Feeds

Moon was formed when PLANET SMASHED INTO EARTH

'Theia' absorbed into core, lies beneath our feet today

  • alert
  • submit to reddit

Business security measures using SSL

That old theory that the Moon was formed out of fragments of Earth blasted into space after a massive planetary collision 4.5 billion years ago has gained support from two new studies.

Giant impact, common at the end of planet formation

Boffins have tried to figure out exactly how a giant impact in our solar system made the Moon. Previous theories have suggested that the celestial body could have been made from pieces of the mysterious planet that crashed into Earth, but recent studies showing that Earth and the Moon have the same isotopic composition pour water on that idea.

To make the Moon out of the Earth however, requires different conditions for proto-Earth.

Matija Cuk of SETI and Sarah Stewart of Harvard reckon the Moon was formed by the rapid spin of the ancient Earth. If its rotation rate at the time of interplanetary dust-up was significantly speedier, giving a "day" of just two to three hours, the planet would have thrown off the necessary material to form the Moon.

If the Earth was spinning through a day of just two hours, it would be near the point when it would start to fly apart itself from rotation forces, making it much easier to throw away loose bits of itself. After that, the so-called "evection" resonance between the orbiting bodies of the Earth round the Sun and the Moon round the Earth eventually changed the planet's rotation rate to the 24-hour day we have today.

The other part of the mystery is the lack of iron on the Moon, which would be taken care of by the planet that smashes into the Earth, named Theia. In computer simulations, Theia has to be half the mass of Mars and strike at 20km/s in order to penetrate into the core of the Earth and throw material out some of which escapes Earth's gravity. In this scenario, Theia's iron core merges with the Earth's core, leaving the mantle to make the Moon, with a similar isotopic composition but a low iron content.

The second study, by Robin Canup at the Southwest Research Institute in Boulder, also backs the impact theory, but she reckons that the Earth and the planet that hit it were each around half of the Earth's current mass.

Both Cuk and Stewart's study and Canup's study were published in Science. ®

Providing a secure and efficient Helpdesk

More from The Register

next story
PORTAL TO ELSEWHERE scried in small galaxy far, far away
Supermassive black hole dominates titchy star formation
Boffins say they've got Lithium batteries the wrong way around
Surprises at the nano-scale mean our ideas about how they charge could be all wrong
Edge Research Lab to tackle chilly LOHAN's final test flight
Our US allies to probe potential Vulture 2 servo freeze
Europe prepares to INVADE comet: Rosetta landing site chosen
No word yet on whether backup site is labelled 'K'
Cracked it - Vulture 2 power podule fires servos for 4 HOURS
Pixhawk avionics juice issue sorted, onwards to Spaceport America
City hidden beneath England's Stonehenge had HUMAN ABATTOIR. And a pub
Boozed-up ancients drank beer before tearing corpses apart
'Duck face' selfie in SPAAAACE: Rosetta's snap with bird comet
Probe prepares to make first landing on fast-moving rock
prev story

Whitepapers

Providing a secure and efficient Helpdesk
A single remote control platform for user support is be key to providing an efficient helpdesk. Retain full control over the way in which screen and keystroke data is transmitted.
WIN a very cool portable ZX Spectrum
Win a one-off portable Spectrum built by legendary hardware hacker Ben Heck
Saudi Petroleum chooses Tegile storage solution
A storage solution that addresses company growth and performance for business-critical applications of caseware archive and search along with other key operational systems.
Protecting users from Firesheep and other Sidejacking attacks with SSL
Discussing the vulnerabilities inherent in Wi-Fi networks, and how using TLS/SSL for your entire site will assure security.
Security for virtualized datacentres
Legacy security solutions are inefficient due to the architectural differences between physical and virtual environments.