Scientists have identified a rare meteorite, NWA 12774, discovered in the Sahara Desert, which serves as a relic of a protoplanet that vanished 4.5 billion years ago. According to research published in the journal Earth and Planetary Science Letters, the rock originated from a body with a radius of at least 1,000 kilometers, comparable in scale to a dwarf planet or the Moon.
What is NWA 12774 and why is it rare?
NWA 12774 is classified as an angrite, an exceptionally rare category of space rock. Out of approximately 80,000 cataloged meteorites, only about 68 belong to this specific family. Unlike common meteorites, which are often simple mixtures of metal and dust, angrites are volcanic rocks.
Their composition indicates they were once molten magma, suggesting they formed on bodies that underwent complex geological evolution. This specific sample, found in 2019, weighed half a kilogram and contains distinct small green crystals.
The name “NWA” in meteorite classification stands for “Northwest Africa,” the region where these samples are frequently recovered by local traders and subsequently analyzed by the scientific community.
How did scientists determine the size of the original protoplanet?
Researchers used a geobarometer to measure the pressure under which the meteorite’s clinopyroxene crystals formed. The analysis revealed these minerals crystallized under pressures reaching 17.6 kilobars.
To put that in perspective, one kilobar is roughly the pressure found at the bottom of the Mariana Trench. Because these crystals formed under nearly 18 times that pressure, they could not have originated from a small asteroid. The data suggests the parent body had a radius between 1,000 and 1,800 kilometers, effectively classifying it as a lost protoplanet from the early solar system.
The geological significance of aluminum-rich crystals
The interior of NWA 12774 contains clinopyroxene crystals that are unusually rich in aluminum. These minerals act as geological time capsules, preserving the physical conditions of the magma from which they cooled. By studying these well-preserved structures, geologists can reconstruct the internal environment of a planetary body that existed billions of years ago. This provides a rare window into the formative years of our solar system, long before the current planetary landscape stabilized.
When reading studies on planetary science, look for mentions of “geobarometry.” It is the primary tool scientists use to interpret the depth and size of a meteorite’s parent body based on mineral pressure markers.
Frequently Asked Questions
- What is an angrite?
An angrite is a rare type of volcanic meteorite that originated from a body capable of producing molten magma. - How large was the protoplanet that produced NWA 12774?
Based on crystal pressure analysis, the parent body had a radius of at least 1,000 kilometers, potentially exceeding 1,800 kilometers. - Where was this meteorite found?
It was discovered in the Sahara Desert in 2019 and reached researchers through a local trader.
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