Ancient Impact Might Have Created the “Man In The Moon”

The Moon. Image credit: NASA Click to enlarge
Ohio State University planetary scientists have found the remains of ancient lunar impacts that may have helped create the surface feature commonly called the “man in the moon.”

Their study suggests that a large object hit the far side of the moon and sent a shock wave through the moon’s core and all the way to the Earth-facing side. The crust recoiled — and the moon bears the scars from that encounter even today.

The finding holds implications for lunar prospecting, and may solve a mystery about how past impacts on Earth affect it’s geology today.

The early Apollo missions revealed that the moon isn’t perfectly spherical. Its surface is warped in two spots; an earth-facing bulge on the near side is complemented by a large depression on the Moon’s far side. Scientists have long wondered whether these surface features were caused by Earth’s gravity tugging on the moon early in its existence, when its surface was still molten and malleable.

According to Laramie Potts and Ralph von Frese, a postdoctoral researcher and professor of geological sciences respectively at Ohio State , these features are instead remnants from ancient impacts.

Potts and von Frese came to this conclusion after they used gravity fluctuations measured by NASA’s Clementine and Lunar Prospector satellites to map the moon’s interior. They reported the results in a recent issue of the journal Physics of the Earth and Planetary Interiors.

They expected to see defects beneath the moon’s crust that corresponded to craters on the surface. Old impacts, they thought, would have left marks only down to the mantle, the thick rocky layer between the moon’s metallic core and its thin outer crust. And that’s exactly what they saw, at first.

Potts pointed to a cross-sectional image of the moon that the scientists created using the Clementine data. On the far side of the moon, the crust looks as though it was depressed and then recoiled from a giant impact, he said. Beneath the depression, the mantle dips down as he and von Frese would expect it to do if it had absorbed a shock.

Evidence of the ancient catastrophe should have ended there. But some 700 miles directly below the point of impact, a piece of the mantle still juts into the moon’s core today.

That was surprising enough. “People don’t think of impacts as things that reach all the way to the planet’s core,” von Frese said.

But what they saw from the core all the way to the surface on the near side of the moon was even more surprising. The core bulges, as if core material was pushed in on the far side and pulled out into the mantle on the near side. Above that, an outward-facing bulge in the mantle, and above that — on the Earth-facing side of the moon — sits a bulge on the surface.

To the Ohio State scientists, the way these features line up suggests that a large object such as an asteroid hit the far side of the moon and sent a shock wave through the core that emerged on the near side.

The scientists believe that a similar, but earlier impact occurred on the near side.

Potts and von Frese suspect that these events happened about four billion years ago, during a period when the moon was geologically active — with its core and mantle still molten and magma flowing.

Back then, the moon was much closer to the Earth than it is today, Potts explained, so the gravitational interactions between the two were stronger. When magma was freed from the Moon’s deep interior by the impacts, Earth’s gravity took hold of it and wouldn’t let go.

So the warped surfaces on the near and far sides of the moon and the interior features that connect them are all essentially signs of injuries that never healed.

“This research shows that even after the collisions happened, the Earth had a profound effect on the moon,” Potts said.

The impacts may have created conditions that led to a prominent lunar feature.

The “man in the moon” is a collection of dark plains on the Earth-facing side of the moon, where magma from the moon’s mantle once flowed out onto the surface and flooded lunar craters. The moon has long since cooled, von Frese explained, but the dark plains are a remnant of that early active time — “a frozen magma ocean.”

How that magma made it to the surface is a mystery, but if he and Potts are right, giant impacts could have created a geologic “hot spot” on the moon ? a site where magma bubbles to the surface. Some time between when the impacts occurred and when the moon solidified, some magma escaped the mantle through cracks in the crust and flooded the nearside surface and formed a lunar ?hot spot?.

A hot spot on Earth forms the volcanoes that make the Hawaiian island chain. The Ohio State scientists wondered: could similar ancient impacts have penetrated the Earth, and caused the hot spots that exist here today? von Frese thinks that it’s possible.

