the acquisition of spectroscopic data under optimized conditions even for particle edges and complex particle morphologies. In addition, multiple viewports have been incorporated into the analysis chamber, improving the flexibility of sample observation and manipulation. Furthermore, by integrating an optical microscope (Leica Emspira 3) into the same system, efficient correlation of spectroscopic data and morphological information has been achieved.

These improvements reflect the operational experience and insights gained from the curation of Ryugu samples. They have contributed not only to enhanced analytical performance but also to improved operational efficiency and sample preservation. In addition, the Bennu curation serves as a technology demonstration platform, bridging the experience gained from Ryugu sample curation to future curation of Phobos samples.

Initial Description

All Bennu samples are subjected to non-destructive analyses under a nitrogen atmosphere with water vapor levels maintained at the ppb level.

The initial description included mass measurement, optical microscopy, visible spectroscopy (MICOSHI), and infrared spectroscopy (microscopic FTIR and MicrOmega). Building on the analytical methods established for Ryugu samples, the Bennu sample curation system provides a more advanced analytical environment.

As a result of the initial description, characteristic absorption bands at 2.7μm (hydrated minerals: Mg-rich phyllosilicates), 3.4 μm (aliphatic organic matter and carbonates), and 3.95 μm (carbonates) were identified in the Bennu samples. These spectral features are consistent with laboratory analyses conducted by NASA and spacecraft observations of Bennu, providing scientific evidence that the samples remained unaltered throughout their return to Earth, transportation, and initial handling processes.

Furthermore, by applying the same instruments and analytical methods used for Ryugu samples, an environment has been established for accurately evaluating the similarities and differences between the two bodies.

Sample Catalog and the Announcement of Opportunity

Information obtained through the initial description of the Bennu samples is compiled into a database and made available online as a sample catalog.

JAXA has also established an international Announcement of Opportunity (AO) for Bennu sample research, enabling researchers worldwide to conduct scientific investigations. The sample information disclosure system and AO framework originally developed for the Ryugu samples have been extended to the Bennu samples, promoting international comparative studies between Ryugu and Bennu.

Samples available through the AO program include aggregate samples derived from bulk samples, individual particles, and particles recovered from the contact pads.

Curation Technologies and Tools

Handling Tools

To minimize sample contamination, JAXA is building upon the technological foundations developed for Hayabusa2, including vacuum tweezers, spatulas, sample dishes, and Facility-to-Facility Transfer Containers (FFTCs), while also introducing new tools and technologies.

A representative example is the micro-tweezer. Conventional vacuum tweezers were only capable of handling particles with diameters down to approximately 500 μm. In contrast, the micro-tweezer enables the direct grasping and precise manipulation of much smaller particles, including fine particles ranging from approximately 100 μm to 1 mm in size. This capability plays a crucial role in recovering particles trapped within the metal loops of contact pads and in selecting specific particles for detailed analyses.

Environmental Assessment / Contamination Control

To preserve the scientific value of returned samples, a comprehensive environmental assessment system has been established.

API-MS (Atmospheric Pressure Ionization Mass Spectrometer) continuously monitors trace impurities in the nitrogen atmosphere, including water vapor, oxygen, carbon dioxide, and methane, in real time at the ppb level.

In addition, organic contamination is evaluated using GC×GC-TOFMS (Comprehensive Two-Dimensional Gas Chromatography–Time-of-Flight Mass Spectrometry), while inorganic elemental contamination is also evaluated using ICP-MS (Inductively Coupled Plasma Mass Spectrometry).

These data also contribute to the development of contamination control standards for future sample return missions, including MMX.

Bennu to MMX

JAXA's extraterrestrial sample curation began with the Itokawa samples, progressed through the Ryugu samples, and has now expanded to the Bennu samples. The environmental assessment technologies, non-destructive analytical techniques, microscopic particle handling techniques, and sample catalog management systems developed through Bennu sample curation will be carried forward to support the future acceptance and curation of Phobos samples.

The Bennu samples serve as a crucial bridge between the Ryugu samples and the future Phobos samples, playing a key role in both technological demonstration and scientific research for next-generation sample-return missions.

References

[1] Fukai R., Nishimura M., Yumoto K., Cho Y., Shimizu Y., Matsuoka M., Tatsumi E., Furukawa S., Yada T., Hatakeda K., Yogata K., Enokido Y., Tahara R., Miyazaki A., Kawasaki S., Sugita S., Mori S., Nakahara S., Aikyo Y., Pilorget C., Loizeau D., Nardelli L., Riu L., Sheppard R., Lantz C., Brunetto R., Jiang T., Mahlke M., Abe M., Usui T. (2025), “Nondestructive analysis of Bennu samples toward comparative studies with Ryugu samples”, Meteoritics & Planetary Science, Volume 61, Issue 1, p. 3-16. https://doi.org/10.1111/maps.70077

[2] Tahara R., Hatakeda K., Nishimura M., Yogata K., Fukai R., Miyazaki A., Yada T., Enokido Y., Abe M., Kawasaki S., Sakurai R., Okada T., Pilorget C., Bibring J. -P., Hamm V., Lourit L., Loizeau D., Riu L., Yumoto K., Cho Y., Sugita S., Nakahara S., Mori S., Aikyo Y., Kameda S., Stabbins R., Shimizu Y., Miyamoto H., Hitomi Y., Nakano A., Nagashima K., Sugahara H., Suzuki S., Kimura S., Usui T. (2025), “JAXA curation for Bennu samples returned by the NASA's OSIRIS-REx mission”, Meteoritics & Planetary Science, Volume 61, Issue 1, p. 182-207. http://doi.org/10.1111/maps.70066