Free Newsletters - Space News - Defense Alert - Environment Report - Energy Monitor
by Staff Writers
Paris (AFP) April 02, 2014
The Moon was formed about 95 million years after the birth of our Solar System, in a collision that also settled the structure of Earth as we know it, according to the latest attempt at dating that impact.
A study in the journal Nature said the crash between an early, proto-Earth and a Mars-sized object that dislodged what would become the Moon, happened some 4.470 billion years ago -- give or take 32 million years.
Apart from creating our satellite, the event is also believed to have marked the final phase of Earth's core formation from molten metals sinking to the centre from a superhot surface.
Previous estimates had ranged from an "early" impact about 30 million years after the start of the Solar System, to a later one as much as 200 million years after.
The Solar System itself is known to be 4.567 billion years old thanks to accurate dating of some components of meteorites -- the oldest materials to be found on our planet.
Earth is believed to have formed at some time during the first 150 million years.
Many earlier age estimates had been based on measuring the rate of radioactive decay of atomic nuclei found in rocks.
For the new study published in the journal Nature, a team of planetary scientists from France, Germany and the United States created a computer model of how dust and rock accumulated in the early Solar System to form tiny planets called planetesimals.
These grew into "planetary embryos" that ended up as the rocky planets we know today -- Mercury, Venus, Earth and Mars -- through a succession of giant impacts, according to the new model.
Each massive collision allowed the planets to "accrete" or accumulate matter. In Earth's case, the lunar impact would have marked its final major growth event.
The team also looked at the chemical composition of the Earth's mantle to trace the amount of material the planet accumulated after the impact -- only about 0.5 percent of its total mass.
If the impact had happened early in the Solar System's history, there would still have been many free-floating planetesimals for the Earth to sweep up, and if it was later, fewer.
The evidence suggested Earth took 95 million years to form, "which confirms it as the planet in our Solar System that took the longest to form," study co-author Alessandro Morbidelli told AFP by email.
Mars News and Information at MarsDaily.com
Lunar Dreams and more
|The content herein, unless otherwise known to be public domain, are Copyright 1995-2014 - Space Media Network. All websites are published in Australia and are solely subject to Australian law and governed by Fair Use principals for news reporting and research purposes. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA news reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement, agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement All images and articles appearing on Space Media Network have been edited or digitally altered in some way. Any requests to remove copyright material will be acted upon in a timely and appropriate manner. Any attempt to extort money from Space Media Network will be ignored and reported to Australian Law Enforcement Agencies as a potential case of financial fraud involving the use of a telephonic carriage device or postal service.|