“Surely Earth was peppered with impacts, too,” he said. “Evidence of impacts here is obscured, but there are hot spots like Hawaii . Some hot spots have corresponding hot spots on the opposite side of the Earth. That could be a consequence of this effect.”

He and Potts are exploring the idea, by studying gravitational anomalies under the Chicxulub Crater on Mexico ‘s Yucatan Peninsula . A giant asteroid struck the spot some 65 million years ago, and is believed to have set off an environmental chain reaction that killed the dinosaurs.

NASA funded this research. The space agency has been charged with returning astronauts to the moon to prospect for valuable gases and minerals.

But even today, scientists don’t entirely know what the moon is made of ? not down to the core, anyway. They can calculate where certain minerals should be, given the conditions they believe existed when the moon formed. But impacts like the one Potts and von Frese discovered have since shuffled materials around. Gravity measurements, they said, will play a key role as scientists figure out what materials lie within the moon, and where.

“We don’t fully understand the way these minerals settle out under temperature and pressure, so the exact composition of the moon is difficult to determine. We have to use gravity measurements to calculate the density of materials, and then use that information to extrapolate the likely composition,” Potts said.

von Frese said a lunar base would be needed before scientists can more completely answer these questions.

Potts agreed. “Once we have more rock samples and soil samples, we will have a lot more to go on. Nothing is better than having a person on the ground,” he said.

Original Source: OSU News Release

The Moon has Alps Too

The lunar Alps border the moon’s Sea of Rains. Image credit: NASA
It’s only a matter of time. One day, winter Olympics will be held on the moon.

The moon’s dust-covered slopes are good places to ski. There’s plenty of powder, moguls and, best of all, low-gravity. With only 1/6th g holding them down, skiers and snowboarders can do tricks they only dreamed of doing on Earth. How about an octuple-twisting quadruple backflip? Don’t worry. Crashes happen in slow-motion, so it won’t hurt so much to wipe out.

And there’s a perfect spot for the Olympic Village: the crater Plato. Most people don’t know it, but Plato of ancient Greece was not only a philosopher, but also an Olympic champion. Twice he won the pankration competition?a grueling mix of boxing and wrestling. A crater named after Plato sounds like a good place for Olympic athletes to stay. The site is flat-bottomed, filled with raw materials for building stadia and habitats, and like Torino, Italy, the site of this year’s games, Plato is near the Alps.

That is, the lunar Alps.

The lunar Alps are a range of mountains on the moon named after the Alps of Europe. They are similar to their Earthly counterparts in height, breath and spectacle. Since the modern Olympics began in 1896, most of the winter games have been held in the Alps. Why should the moon be different?

You can see the lunar Alps using a small backyard telescope. This week is an excellent time to try: Step outside at sundown and look up at the moon. The Olympic Village, crater Plato, is a conspicuous dark oval on the northern shore of Mare Imbrium, the “Sea of Rains.” Your unaided eye is sufficient to see it.

Next, train your telescope on Plato. The Alps begin there. They stretch around the rim of the Sea of Rains from Plato through the spectacular Alpine Valley to towering Mont Blanc. Amateur astronomer Alan Friedman of Buffalo, New York, used a 10-inch telescope to take this picture of the scene.***image4:left***

Although the two Alps look much alike, they formed in different ways:

The Alps of Earth grew over a period of millions of years. Powered by plate tectonics, sections of Earth’s crust pushed together, squeezing the land to produce jagged mountains. The range stretches from France through Italy all the way to Albania; the tallest peak is Mont Blanc, 15,700 ft or 4800 m high.

The Alps of the moon were formed in an instant some 4 billion years ago when a huge asteroid struck. The collision blasted out the Sea of Rains, which, contrary to its name, is a big crater, not a big sea. The Alps are “splash” from the impact.

In those early days, lunar Alps were probably as jagged and rough as the Alps of Earth. But in eons that followed, meteoroids relentlessly pounded the moon, smashing rocks into dust and blunting the sharp edges of mountain peaks. Today’s lunar Alps are a bit shorter (the moon’s Mont Blanc is only 11,800 ft or 3600 m high) and a lot smoother than their terrestrial counterparts?perfect for Olympics.

