In preparing to visit the Moon\u2019s surface, soon-to-be lunar explorers in NASA\u2019s 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\u2019s remote Katmai National Park<\/a> for simulations of field geology in Moon-like environments.<\/p>\n In one exercise, which they called \u201cplaying the Moon game,\u201d pairs of astronauts were placed at unfamiliar field sites and asked to pretend as if they were on the Moon. By the account<\/a> of William Phinney, Apollo\u2019s science training coordinator, they were tasked with collecting representative geologic samples and practicing how to communicate their observations to scientists.<\/p>\n 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\u2014the largest volcanic event on Earth in the 20th century.<\/p>\n The\u00a0images\u00a0above,\u00a0acquired\u00a0on\u00a0September 29, 2025,\u00a0with\u00a0the\u00a0OLI<\/a>\u202f(Operational Land Imager) on\u202fLandsat 9<\/a>, show the\u00a0massive\u00a0ash\u00a0flow\u00a0deposited by\u00a0Novarupta.\u00a0The layer measures up to 660 feet (200 meters) thick and was emplaced at a searing 1,380 degrees Fahrenheit (750 degrees Celsius).\u00a0<\/p>\n The Valley of Ten Thousand Smokes, shown in the 1917 photo below, is so named because of the abundance of fumaroles<\/a>\u2014gas and steam-emitting vents\u2014that filled the valley for a decade after the eruption. A few hundred persisted more than 10 years, with some lasting until the 1990s.<\/p>\n Scientists initially suspected that\u00a0the\u00a0monster eruption<\/a>\u00a0occurred at\u00a0Mount Katmai,\u00a0a neighboring volcano with a large caldera located 6 miles (10 kilometers) east of Novarupta\u2019s dome. However, they later determined that the eruption actually occurred at Novarupta\u2014whose name means \u201cnew eruption\u201d\u2014after stealing magma from beneath Katmai. As the magma chamber emptied, Katmai collapsed<\/a>, forming the 2.5-mile-wide (4-kilometer-wide) caldera present today.<\/p>\n The volcanic landscape in the Valley of Ten Thousand Smokes is far fresher than the ancient lava flows<\/a> that formed the Moon\u2019s volcanic features. But for the Apollo astronauts, it offered an \u201cexcellent opportunity to view volcanic materials and landforms in nearly pristine condition,\u201d Phinney wrote. They studied evidence of fumaroles and examined vertical sections of the deposits where streams had eroded deep gorges.<\/p>\n 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<\/a> (GIFT) trekked to the Valley of Ten Thousand Smokes to study its icy volcanic landscape<\/a>. Like the valley, Mars contains glaciers and ice sheets layered with dust and ash, a dynamic and difficult-to-interpret environment.<\/p>\n Advancing lunar science, the GIFT team also collected samples from rock formations comparable to the Moon\u2019s Gruithuisen Domes<\/a>. 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.<\/p>\n NASA Earth Observatory images by Lauren Dauphin, using Landsat data from the\u00a0U.S. Geological Survey.<\/a>\u00a0Photos\u00a0from National Geographic Society\u00a0Katmai expeditions photographs<\/a>, Archives and Special Collections, Consortium Library, University of Alaska Anchorage, and from the U.S. Geological Survey\u00a0Volcano Hazards Program<\/a>.\u00a0Story\u00a0by Lindsey Doermann.\u00a0<\/em><\/p>\n![\"A](\"https:\/\/assets.science.nasa.gov\/dynamicimage\/assets\/science\/esd\/eo\/images\/iotd\/2026\/playing-the-moon-game-\/tenthousandsmokes_oli2_20250929_lrg.jpg?w=3272&h=2181&fit=clip&crop=faces%2Cfocalpoint\")
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