What lies beneath the Moon's surface? Water ice, mineral resources, or stable ground for lunar bases? A "walking stick" developed in Japan aims to help uncover these mysteries. Wielded by astronauts on the lunar surface, it could reshape humanity's approach to Moon exploration.

Japanese Technology Selected for NASA's Lunar Mission

In December 2025, NASA officially announced that PASS (Portable Active Seismic Source), a compact seismic device developed by Professor Takeshi Tsuji and his team at the University of Tokyo's Graduate School of Engineering, has been selected for the Artemis IV mission.

The Artemis program is NASA's flagship human spaceflight initiative, conducted in partnership with Japan and other international partners. It aims to return humans to the Moon for the first time since the Apollo missions ended in 1972, making this one of the most significant space exploration efforts in half a century.

Artemis IV, the mission carrying PASS, is scheduled for launch in 2028. It will be the first crewed lunar landing since Apollo, and the first mission where astronauts conduct comprehensive geological surveys on the surface. There's even a possibility that Japanese astronauts will participate, potentially making them the first to use Japanese-made equipment on the Moon.

What is PASS: A Staff-Like Seismic Source

PASS stands for "Portable Active Seismic Source." The device resembles a walking stick or staff, compact enough for astronauts to operate by hand while wearing bulky spacesuits.

Here's how it works:

  1. Astronauts deploy seismometers on the lunar surface
  2. Using PASS near the seismometers, they repeatedly generate small artificial vibrations
  3. These vibrations travel through the Moon's interior as waves
  4. The seismometers record changes in wave velocity and intensity
  5. Scientists analyze the data to create "cross-sectional maps" of the subsurface structure

Traditional seismic survey equipment is large and heavy, far too bulky for space missions. PASS achieved the necessary miniaturization and weight reduction while incorporating space-grade features: resistance to vacuum conditions, extreme temperature fluctuations (ranging from minus 280°F to plus 250°F), and the fine lunar dust known as "regolith."

What Will Be Explored on the Moon

Artemis IV's PASS-equipped surveys aim to visualize subsurface structures up to approximately 16 feet (5 meters) deep. The data gathered will serve several crucial purposes:

Water and Mineral Resource Exploration The Moon's south polar region is believed to contain water ice in permanently shadowed craters, areas where sunlight never reaches. Finding water would be transformative: it could serve as drinking water for astronauts and, through electrolysis, be split into hydrogen and oxygen for rocket fuel. Producing fuel on the Moon rather than transporting it from Earth could dramatically reduce space exploration costs.

Foundation Assessment for Lunar Bases Plans exist for establishing permanent human habitations on the Moon. Building safely requires precise knowledge of ground conditions, hardness, composition, and structural integrity. PASS survey data will be essential for selecting optimal construction sites.

Understanding Lunar Formation The Moon's formation remains incompletely understood. Subsurface data provides valuable scientific insights into how our nearest celestial neighbor came to be.

Proven Technology on Earth

PASS wasn't originally developed for space. It was created for terrestrial subsurface exploration and has already accumulated an impressive track record:

Carbon Capture Monitoring As nations pursue carbon neutrality, injecting CO₂ deep underground has emerged as a key strategy. PASS monitors these storage sites to ensure the captured carbon isn't leaking back to the surface.

Geothermal Exploration In Japan's geothermal regions, PASS-based elastic wave surveys have successfully mapped fault structures at depths of approximately 3,300 feet (1,000 meters), improving the efficiency of geothermal resource development.

Tunnel Construction Safety The technology can detect underground cavities and monitor collapse risks during tunnel construction, a growing concern as infrastructure ages.

Infrastructure Inspection PASS enables non-destructive examination of aging levees, bridges, and other structures.

A University of Tokyo spinoff company called "Wavelet" is commercializing this technology, with the goal of making subsurface investigation accessible to anyone.

International Collaboration in Lunar Exploration

PASS will operate as part of SPSS (South Pole Seismic Station), a packaged system combining the seismic source with seismometers. This station exemplifies international collaboration:

  • NASA (USA): Jet Propulsion Laboratory (JPL) leads overall project coordination
  • CNES (France): French National Space Agency develops seismometers
  • IPGP (France): Paris Institute of Earth Physics develops seismometers
  • JAXA & University of Tokyo (Japan): Provides PASS and conducts elastic wave surveys

Japan's contribution through tangible exploration equipment marks a significant milestone, following the successful lunar landing of the SLIM probe in January 2024, in the nation's growing role in lunar exploration.

The Artemis Timeline

The Artemis program is progressing through several phases:

  • Artemis I (completed 2022): Uncrewed flight test
  • Artemis II (completed April 2026): Successful crewed lunar flyby
  • Artemis III (planned 2027): Crewed test of the Human Landing System in Earth orbit (reassigned from the original crewed landing)
  • Artemis IV (planned 2028): First crewed lunar landing since Apollo, with comprehensive geological surveys using PASS

PASS's selection validates Japanese space technology on the international stage. It also demonstrates the "spinoff" phenomenon, how technology developed for space can solve terrestrial challenges and vice versa.

In Japan, there's considerable pride that university-developed basic research has been selected for major international space projects. How is your country contributing to space exploration and lunar development? What applications do you see for subsurface investigation technology? Share your thoughts in the comments!

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