Did an Asteroid Strike Billions of Years Ago Flip the Moon Around?

By Eliza Strickland | January 26, 2009 2:36 pm

moon far sideAround 3.9 billion years ago a massive asteroid may have slammed into the moon with such force that it changed the satellite’s rotation, according to a new analysis by a pair of astrophysicists. The impact may have set the moon to spinning, so that it eventually settled down with a 180 rotation from its previous orientation. Currently, earthlings looking up at the moon always see its same side; the other “dark side” of the moon is pointed away as a result of synchronous rotation, a sort of orbital lockstep that keeps the moon rotating once for every lap it takes around Earth [Scientific American]. The new findings suggest that Earth had a different view of the moon 3.9 billion years ago, although there was probably no life on the planet to take notice.

The researchers came to this surprising conclusion by analyzing the moon’s craters. According to earlier computer simulations, the moon’s western hemisphere as viewed from Earth should have about 30 per cent more craters than the eastern hemisphere. That’s because the west always faces in the direction in which the moon orbits, which makes it more likely to be hit by debris, for the same reason that more raindrops strike a moving car’s front windshield than its rear [New Scientist]. When researchers examined the age of the craters, however, they found a more complex scenario. The western hemisphere did have the greatest concentration of young impact basins, but the eastern hemisphere had most of the old craters. This suggests that the eastern hemisphere was once positioned to receive a heavy bombardment, and that the moon once had a different orientation.

Researchers believe that our young solar system was a violent place around 4 billion years ago, when the Earth and moon were subject to a series of impacts known as the “late heavy bombardment.” In the new study, to be published in the journal Icarus [subscription required], researchers suggest that one of these large impacts would have put the satellite’s rotation rate out of whack, so that for tens of thousands of years it would have appeared to slowly turn as viewed from Earth. Eventually, it would have settled into the current position [New Scientist].

Study coauthor Mark Wieczorek says that before the asteroid the moon was in a synchronous rotation, and that the altered orientation would likely have been a 180-degree-turn from its previous alignment. He notes that the tidal bulges on the lunar surface induced by Earth’s gravity, which deform the moon into an elongated shape that helps stabilize its position, would prevent the moon from easing into synchrony at any intermediate orientation…. “Just based on the physics, it’s very, very, very probable that at least one and perhaps more of these impacts did this to the moon,” Wieczorek says [Scientific American].

Related Content:
80beats: Moon Rock Suggests the Young Moon Had a Fiery Core and a Magnetic Field
80beats: The Moon Once Held Water, Moon Pebbles Show
80beats: Space Explorers Plead With UN to Prepare for Killer Asteroids
80beats: Massive Asteroid Impact Made Mars Lopsided
DISCOVER: Where Did the Moon Come From?

Image: NASA, a picture of the far side of the moon taken by the Apollo 16 mission

  • http://pwnsyou.com pwnage

    So what ?

  • Bruce Voigt

    The forces of the Sun, Moon and Earth dance together giving us seasons, tides etc. The Sun recently has been stepping on toes as it glides through this dance sending our north magnetic pole whizzing away a thousand miles to wards Russia then coming home to dance around an 85km oval every 24hr.

    This seemingly little dance is causing all kinds of hell for a species that thinks its the be and end all of the Universe. This Sun activity can muck around with slivers of Earth energy causing the Earth to tip, compasses to swing, radio reception, gps problems, tornado’s, tsunami, re location of oceans and climate etc. (BUT)

    The big kahuna Earths NUCLEUS is not PHASED by this UNTIL!

    Our NINTH Planet third or fourth from the sun comes bar-ling around the Sun appearing to be heading right for us.

    I Bruce Voigt claim that the recently discovered Asteroid 2002 AA 29 is really a Moon of (and yes I have named this Planet) OLD BRUCE.

    OLD BRUCE orbits the Sun in close proximity to Earths orbit every 365 point something day’s and the Earth is slowly catching up or visa versa.

    In approximately sixty five million years from now OLD BRUCE will be close enough to change (like a magnet) Earths Nucleus direction. At that very moment instant freezing takes place and because of no gravity any thing not attached drifts out into Earth orbit to be collected by the Moon. (Good real estate investment for an optimist).

    These are the Three true Ice ages, one in coming, two as Old Bruce eclipses Earth (the really big sleep) and three as Old Bruce again changes the Earths nucleus and nuclei direction. It is this that reverses Earths rotation direction (for every reaction there is an equal—-

    So now after all that you now know what happened to DINO!

    PS – Old Bruce solves the mystery of the constant changing rotation of Venus

  • http://www.realtimealerts.org RealTimeAlerts

    interesting, why don’t back to the moon and search more info?




  • http://olderbruce.com OLDER BRUCE


  • http://Fark.com Some Farker

    The universe is only 6000 years old. How could this have happened billions of years ago then?

  • Bruce Voigt

    On your next Arctic trip ask the locals if they have noticed winter light or the location of spring Sunrise and Sunset to be abnormal!

    “There is NO such thing as Global Warming”! Dramatic Earth tippings has the Earth changing its exposure to both the Sun and Moon. Moon exposure the reason for water movement (ocean level), Sun exposure the reason for the melting of Kilimanjaro. These tippings for now have alternating cooling and warming happening. Where it is warmer in one area it will be cooler in another. (more water in one area less in another. Thats for now, eventually and again the Arctic becomes tropical and the Ocean resides in Nevada.

    It is of GREAT IMPORTANCE to establish a constant monitoring system for Canada’s North Magnetic Pole Movements.

  • Astronomy Student

    How old is this article? Most of the moon surface can be dated to 4.5 billion years! It is the same age as us. The flat parts on the Moon are not because it is facing us. They are from big impacts early in the moons life while the Moon had not cooled and the core was much bigger. That is why they appear less scared. The core of the Moon is not centered, it is toward the Earths gravitational pull. If the moon flipped, it would flip back immediately. It could not stay 180 out from us. At least that is my understanding…. What do I know I am just a student…


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