. Space Travel News .




.
MOON DAILY
"Big Splat" May Explain The Moon's Mountainous Far Side
by Staff Writers
Santa Cruz CA (SPX) Aug 04, 2011

illustration only

The mountainous region on the far side of the Moon, known as the lunar farside highlands, may be the solid remains of a collision with a smaller companion moon, according to a new study by planetary scientists at the University of California, Santa Cruz.

The striking differences between the near and far sides of the Moon have been a longstanding puzzle. The near side is relatively low and flat, while the topography of the far side is high and mountainous, with a much thicker crust.

The new study, published in the August 4 issue of Nature, builds on the "giant impact" model for the origin of the Moon, in which a Mars-sized object collided with Earth early in the history of the solar system and ejected debris that coalesced to form the Moon.

The study suggests that this giant impact also created another, smaller body, initially sharing an orbit with the Moon, that eventually fell back onto the Moon and coated one side with an extra layer of solid crust tens of kilometers thick.

"Our model works well with models of the Moon-forming giant impact, which predict there should be massive debris left in orbit about the Earth, besides the Moon itself. It agrees with what is known about the dynamical stability of such a system, the timing of the cooling of the Moon, and the ages of lunar rocks," said Erik Asphaug, professor of Earth and planetary sciences at UC Santa Cruz.

Asphaug, who coauthored the paper with UCSC postdoctoral researcher Martin Jutzi, has previously done computer simulations of the Moon-forming giant impact. He said companion moons are a common outcome of such simulations.

In the new study, he and Jutzi used computer simulations of an impact between the Moon and a smaller companion (about one-thirtieth the mass of the Moon) to study the dynamics of the collision and track the evolution and distribution of lunar material in its aftermath.

In such a low-velocity collision, the impact does not form a crater and does not cause much melting. Instead, most of the colliding material is piled onto the impacted hemisphere as a thick new layer of solid crust, forming a mountainous region comparable in extent to the lunar farside highlands.

"Of course, impact modelers try to explain everything with collisions. In this case, it requires an odd collision: being slow, it does not form a crater, but splats material onto one side," Asphaug said. "It is something new to think about."

He and Jutzi hypothesize that the companion moon was initially trapped at one of the gravitationally stable "Trojan points" sharing the Moon's orbit, and became destabilized after the Moon's orbit had expanded far from Earth. "The collision could have happened anywhere on the Moon," Jutzi said. "The final body is lopsided and would reorient so that one side faces Earth."

The model may also explain variations in the composition of the Moon's crust, which is dominated on the near side by terrain comparatively rich in potassium, rare-earth elements, and phosphorus (KREEP).

These elements, as well as uranium and thorium, are believed to have been concentrated in the magma ocean that remained as molten rock solidified under the Moon's thickening crust. In the simulations, the collision squishes this KREEP-rich layer onto the opposite hemisphere, setting the stage for the geology now seen on the near side of the Moon.

Other models have been proposed to explain the formation of the highlands, including one published last year in Science by Jutzi and Asphaug's colleagues at UC Santa Cruz, Ian Garrick-Bethell and Francis Nimmo. Their analysis suggested that tidal forces, rather than an impact, were responsible for shaping the thickness of the Moon's crust.

"The fact that the near side of the Moon looks so different to the far side has been a puzzle since the dawn of the space age, perhaps second only to the origin of the Moon itself," said Nimmo, a professor of Earth and planetary sciences. "One of the elegant aspects of Erik's article is that it links these two puzzles together: perhaps the giant collision that formed the Moon also spalled off some smaller bodies, one of which later fell back to the Moon to cause the dichotomy that we see today."

For now, he said, there is not enough data to say which of the alternative models offers the best explanation for the lunar dichotomy. "As further spacecraft data (and, hopefully, lunar samples) are obtained, which of these two hypotheses is more nearly correct will become clear," Nimmo said.

The new study was supported by NASA's Planetary Geology and Geophysics Program. Simulations were run on the NSF-sponsored UC Santa Cruz astrophysics supercomputer Pleiades.




Related Links
The Lunar Farside
Mars News and Information at MarsDaily.com
Lunar Dreams and more

.
Get Our Free Newsletters Via Email
...
Buy Advertising Editorial Enquiries








. 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



MOON DAILY
LADEE Completes Mission Critical Design Review
Washington DC (SPX) Aug 04, 2011
NASA's Lunar Atmosphere and Dust Environment Explorer (LADEE) has passed its most significant mission milestone to date, the Mission Critical Design Review, or MCDR. This means the LADEE observatory is cleared to go forward and complete the flight hardware fabrication necessary to meet all science and engineering requirements for its 2013 mission to explore the moon. LADEE will gather deta ... read more


MOON DAILY
Arianespace blasts another pair of satellites into orbit

64 satellites launched by ISRO so far

Ariane 5 ready for next heavy-lift flight

Inmarsat Selects ILS Proton For Inmarsat-5

MOON DAILY
Nearing First Landfall of Large Crater

Flowing water on Mars sparks new hunt for life traces

Opportunity Past 20-Mile Mark As it Nears Large Crater

NASA Spacecraft Data Suggest Water Flowing on Mars

MOON DAILY
"Big Splat" May Explain The Moon's Mountainous Far Side

LADEE Completes Mission Critical Design Review

Moon's mountains made by slo-mo crash: study

Unique volcanic complex discovered on Lunar far side

MOON DAILY
Citizen Scientists Discover a New Horizons Flyby Target

View from the Summit: Hunting for KBOs at the Top of the World

Hubble telescope spots tiny fourth moon near Pluto

NASA's Hubble Discovers Another Moon Around Pluto

MOON DAILY
Exoplanet Aurora Makes For An Out-of-this-World Sight

Distant planet aurorae modeled

Exoplanet Aurora: An Out-of-this-World Sight

Ten new distant planets detected

MOON DAILY
NASA Selects Companies To Study Storing Cryogenic Propellants In Space

Ball Aerospace Develops Flight Computers for Next-Generation Launch Vehicles

New Russian carrier rockets to the Moon

Gantry's First Splash Test Is a Booming Success

MOON DAILY
Why Tiangong is not a Station Hub

China to launch experimental satellite in coming days

Spotlight Time for Tiangong

China launches new data relay satellite

MOON DAILY
Another step closer to Vesta

Dawn Spacecraft Begins Science Orbits of Vesta

SOHO Watches a Comet Fading Away

Dawn Views Dark Side of Vesta


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

The content herein, unless otherwise known to be public domain, are Copyright 1995-2011 - Space Media Network. AFP and UPI Wire Stories are copyright Agence France-Presse and United Press International. 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