NWA 12774 Points to Lost 1,200-Mile Protoplanet 4.5 Billion Years Ago

Q: A Mars-sized planet was destroyed long ago. How many other 'ghost worlds' were shattered in our solar system's birth?

There was likely not just one lost world, but many—probably tens, and possibly more than a hundred Moon-to-Mars-sized bodies were destroyed, merged, or scattered during the solar system’s violent infancy. The new evidence comes from meteorite NWA 12774, a 4.5-billion-year-old angrite whose minerals appear to have formed under pressures too high for a small asteroid. Aaron S. Bell and colleagues argue its parent body was at least about 1,200 miles across and perhaps as large as the Moon or even Mars. That points to a previously unknown protoplanet that no longer exists, preserved only in meteorite fragments. This fits the broader picture of early solar system formation. Models of the inner solar system suggest it began with roughly 50 to 100 Moon-to-Mars-sized protoplanets that repeatedly collided and merged over less than 100 million years to produce Mercury, Venus, Earth and Mars. In the asteroid belt region, another 20 to 30 planetary embryos may also have formed, only to be shattered or flung away under Jupiter’s gravitational influence. So the best answer is that NWA 12774 probably records one of many “ghost worlds.” Scientists cannot yet give an exact body count, because most of those worlds were recycled into today’s planets or erased by impacts. But current evidence suggests the early solar system was crowded with large, short-lived protoplanets, and many of them did not survive.

3 articles · Updated · Smithsonian Magazine · Jun 11

Researchers say the Sahara meteorite NWA 12774 likely formed inside a massive early protoplanet, not a small asteroid, based on newly analyzed mineral and pressure evidence.
Clinopyroxene crystals unusually rich in aluminum indicate formation at at least 17.5 kilobars of pressure—far beyond what a small asteroid could generate, according to the team's computer modeling.
That pressure implies a parent body at least 1,200 miles across; sharp-edged crystals suggest the rock formed closer to the surface, meaning the body may have been moon-sized at roughly 2,200 miles or even larger.
NWA 12774 is one of just 68 known angrites among roughly 80,000 meteorites found on Earth, making it a rare record of planetary formation in the solar system's first few million years.
The study, published in Earth and Planetary Science Letters, adds to evidence that some early protoplanets formed rapidly and were later destroyed, with fragments potentially incorporated into Earth and other rocky planets.

Sources

Smithsonian Magazine2d ago

NWA 12774 Meteorite Reveals Evidence of Massive Lost Protoplanet

AOL2d ago

Rare meteorite points to a long-lost planet from our early solar system - AOL

The Watchers16h ago

Rare meteorite points to Moon-sized parent body in early Solar System - The Watchers

7 Sources

A Mars-sized planet was destroyed long ago. How many other 'ghost worlds' were shattered in our solar system's birth?

A lost protoplanet was chemically unlike Earth or Mars. What does this reveal about our solar system's unique origins?

Discovery of NWA 12774: Evidence for a Massive, Lost Protoplanet the Size of the Moon or Mars in the Early Solar System

Overview

In 2019, scientists discovered the meteorite NWA 12774 in the Sahara Desert. This rare angrite, with its pristine green olivine crystals, provided strong evidence for a massive, long-lost protoplanet that once orbited the sun about 4.5 billion years ago. The unique condition of its crystals suggested the parent body was much larger than previously thought, with estimates ranging from 1,000 to 3,300 kilometers in radius. This finding challenged old ideas about angrites and revealed that such meteorites can unlock secrets about the early solar system and its hidden planetary building blocks.

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