Scientists talked about the similarity of ancient rocks of Madagascar with lunar rocks
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- Scientists talked about the similarity of ancient rocks of Madagascar with lunar rocks
In the south of Madagascar, an astronaut of the International Space Station photographed a light rock massif with an area of about 100 square kilometers. It is composed of anorthosite, a rock widely distributed in the lunar highlands, which are visible from Earth with the naked eye. The age of the land mass is at least 600 million years old, and the surrounding rocks have preserved traces of the collision of ancient continents. Why rocks similar to lunar rocks are found on Earth, and how they help to explore the past of two celestial bodies — in the Izvestia material.
A bright spot among the reddish rocks
From the height of the orbit, the Saririaki massif stands out against the arid landscape of southern Madagascar. The rounded, light-colored area is surrounded by darker and reddish rocks, which have elongated bands from north to south. One image shows both an ancient magmatic formation and traces of forces that later changed the surrounding Earth's crust.
The photo was taken on August 28, 2026 from the ISS. A member of the Expedition 75 crew used a Nikon Z9 camera with a lens set to a focal length of 400 mm. Before publishing, the image was cropped, its contrast was increased, and optical artifacts were removed.
The unusual appearance of the massif is related to the composition of the rock. Anorthosite belongs to igneous rocks: it is formed during the cooling and solidification of molten matter. On Earth, such arrays form deep in the crust, where slow cooling gives minerals time to grow into large crystals.
Saririaki himself has long been known to researchers. Therefore, the NASA image does not show a newly discovered object, but a geological formation that has already been studied locally and described in scientific papers. The view from space allows you to estimate its size and position among neighboring rocks.
Why does this breed resemble the Moon
If you look at the moon on a clear night, you can see dark areas and lighter areas on its disk. The latter are called lunar highlands. A significant part of their rocks are anorthosites, so the name of the land mass in the NASA publication has a very specific geological explanation.
Anorthosite is rich in plagioclase, a mineral from the feldspar group. On the moon, its accumulation played an important role in the formation of the early crust. Light highlands reflect sunlight more strongly than dark areas and are visible even without a telescope.
Anorthosite is also found in other parts of our planet. Large formations are known in eastern Canada, Scandinavia and southern India. The Madagascar massif looks particularly striking from orbit due to the contrast with the surrounding landscape.
The stone is older than the usual world map
The history of Saririaki began long before the appearance of the modern outlines of the continents. NASA indicates that the massif was formed in the late Precambrian, at least 600 million years ago. A more detailed assessment was presented by the authors of a study in Contributions to Mineralogy and Petrology, published in 1998. Based on the results of isotope analysis, they estimated the crystallization age of the Saririaki anorthosites and the neighboring Ankafotia massif at 660 million years with an error of about 60 million years.
In the same paper, scientists described coarse-grained rocks in which feldspar crystals usually reach several centimeters. Subsequent transformations have changed the original structure of the minerals, so the history of the massif includes both its formation from magma and later exposure to high temperatures and pressure.
The authors attributed the intense metamorphism of the region to events around 630-550 million years ago. This period coincides with the collision and unification of the eastern and western parts of Gondwana. Thus, the initial formation of the rock and its subsequent deformation belong to different stages of the geological history.
How the collision of continents changes solid rocks
Today Madagascar is an island in the Indian Ocean. However, the rocks of its southern part have preserved evidence of an era when ancient continental blocks converged and formed Gondwana. This supercontinent includes territories that now belong to Africa, India, Madagascar, Australia and Antarctica.
When such blocks collide, the earth's crust experiences enormous loads. In depth, at high temperatures and pressures, hard rocks can gradually deform: bend, stretch, and change their internal structure. They don't have to melt completely to do this.
Saririaki is located in the zone of plastic shear, an area where sections of the crust moved relative to each other, and rocks were subjected to severe deformation. The north-south elongated structures around the light massif reflect this story.
High temperature and pressure also cause metamorphism. Minerals recrystallize, and their combinations and arrangement change. Therefore, the rocks surrounding Saririaki allow us to explore the conditions under which the ancient supercontinent was assembled.
One array could turn into two
About 60 km north of Saririaki is another anorthosite massif. According to one interpretation provided by NASA, both formations once formed a single body, which was later stretched and separated by tectonic forces.
Geologists call this division a budinage. It occurs when a relatively strong rock is located inside a material that deforms more easily. When stretched, a solid body can split into separate segments, and the surrounding rock continues to change shape.
To understand the process, you can imagine a dense layer inside a more malleable mass. If the entire system is slowly stretched, its parts will react differently: the layer will begin to narrow in some places and may break into fragments.
The hypothesis of the connection between the two Madagascar massifs shows how significant the transformations of the crust could be during the formation of Gondwana. However, the image from the ISS itself does not prove that they formed a single whole: such a reconstruction requires studying the composition of the rocks and their geological position.
What does anorthosite tell you about the new Moon
Lunar anorthosites have a different story and a much older age — more than four billion years. According to the model described by the Institute of the Moon and Planets, the surface of the young moon was covered with an ocean of magma.
As the melt cooled, crystals formed in it. Denser minerals, including olivine and pyroxene, sank down. Less dense plagioclase rose to the surface and accumulated there, participating in the formation of the anorthosite crust.
The astronauts of the Apollo program delivered samples of lunar anorthosites to Earth. They have become an important source of information about the ancient crust, but the amount of available material is limited. Therefore, scientists are also studying Earth rocks, which allow us to compare the composition of minerals and the processes of their formation.
However, not every anorthosite is equally well suited for such a comparison. The general name of the breed is not enough: the chemical composition and the changes it has experienced over its history are important.
Earth rocks help to prepare lunar equipment
One of the most suitable analogues is located in the Stillwater complex in the Beartooth Mountains of the American state of Montana. According to NASA, the local rocks contain calcium-rich plagioclase, similar in composition to the lunar one.
"The Stillwater complex can tell us about the formation of the anorthosite itself," explained Sarah Dietrich, a specialist in lunar geology at NASA's Johnson Space Center.
Such analogues also have practical applications. Stillwater material is used to make simulators of lunar regolith, a loose substance covering the surface of the satellite. They are needed for testing equipment, spacesuits and other systems that will have to come into contact with the lunar soil.
At the same time, terrestrial rocks do not reproduce lunar matter in all its details. They were affected by water, temperature and pressure in the conditions of our planet. Researchers have to take these differences into account when preparing simulators.
Переведено сервисом «Яндекс Переводчик»
