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Did a Planet Once Orbit Between Mars and Jupiter?

The region between Mars and Jupiter, known as the main asteroid belt, hosts a vast number of celestial bodies. However, it is improbable that these bodies were ever part of a single planet.

The main belt is home to a multitude of asteroids, and estimates suggest there are between 1.1 million and 1.9 million asteroids with diameters greater than 0.6 miles (1 kilometer). In addition to these, there are likely millions of smaller asteroids. The sheer number of these rocks might lead one to assume they could form a planet. Yet, if all the material from the main-belt asteroids were to merge, the total mass would only amount to a mere 4 percent of the Moon’s mass. In comparison, the Moon itself has a mass that is about 1.2 percent of Earth’s mass. Notably, about half of the mass of the main belt is concentrated in four large asteroids: Ceres, Vesta, Pallas, and Hygiea.

The Hypothetical Planet: Phaëthon

The idea that these asteroids might originate from a former planet emerged following the discoveries of Ceres by Giuseppe Piazzi in 1801 and Pallas by Heinrich Olbers in 1802. Olbers theorized that these two asteroids were fragments of a larger world that once existed. This notion was supported by the later discoveries of Juno in 1804 and Vesta in 1807. The theorized planet was dubbed Phaëthon, named after the tragic figure from Greek mythology who attempted to control his father’s sun chariot and met with disaster. This concept evolved into the disruption theory in the 20th century, suggesting that the supposed planet was obliterated by an unknown event, potentially involving gravitational forces from Jupiter or a catastrophic collision with another celestial body.

Questions remain about the main asteroid belt’s origins and whether it truly consists of debris from a destroyed planet. A critical piece of evidence that sheds light on this mystery comes from the study of iron meteorites found on Earth. Analysis has shown that these meteorites, sourced from the main belt, did not originate from a single body. The varying compositions of these meteorites suggest that if they were pieces of one world, they would exhibit more similarities. The unique characteristics observed in these fragments, together with the relative scarcity of material within the belt, strongly indicate that no planet once existed in this region. Instead, these asteroids are likely remnants from the solar system’s formative period.

Furthermore, the gravitational influence of Jupiter hampers any potential for planet formation within the main belt. The constant gravitational forces exerted by Jupiter keep the asteroids in a dynamic state, making it impossible for them to coalesce into a new planet.

While we cannot definitively rule out the existence of a planet between Mars and Jupiter, the evidence suggests it is highly improbable that one ever existed.

Source
www.astronomy.com