Sahara Meteorite Reveals Evidence of a Vanished Planet

A rare meteorite discovered in the Sahara Desert is providing a glimpse into a vanished world, suggesting the existence of a massive protoplanet that disappeared billions of years ago.

Key Findings

• Meteorite NWA 12774, an angrite found in the Sahara, contains minerals that indicate it formed under extreme pressure.
• Researchers identified clinopyroxene rich in aluminum, requiring pressures of at least 17.5 kilobars to form.
• The findings suggest the rock originated from a body as large as the Moon or Mars, rather than a modest asteroid.
• The parent body likely existed during the early Solar System’s formation and was subsequently destroyed.

Evidence of a Lost Protoplanet

Scientists at the University of Colorado Boulder have analyzed a sample of the meteorite known as NWA 12774, which was most likely recovered in Mauritania. The rock belongs to a group called angrites, which are among the oldest volcanic rocks in the Solar System, forming just a few million years after the system’s birth approximately 4.56 billion years ago.

While angrites are highly prized by planetologists for their age, they are exceptionally rare. Out of more than 80,000 meteorites known to exist on Earth, only 68 are classified as angrites.

The Role of High-Pressure Minerals

The determination that NWA 12774 came from a large planetary body rests on the analysis of clinopyroxene, a mineral also found in the Earth’s crust and mantle. In this specific sample, the clinopyroxene is unusually rich in aluminum, a chemical signature that occurs only under intense pressure deep below a celestial body’s surface.

Calculations indicate that a pressure of at least 17.5 kilobars is necessary for this type of mineral to form. To put this in perspective, the pressure at the bottom of the Mariana Trench—the deepest point in Earth’s oceans—is only about 1 kilobar. Because such extreme pressure cannot be generated within a small asteroid, researchers concluded the meteorite must have originated from a much larger mass.

Shifting Scientific Perspectives

The discovery challenges previous assumptions about the origin of angrites. Because these rocks contain very little silicon dioxide (silica)—the primary component of Earth-like planets—scientists previously believed they originated exclusively from asteroids with a radius of less than 200 kilometers.

The data from NWA 12774 suggests instead that these rocks may be debris from a large embryo planet. This vanished body, which may have reached the size of the Moon or Mars, likely existed during the early stages of the Solar System before being destroyed, potentially in a massive collision.