An ancient formation of bright anorthosite, a rock commonly found on the Moon, stands out among the heavily deformed rocks of southern Madagascar.
A bright, unusual patch of rock in southern Madagascar has a surprising connection to the Moon. Seen from space, the formation stands out against the surrounding dry landscape. Although it may look unusual on Earth, the same type of rock is widespread across the lunar surface.
The rock, called anorthosite, is an igneous material that makes up much of the Moon’s bright, reflective highlands. These light-colored regions are visible to the naked eye when looking at the Moon from Earth.
Anorthosite is not exclusive to the Moon. Large deposits also occur in several regions of Earth, including eastern Canada, Scandinavia, southern India, and Madagascar. In southern Madagascar, one particularly striking deposit forms a roughly circular feature that is easily distinguishable from the surrounding terrain.
NASA Astronaut Photographs Ancient Rock Formation
On August 28, 2026, an astronaut aboard the International Space Station photographed the Saririaky anorthosite massif, a large body of rock exposed at Earth’s surface.
Anorthosite is classified as an intrusive igneous rock, meaning it forms when molten material cools and solidifies beneath Earth’s surface. Because this cooling process takes place underground, the minerals have time to develop into relatively large crystals.
Geological research suggests that the Saririaky formation originated during the late Precambrian, at least 600 million years ago. Today, the exposed rock covers approximately 100 square kilometers (40 square miles).
Although the formation is remarkable on its own, the surrounding landscape tells an equally fascinating story. The neighboring rocks preserve evidence of enormous forces that reshaped the region hundreds of millions of years ago.
Ancient Continental Collisions Reshaped Madagascar
The Saririaky massif lies within what geologists call a ductile shear zone. In these regions, rocks undergo intense deformation as powerful geological forces act on them deep within Earth’s crust.
Under sufficiently high temperatures and pressures, solid rock can gradually bend, stretch, and change its structure rather than simply breaking apart. This process can also transform the minerals and textures within the rock, a phenomenon known as metamorphism.
Studies of the region have identified long, roughly parallel geological features extending from north to south. These patterns record the powerful deformation that affected the rocks surrounding Saririaky.
Scientists believe much of this transformation occurred as ancient landmasses collided during the formation of Gondwana, a vast supercontinent that eventually included parts of present-day Africa, India, Madagascar, Australia, and Antarctica.
As these continental fragments came together, immense pressure and heat reshaped large sections of Earth’s crust.
Some researchers have suggested that a second anorthosite massif, located approximately 60 kilometers (40 miles) north of Saririaky within the same shear zone, was once connected to it.
According to this interpretation, the original rock body was stretched and separated by tectonic forces. The resulting structure is known as boudinage, a geological process in which a relatively strong layer or body of rock is pulled into separate segments as the surrounding material deforms.
If this explanation is correct, the two formations preserve evidence of the tremendous forces involved in assembling one of Earth’s ancient supercontinents.
How Earth’s Moon-Like Rocks Reveal Lunar History
The scientific importance of anorthosite extends far beyond Earth’s geological history. Similar rocks provide an important opportunity to investigate how the Moon formed and evolved.
The Moon’s anorthosite-rich highlands are more than 4 billion years old. Scientists believe these rocks formed early in lunar history, when much of the young Moon was covered by an enormous ocean of molten rock.
As this magma ocean gradually cooled, certain minerals crystallized and accumulated near the surface, helping form the Moon’s early outer crust. The anorthosite produced by this process remains a major component of the bright lunar highlands visible today.
Apollo astronauts returned samples of lunar anorthosite to Earth, giving researchers valuable material for studying the Moon’s distant past. However, the quantity of available lunar rock is limited, making similar geological formations on Earth especially useful for comparison.
One particularly close match occurs in Montana’s Beartooth Mountains, where anorthosite deposits have a composition that closely resembles their lunar counterparts.
By examining these terrestrial rocks, scientists can investigate geological processes associated with the formation and evolution of anorthosite, helping them interpret the much older material found on the Moon.
The Saririaky formation offers another striking example of the geological similarities between Earth and its nearest celestial neighbor. Its bright appearance and dramatic surroundings also reveal how hundreds of millions of years of tectonic activity can transform ancient rock into a distinctive landscape visible from orbit.
About the NASA Astronaut Photograph
Astronaut photograph ISS075-E-85249 was taken on August 28, 2026, by a member of the Expedition 75 crew aboard the International Space Station. The astronaut used a Nikon Z9 digital camera equipped with a 400-millimeter focal-length lens.
The photograph was provided by the ISS Crew Earth Observations Facility and the Earth Science and Remote Sensing Unit at NASA’s Johnson Space Center. It was cropped and adjusted to improve contrast, and lens artifacts were removed.