In the weeks ahead, [email protected] will publish a series of stories exploring the physics of low-gravity Olympics. Is an octuple-twisting quadruple backflip really possible? Should snowboarders be allowed to pilot lunar landers? How is a bobsled like a spaceship? Stay tuned for the answers to these questions and others?with exclusive video from Olympic athletes.

Let the Games begin!

Original Source: NASA News Release

The Smell of Moondust

Apollo 17 astronaut Jack Schmitt, with his spacesuit grayed by moondust. Image credit: NASA Click to enlarge
Moondust. “I wish I could send you some,” says Apollo 17 astronaut Gene Cernan. Just a thimbleful scooped fresh off the lunar surface. “It’s amazing stuff.”

Feel it?it’s soft like snow, yet strangely abrasive.

Taste it?”not half bad,” according to Apollo 16 astronaut John Young.

Sniff it?”it smells like spent gunpowder,” says Cernan.

How do you sniff moondust?

Every Apollo astronaut did it. They couldn’t touch their noses to the lunar surface. But, after every moonwalk (or “EVA”), they would tramp the stuff back inside the lander. Moondust was incredibly clingy, sticking to boots, gloves and other exposed surfaces. No matter how hard they tried to brush their suits before re-entering the cabin, some dust (and sometimes a lot of dust) made its way inside.

Once their helmets and gloves were off, the astronauts could feel, smell and even taste the moon.

The experience gave Apollo 17 astronaut Jack Schmitt history’s first recorded case of extraterrestrial hay fever. “It’s come on pretty fast,” he radioed Houston with a congested voice. Years later he recalls, “When I took my helmet off after the first EVA, I had a significant reaction to the dust. My turbinates (cartilage plates in the walls of the nasal chambers) became swollen.”

Hours later, the sensation faded. “It was there again after the second and third EVAs, but at much lower levels. I think I was developing some immunity to it.”

Other astronauts didn’t get the hay fever. Or, at least, “they didn’t admit it,” laughs Schmitt. “Pilots think if they confess their symptoms, they’ll be grounded.” Unlike the other astronauts, Schmitt didn’t have a test pilot background. He was a geologist and readily admitted to sniffles.

Schmitt says he has sensitive turbinates: “The petrochemicals in Houston used to drive me crazy, and I have to watch out for cigarette smoke.” That’s why, he believes, other astronauts reacted much less than he did.

But they did react: “It is really a strong smell,” radioed Apollo 16 pilot Charlie Duke. “It has that taste — to me, [of] gunpowder — and the smell of gunpowder, too.” On the next mission, Apollo 17, Gene Cernan remarked, “smells like someone just fired a carbine in here.”

Schmitt says, “All of the Apollo astronauts were used to handling guns.” So when they said ‘moondust smells like burnt gunpowder,’ they knew what they were talking about.

To be clear, moondust and gunpowder are not the same thing. Modern smokeless gunpowder is a mixture of nitrocellulose (C6H8(NO2)2O5) and nitroglycerin (C3H5N3O9). These are flammable organic molecules “not found in lunar soil,” says Gary Lofgren of the Lunar Sample Laboratory at NASA’s Johnson Space Center. Hold a match to moondust–nothing happens, at least, nothing explosive.

What is moondust made of? Almost half is silicon dioxide glass created by meteoroids hitting the moon. These impacts, which have been going on for billions of years, fuse topsoil into glass and shatter the same into tiny pieces. Moondust is also rich in iron, calcium and magnesium bound up in minerals such as olivine and pyroxene. It’s nothing like gunpowder.

So why the smell? No one knows.

ISS astronaut Don Pettit, who has never been to the moon but has an interest in space smells, offers one possibility:

“Picture yourself in a desert on Earth,” he says. “What do you smell? Nothing, until it rains. The air is suddenly filled with sweet, peaty odors.” Water evaporating from the ground carries molecules to your nose that have been trapped in dry soil for months.

Maybe something similar happens on the moon.

“The moon is like a 4-billion-year-old desert,” he says. “It’s incredibly dry. When moondust comes in contact with moist air in a lunar module, you get the ‘desert rain’ effect–and some lovely odors.” (For the record, he counts gunpowder as a lovely odor.)

