XRISM Mission

August 3, 2025

NASA and JAXA’s XRISM mission—the X-ray Imaging and Spectroscopy Mission—is a collaborative effort to explore the hidden chemistry of the Milky Way by detecting and analyzing sulfur in the interstellar medium. Launched in 2023, XRISM is equipped with a powerful X-ray spectrometer called Resolve, which allows scientists to study the composition of cosmic material with unprecedented precision.

Sulfur plays a vital role in biological systems on Earth, but its distribution in space has long been a mystery. In the diffuse regions between stars, sulfur is often found in gaseous form. However, in denser molecular clouds—where stars and planets are born—this gaseous sulfur tends to vanish. Scientists have theorized that it condenses into solid compounds, possibly bonding with ice or metals like iron, but direct evidence has been elusive.

XRISM’s mission is to uncover where sulfur goes and how it transforms. To do this, researchers selected bright X-ray sources located behind targeted regions of the interstellar medium. As X-rays from these sources pass through the gas and dust, they interact with sulfur atoms, leaving behind spectral fingerprints that XRISM can detect. In one study, the spacecraft observed the binary star system GX 340+0, located over 35,000 light-years away in the constellation Scorpius. The data revealed sulfur not only in its gaseous state but also as a solid—possibly mixed with iron in compounds like pyrrhotite or troilite. This marks the first time sulfur has been directly observed in both phases using X-ray spectroscopy. The findings help scientists understand how sulfur cycles through space, how it contributes to the formation of stars and planets, and how it might be incorporated into meteorites and other celestial bodies. Learn more at XRISM at NASA.

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