NASA’s upcoming SPHEREx mission is on a quest to track down cosmic reservoirs of frozen water and life-essential molecules in deep space.

Using a unique 3D spectral approach, it will scan molecular clouds where stars and planets are born, revealing how ice forms and evolves. By surveying millions of targets, SPHEREx will create the largest-ever map of frozen compounds in the galaxy, deepening our understanding of planet formation and the origins of water. Past missions found far less gaseous water than expected, hinting that vast quantities might be locked in icy grains hidden from view — until now.

Following the Water: A Cosmic Search Begins

Every living organism on Earth depends on water, so when scientists search for life beyond our solar system, they often follow one key principle: “follow the water.” NASA’s SPHEREx mission — short for Spectro-Photometer for the History of the Universe, Epoch of Reionization, and Ices Explorer — is set to launch Thursday, March 6, to support that search.

After launching aboard a SpaceX Falcon 9 rocket from Vandenberg Space Force Base in California, SPHEREx will scan the cosmos for frozen water, carbon dioxide, carbon monoxide, and other essential molecules. These compounds are found on the surface of tiny dust grains within vast clouds of gas and dust — regions where stars and planets eventually form.

The Mission’s Unique Capabilities

While there are no free-floating oceans or lakes in space, scientists believe that most of the universe’s water exists as ice, bound to these microscopic dust grains. In fact, the water in Earth’s oceans, as well as on other planets and moons in our galaxy, likely originated in such icy reservoirs.

SPHEREx will focus on massive gas and dust regions known as molecular clouds. Within these clouds, the telescope will also examine newly formed stars and the surrounding disks of material from which planets take shape.

Beyond Previous Space Telescopes

Although space telescopes like NASA’s James Webb and the now-retired Spitzer have detected water, carbon dioxide, and carbon monoxide in specific targets, SPHEREx is the first mission designed to conduct a large-scale survey of the galaxy, mapping frozen compounds across vast cosmic landscapes.

Rather than taking 2D images of a target like a star, SPHEREx will gather 3D data along its line of sight. That enables scientists to see the amount of ice present in a molecular cloud and observe how the composition of the ices throughout the cloud changes in different environments.

By making more than 9 million of these line-of-sight observations and creating the largest-ever survey of these materials, the mission will help scientists better understand how these compounds form on dust grains and how different environments can influence their abundance.

Tip of the Iceberg: A Cosmic Puzzle

It makes sense that the composition of planets and stars would reflect the molecular clouds they formed in. However, researchers are still working to confirm the specifics of the planet formation process, and the universe doesn’t always match scientists’ expectations.

For example, a NASA mission launched in 1998, the Submillimeter Wave Astronomy Satellite (SWAS), surveyed the galaxy for water in gas form — including in molecular clouds — but found far less than expected.

“This puzzled us for a while,” said Gary Melnick, a senior astronomer at the Center for Astrophysics | Harvard & Smithsonian and a member of the SPHEREx science team. “We eventually realized that SWAS had detected gaseous water in thin layers near the surface of molecular clouds, suggesting that there might be a lot more water inside the clouds, locked up as ice.”

How Ice Survives in Deep Space

The mission team’s hypothesis also made sense because SWAS detected less oxygen gas (two oxygen atoms bound together) than expected. They concluded that the oxygen atoms were sticking to interstellar dust grains, and were then joined by hydrogen atoms, forming water. Later research confirmed this. What’s more, the clouds shield molecules from cosmic radiation that would otherwise break those compounds apart. As a result, water ice and other materials stored deep in a cloud’s interior are protected.

As starlight passes through a molecular cloud, molecules like water and carbon dioxide block certain wavelengths of light, creating a distinct signature that SPHEREx and other missions like Webb can identify using a technique called absorption spectroscopy.

In addition to providing a more detailed accounting of the abundance of these frozen compounds, SPHEREx will help researchers answer questions including how deep into molecular clouds ice begins to form, how the abundance of water and other ices changes with the density of a molecular cloud, and how that abundance changes once a star forms.

Powerful Partnerships in Space Exploration

As a survey telescope, SPHEREx is designed to study large portions of the sky relatively quickly, and its results can be used in conjunction with data from targeted telescopes like Webb, which observe a significantly smaller area but can see their targets in greater detail.

“If SPHEREx discovers a particularly intriguing location, Webb can study that target with higher spectral resolving power and in wavelengths that SPHEREx cannot detect,” said Melnick. “These two telescopes could form a highly effective partnership.”

More About SPHEREx

SPHEREx (Spectro-Photometer for the History of the Universe, Epoch of Reionization, and Ices Explorer) is a NASA space telescope designed to survey the sky in infrared light, searching for frozen water and other key molecules across the galaxy. Managed by NASA’s Jet Propulsion Laboratory (JPL) in Southern California, SPHEREx is part of the Astrophysics Division within NASA’s Science Mission Directorate.

Built by BAE Systems (formerly Ball Aerospace), the spacecraft will conduct a large-scale spectral survey, mapping interstellar ice, carbon compounds, and the conditions where stars and planets form. A global team of scientists, including researchers from 10 U.S. institutions, two in South Korea, and one in Taiwan, will analyze the data. The mission’s principal investigator is based at Caltech, with a joint JPL appointment.

Data from SPHEREx will be processed and archived at IPAC at Caltech, which also manages JPL for NASA. Once collected, the full dataset will be made publicly available through the NASA/IPAC Infrared Science Archive, providing an unprecedented resource for astronomers worldwide.