Gary Lofgren has a related idea: “The gases ‘evaporating’ from the moondust might come from the solar wind.” Unlike Earth, he explains, the moon is exposed to the hot wind of hydrogen, helium and other ions blowing away from the sun. These ions hit the moon’s surface and get caught in the dust.

It’s a fragile situation. “The ions are easily dislodged by footsteps or dustbrushes, and they would be evaporated by contact with warm air inside the lunar module. Solar wind ions mingling with the cabin’s atmosphere would produce who-knows-what odors.”

Want to smell the solar wind? Go to the moon.

Schmitt offers yet another idea: The smell, and his reaction to it, could be a sign that moondust is chemically active.

“Consider how moondust is formed,” he says. “Meteoroids hit the moon, reducing rocks to jagged dust. It’s a process of hammering and smashing.” Broken molecules in the dust have “dangling bonds”–unsatisfied electrical connections that need atomic partners.

Inhale some moondust and what happens? The dangling bonds seek partners in the membranes of your nose. You get congested. You report strange odors. Later, when the all the bonds are partnered-up, these sensations fade.

Another possibility is that moondust “burns” in the lunar lander’s oxygen atmosphere. “Oxygen is very reactive,” notes Lofgren, “and would readily combine with the dangling chemical bonds of the moondust.” The process, called oxidation, is akin to burning. Although it happens too slowly for smoke or flames, the oxidation of moondust might produce an aroma like burnt gunpowder. (Note: Burnt and unburnt gunpowder do not smell the same. Apollo astronauts were specific. Moondust smells like burnt gunpowder.)

Curiously, back on Earth, moondust has no smell. There are hundreds of pounds of moondust at the Lunar Sample Lab in Houston. There, Lofgren has held dusty moon rocks with his own hands. He’s sniffed the rocks, sniffed the air, sniffed his hands. “It does not smell like gunpowder,” he says.

Were the Apollo crews imagining things? No. Lofgren and others have a better explanation:

Moondust on Earth has been “pacified.” All of the samples brought back by Apollo astronauts have been in contact with moist, oxygen-rich air. Any smelly chemical reactions (or evaporations) ended long ago.

This wasn’t supposed to happen. Astronauts took special “thermos” containers to the moon to hold the samples in vacuum. But the jagged edges of the dust unexpectedly cut the seals of the containers, allowing oxygen and water vapor to sneak in during the 3-day trip back to Earth. No one can say how much the dust was altered by that exposure.

Schmitt believes “we need to study the dust in situ–on the moon.” Only there can we fully discover its properties: Why does it smell? How does it react with landers, rovers and habitats? What surprises await?

NASA plans to send people back to the moon in 2018, and they’ll stay much longer than Apollo astronauts did. The next generation will have more time and better tools to tackle the mystery.

We’ve only just begun to smell the moondust.

Original Source: NASA News Release

Shadows on the Moon

The full moon. Image credit: Robert Gendler. Click to enlarge
The moon is utterly familiar. We see it all the time, in the blue sky during the day, among the stars and planets at night. Every child knows the outlines of the moon’s lava seas: they trace the Man in the Moon or, sometimes, a Rabbit.

This familiarity goes beyond appearances. The moon is actually made of Earth. According to modern theories, the moon was born some 4.5 billion years ago when an oversized asteroid struck our planet. Material from Earth itself spun out into space and coalesced into our giant satellite.

Yet when Apollo astronauts stepped out onto this familiar piece of home, they discovered that it only seems familiar. From the electrically-charged dust at their feet to the inky-black skies above, the moon they explored was utterly alien.

Thirty years ago their strange experiences were as well-known to the public as the Man in the Moon. Not anymore. Many of the best tales of Apollo have faded with the passage of time. Even NASA personnel have forgotten some of them.

Now, with NASA going back to the moon in search of new tales and treasures, we revisit some of the old ones, with a series of [email protected] stories called “Apollo Chronicles.” This one, the first, explores the simple matter of shadows.

