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There may have been many planetary embryos in the early Solar System, but the only one that still survives is Mars, which is not a fully fledged planet like Earth or Venus.
Read just the next sentence following the part you have qouted:swampwiz said:Why is Mars not considered a "fully fledged" planet?
As it is believed that Mars didn't experience such a big impact, from this point of view it didn't go through the last stage of planetary formation. I am not sure how much is this hypothesis respected, but other sources mention it too, see below quotes and links.There may have been many planetary embryos in the early Solar System, but the only one that still survives is Mars, which is not a fully fledged planet like Earth or Venus.
The late stages of accretion involve giant impacts that release enormous amounts of energy. We think the last impact in Earth’s accretion involved a Mars-sized embryo hitting the growing Earth...
With approximately one ninth of Earth's mass, Mars is widely considered to be a stranded planetary embryo that never became a fully-grown planet.
According to planet formation theory, there was a process of building that went on in the early solar system – smaller planetesimals to larger planetary embryos to actual planets. The idea here is that – while Earth formed slowly from planetary embryos colliding – Mars is itself a solitary planetary embryo that formed very early in the history of our solar system.
By modelling this process, astro-physicists can determine the size of planets they expect to form at a given distance from the Sun. Mars is an outlier; it should have grown to around the size of the Earth, but remains about one-tenth its size.
Because of Mars' small size, many scientists have long suspected that the Red Planet avoided the collisions that allowed other neighbouring planets to increase their girth
Venus does not have much magnetic field either.hutchphd said:Perhaps the designation has to do with lack of internal dynamics sufficient to create a Magnetic field. As I understand it this may be responsible for the "ablation" of the Martian atmosphere by solar wind, (but I don't understand much).
Mars is not considered a "full-fledged" planet because it does not meet all of the criteria set by the International Astronomical Union (IAU) for a planet. According to the IAU, a planet must orbit the sun, have enough mass to assume a nearly round shape, and have cleared its orbit of other objects. Mars meets the first two criteria, but it has not cleared its orbit of other objects, as it shares its orbit with thousands of other asteroids.
The main difference between a "full-fledged" planet and a dwarf planet is that a dwarf planet has not cleared its orbit of other objects. This means that while a dwarf planet may have enough mass to assume a round shape, it is not the dominant object in its orbit. Additionally, dwarf planets are not considered moons or satellites of other planets.
Yes, Mars was considered a "full-fledged" planet before the IAU's definition of a planet was established in 2006. Prior to this, there were nine planets in our solar system, including Mars. However, with the new criteria, Mars and several other objects were reclassified as dwarf planets.
Yes, there are two other planets in our solar system that are not considered "full-fledged" planets: Ceres and Pluto. Ceres is located in the asteroid belt between Mars and Jupiter, and Pluto is located in the Kuiper Belt beyond Neptune. Both Ceres and Pluto have not cleared their orbits of other objects, leading to their classification as dwarf planets.
It is unlikely that Mars will ever become a "full-fledged" planet, as it would need to clear its orbit of other objects. However, it is possible that the IAU's definition of a planet could change in the future, which could potentially lead to Mars being reclassified as a planet. Additionally, with advancements in technology and further exploration of our solar system, our understanding of planets and their classifications may also evolve.