The history of planet Earth is a fascinating story, involving catastrophic collisions with other small planets and a veritable plethora of asteroid impacts. What we see around us today has been here for a relatively short amount of time, and what came before is of great interest to many of us. So I was immediately intrigued by the possibility that, in our past, we had more than one moon.
The prevailing theory as to how our moon got to be, is called the giant impact hypothesis, or, if you want a more colorful title, the big whack or the big splash. Either way, the theory goes that a Mars-sized object, known as Theia, crashed in to the young Earth. What was left was Earth, and its moon.
A new computer model suggests, however that the Moon may not have been the only reminder of that big collision. Jack J. Lissauera, of the Space Science and Astrobiology Division, NASA Ames Research Center, and John E. Chambers of the Department of Terrestrial Magnetism, Carnegie Institution of Washington, have suggested that moonlets may have been left behind in the two Earth-Moon Langrangian points.
The Langrangian points are points in space where the gravity between two objects cancels the other out. Their theory places small moonlets, or Trojans, in these places, for up to 100 million years. "The giant impact that likely led to the formation of the Moon launched a lot of material into Earth orbit, and some could well have been caught in the Langrangian points," says study team member Lissauer.
Over time, gravitational tugs from other planets would have eventually altered Earth’s orbit, even if it was only slightly. Thus, the Langrangian points would have altered, leaving the Trojans once again susceptible to gravity. From there, they could be anywhere by now, or destroyed entirely.
"The perturbations from the other planets are very, very tiny," said Lissauer. But they change the shape of Earth's orbit, which subsequently changes the effect that the Sun's gravity has on the moons, that "...is what ultimately destabilises the Trojans."
A separate yet similar model created by Matija Cuk, an astrophysicist at the University of British Columbia in Canada, has suggested that smaller, asteroid sized objects, only a few tens of kilometers in width, could have lasted longest in those stationary positions. She believes that they could have lasted a lot longer too, up to a billion years or more.
However she noted that “they would have looked more like Jupiter or Venus in the sky than a satellite. They would have resembled very bright stars.”
space.newscientist.com
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.