On the next sunny day, step outdoors and look inside your shadow. It’s not very dark, is it? Grass, sidewalk, toes–whatever’s in there, you can see quite well.

Your shadow’s inner light comes from the sky. Molecules in Earth’s atmosphere scatter sunlight (blue more than red) in all directions, and some of that light lands in your shadow. Look at your shadowed footprints on fresh sunlit snow: they are blue!

Without the blue sky, your shadow would be eerily dark, like a piece of night following you around. Weird. Yet that’s exactly how it is on the Moon.

To visualize the experience of Apollo astronauts, imagine the sky turning completely and utterly black while the sun continues to glare. Your silhouette darkens, telling you “you’re not on Earth anymore.”

Shadows were one of the first things Apollo 11 astronaut Neil Armstrong mentioned when he stepped onto the surface of the moon. “It’s quite dark here in the shadow [of the lunar module] and a little hard for me to see that I have good footing,” he radioed to Earth.

The Eagle had touched down on the Sea of Tranquility with its external equipment locker, a stowage compartment called “MESA,” in the shadow of the spacecraft. Although the sun was blazing down around them, Armstrong and Buzz Aldrin had to work in the dark to deploy their TV camera and various geology tools.

“It is very easy to see in the shadows after you adapt for a while,” noted Armstrong. But, added Aldrin, “continually moving back and forth from sunlight to shadow should be avoided because it’s going to cost you some time in perception ability.”

Truly, moon shadows aren’t absolutely black. Sunlight reflected from the moon’s gently rounded terrain provides some feeble illumination, as does the Earth itself, which is a secondary source of light in lunar skies. Given plenty of time to adapt, an astronaut could see almost anywhere.

Almost. Consider the experience of Apollo 14 astronauts Al Shepard and Ed Mitchell:

They had just landed at Fra Mauro and were busily unloading the lunar module. Out came the ALSEP, a group of experiments bolted to a pallet. Items on the pallet were held down by “Boyd bolts,” each bolt recessed in a sleeve used to guide the Universal Handling Tool, a sort of astronaut’s wrench. Shepard would insert the tool and give it a twist to release the bolt–simple, except that the sleeves quickly filled with moondust. The tool wouldn’t go all the way in.

The sleeve made its own little shadow, so “Al was looking at it, trying to see inside. And he couldn’t get the tool in and couldn’t get it released–and he couldn’t see it,” recalls Mitchell.

“Remember,” adds Mitchell, “on the lunar surface there’s no air to refract light–so unless you’ve got direct sunlight, there’s no way in hell you can see anything. It was just pitch black. That’s an amazing phenomenon on an airless planet.”

(Eventually they solved the problem by turning the entire pallet upside down and shaking loose the moondust. Some of the Boyd bolts, loosened better than they thought, rained down as well.)

Tiny little shadows in unexpected places would vex astronauts throughout the Apollo program–a bolt here, a recessed oxygen gauge there. These were minor workaday nuisances, mostly, but astronauts were jealous of the minutes lost from their explorations.

Shadows could also be mischievous:

Apollo 12 astronauts Pete Conrad and Al Bean landed in the Ocean of Storms only about 600 yards from Surveyor 3, a robotic spacecraft sent by NASA to the moon three years earlier. A key goal of the Apollo 12 mission was to visit Surveyor 3, to retrieve its TV camera, and to see how well the craft had endured the harsh lunar environment. Surveyor 3 sat in a shallow crater where Conrad and Bean could easily get at it–or so mission planners thought.

The astronauts could see Surveyor 3 from their lunar module Intrepid. “I remember the first time I looked at it,” recalls Bean. “I thought it was on a slope of 40 degrees. How are we going to get down there? I remember us talking about it in the cabin, about having to use ropes.”

But “it turned out [the ground] was real flat,” rejoined Conrad.

