The Northwest Africa (NWA) 12774, identified as an angrite meteorite and unearthed in the Sahara Desert, potentially within Mauritania, presents compelling evidence of originating from a now-extinct protoplanet. This discovery offers the most significant indication to date that a substantial planetary entity formed and subsequently disintegrated during the Solar System’s tumultuous nascent period.
This is an artist impression of the protoplanetary disk around HD 107146. Image credit: A. Angelich / NRAO / AUI / NSF.
“The sheer scale of this former world is astonishing to contemplate,” remarked Dr. Aaron Bell from the University of Colorado Boulder, the principal investigator of the research endeavor.
“Our awareness of its existence stems solely from the serendipitous arrival of a few of its fragments on our planet.”
“These extraterrestrial specimens harbor definitive traces of a developmental trajectory for early planets that diverges entirely from what we previously understood.”
Within the scope of their investigation, Dr. Bell and his associates undertook a detailed analysis of a segment of the NWA 12774 angrite meteorite.
“Angrites are recognized as among the most ancient volcanic rocks within our Solar System, having solidified mere millions of years after its inception approximately 4.56 billion years ago,” they articulated.
“Furthermore, they are exceedingly unusual. Among the more than 80,000 meteoritic samples cataloged on Earth, a mere 68 are classified as angrites.”
“What renders angrites particularly enigmatic is their chemical composition. In stark contrast to terrestrial planets such as Earth and Mars, angrites exhibit a pronounced scarcity of silicon dioxide, commonly known as silica, which constitutes a fundamental component of virtually every known rocky planet within the Solar System.”
“Consequently, the scientific consensus previously posited that angrites must invariably originate from an asteroid, a celestial body with a radius not exceeding 200 kilometers (approximately 124 miles).”
The research team’s findings revealed that NWA 12774 contained clinopyroxene, a crystalline mineral frequently encountered in Earth’s crust and mantle.
Specifically, the clinopyroxene within NWA 12774 was remarkably rich in aluminum, serving as a definitive indicator that the rock originated under immense geological pressure deep beneath the surface.
Subsequently, the scientists meticulously recreated the pressure conditions that likely prevailed during the formation of NWA 12774.
The X-ray image of NWA 12774. Image credit: Aaron Bell / CU Boulder.
To their astonishment, the aluminum-rich clinopyroxene necessitated a pressure of at least 17.5 kilobars. For comparative context, the formidable pressure at the ocean floor of the Mariana Trench, Earth’s deepest oceanic abyss, registers only around 1 kilobar.
Such a magnitude of pressure would be entirely absent within a diminutive asteroid.
Conversely, the computational analyses implied that the parent body from which angrites originated must have possessed a radius of at least 1,000 kilometers (approximately 621 miles).
Additional corroborating evidence embedded within the meteorite hinted at an even more remarkable conclusion.
The crystalline structures observed within NWA 12774 still retained their sharp facets and intricate chemical signatures, features that would have been obliterated had they formed deep within a planetary interior.
This observation suggested that the crystals likely coalesced at relatively superficial strata within the parent body, thus mandating an even greater celestial dimension.
Under this theoretical framework, the angrite parent body could have spanned a radius exceeding 1,800 kilometers (approximately 1118 miles), positioning it in terms of size comparable to Earth’s Moon and potentially rivalling a Mars-sized world, which has a radius of 3,300 kilometers (2,050 miles).
“Numerous meteorites remain sequestered in archival collections, awaiting comprehensive scientific scrutiny, implying the probable existence of additional, yet undiscovered, protoplanets,” Dr. Bell conveyed.
“The ultimate fate of this protoplanet remains an unresolved enigma. A compelling hypothesis posits that a cataclysmic event in the early Solar System shattered it, with its subsequent fragments serving as foundational elements for other terrestrial planets, including our own Earth.”
“The elemental constituents that formed the angrite parent body are fundamentally dissimilar from the raw materials that comprise Earth and Mars.”
“This disparity underscores a distinct and separate developmental trajectory in the formation of planets during the primordial epochs of our Solar System,” Dr. Bell emphasized.
The comprehensive research paper received online publication on April 10 in the esteemed journal Earth and Planetary Science Letters.
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Aaron S. Bell et al. 2026. High-pressure clinopyroxene in Northwest Africa 12774 and new geobarometric evidence for a planetary embryo-sized angrite parent body. Earth and Planetary Science Letters 685: 120029; doi: 10.1016/j.epsl.2026.120029
