How comets paint swirls on the Moon


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.

From Crashing comets may explain mysterious lunar swirls

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American geophysicists believe the moon’s Procellarum region, a dark patch more than half the size of Australia, resulted from a magma plume rather than a massive asteroid strike, as previously thought. The finding “deals a big blow to the asteroid theory”, said Brown University, which contributed to the study. Procellarum is the only lunar “sea” big enough to be called an ocean and is one of a number of dark spots on the moon’s surface that, when seen from Earth, resemble a face. Unlike other dark areas such as the Sea of Rains and Sea of Seren­ity, Procellarum is not surrounded by signs of impact, such as mountains and scars. Scientists have long debated whether Procel­larum is so old that the impact signs have been eroded, or was formed by a different process. Now researchers say they have settled the argument, using data from twin NASA spacecraft that orbited the moon in 2012 and mapped its gravity. The team ­created a high-resolu­tion map showing Procellarum’s border composed of sharp angles that could not have been created by an asteroid. The researchers believe the angular outline was produced by giant tension cracks in the crust as it cooled around magma from deep inside the moon. Maria Zuber, co-author of a paper in the journal Nature, said tthe cracks had formed a “plumbing system” which had allowe­d magma to ­meander to the surface and created the dark spots we see.

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Among the things the astronauts left to lighten the load for the return trips were their “defecation collection devices,” also known as emesis bags (top). So decades-old containers filled with decades-old astronaut turds are still hanging out on the Moon.

In addition to the cool-gross factor, this astro-poop has some scientific and, with the other artifacts up there, cultural value. Some astrobiologists are interested in how bacteria in the abandoned feces have fared, and some anthropologists and historians would like to see the moon landing sites and all the artifacts there protected as part of a World Heritage Site. 

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Since 1996, scientists have debated about whether the Martian meteorite ALH84001 contains evidence that life once existed on Mars. The rock holds some microscopic wormy-looking structures that some scientists have suggested could be fossilized remains of life on Mars, whereas others say the weird shapes derive from normal geochemical processes.

In a new study, physicists at University of Kent tested the hypothesis with a big gun. More specifically, they took powdered diatoms (a type of microscopic algae with a hard silica shell), packed them inside a nylon bullet, added water, and froze the sample. Then, they loaded the bullets inside a light gas gun and fired them at a sack of water at speeds ranging between 0.25 and 3.1 miles per second.

When they looked in the water afterwards, the researchers analyzed the whole and partial remains of the little diatom fossils. They concluded that small fossils could survive a meteorite impact, and that if they exist, then it’s possible to find them inside meteorites.

But there are a few important caveats.  At impact speeds above 0.62 miles per second, none of the diatom fossils survived in one piece—they broke into tiny shards. And the faster they crashed into the water, the tinier the diatom bits became.  That’s a problem for any potential fossils that would fall to Earth from other planets, because meteoroids enter the Earth’s atmosphere at speeds between 6.8 and 44.7 miles per second before they hit Earth, according to the American Meteor Society.

The other important limitation is that the diatoms were shot frozen in ice, meaning they potentially behave differently during impact than they would if they were encapsulated in rock.

So the jury is definitely still out on ALH84001, and it probably will be for many years. Even if tests provide stronger evidence that fossils can travel between planetary bodies, it doesn’t necessarily mean they did.

What is pretty neat is that, because meteorite impacts tend to be slower on the Moon, it looks like fossils that have been smashed off from Earth could survive a collision with our natural satellite.  The authors conclude that the lunar surface could be a good place to scout for fossils, and those terrestrial transplants may be better preserved on the Moon than if they had remained on Earth.

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Gregory Benford’s Guide to Terraforming the Moon


When it comes to remaking a celestial body in Earth’s image—“terraforming” it—the moon has clear advantages: It gets twice the sunlight of Mars. It’s a three-day trip with current technology, while getting people to Mars would take six months. Furthermore, the moon is dead and it’s small, so it…

Stick with me kids and you could have a job in the Kuiper Belt firing comets into the Moon, making it rain there for ten thousand years. In your new space-hardened, posthuman body. Would you like to know more?

