But a new study led by researchers at the University of California, Santa Cruz, shows that the highlands may be the result of tidal forces acting early in the moon's history when its solid outer crust floated on an ocean of liquid rock.
Ian Garrick-Bethell, an assistant professor of Earth and planetary sciences at UC Santa Cruz, found that the shape of the moon's bulge can be described by a surprisingly simple mathematical function. "What's interesting is that the form of the mathematical function implies that tides had something to do with the formation of that terrain," said Garrick-Bethell, who is the first author of a paper on the new findings published in the November 11 issue of Science.
The paper describes a process for formation of the lunar highlands that involves tidal heating of the moon's crust about 4.4 billion years ago. At that time, not long after the moon's formation, the crust was decoupled from the mantle below it by an intervening ocean of magma. As a result, the gravitational pull of the Earth caused tidal flexing and heating of the crust. At the polar regions, where the flexing and heating was greatest, the crust became thinner, while the thickest crust would have formed in the regions in line with the Earth.
This process still does not explain why the bulge is now found only on the farside of the moon. "You would expect to see a bulge on both sides, because tides have a symmetrical effect," Garrick-Bethell said. "It may be that volcanic activity or other geological processes over the past 4.4 billion years have changed the expression of the bulge on the nearside."
The paper's coauthors include Francis Nimmo, associate professor of Earth and planetary sciences at UCSC, and Mark Wieczorek, a planetary geophysicist at the Institut de Physique du Globe in Paris. The researchers analyzed topographical data from NASA's Lunar Reconnaissance Orbiter and gravitational data from Japan's Kaguya orbiter.
A map of crustal thickness based on the gravity data showed that an especially thick region of the moon's crust underlies the lunar farside highlands. The variations in crustal thickness on the moon are similar to effects seen on Jupiter's moon Europa, which has a shell of ice over an ocean of liquid water. Nimmo has studied the effects of tidal heating on the structure of Europa, and the researchers applied the same analytical approach to the moon.
"Europa is a completely different satellite from our moon, but it gave us the idea to look at the process of tidal flexing of the crust over a liquid ocean," Garrick-Bethell said.
The mathematical function that describes the shape of the moon's bulge can account for about one-fourth of the moon's shape, he said. Although mysteries still remain, such as what made the nearside so different, the new study provides a mathematical framework for further investigations into the shape of the moon.
"It's still not completely clear yet, but we're starting to chip away at the problem," Garrick-Bethell said.
Tim Stephens | EurekAlert!
Smart Data Transformation – Surfing the Big Wave
02.12.2016 | Fraunhofer-Institut für Angewandte Informationstechnik FIT
Climate change could outpace EPA Lake Champlain protections
18.11.2016 | University of Vermont
In recent years, lasers with ultrashort pulses (USP) down to the femtosecond range have become established on an industrial scale. They could advance some applications with the much-lauded “cold ablation” – if that meant they would then achieve more throughput. A new generation of process engineering that will address this issue in particular will be discussed at the “4th UKP Workshop – Ultrafast Laser Technology” in April 2017.
Even back in the 1990s, scientists were comparing materials processing with nanosecond, picosecond and femtosesecond pulses. The result was surprising:...
Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...
A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.
Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...
In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.
“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...
The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.
The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...
16.11.2016 | Event News
01.11.2016 | Event News
14.10.2016 | Event News
06.12.2016 | Power and Electrical Engineering
06.12.2016 | Earth Sciences
06.12.2016 | Physics and Astronomy