From an astronaut’s perspective looking back at Earth, a patch of bright rock in arid southern Madagascar may appear out of place.
But it wouldn’t on the Moon.
The igneous rock anorthosite, common on the Moon’s surface, is visible from Earth with the unaided eye as the light-colored, highly reflective areas known as thelunar highlands.
Anorthosite also crops up across Earth’s surface, from eastern Canada and Scandinavia to southern India and Madagascar, where it forms a striking round feature.
An astronaut aboard the International Space Station captured this photo of the Saririaky anorthositemassifon August 28, 2026.
Anorthosite is an intrusive igneous rock—formed from magma that cools beneath the surface—made up of large mineral crystals.
Scientists thinkthe massif seen here formed in the late Precambrian, at least 600 million years ago.
Its present-day outcrop covers about 100 square kilometers.
The rocks surrounding the anorthosite reveal a dynamic chapter in the area’s geologic past.
Researchers havedeterminedthat the Saririaky massif lies within aductile shear zone, where high pressures and temperaturesmetamorphosedand reshaped the rock, imparting north-south-trending linear patterns.
Geologists think this deformation occurred when pieces of what are now Africa, India, Madagascar, Australia, and Antarctica were colliding to form the supercontinent Gondwana.
Some scientists have posited thatanother anorthosite massifin the shear zone, located about 60 kilometers to the north, was pulled apart from the Saririaky massif in the process, creating a large-scaleboudinagestructure.
Anorthosites on Earth have proven useful for scientists studying the Moon’s past.
Lunar anorthositesare more than 4 billion years old, having crystallized from the Moon’smagma oceanto form its outer crust.
Researchers have analyzed samples brought back to Earth by Apollo astronauts, but because that material is limited, they also look to analogous terrestrial rocks.
The anorthosites in the Beartooth Mountains of Montanamatch the compositionof the lunar version particularly well.
Astronaut photographISS075-E-85249was acquired on August 28, 2026, with a Nikon Z9 digital camera using a focal length of 400 millimeters.
It is provided by the ISS Crew Earth Observations Facility and the Earth Science and Remote Sensing Unit at NASA Johnson Space Center.
The image was taken by a member of the Expedition 75 crew.
The image has been cropped and enhanced to improve contrast, and lens artifacts have been removed.
TheInternational Space Station Programsupports the laboratory as part of theISS National Labto help astronauts take pictures of Earth that will be of the greatest value to scientists and the public, and to make those images freely available on the internet.
Additional images taken by astronauts and cosmonauts can be viewed at the NASA/JSCGateway to Astronaut Photography of Earth.
Story by Lindsey Doermann.
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Ashwal, L.D.,et al.Geology, petrology and isotope geochemistry of massif-type anorthosites from southwest Madagascar. Contributions to Mineralogy and Petrology, 133, 389-401.
Earth & Solar SystemImpact Shock State of the Lunar Highlands. Accessed October 2, 2026.
Martelat, J.,et al.Strain pattern and late Precambrian deformation history in southern Madagascar. Precambrian Research, 102, 1–2.
NASA Earth ObservatoryMontana’s Moon-Like Rocks. Accessed October 2, 2026.
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