Free Newsletters - Space - Defense - Environment - Energy - Solar - Nuclear
..
. Space Travel News .




MOON DAILY
Model reconciles Lunar Earth composition with giant impact theory
by Staff Writers
Boulder CO (SPX) Oct 18, 2012


Shown is an off-center, low-velocity collision of two protoplanets containing 45 percent and 55 percent of the Earth's mass. Color scales with particle temperature in kelvin, with blue-to-red indicating temperatures from 2,000 K to in excess of 6,440 K. After the initial impact, the protoplanets re-collide, merge and form a rapidly spinning Earth-mass planet surrounded by an iron-poor protolunar disk containing about 3 lunar masses. The composition of the disk and the final planet's mantle differ by less than 1 percent. For a larger version of this image please go here.

The giant impact believed to have formed the Earth-Moon system has long been accepted as canon. However, a major challenge to the theory has been that the Earth and Moon have identical oxygen isotope compositions, even though earlier impact models indicated they should differ substantially.

In a paper published in the journal Science online, a new model by Southwest Research Institute (SwRI), motivated by accompanying work by others on the early dynamical history of the Moon, accounts for this similarity in composition while also yielding an appropriate mass for Earth and Moon.

In the giant impact scenario, the Moon forms from debris ejected into an Earth-orbiting disk by the collision of a smaller proto-planet with the early Earth. Earlier models found that most or much of the disk material would have originated from the Mars-sized impacting body, whose composition likely would have differed substantially from that of Earth.

The new models developed by Dr. Robin M. Canup, an associate vice president in the SwRI Space Science and Engineering Division, and funded by the NASA Lunar Science Institute, involve much larger impactors than were previously considered. In the new simulations, both the impactor and the target are of comparable mass, with each containing about 4 to 5 times the mass of Mars.

The near symmetry of the collision causes the disk's composition to be extremely similar to that of the final planet's mantle over a relatively broad range of impact angles and speeds, consistent with the Earth-Moon compositional similarities.

The new impacts produce an Earth that is rotating 2 to 2.5 times faster than implied by the current angular momentum of the Earth-Moon system, which is contained in both the Earth's rotation and the Moon's orbit.

However, in an accompanying paper in Science, Dr. Matija Cuk, SETI Institute, and Dr. Sarah T. Stewart, Harvard University, show that a resonant interaction between the early Moon and the Sun - known as the evection resonance - could have decreased the angular momentum of the Earth-Moon system by this amount soon after the Moon-forming impact.

"By allowing for a much higher initial angular momentum for the Earth-Moon system, the Cuk and Stewart work allows for impacts that for the first time can directly produce an appropriately massive disk with a composition equal to that of the planet's mantle," says Canup.

In addition to the impacts identified in Canup's paper, Cuk and Stewart show that impacts involving a much smaller, high-velocity impactor colliding into a target that is rotating very rapidly due to a prior impact can also produce a disk-planet system with similar compositions.

"The ultimate likelihood of each impact scenario will need to be assessed by improved models of terrestrial planet formation, as well as by a better understanding of the conditions required for the evection resonance mechanism," adds Canup.

Canup used smoothed-particle hydrodynamics (SPH) to simulate the colliding planetary objects using 300,000 discrete particles whose individual thermodynamic and gravitational interactions were tracked with time.

The paper, "Forming a Moon with an Earth-like composition via a Giant Impact," by R.M Canup, was published Oct. 17, 2012, in the journal Science online, at the Science Express website. The results also will be presented at the 44th Meeting of the AAS Division for Planetary Sciences in Reno, Nev.

.


Related Links
Southwest Research Institute
Mars News and Information at MarsDaily.com
Lunar Dreams and more






Comment on this article via your Facebook, Yahoo, AOL, Hotmail login.

Share this article via these popular social media networks
del.icio.usdel.icio.us DiggDigg RedditReddit GoogleGoogle




Memory Foam Mattress Review
Newsletters :: SpaceDaily :: SpaceWar :: TerraDaily :: Energy Daily
XML Feeds :: Space News :: Earth News :: War News :: Solar Energy News





MOON DAILY
Massive planetary collision may have zapped key elements from moon
San Diego CA (SPX) Oct 18, 2012
Fresh examinations of lunar rocks gathered by Apollo mission astronauts have yielded new insights about the moon's chemical makeup as well as clues about the giant impacts that may have shaped the early beginnings of Earth and the moon. Geochemist James Day of Scripps Institution of Oceanography at UC San Diego and colleagues Randal Paniello and Frederic Moynier at Washington University in ... read more


MOON DAILY
AFSPC commander convenes AIB

Proton Lofts Intelsat 23 For Americas, Europe and Africa Markets

India to launch 58 space missions in next 5 years

SpaceX Dragon Successfully Attaches To Space Station

MOON DAILY
Opportunity Is On The Move Around 'Matijevic Hill'

NMSU Graduate Student Looks For Indications Of Life On Mars In Possible Trace Methane Gas

Rover's Second Scoop Discarded, Third Scoop Commanded

Robotic Arm Tools Get To Work On Rock Outcrop

MOON DAILY
Model reconciles Lunar Earth composition with giant impact theory

Massive planetary collision may have zapped key elements from moon

Proof at last: Moon was created in giant smashup

Giant smashup created the Moon, say scientists

MOON DAILY
Keck Observations Bring Weather Of Uranus Into Sharp Focus

At Pluto, Moons and Debris May Be Hazardous to New Horizons Spacecraft During Flyby

Sharpest-ever Ground-based Images of Pluto and Charon: Proves a Powerful Tool for Exoplanet Discoveries

The Kuiper Belt at 20: Paradigm Changes in Our Knowledge of the Solar System

MOON DAILY
Most Planetary Systems are 'Flatter than Pancakes'

Glitch could end NASA planet search

Ultra-Compact Planetary System Is A Touchstone For Understanding New Planet Population

Nearest Star Has Earth Mass Planet

MOON DAILY
Space Launch System Providing Engine 'Brains' With an Upgrade

J-2X Engine Offers A Powerful Line Up

Blue Origin Tests Rocket Engine Thrust Chamber

India testfires Mars mission engine

MOON DAILY
China launches civilian technology satellites

ChangE-2 Mission To Lagrange L2 Point

Meeting of heads of ESA and China Manned Space Agency

China Spacesat gets 18-million-USD gov't support

MOON DAILY
Lost asteroid rediscovered with a little help from ESA

First Evidence of Dynamo Generation in an Asteroid

Asteroid fragments could hint at the origin of the solar system

A New Dawn For NASA's Asteroid Explorer




The content herein, unless otherwise known to be public domain, are Copyright 1995-2014 - Space Media Network. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA Portal 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