Image of the Day for June 24, 2026

Apollo astronauts previewed their roles as lunar field geologists in Alaska’s Valley of Ten Thousand Smokes.

Jun 24, 2026

In preparing to visit the Moon’s surface, soon-to-be lunar explorers in NASA’s Apollo program first ventured into a variety of unfamiliar landscapes on Earth. A couple of these trips, in the summers of 1965 and 1966, took astronauts to Alaska’s remote Katmai National Park for simulations of field geology in Moon-like environments.

In one exercise, which they called “playing the Moon game,” pairs of astronauts were placed at unfamiliar field sites and asked to pretend as if they were on the Moon. By the account of William Phinney, Apollo’s science training coordinator, they were tasked with collecting representative geologic samples and practicing how to communicate their observations to scientists.

The Alaskan setting for the Moon game was an unusual volcanic landscape called the Valley of Ten Thousand Smokes. The valley is full of debris deposited by the 1912 eruption of Novarupta—the largest volcanic event on Earth in the 20th century.

The images above, acquired on September 29, 2025, with the OLI (Operational Land Imager) on Landsat 9, show the massive ash flow deposited by Novarupta. The layer measures up to 660 feet (200 meters) thick and was emplaced at a searing 1,380 degrees Fahrenheit (750 degrees Celsius). 

The Valley of Ten Thousand Smokes, shown in the 1917 photo below, is so named because of the abundance of fumaroles—gas and steam-emitting vents—that filled the valley for a decade after the eruption. A few hundred persisted more than 10 years, with some lasting until the 1990s.

Scientists initially suspected that the monster eruption occurred at Mount Katmai, a neighboring volcano with a large caldera located 6 miles (10 kilometers) east of Novarupta’s dome. However, they later determined that the eruption actually occurred at Novarupta—whose name means “new eruption”—after stealing magma from beneath Katmai. As the magma chamber emptied, Katmai collapsed, forming the 2.5-mile-wide (4-kilometer-wide) caldera present today.

The volcanic landscape in the Valley of Ten Thousand Smokes is far fresher than the ancient lava flows that formed the Moon’s volcanic features. But for the Apollo astronauts, it offered an “excellent opportunity to view volcanic materials and landforms in nearly pristine condition,” Phinney wrote. They studied evidence of fumaroles and examined vertical sections of the deposits where streams had eroded deep gorges.

Researchers continue to visit this Alaskan wilderness in search of clues that could help decipher the geology of the Moon and Mars. In 2024, the Goddard Instrument Field Team (GIFT) trekked to the Valley of Ten Thousand Smokes to study its icy volcanic landscape. Like the valley, Mars contains glaciers and ice sheets layered with dust and ash, a dynamic and difficult-to-interpret environment.

Advancing lunar science, the GIFT team also collected samples from rock formations comparable to the Moon’s Gruithuisen Domes. These mysterious features are made of hardened lava with a different composition than the surrounding rock. With more to learn about our nearest celestial neighbor, the spirit of the Moon game lives on in the 21st century.

NASA Earth Observatory images by Lauren Dauphin, using Landsat data from the U.S. Geological Survey. Photos from National Geographic Society Katmai expeditions photographs, Archives and Special Collections, Consortium Library, University of Alaska Anchorage, and from the U.S. Geological Survey Volcano Hazards Program. Story by Lindsey Doermann. 

• NASA Lunar Volcanism. Accessed June 23, 2026. 
• NASA (2024, August 24) Into The Field With NASA: Valley Of Ten Thousand Smokes. Accessed June 23, 2026. 
• NASA (2015, November) Science Training History of the Apollo Astronauts. Accessed June 23, 2026. 
• NASA Earth Observatory (2024, August 22) Under the Ash: Glacier Science at a Volcano. Accessed June 23, 2026. 
• NASA Earth Observatory (2016, May 14) Katmai National Park, Alaska. Accessed June 23, 2026. 
• NASA Earth Observatory (2012, June 9) Remembering a Monster Eruption. June 23, 2026.
• National Park Service (2023, April 18) Fumaroles. Accessed June 23, 2026. 
• National Park Service (2021, August 24) Following in the Footsteps of Astronauts. Accessed June 23, 2026.