Harvard Scientists to Help Lead NASA’s New SPHEREx Mission

Scientists at the Harvard-Smithsonian Center for Astrophysics are leading a major part of NASA’s new SPHEREx mission to study how water and other molecules form in space and may reach planets like Earth.

The SPHEREx mission — short for Spectro-Photometer for the History of the Universe, Epoch of Reionization, and Ices Explorer — was launched on March 11. The two-year mission will explore the origins of the universe by providing a full spectral survey of the sky.

Harvard astrophysicist Gary J. Melnick said the mission was developed around three themes: cosmology and the early universe, the origin and evolution of galaxies, and the origin of water and other key biological ingredients in planetary systems.

Melnick and three other Center scientists are leading the third aspect of the mission — known as the Interstellar Ices Investigation — that focuses on detecting frozen water in the Milky Way and nearby galaxies.

The team is collecting data on starlight that passes through dust clouds — which is absorbed at specific wavelengths by various ice samples — to measure how much light is absorbed by frozen molecules like water, carbon dioxide, and carbon monoxide.

Each type of ice “has a very specific wavelength at which it absorbs background light,” Melnick said. “The strength of the absorption is proportional to the amount of ice in that species along that line of sight.”

The ice samples will be scanned from more than 10 million lines of sight in the sky. These lines of sight cover the Milky Way of Magellanic Clouds, two bordering dwarf galaxies. In total, NASA will collect data on over 450 million galaxies.

SPHEREx is currently at the end of its in-orbit testing phase — known as the ‘orbit checkout period’ — and full scientific operations are expected to begin later this month.

So far, everything is on track.

SPHEREx will soon test whether there is a reservoir of frozen water in dust-laden molecular clouds — a step that researchers said was critical to the mission.

“It is within these molecular clouds that new stars and planets form,” Melnick said, “It’s in the denser regions of these clouds where gravity takes over and pulls in not just the gas, but also these dust grains with ice on their surface.”

During the 25-month mission, the Center will “obtain spectra toward every position on the celestial sphere” every six months using infrared light, according to Melnick.

“SPHEREx will help to provide a global census — at least in the Milky Way — of the quantity and distribution of these essential ingredients for life,” he said. The resulting scale of information will not only be global, but connected to millions of other solar systems’ acquisition of water.

The mission will raise and attempt to answer questions about Earth’s origins, its formation and development into a habitable planet, and whether a similar phenomenon has occurred elsewhere in the universe.

Joseph L. Hora, another one of the Center’s lead researchers working on SPHEREx, said while the water on Earth likely originated from outer space, it is “a mystery of exactly how it got here.”

“How the Earth formed, how it developed into a habitable place where there’s water and oxygen to breathe and life can exist as we know it — we’re interested in our origins,” Hora said. “And then we are interested in, has this happened in other places in the universe?”

Melnick said that understanding the amount of frozen water in space and its role in the formation of new stars and their orbiting planets is “an essential piece of the puzzle” in going from “the material that is available in space — we know is available in space — to habitable and possibly inhabited planets around other stars.”

“NASA has had a mantra for decades now of ‘follow the water,’” he added. Now, Harvard’s role in this mission is to do just that.

—Staff writer Ella F. Niederhelman can be reached at ella.niederhelman@thecrimson.com. Follow her on X @eniederhelman.

— Staff writer David D. Dickson can be reached at david.dickson@thecrimson.com.