Photo: NASA/JPL-Caltech
A new study suggests that a long-lost planet may have once existed in the early Solar System and could have been roughly the size of Mars — or even slightly smaller — before being destroyed in a cosmic collision or ejected from its orbit.
Researchers point to a rare meteorite discovered in 2019 in the Sahara Desert, known as NWA 12774, as a potential clue. The rock belongs to an extremely rare class of meteorites called angrites, which make up less than 0.1% of all known meteorites found on Earth. These ancient igneous rocks formed very early in the Solar System’s history, shortly after the first solid materials condensed from the solar nebula.
The meteorite contains crystals of olivine and other minerals that suggest it originated from a much larger parent body, often referred to as the angrite parent body (APB). While earlier estimates ranged from a small asteroid only a few hundred kilometers wide to a larger planetary object, new analyses of NWA 12774 point to formation under high-pressure conditions that are difficult to explain within a small asteroid.
Using advanced microanalysis and geophysical modelling, scientists concluded that the material likely formed deep within a differentiated planetary body with a minimum radius between 1,000 and 3,300 kilometers. This range suggests an object comparable in size from a large Moon-like body up to something approaching Mars.
The findings support the idea that early Solar System evolution involved more planetary embryos than previously thought, many of which were destroyed, merged, or ejected during chaotic gravitational interactions. Some of their remnants may still be preserved today as rare meteorites found on Earth.
Researchers caution that while the results are intriguing, the existence of a fully formed Mars-sized “lost planet” remains hypothetical, and further evidence is needed to confirm its history.
