Just as early man would slowly discover the land "just over the mountain", so has modern man furthered our knowledge of the Sol system. First we were at its center, then the church allowed us to orbit the sun--how gracious of them. We knew of 5 planets in the solar system along with our own, and then we knew 6, 7, and then 8. Pluto came last, closely followed by the now debunked Planet-X.
Pluto then got demoted to a dwarf-planet along with Eris and Ceres, two bodies that--I personally--had no idea existed. Eris was discovered on October the 21st, 2003, and is the largest known dwarf-planet in our solar system. It exists three times the distance Pluto is from our sun, and was indeed the "tenth planet" for a little while.
Ceres though, is the smallest dwarf-planet in our solar system, and orbits through the asteroid belt that sits between Mars and Jupiter. Discovered January 1, 1801, it makes up for its size by being the largest body within the asteroid belt, taking up approximately a third of the belt's total mass.
And it's the asteroid belt that may have presented us with another answer, one that has endured theory after theory.
The Late Heavy Bombardment is a period of time approximately 3800 to 4100 million years ago during which the Moon--and due to its small size and subsequent inability to take the entire brunt, Mercury, Venus, Earth and Mars--was battered by space debris.
Theory after theory has been posited, debunked or simply added to the pile, of what caused the LHB. One popular theory is that the gas giants of our system migrated, gravitationally affected the orbits of asteroids within the asteroid belt and the Kuiper belt.
However a theory that was (from what I can tell) put forth in 2002 by John Chambers and Jack Lissauer at the 33rd Lunar and Planetary Science Conference is gaining more ground.
The theory posits that an unknown fifth planet existed between Mars and the asteroid belt, and that its disappearance caused the impacts that are visible across the surface of the Moon.
Recently published in an issue of the Journal Icarus--International Journal of Solar System Studies--Chambers has used a new computer model to add further weight to his theory.
"Before it was lost, its orbit would have moved across the Asteroid Belt for quite a long period of time, scattering asteroids as a result," Chambers said. "My model would predict that it's only asteroids, and not comets, that caused the impacts, and that the asteroids would tend to come from the inner asteroid belt."
The evidence springs originally from the pock-marked surface of the Moon. Due to its conditions, it has not managed to recover from the damage done, and craters still mark the Moon's surface. In addition, rocks gathered by the Apollo missions--though restricted to a limited area of the Moon--all record a similar age of 3.9 billion years old, and none older.
Though Earth's conditions allow for recovery and thus the ability to hide such impacts, the Moon's lack of size precludes the theory that it was the only one hit. It is simply too small to have sustained such damage, and for Earth to have gone unscathed.
Chambers' theory puts forth that the fifth planet would have been smaller than Mars, but larger than the Moon. "If it was bigger than Mars, then Mars should have been the one that was lost," Chambers said. "If it's smaller than the Moon, that's not really big enough to disturb the Asteroid Belt much."
Confirmation of this theory is only likely to happen, when man returns to the Moon. Without further geologic samples recovered from the Moon's surface--still relatively untouched since that time--no solid proof can be garnered. Nonetheless, the Planet V hypothesis is fast gaining popularity and rising to number 1 spot on the reasons for the Late Heavy Bombardment.
Joshua Hill, a Geek’s-Geek from Melbourne, Australia, Josh is an aspiring author with dreams of publishing his epic fantasy, currently in the works, sometime in the next 5 years. A techie, nerd, sci-fi nut and bookworm.
