Scientists are studying whether the catastrophe that gave birth to the Moon, also gave rise to several other satellites. These additional satellites could have been seen in Earth's skies for tens of millions of years, they say.
They suggest that the two Earth-Moon Lagrangian points, parts of space where the gravitational pull of the Earth and Moon cancel each other out, may have contained several other satellites or moonlets. Experts say objects present in these regions, if left undisturbed, could remain stationery forever.
Studies have estimated that the Moon was created when an object this size of Mars struck Earth approximately 4.5 billion years ago.
"The giant impact that likely led to the formation of the Moon launched a lot of material into Earth's orbit, and some could well have been caught in the Lagrangian points," New Scientist quoted study team member Jack Lissauer of NASA Ames Research Center in California, US, as saying.
Trojan satellites typically remain in their orbits for up to 100 million years, Lissauer and co-author John Chambers of the Carnegie Institution of Washington was quoted as saying. After that, gravitation pull from other planets would cause changes in Earth's orbit, causing these moons to either drift away or crash into the Moon or Earth.
"The perturbations from the other planets are very, very tiny. But they change the shape of Earth's orbit, which changes the effect that the Sun's gravity has on the moons. (That) is what ultimately destabilises the Trojans," Lissauer told New Scientist.
A different model by Matija Cuk, an astrophysicist at the University of British Columbia in Canada, estimates that objects tens of kilometres in size would have been ideal to last longer as Trojans. Cuk suggests the 'lost moons' may have orbited Earth for over a billion years after the Moon's formation.
"They would have looked more like Jupiter or Venus in the sky than a satellite. They would have resembled very bright stars," Cuk told New Scientist.
Image: A full moon as seen from Mexico City | Photograph: Omar Torres-Jorge Silva/AFP/Getty Images