What happened? When Conrad and Bean landed, the sun was low in the sky. The top of Surveyor 3 was sunlit, while the bottom was in deep darkness. “I was fooled,” says Bean, “because, on Earth, if something is sunny on one side and very dark on the other, it has to be on a tremendous slope.” In the end, they walked down a gentle 10 degree incline to Surveyor 3–no ropes required.

see captionA final twist: When astronauts looked at the shadows of their own heads, they saw a strange glow. Buzz Aldrin was the first to report “?[there’s] a halo around the shadow of my helmet.” Armstrong had one, too.

This is the “opposition effect.” Atmospheric optics expert Les Cowley explains: “Grains of moondust stick together to make fluffy tower-like structures, called ‘fairy castles,’ which cast deep shadows.” Some researchers believe that the lunar surface is studded with these microscopic towers. “Directly opposite the sun,” he continues,” each dust tower hides its own shadow and so that area looks brighter by contrast with the surroundings.”

Sounds simple? It’s not. Other factors add to the glare. The lunar surface is sprinkled with glassy spherules (think of them as lunar dew drops) and crystalline minerals, which can reflect sunlight backwards. And then there’s “coherent backscatter”–specks of moondust smaller than the wavelength of light diffract sunlight, scattering rays back toward the sun. “No one knows which factor is most important,” says Cowley.

We can experience the opposition effect here on Earth, for example, looking away from the sun into a field of tall dewy grass. The halo is there, but our bright blue sky tends to diminish the contrast. For full effect, you’ve got to go to the Moon.

Luminous halos; mind-bending shadows; fairy-castles made of moondust. Apollo astronauts discovered a strange world indeed.

Original Source: NASA News Release

Meteor Strike on the Moon

The red dot indicates the location of the recent meteoroid impact. Image credit: NASA/MSFC/Bill Cooke. Click to enlarge
NASA scientists have observed an explosion on the moon. The blast, equal in energy to about 70 kg of TNT, occurred near the edge of Mare Imbrium (the Sea of Rains) on Nov. 7, 2005, when a 12-centimeter-wide meteoroid slammed into the ground traveling 27 km/s.

“What a surprise,” says Marshall Space Flight Center (MSFC) researcher Rob Suggs, who recorded the impact’s flash. He and colleague Wes Swift were testing a new telescope and video camera they assembled to monitor the moon for meteor strikes. On their first night out, “we caught one,” says Suggs.

The object that hit the moon was “probably a Taurid,” says MSFC meteor expert Bill Cooke. In other words, it was part of the same meteor shower that peppered Earth with fireballs in late October and early November 2005. (See “Fireball Sightings” from [email protected])

The moon was peppered, too, but unlike Earth, the moon has no atmosphere to intercept meteoroids and turn them into harmless streaks of light. On the moon, meteoroids hit the ground–and explode.

“The flash we saw,” says Suggs, “was about as bright as a 7th magnitude star.” That’s two and a half times dimmer than the faintest star a person can see with their unaided eye, but it was an easy catch for the group’s 10-inch telescope.

Cooke estimates that the impact gouged a crater in the moon’s surface “about 3 meters wide and 0.4 meters deep.” As moon craters go, that’s small. “Even the Hubble Space Telescope couldn’t see it,” notes Cooke. The moon is 384,400 km away. At that distance, the smallest things Hubble can distinguish are about 60 meters wide.

This isn’t the first time meteoroids have been seen hitting the moon. During the Leonid meteor storms of 1999 and 2001, amateur and professional astronomers witnessed at least half-a-dozen flashes ranging in brightness from 7th to 3rd magnitude. Many of the explosions were photographed simultaneously by widely separated observers.

Since the Leonids of 2001, astronomers have not spent much time hunting for lunar meteors. “It’s gone out of fashion,” says Suggs. But with NASA planning to return to the moon by 2018, he says, it’s time to start watching again.

There are many questions that need answering: “How often do big meteoroids strike the moon? Does this happen only during meteor showers like the Leonids and Taurids? Or can we expect strikes throughout the year from ‘sporadic meteors?'” asks Suggs. Explorers on the moon are going to want to know.

“The chance of an astronaut being directly hit by a big meteoroid is miniscule,” says Cooke. Although, he allows, the odds are not well known “because we haven’t done enough observing to gather the data we need to calculate the odds.” Furthermore, while the danger of a direct hit is almost nil for an individual astronaut, it might add up to something appreciable for an entire lunar outpost.

