NASA's GAPS Experiment Launches from Antarctica to Probe Dark Matter

The General AntiParticle Spectrometer (GAPS) experiment successfully began its mission from Antarctica on December 16, 2025, utilizing a large scientific balloon to conduct a high-altitude search for evidence of dark matter. Managed by NASA, the endeavor is specifically engineered to detect rare cosmic antimatter nuclei, such as antideuterons, which could provide the first observational evidence regarding the particle nature of dark matter.

The launch originated near the U.S. National Science Foundation's McMurdo Station on the Ross Ice Shelf, a site selected for its environmental suitability for long-duration flights. The GAPS payload is scheduled to ascend to an operational altitude of approximately 120,000 feet, or 36 kilometers, positioning the instrument above the majority of the Earth's atmosphere that would otherwise interfere with the low-energy cosmic rays under investigation. The mission is designed for a multi-week flight circling the Antarctic continent, maximizing data collection during the continuous daylight of the austral summer.

The core scientific objective of GAPS is to execute a highly sensitive search for low-energy antideuterons, specifically those with kinetic energies below 0.25 GeV/n, a range largely unexplored by previous instruments. The detection principle relies on a novel 'exotic atom' technique, where an incoming antiparticle forms a transient exotic atom that decays, emitting unique X-rays and producing a correlated pion and proton signature from annihilation. This method offers superior background suppression for negatively charged antinuclei compared to magnetic spectrometers and does not require a magnetic field, enabling a large sensitive area necessary for capturing infrequent events. The experiment will also precisely measure the cosmic-ray antiproton spectrum at these low energies, which aids in constraining various dark matter models.

The successful deployment marks a significant milestone for the international collaboration, which includes contributions from institutions such as Columbia University, the University of California, Los Angeles (UCLA), and Northeastern University, alongside partners from Japan, Italy, and China. The University of Hawaiʻi at Mānoa received a $1.4 million portion of a larger NASA grant to support its role in detector development, building upon prior calibration work. The underlying detection concept has been previously validated through an accelerator beam test at KEK, Japan, in 2005, and a successful prototype flight, pGAPS, in June 2012. The GAPS instrument itself was assembled and prepared for this flight at the Long Duration Balloon facility at McMurdo Station in November 2024. The ongoing data collection phase aims either to yield the first definitive detection of a cosmic-ray antideuteron or to establish stringent upper limits that will inform future astrophysics efforts regarding the universe's invisible mass composition.