These
observations made by NASA’s SPHEREx mission reveal vast frozen complexes in the
Cygnus X star-forming region of the Milky Way galaxy. Water ice, shown as
bright blue structures at left, exactly overlays the dark lanes of interstellar
dust, shown in different wavelengths at right.
NASA’s SPHEREx (Spectro-Photometer for the History of the Universe, Epoch
of Reionization, and Ices Explorer) mission has mapped interstellar ice at an
unprecedented scale. Covering regions in our Milky Way galaxy more than 600
light-years across, the ice was found inside giant molecular clouds — vast
regions of gas and dust where dense clumps of matter collapse under gravity,
giving birth to stars. A study describing these findings published Wednesday in The Astrophysical Journal.
One of SPHEREx’s main goals is to map the chemical signatures of various types of
interstellar ice. This ice includes molecules like water, carbon dioxide, and
carbon monoxide, which are vital to the chemistry that allows life to develop.
Researchers believe these ice reservoirs, attached to the surfaces of tiny dust
grains, are where most of the universe’s water is formed and stored. The water
in Earth’s oceans — and the ices in comets and on other planets and moons in
our galaxy — originates from these regions.
“These vast frozen complexes are
like ‘interstellar glaciers’ that could deliver a massive water supply to new
solar systems that will be born in the region,” said study coauthor Phil
Korngut, the instrument scientist for SPHEREx at Caltech in Pasadena, California.
“It’s a profound idea that we are looking at a map of material that could rain
on nascent planets and potentially support future life.”
Thanks to its spectral
capabilities, SPHEREx can measure the amounts of various ices and
molecules, such as polycyclic aromatic hydrocarbons, in and around molecular
clouds, helping scientists better understand their composition and
environment.
Although space telescopes such as
NASA’s James
Webb Space Telescope and the agency’s retired Spitzer have detected water, carbon dioxide, carbon monoxide, and other icy molecules
throughout our galaxy, the SPHEREx observatory is the first infrared mission
specifically designed to find such molecules over the entire sky via the
mission’s large-scale spectral survey.
“We expected to detect these ices
in front of individual bright stars: The light from a star acts like a
spotlight, revealing any ice in the space between us and that star. But this is
something different,” said lead author Joseph Hora, an astronomer at the Center
for Astrophysics (CfA) at Harvard & Smithsonian in Cambridge,
Massachusetts. “When looking along the galactic plane — where most of the
stars, gas, and dust of our galaxy are concentrated — there’s a lot of diffuse
background light shining through entire dust clouds, and SPHEREx can see the
spatial distribution of the ices they contain in incredible detail.”
Managed by NASA’s Jet Propulsion
Laboratory in Southern California, the SPHEREx observatory launched March 11, 2025, and has the unique ability to see the sky in 102
colors, each representing a different wavelength of infrared light that offers
distinctive information about galaxies, stars, planet-forming regions, and
other cosmic features. By late 2025, SPHEREx had completed the first of four all-sky infrared maps of the universe, charting the
positions of hundreds of millions of galaxies in 3D to help answer major
questions about the cosmos, including those about the origins of water and
life.
Icy origins
Using the SPHEREx maps of various
icy molecules, the study’s authors were able to look deep into many molecular
clouds in the Cygnus X and North American Nebula regions of the Milky Way. In
the densest areas, where the amount of dust is greatest, dark filamentary lanes
block the visible light from the stars behind. With its infrared eye, the space
telescope also revealed where the different ices — which absorb specific
wavelengths of infrared light that would pass through the clouds if they
consisted only of dust — are at their densest.
This finding supports the
hypothesis that interstellar ice forms on the surface of tiny dust particles,
which are no larger than particles found in candle smoke, and that the dense
regions of dust shield the ices from the intense ultraviolet radiation emitted
by newborn stars. However, not all ices are treated the same way in the
interstellar medium.
“We can investigate the
environmental factors that contribute to different ice formation rates across
large areas of interstellar space,” said study coauthor Gary Melnick, also an
astronomer at the CfA. “The SPHEREx mission’s ‘big picture’ view provides valuable
new information you can’t get when zooming in on a small region.”
Within this broad perspective, adds
Melnick, SPHEREx can do something ground-based observatories cannot: detect
varying amounts of water and carbon dioxide, two ices that respond differently
to environmental factors. For example, the presence of intense ultraviolet
light from nearby massive young stars or the heating of these dust grains by
that light affects the abundances of different ices in distinct ways.
This is just the beginning for the
mission. Observations from SPHEREx will provide scientists with a powerful tool
to explore the various components of our galaxy, the physics of the
interstellar medium that lead to star and planet formation, and the chemical
processes that deliver molecules essential for life to newly formed planets.
More about SPHEREx
The mission is managed by JPL for
the agency’s Astrophysics Division within the Science Mission Directorate in
Washington. The telescope and the spacecraft bus were built by BAE Systems in
Boulder, Colorado. The science analysis of the SPHEREx data is being conducted
by a team of scientists at 13 institutions across the U.S. and in South Korea
and Taiwan, led by Principal Investigator Jamie Bock, who is based at Caltech
with a joint JPL appointment, and by JPL Project Scientist Olivier Doré. Data
is processed and archived at IPAC at Caltech in Pasadena, which manages JPL for
NASA. The SPHEREx dataset is freely available to scientists and the
public.
For more information about the SPHEREx mission visit: https://science.nasa.gov/mission/spherex/
Source: ‘Interstellar Glaciers’: NASA’s SPHEREx Maps Vast Galactic Ice Regions - NASA
