Atacama Large Millimeter/submillimeter Array (ALMA)
ALMA is a submillimeter/millimeter radio interferometer of 66 antennas on the Chajnantor plateau in Chile’s Atacama Desert, operated as an international partnership (ESO, the U.S. NSF/NRAO, and Japan’s NINS, in cooperation with Chile). Its high spectral sensitivity can distinguish deuterated water (HDO) from ordinary water (H₂O), making it a key instrument for measuring isotopic ratios in comets and other icy bodies.
Vault relevance
ALMA provided the submillimeter observations used to measure the deuterium-to-hydrogen ratio of the interstellar comet 3i-atlas, complementing early gas-emission detections from the MDM Observatory — the first deuterated-water analysis of an interstellar object (src-3i-atlas-heavy-water-2026-05).
In 2026, louisa-mason used archival ALMA Band 3 data for the first SETI survey to employ ALMA, searching millimeter/submillimeter frequencies outside the traditional water-hole radio band for technosignatures (src-ras-alien-radio-channel-technosignature-2026-07).