Macha
Key facts
- Country
- Russia
- Diameter
- 300 m
- Age
- probably less than about 7,300 years
- Location
- 60.10° N, 117.58° E
A small group of shallow, round depressions in the forested lowlands of Yakutia in eastern Siberia, the largest about 300 m across, hard to pick out among the trees and permafrost lakes.
Macha is a field of small impact craters in the Sakha Republic, also known as Yakutia, in eastern Siberia. It lies in a landscape of taiga forest and permafrost, far from cities and roads. Few people have ever seen it, but it is one of a small number of known crater fields formed in the last few thousand years.
The impact. Macha consists of five craters, the largest about 300 m across and the smallest a few tens of metres. They are thought to have formed within the last 7,300 years or so, when a meteorite broke apart in the atmosphere and its fragments struck the ground close together. They are now shallow, partly filled and covered with vegetation.
What makes a crater field. When a meteorite enters the atmosphere, it is slowed and squeezed by the air in front of it. If the pressure becomes greater than the meteorite's strength, it breaks into pieces, which spread apart as they fall. If the pieces are large enough to reach the ground at high speed, each makes its own crater, creating a crater field. Macha, Henbury in Australia, Kaali in Estonia, Wabar in Saudi Arabia, Morasko in Poland and Sikhote-Alin in Russia are all examples. The size and arrangement of the craters can tell scientists how the meteorite broke up and how it was travelling.
Evidence of impact. Macha's craters were recognised as impact features by Russian scientists, and the site is included in international lists of confirmed impact structures. Because the region is so remote, it has been studied much less than crater fields such as Henbury or Kaali, and many details, including its exact age and the type of meteorite that made it, are still poorly known. Scientists usually treat such sites with caution, and new fieldwork could refine what we know.
Craters in permafrost. Yakutia is a land of permafrost, ground that stays frozen all year round, and its surface is dotted with countless round lakes and hollows formed when ground ice melts. Picking out impact craters in such a landscape is difficult, because many natural features look similar from the air. Only careful fieldwork, looking for shocked rocks and meteorite material, can tell an impact crater apart from a thaw lake.
Why it matters. Macha adds to our picture of how often small impacts happen. Crater fields a few thousand years old suggest that the Earth is struck every so often by meteorites large enough to make craters a few hundred metres across. Such impacts would be devastating locally but have no global effect.
Visiting. Macha is extremely remote and is visited only by scientific expeditions.
Did you know?
Macha is a field of five craters made by fragments of a single meteorite.
It lies in Siberian permafrost, where many natural round lakes make craters hard to spot.
The craters probably formed within the last 7,300 years or so.