For years scientists have struggled to determine the origin of our Moon that lights the night sky faithfully every single night. Now, many believe that the moon may have been formed by a collision between the Earth and another object that happened to be strikingly similar in composition to our own planet.
Scientists believe that this may help resolve why rocks from the Earth and the Moon are so much more similar than one would expect. They say that can now paint a much clearer and more consistent picture of the history of our satellite.
One modeling study, performed by researchers from France and Israel, precisely simulates the turmoil of the inner Solar System in its earlier days and quantifies the collisions that may have occurred. During this state, the Earth would have been subjected to a series of brutal collisions with other proto-planets.
According our best understanding, the last of these was a cataclysmic collision with a planetary body just ten times lighter than the Earth. Following the collision the debris clumpted together to make the Moon.
The problem is that most of what became the Moon should have come from the body that collided with the Earth. But our existing knowledge leads us to believe that the other body was a very different type of planet.
"So if the impactor had a different composition from the Earth, we should expect the Moon to have a different composition," Dr. Hagai Perets, one of the study's authors,
But after examined rocks from the Moon, this is clearly not the case. "They are almost identical. This is one of the major challenges for this really beautiful giant impact hypothesis," said Dr. Perets, from the Technion-Israel Institute of Technology.
Dr. Perets and his colleagues found in their new simulations that the impactor planet might, in fact, have been made of very similar material to that of the Earth causing only subtle differences today that we see in lunar material.
"What we found is that many of these impactors on a planet have very similar composition to that of the planets they impact - as similar as what we measure between the Earth and the Moon," Dr. Perets explained.
A different challenge is determining what happened to both the Earth and Moon after this impact. The leading theory holds that both bodies contained extra material during a period of meteorite impacts. These impacts gradually wore out this veneer to the planet we have today.
This theory also left a trail of evidence that until now has gone undetected.
"The small, but significant, difference in the tungsten isotopic composition between Earth and the Moon perfectly corresponds to the different amounts of material gathered by Earth and the moon post-impact," said Professor Richard Walker from the University of Maryland, one of the authors on the US study.
Dr Matthias Willbold from the University of Manchester told the BBC he was impressed and excited.
"They all tell the same story - it all falls into place," said Dr Willbold, a planetary scientist who has also investigated the late veneer idea using tungsten ratios. "It's quite striking. [The lunar rock studies] mention that it is quite baffling that the Earth and Moon have the same starting composition, before the bombardment."
"And that links perfectly into the modelling paper, where they say look - we can resolve that. If you look at the models, the impactor and the Earth were similar, so we just solved your problem!"
