Олон улсын сансрын станцын сансрын нисгэгчид Мадагаскарын өмнөд хэсэгт орших Сарны хөрсний найрлагатай төстэй анортозит чулуулгийн том тогтцыг илрүүлэн гэрэл зурагт буулгасан байна.
Мадагаскарын өмнөд нутгийн улбар шар өнгийн чулуулгийн дунд тод ялгарч харагдах “Саририаки” (Saririaky) хэмээх энэхүү цагаан өнгийн тогтцыг 2026 оны наймдугаар сарын 28-нд сансрын станцаас авсан зурагт анх бүртгэжээ. Ойролцоогоор 100 хавтгай дөрвөлжин км талбайг эзлэх энэхүү чулуулаг нь дор хаяж 600 сая жилийн өмнө үүссэн бөгөөд Сарны өндөрлөг хэсгийн цайвар өнгийн бүрхүүлийг бүрдүүлэгч анортозит эрдсээс бүрддэг байна.
Анортозит нь магмын удаан хөрөлтийн үр дүнд үүсдэг магмын чулуулаг бөгөөд ихэвчлэн плагиоклаз хэмээх хөнгөн цагаан, кальциар баялаг эрдсээс бүрддэг. Эрдэмтдийн таамаглалаар, Сарны үүсэлтийн эхэн үед хайлмал байсан гадаргуу хөрөх явцад энэхүү нягт багатай эрдэс нь дээш хөвж, Сарны царцдасыг бүрдүүлсэн гэж үздэг. Дэлхий дээрх анортозитын тогтоц нь өөр замаар үүсдэг ч эрдэмтэд үүнийг Сарны чулуулгийн найрлагыг судлах жишиг материал болгон ашигладаг.
Геологийн судалгаагаар Саририаки нь 660 сая жилийн өмнө үүссэн бөгөөд хожим нь Гондвана супертив тив бүрэлдэх үеийн хүчтэй даралт, халууны нөлөөнд автсан болохыг тогтоожээ. Энэхүү үйл явц нь чулуулгийн давхаргыг сунган татаж, улмаар “будинаж” хэмээх бүтэц үүсгэн, чулуулгийн биетийг хэсэгчлэн тасалсан байж болзошгүй гэж геологичид тайлбарладаг.
Анортозит нь сансрын шинжлэх ухааны түүхэнд онцгой байр суурь эзэлдэг бөгөөд 1971 онд Аполло 15 номлолын үеэр сансрын нисгэгчид Сарнаас ийм төрлийн “Генезис чулуу” хэмээх дээжийг авчирч байсан түүхтэй. Өнөөдөр судлаачид дэлхий дээрх ижил төстэй бүтэцтэй чулуулгуудыг судлах замаар Сарны анхны царцдасын үүсэл хөгжлийг илүү гүнзгий ойлгохыг зорьж байна.
Дэлгэрэнгүйг эх сурвалжаас харах
↓Эх сурвалжийг нээх ↓
From 400 kilometers up, most of southern Madagascar looks like rust. Orange rock runs in long, parallel stripes from north to south, and dry riverbeds branch across it like cracks in old paint.
Then, in the middle of all that orange, there is a pale blot. It is roughly round, nearly white, and it does not seem to belong to the landscape around it. If it looks like a piece of the Moon dropped onto Africa’s largest island, that is not far from the truth.
The blot is the Saririaky anorthosite massif, a body of rock that covers about 100 square kilometers (40 square miles) of southern Madagascar and formed at least 600 million years ago. An astronaut on the International Space Station photographed it on Aug. 28, 2026, and NASA published the image on Oct. 5. The rock it is made of is the same kind that forms the bright highlands of the Moon.
A White Blot in a Land of Orange Stripes
The photo was taken by a member of the Expedition 75 crew with a Nikon Z9 camera and a 400-millimeter lens, the kind of long telephoto a wildlife photographer might use. Specialists at NASA’s Johnson Space Center cropped it, adjusted the contrast and removed lens artifacts before release.
The stripes around the massif are not decoration. Saririaky sits inside a ductile shear zone, a belt where rock was buried deep enough, and heated enough, to bend and smear instead of snapping. Over millions of years, that slow deformation stretched the surrounding rock into the north-south grain that shows up so clearly from orbit.
The massif held its shape. It stands out as a rounded, light-colored mass while the rock around it was drawn into lines, and branching riverbeds now cut across both. The whole scene lies in the arid south of the island.
The Rock That Floated to the Top of the Moon
Saririaky is made of anorthosite, an igneous rock that forms when magma cools slowly underground and grows large crystals. Most of those crystals are plagioclase, a pale feldspar mineral, which is what gives the rock its light color.
On Earth, anorthosite is much less common, though large bodies of it turn up in places such as eastern Canada, Scandinavia, southern India and Madagascar. On the Moon, it is the crust. Look up at a full moon and the bright, pale regions are the lunar highlands, built largely of anorthosite more than 4 billion years old.
The leading explanation for that lunar crust starts with a magma ocean. Soon after the Moon formed, its outer layers were molten. As that ocean cooled, plagioclase crystallized, and because it is less dense than the surrounding liquid, it floated to the top and piled up into a light-colored shell.
Earth’s anorthosites formed in a different way, from magma that cooled underground. But because the Apollo missions brought home a limited supply of lunar samples, researchers study rocks like Saririaky as stand-ins. Some match remarkably well. The anorthosites in Montana’s Beartooth Mountains come especially close to the composition of lunar anorthosite.
Squeezed and Pulled Apart as Gondwana Formed
Saririaky’s age comes from the chemistry of its minerals. A 1998 study of southwest Madagascar’s anorthosites put the crystallization of the magma at about 660 million years ago, give or take 60 million years, using samarium-neodymium dating. Soon after, the rock was caught in an episode of intense heat and pressure that lasted from about 630 million to 550 million years ago.
That episode had a cause on a continental scale. It coincided with the assembly of Gondwana, the supercontinent formed when pieces of what are now Africa, India, Madagascar, Australia and Antarctica collided.
The collision may also have torn Saririaky in two. Some geologists think another anorthosite massif, about 60 kilometers (40 miles) to the north, was once part of the same body and was dragged away along the shear zone. Geologists call this kind of structure boudinage, from the French word for sausage: a stiff layer stretched inside softer rock until it pinches apart into separate links.
Learning the Moon’s Rock on Earth
Anorthosite has a special place in the history of space exploration. By the early 1970s, fragments of it had turned up in lunar samples, but no astronaut had brought back a whole piece of the Moon’s original crust. Finding one became a priority.
Before Apollo 15, commander David Scott and lunar module pilot James Irwin made field trips across the United States with Caltech geologist Lee Silver. On one of those trips, in the San Gabriel Mountains of Southern California, Silver taught them how to recognize anorthosite on sight.
They landed at Hadley-Apennine on July 30, 1971. Two days later, at about 10 a.m. on Sunday, Aug. 1, Scott spotted a fist-sized white rock on the slope of Hadley Delta. “Guess what we just found!” he radioed. “I think we found what we came for.” It was anorthosite, later nicknamed the Genesis Rock, and it remains one of the oldest pieces of the Moon’s crust ever brought to Earth.
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