Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Crashing comets may explain mysterious lunar swirls

02.06.2015

Brown University researchers have produced new evidence that lunar swirls -- wispy bright regions scattered on the moon's surface -- were created by several comet collisions over the last 100 million years.

In a paper published in the journal Icarus, the researchers use state-of-the-art computer models to simulate the dynamics of comet impacts on the lunar soil. The simulations suggest that such impacts can account for many of the features in the mysterious swirls.


A closer look at the Reiner Gamma.

Courtesy of NASA/Lunar Reconnaissance Orbiter

'We think this makes a pretty strong case that the swirls represent remnants of cometary collisions,' said Peter Schultz, a planetary geoscientist at Brown University. Schultz co-wrote the paper with his former graduate student, Megan Bruck-Syal, who is now a researcher at the Lawrence Livermore National Laboratory.

Lunar swirls have been the source of debate for years. The twisting, swirling streaks of bright soil stretch, in some cases, for thousands of miles across the lunar surface. Most are found on the unseen far side of the moon, but one famous swirl called Reiner Gamma can be seen by telescope on the southwestern corner of the moon's near side. 'It was my favorite object to look at when I was an amateur astronomer,' Schultz said.

At first glance, the swirls do not appear to be related to large impact craters or any other topography. 'They simply look as if someone had finger-painted the surface,' Schultz said. 'There has been an intense debate about what causes these features.'

In the 1970s, scientists discovered that many of the swirls were associated with anomalies of the moon's crustal magnetic field. That revelation led to one hypothesis for how the swirls may have formed. Rocks below the surface in those spots might contain remanent magnetism from early in the moon's history, when its magnetic field was much stronger than it is now. It had been proposed that those strong, locally trapped magnetic fields deflect the onslaught of the solar wind, which was thought to slowly darken the moon's surface. The swirls would remain brighter than the surrounding soil because of those magnetic shields.

But Schultz had a different idea for how the swirls may form -- one that has its roots in watching the lunar modules land on the moon during the Apollo program.

'You could see that the whole area around the lunar modules was smooth and bright because of the gas from the engines scoured the surface,' Schultz said. 'That was part of what got me started thinking comet impacts could cause the swirls.'

Comets carry their own gaseous atmosphere called a coma. Schultz thought that when small comets slam into the moon's surface -- as they occasionally do -- the coma may scour away loose soil from the surface, not unlike the gas from the lunar modules. That scouring may produce the bright swirls.

Schultz first published a paper outlining the idea in the journal Nature in 1980. That paper focused on how the scouring of the delicate upper layer of lunar soils could produce brightness consistent with the swirls. The structure of the grains in the upper layer (termed the 'fairy castle structure' because of the way grains stick together) scatters the sun's rays, causing a dimmer and darker appearance. When this structure is stripped away, the remaining smoothed surface would be brighter than unaffected areas, especially when the sun's rays strike it at certain angles. For Reiner Gamma on the lunar nearside, those areas appear brightest during the crescent moon just before sunrise.

As computer simulations of impact dynamics have gotten better, Schultz and Bruck-Syal decided it might be time to take a second look at whether comet impacts could produce that kind of scouring. Their new simulations showed that the impact of a comet coma plus its icy core would indeed have the effect of blowing away the smallest grains that sit atop the lunar soil. The simulations showed that the scoured area would stretch for perhaps thousands of kilometers from the impact point, consistent with the swirling streaks that extend across the moon's surface. Eddies and vortices created by the gaseous impact would explain the swirls' twisty, sinuous appearance.

The comet impact hypothesis could also explain the presence of magnetic anomalies near the swirls. The simulations showed that a comet impact would melt some of the tiny particles near the surface. When small, iron-rich particles are melted and then cooled, they record the presence of any magnetic field that may be present at the time. 'Comets carry with them a magnetic field created by streaming charged particles that interact with the solar wind,' Schultz said. 'As the gas collides with the lunar surface, the cometary magnetic field becomes amplified and recorded in the small particles when they cool.'

Taken together, the results offer a more complete picture of how the swirls form, the researchers say.

