The results support the idea that water permeates the building materials of the galaxy’s planets.
A vast frozen fog of interstellar ice has been mapped across the expanses of the Milky Way, ready to provide water to newborn worlds.
Reach hundreds of light years longicy clouds cover two of the galaxy’s active star-forming regions, astronomer Gary Melnick and colleagues report in the April 20 issue. Astrophysics Journal. The results paint the broadest picture to date of interstellar iceand appear to confirm predictions that water, a key ingredient of life on Earth, is present in large areas of interstellar space, says Melnick, of the Harvard-Smithsonian Center for Astrophysics.
This is important because as stars form, some of this ice may be pulled into the gravitational collapse of giant clouds of dust and gas, where it could merge with other materials to form new planets. If there’s a lot of this ice nearby, Melnick says, “that provides a likely answer to how these newly formed worlds might acquire their own oceans.”
In fact, he says, much, if not all, of Earth’s water probably comes from interstellar ice.
Frozen dust clouds
SPHEREx observations show that large amounts of water ice are found in the dust-rich regions of Cygnus X, a star nursery. Use the slider to compare how the ice, shown in blue in the false-color infrared image on the left, coincides with the dark filaments of interstellar dust, shown in different wavelengths of light on the right.
The observations were made by – take a deep breath – NASA’s Spectro-Photometer for the History of the Universe, Reionization Epoch and Ice Explorer, or SPHEREx. Since its launch into low Earth orbit in March 2025, SPHEREx has used its infrared eyes to study the entire sky, a process it will perform four times during its two-year mission. The observatory can discern ice within clouds of gas and dust because ice absorbs certain wavelengths of infrared light and thus appears dark in starlight.
Within a few stellar nurseries known as Cygnus This supports the hypothesis that ice is scattered on the surface of countless dust grains in these stellar nurseries, Melnick says.
While the James Webb Space Telescope has already generated maps of interstellar ice, the new SPHEREx maps are dozens of times larger. SPHEREx provides a more magnified view of the environments in which these ices occur, Melnick says. “We see the bigger picture.”
Researchers hope to soon use SPHEREx data to determine the abundance of interstellar ice, which could help reveal regions where newborn worlds are likely to have oceans of water.