A new study, published in Astronomy & Astrophysics, has revealed the location of a significant portion of the missing sulfur in interstellar ice. The research, led by Katerina Slavicinska, a PhD student at Leiden Observatory, combined laboratory experiments with data from the James Webb Space Telescope (JWST).
Scientists have long been puzzled by the scarcity of sulfur in dense star-forming clouds, where it is found in concentrations hundreds of times lower than in typical interstellar space. This study suggests that sulfur is hiding within ice grains, specifically in the form of ammonium hydrosulfide (NH4SH).
The discovery was made possible by recreating the frigid conditions of space in a laboratory setting. By combining ammonia (NH3) and hydrogen sulfide (H2S) at temperatures of 15 Kelvin (-258 degrees Celsius), the researchers successfully synthesized NH4SH, a salt that had previously been detected on comet 67P by the Rosetta mission.
This finding not only sheds light on the missing sulfur but also provides valuable insights into the composition of interstellar ice, which plays a crucial role in the formation of planets and stars. The identification of NH4SH in interstellar ice opens new avenues for understanding the chemical evolution of the universe and the origins of life.