The key facts

  • The image was taken on August 28, 2026 from the ISS (Expedition 75); on October 5 NASA selected it as the 'Picture of the Day'.
  • The bright patch is an outcrop of anorthosites; in 1998, under the leadership of Lewis Ashwal, their crystallization age was estimated at ~660 million years (±60 million).
  • Lunar anorthosites are older — over 4 billion years; sample 15415 ('Genesis Rock', Apollo 15, August 1, 1971) is dated to ~4 billion years.

Image from the ISS

NASA has published an image of the Saribara massif in Madagascar, where a large light rounded field is visible among the brown rocks — an outcropping anorthosite. The photo was taken on August 28, 2026 by a member of Expedition 75 of the International Space Station, and on October 5 NASA selected it as the 'Picture of the Day'.

What anorthosites are

Anorthosite is an igneous rock that forms as melt cools underground and retains large mineral crystals. The same rocks exist on the Moon: they make up the light 'highland' areas visible from Earth even without a telescope. According to the early lunar magma ocean model, light plagioclase crystals floated to the surface of the melt and formed the outer crust, while heavier minerals sank deeper.

The massif has long been studied

Saribara is not a new discovery: geologists studied it long before this image. In 1998, a team led by Lewis Ashwal estimated the crystallization age of the anorthosites of Saribara and the neighboring Ankafotra massif at about 660 million years with an uncertainty of 60 million years. The dating used the ratio of samarium and neodymium isotopes in the rocks and individual minerals. According to the analysis, the original melt that produced these rocks came from the Earth's mantle.

Metamorphism and Gondwana

Later, the rocks were strongly altered under high temperatures and pressure. Researchers linked this process to the collision of the eastern and western parts of Gondwana approximately 630–550 million years ago; this supercontinent included the territories of present-day Africa, India, Madagascar, Australia and Antarctica. Traces of ancient deformation are visible in the elongated rock layers around the massif: in a 2000 study, scientists identified two stages of change in this area — approximately 590–530 and 530–500 million years ago.

Comparison with the Moon

Lunar anorthosites are considerably older than the Madagascar ones — their age exceeds four billion years. Apollo program crew members brought such ancient samples to Earth. One of them is sample No. 15415, known as the 'Genesis Rock', found by Apollo 15 astronauts on August 1, 1971; its age is estimated at about four billion years.