Of greater concern, believes Suggs, is the spray??bf?”the secondary meteoroids produced by the blast.” No one knows how far the spray reaches and exactly what form it takes.

Also, ground-shaking impacts could kick up moondust, possibly over a wide area. Moondust is electrostatically charged and notoriously clingy. (See “Mesmerized by Moondust” from [email protected]) Even a small amount of moondust can be a great nuisance: it gets into spacesuit joints and seals, clings to faceplates, and even makes the air smell when it is tramped indoors by moonwalkers. Could meteoroid impacts be a source of lunar “dust storms?” Another question for the future….

Suggs and his team plan to make more observations. “We’re contemplating a long-term monitoring program active not only during major meteor showers, but also at times in between. We need to develop software to find these flashes automatically,” he continues. “Staring at 4 hours of tape to find a split-second flash can get boring; this is a job for a computer.”

With improvements, their system might catch lots of lunar meteors. Says Suggs, “I’m ready for more surprises.”

Original Source: NASA News Release

New Imaging Technique Reveals the Moon’s Secrets

Remote-sensing instruments on SMART-1 scan the Moon’s surface. Image credit: ESA Click to enlarge
ESA’s SMART-1 spacecraft has been surveying the Moon’s surface in visible and near-infrared light using a new technique, never before tried in lunar orbit.

For the last few months, the Advanced Moon Imaging Experiment (AMIE) on board SMART-1, has been opening new ground by attempting multi-spectral imaging in the ‘push-broom’ mode. This technique is particularly suited to colour imaging of the lunar surface.

(Note that ‘colour imaging’ here does not mean natural colour, the colour bands of the AMIE filters are in the infrared region and are selected such that the intensity of the iron absorption line can be determined from brightness ratios of the images.)

In this mode, AMIE takes images along a line on the Moon’s surface perpendicular to the ground track of the spacecraft.

It relies on the orbital motion of the spacecraft to reposition it as it records a sequence of images known as an ‘image swath’.

The AMIE camera on board SMART-1 has fixed-mounted filters which see the Moon in different colour bands. The figure shows four consecutive images taken by AMIE from left to right. The fixed filters are indicated by coloured frames.

The images, taken only a few seconds apart, show how the surface is moving through the different filters. The spacecraft is moving over the Moon’s surface at a speed of more than a kilometre per second!

By combining images showing the same feature on the Moon as seen through different filters, colour information can be obtained. This allows to study the mineralogical composition on the lunar surface, which in turn lets scientists deduce details of the formation of our celestial companion.

Whereas the multi-spectral camera aboard the US Clementine mission had constant illumination conditions, SMART-1’s orbit will offer different viewing angles. AMIE’s views correlated with Clementine data of the same lunar areas will allow scientists to better interpret such spectral data.

Original Source: ESA Portal

Dust Storms on the Moon

The Lunar Ejecta and Meteorites Experiment (LEAM). Image credit: NASA Click to enlarge
Every lunar morning, when the sun first peeks over the dusty soil of the moon after two weeks of frigid lunar night, a strange storm stirs the surface.

The next time you see the moon, trace your finger along the terminator, the dividing line between lunar night and day. That’s where the storm is. It’s a long and skinny dust storm, stretching all the way from the north pole to the south pole, swirling across the surface, following the terminator as sunrise ceaselessly sweeps around the moon.

see captionNever heard of it? Few have. But scientists are increasingly confident that the storm is real.

The evidence comes from an old Apollo experiment called LEAM, short for Lunar Ejecta and Meteorites. “Apollo 17 astronauts installed LEAM on the moon in 1972,” explains Timothy Stubbs of the Solar System Exploration Division at NASA’s Goddard Space Flight Center. “It was designed to look for dust kicked up by small meteoroids hitting the moon’s surface.”

Billions of years ago, meteoroids hit the moon almost constantly, pulverizing rocks and coating the moon’s surface with their dusty debris. Indeed, this is the reason why the moon is so dusty. Today these impacts happen less often, but they still happen.