'This is the first time anyone has looked at this using modern computational techniques,' Schultz said. 'Everything we see in simulations of comet impacts is consistent with the swirls as we see them on the moon. We think this process provides a consistent explanation, but may need new moon missions to finally resolve the debate.'

Kevin Stacey | EurekAlert!

Further reports about: Comets Crashing Crashing comets Gamma lunar magnetic field solar wind structure

More articles from Physics and Astronomy:

nachricht NASA's James Webb Space Telescope completes final cryogenic testing
21.11.2017 | NASA/Goddard Space Flight Center

nachricht Previous evidence of water on mars now identified as grainflows
21.11.2017 | US Geological Survey

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Nanoparticles help with malaria diagnosis – new rapid test in development

The WHO reports an estimated 429,000 malaria deaths each year. The disease mostly affects tropical and subtropical regions and in particular the African continent. The Fraunhofer Institute for Silicate Research ISC teamed up with the Fraunhofer Institute for Molecular Biology and Applied Ecology IME and the Institute of Tropical Medicine at the University of Tübingen for a new test method to detect malaria parasites in blood. The idea of the research project “NanoFRET” is to develop a highly sensitive and reliable rapid diagnostic test so that patient treatment can begin as early as possible.

Malaria is caused by parasites transmitted by mosquito bite. The most dangerous form of malaria is malaria tropica. Left untreated, it is fatal in most cases....

Im Focus: A “cosmic snake” reveals the structure of remote galaxies

The formation of stars in distant galaxies is still largely unexplored. For the first time, astron-omers at the University of Geneva have now been able to closely observe a star system six billion light-years away. In doing so, they are confirming earlier simulations made by the University of Zurich. One special effect is made possible by the multiple reflections of images that run through the cosmos like a snake.

Today, astronomers have a pretty accurate idea of how stars were formed in the recent cosmic past. But do these laws also apply to older galaxies? For around a...

Im Focus: Visual intelligence is not the same as IQ

Just because someone is smart and well-motivated doesn't mean he or she can learn the visual skills needed to excel at tasks like matching fingerprints, interpreting medical X-rays, keeping track of aircraft on radar displays or forensic face matching.

That is the implication of a new study which shows for the first time that there is a broad range of differences in people's visual ability and that these...

Im Focus: Novel Nano-CT device creates high-resolution 3D-X-rays of tiny velvet worm legs

Computer Tomography (CT) is a standard procedure in hospitals, but so far, the technology has not been suitable for imaging extremely small objects. In PNAS, a team from the Technical University of Munich (TUM) describes a Nano-CT device that creates three-dimensional x-ray images at resolutions up to 100 nanometers. The first test application: Together with colleagues from the University of Kassel and Helmholtz-Zentrum Geesthacht the researchers analyzed the locomotory system of a velvet worm.

During a CT analysis, the object under investigation is x-rayed and a detector measures the respective amount of radiation absorbed from various angles....

Im Focus: Researchers Develop Data Bus for Quantum Computer

The quantum world is fragile; error correction codes are needed to protect the information stored in a quantum object from the deteriorating effects of noise. Quantum physicists in Innsbruck have developed a protocol to pass quantum information between differently encoded building blocks of a future quantum computer, such as processors and memories. Scientists may use this protocol in the future to build a data bus for quantum computers. The researchers have published their work in the journal Nature Communications.

Future quantum computers will be able to solve problems where conventional computers fail today. We are still far away from any large-scale implementation,...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Ecology Across Borders: International conference brings together 1,500 ecologists

15.11.2017 | Event News

Road into laboratory: Users discuss biaxial fatigue-testing for car and truck wheel

15.11.2017 | Event News

#Berlin5GWeek: The right network for Industry 4.0

30.10.2017 | Event News

 
Latest News

Previous evidence of water on mars now identified as grainflows

21.11.2017 | Physics and Astronomy

NASA's James Webb Space Telescope completes final cryogenic testing

21.11.2017 | Physics and Astronomy

New catalyst controls activation of a carbon-hydrogen bond

21.11.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>