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Many of the astronauts that White interviews argue that the experience would be a powerful political tonic, if you could somehow impel it upon the rulers of the planet. As Joseph Allen, a veteran of several Space-Shuttle flights, said:

A steady stream of world leaders should go into orbit. It would have a profound affect on their wisdom …. It is similar to the time of Copernicus; we have a broadened view of our place in the universe, and more educated view.

In his book Moondust, the author Andrew Smith argues that the moon landing was in some respects an art project, as gesture “as primitive as song”. We went there not so much to see the moon as to gaze back at Earth. It was “a unique opportunity to look at ourselves,” he writes, an accomplishment less of technology than of aesthetics, culture, and spirituality. “How madly, perfectly human.” Many of the astronauts White interviews in The Overview Effect lament the difficulty they have in putting their new perspective into words, of communicating its sheerly alien quality to other people. Gemini X astronaut Michael Collins concluded that that the ideal crew for an Apollo mission would have been a “philosopher, a priest, and a poet.” (“Unfortunately,” he added, “they would kill themselves trying to fly the spacecraft.”)

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In order to bring broadband to the moon, scientists used four separate telescopes based in New Mexico to send an uplink signal to a receiver mounted on a satellite orbiting the moon. Each telescope is about 6 inches in diameter and is fed by a laser transmitter that beams information in coded pulses of infrared light.

Since our atmosphere bends the signal as it travels to the moon, the four telescopes transmit the light through different columns of air, each with different bending effects. This setup increases the chance that at least one of the laser beams will interact with the receiver, and establish a connection with the moon.

And if you’re fixing to binge on Netflix on the moon, the connection isn’t too bad, either. Scientists managed to send data from Earth to the moon at a rate of 19.44 megabits per second — on par with slower broadband speeds — and could download information from the moon at a rate of whopping 622 megabits per second. According to Wired UK, that’s over 4,000 times faster than current radio transmission speeds.

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Eventually, commercial moon landers may help carry a diverse library of cultural and biological records to the lunar surface, where they would be preserved in case Earth suffers a pandemic plague, nuclear holocaust or lethal asteroid strike.

The first artefacts to shoot for the moon could be three religious and philosophical texts. The Torah on the Moon project, based in Tel Aviv, Israel, has been courting private firms to deliver a handwritten Jewish scroll, the Sefer Torah, to the lunar surface. If they succeed, later flights will carry Hindu scriptures called the Vedas and the ancient Chinese philosophical work, the I-Ching.

Each document will be housed in a space-ready capsule designed to protect it from harsh radiation and temperature changes on the moon for at least 10,000 years.

The texts would join a Bible left on the moon in 1971 by Apollo 15 commander David Scott. The red leather Bible sits on the control console of an Apollo moon buggy.

“I don’t think these religions are claiming the moon. It’s about saving our culture, saving the humanities,” says Naveen Jain, CEO of the California-based X Prize hopeful Moon Express.

Jain thinks future projects should find a representative sample of humanity, perhaps a million people, take their DNA and store it on the moon. “So in case of an asteroid strike that wipes us out like the dinosaurs, humanity can be saved.”

Jain’s idea may become a reality: New Scientist has learned that a UK-based venture is quietly developing a mission to store human, animal and plant genomes on the moon – although flaws in this plan are turning up in seed banks on Earth (see “Banked seeds are plants out of time”).

Such off-planet backup missions are proliferating, says Joanne Wheeler, a lawyer specialising in space issues at CMS Cameron McKenna in London. “There are several missions planned to put religious and spiritual icons on the moon and also to preserve some trace of humanity on it,” she says.

Evolutionary biologist Richard Dawkins says that the moon could even become a “cosmic tombstone” if humans become extinct.

“We should be using it to store the best humanity has ever had to offer, like the works of Michelangelo, Beethoven, Schubert and Shakespeare,” he says.

Meanwhile, Roger Launius at the Smithsonian Institution in Washington DC thinks it apt that such space flight projects should be tied to religion, because space flight advocacy itself has many of the hallmarks of a religion. “There is salvation theology, in that they believe the human race will be saved by space flight’s ability to make us a multi-planetary species,” he says. “And we have pilgrimages at gatherings like launches, which are like a euphoric religious experience.”

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