The solar system is currently made up of four planets of primarily silicate rocks or metals, these include Mercury, Venus, Earth and Mars. These planets have a solid surface, making them substantially different from the larger “gas giant planets”, which are composed mostly of some combination of hydrogen, helium, and water existing in various physical states. However, NASA scientists John Chambers and Jack Lissauer have theorised a similar fifth planet once existed between Mars and the asteroid belt.
They made this claim after Apollo astronauts brought back rocks from the moon which shared characteristics.
These melted remains from asteroids seemed to have hit the Moon around the same time – 3.8 billion years ago.
When the scientists looked at other rocky objects in the solar system, including craters on Mars and the surface of Mercury, they found consistent results.
Researchers now call this period the Late Heavy Bombardment (LHB) and Mr Chambers and Mr Lissauer believe it was caused by a rogue planet colliding with Mercury, Venus and Mars on its way through.
They carried out a series of simulations in which they tweaked the asteroid belt to account for mass lost and orbits of other planets, posting their results in a 2002 paper.
An abstract read: “In simulations in which the belt was inclined relative to the binary orbital plane, three to five terrestrial planets were formed around the solar system.
“When the embryos in the disk were moving relative to the binary plane, four or five terrestrial planets formed.
“In systems with the accreting disk initially inclined relative to the binary star orbit, two to five planets formed despite the fact that more than half of the disk mass was perturbed into the central star.
”Essentially the scientists carried out three separate experiments, which all resulted with the possibility of a fifth planet being involved.
While it is a fascinating hypothesis, it is still lacking hard evidence.
It is clear something caused LHB, but it is still a mystery exactly what happened.