The day Earth slipped behind the moon: the Artemis II crew's eclipse

Artemis II astronauts will watch Earth sink and rise behind the moon's curved edge today and ride through a slow solar eclipse unlike anything anyone has seen from home.

From the windows of the Orion spacecraft, the crew will see Earth as a bright, blue orb hanging above a stark gray foreground. Sunlight reflecting off oceans, clouds, and continents will turn our planet into a luminous beacon in the blackness of deep space. As the spacecraft curves around the moon, that beacon will drift lower and finally slide behind the cratered lunar rim in a slow-motion Earthset.

Unlike a sunset on Earth, where the sun drops beneath a distant horizon, this Earthset involves the entire planet. To the astronauts, Earth will seem to glide across the sky and then vanish. In that moment, the place where everyone they know lives will disappear from view, replaced by a silent, airless world.

All of this unfolds during today's close lunar flyby, the centerpiece of NASA's Artemis II mission. This swing around the lunar far side marks the climax of the 10-day spaceflight, when astronauts Reid Wiseman, Christina Koch, Victor Glover, and Jeremy Hansen come closest to the moon's surface, lose contact with Earth for over 40 minutes, and experience the rare combination of Earthset, a drawn-out solar eclipse, and Earthrise in a single sweeping arc.

As Earth goes out of sight, radio contact with mission control will drop for roughly 40 minutes because the moon itself blocks the line of sight back home. Even without that link, the crew will keep working in the Orion spacecraft, dubbed Integrity, using onboard devices to capture images, measurements, and notes. 

"I would love it if the entire world could come together and just be hoping and praying for us to get that acquisition of signal," said Glover, the mission's pilot.

Apollo 8 astronauts captured Earthrise, the first color photograph of Earth taken by a person in lunar orbit, on Dec. 24, 1968. Credit: NASA

In that radio silence, the crew will also experience a unique kind of solar eclipse. On Earth, when the moon passes in front of the sun, the two appear almost the same size in the sky, and people on the ground see the sun's hazy outer atmosphere, called the corona, spread around a dark lunar disk. 

Near the moon, the geometry changes. From the astronauts' perspective, this is still a solar eclipse: The moon slides in front of the sun and blocks its light. The difference is our planet will appear off to the side, rising and setting near the rim, while the shrunken sun slowly disappears behind the much larger lunar surface.

The crew will use protective eyewear similar to the eclipse glasses people wore during the total solar eclipse across North America in April 2024. Those filters will let them safely look toward the sun in the moments before it vanishes and just after it returns.

"It's a little bit different, just based on the sizes of the objects. When we experience an eclipse here on Earth, the sun is about the same size whenever it's eclipsed by the moon," said Trevor Graff, an Artemis science officer, during a NASA broadcast. "The Integrity crew is going to be much closer to the moon at that time, so they're going to see the sun as a small disk [that] disappears."

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Once the sun is concealed, the scene will change again. With direct sunlight blocked, the astronauts will have a rare chance to study the moon without glare. Subtle features in the landscape may stand out more clearly against the dim, scattered light that remains. In that extended twilight, the moon itself becomes the main subject, lit only by reflected light and the faint glow of the distant universe.

"The moon will look about like holding a basketball at arm's reach," said Jacob Bleacher, NASA's chief exploration scientist, "so they'll be able to see a good bit of the moon."

A stuffie designed by an eight-year-old child serves as the zero-gravity indicator in the Orion spacecraft for the Artemis II mission. Credit: NASA / Youtube screenshot

As they round the moon, the planet will reappear as an Earthrise, echoing the famous scene first photographed during Apollo 8: the gray curve of the Moon in the foreground, with a colorful Earth lifting into view above it. Rise, the mission's zero gravity indicator and plush mascot, celebrates that moment and bridges history with NASA's return to lunar space after more than 50 years. The little guy who freely floats through the cabin was designed by a second-grader in California.

If communications return on schedule, people on the ground may see elements of this sequence almost in real-time, sharing the instant when Earth clears the lunar edge and brightens the spacecraft windows. Behind the scenes, a dedicated science evaluation team will begin sorting through the flood of images and measurements, helping mission controllers decide what to prioritize for early analysis.

By the end of this long day, the spacecraft will have begun the journey home for a nailbiting splashdown off the California coast on Friday, April 10.