Apollo-era scientists wanted to know, how much dust is ejected by daily impacts? And what are the properties of that dust? LEAM was to answer these questions using three sensors that could record the speed, energy, and direction of tiny particles: one each pointing up, east, and west.

LEAM’s three-decade-old data are so intriguing, they’re now being reexamined by several independent groups of NASA and university scientists. Gary Olhoeft, professor of geophysics at the Colorado School of Mines in Golden, is one of them:

“To everyone’s surprise,” says Olhoeft, “LEAM saw a large number of particles every morning, mostly coming from the east or west–rather than above or below–and mostly slower than speeds expected for lunar ejecta.”
What could cause this? Stubbs has an idea: “The dayside of the moon is positively charged; the nightside is negatively charged.” At the interface between night and day, he explains, “electrostatically charged dust would be pushed across the terminator sideways,” by horizontal electric fields. (Learn more: “Moon Fountains.” )

Even more surprising, Olhoeft continues, a few hours after every lunar sunrise, the experiment’s temperature rocketed so high–near that of boiling water–that “LEAM had to be turned off because it was overheating.”

Those strange observations could mean that “electrically-charged moondust was sticking to LEAM, darkening its surface so the experiment package absorbed rather than reflected sunlight,” speculates Olhoeft.

But nobody knows for sure. LEAM operated for a very short time: only 620 hours of data were gathered during the icy lunar night and a mere 150 hours of data from the blazing lunar day before its sensors were turned off and the Apollo program ended.

Astronauts may have seen the storms, too. While orbiting the Moon, the crews of Apollo 8, 10, 12, and 17 sketched “bands” or “twilight rays” where sunlight was apparently filtering through dust above the moon’s surface. This happened before each lunar sunrise and just after each lunar sunset. NASA’s Surveyor spacecraft also photographed twilight “horizon glows,” much like what the astronauts saw.

It’s even possible that these storms have been spotted from Earth: For centuries, there have been reports of strange glowing lights on the moon, known as “lunar transient phenomena” or LTPs. Some LTPs have been observed as momentary flashes–now generally accepted to be visible evidence of meteoroids impacting the lunar surface. But others have appeared as amorphous reddish or whitish glows or even as dusky hazy regions that change shape or disappear over seconds or minutes. Early explanations, never satisfactory, ranged from volcanic gases to observers’ overactive imaginations (including visiting extraterrestrials).

Now a new scientific explanation is gaining traction. “It may be that LTPs are caused by sunlight reflecting off rising plumes of electrostatically lofted lunar dust,” Olhoeft suggests.

All this matters to NASA because, by 2018 or so, astronauts are returning to the Moon. Unlike Apollo astronauts, who never experienced lunar sunrise, the next explorers are going to establish a permanent outpost. They’ll be there in the morning when the storm sweeps by.

The wall of dust, if it exists, might be diaphanous, invisible, harmless. Or it could be a real problem, clogging spacesuits, coating surfaces and causing hardware to overheat.

Which will it be? Says Stubbs, “we’ve still got a lot to learn about the Moon.”

Original Source: NASA News Release

Eternally Lit Lunar Peaks

The lunar surface taken by SMART-1. Image credit: ESA Click to enlarge
While the Earth is tilted at an angle of about 23 degrees, the moon’s tilt is just over 1 degree. Because of this, the summits of some lunar crater rims are sunlit over very long periods. In some locations, there are “peaks of eternal light,” or pics de lumiere eternelle, as the French astronomer Camille Flammarion called them at the end of the nineteenth century.

NASA’s Clementine spacecraft orbited the moon for three months in 1994. It identified some spots in the north polar region that are illuminated all the time during the summer, and others that are illuminated 80 percent of the time. This was not a big surprise, because we know that on Earth the poles receive a lot of sunlight during the summer. A question that the European Space Agency wanted to answer with the SMART-1 mission was whether there is enough solar light to still illuminate these places in winter.

SMART-1 mapped the polar areas on the moon, and we recently found an illuminated site about 15 kilometers from the north pole. Even though most of the moon is dark in that region, there’s a crater wall tall enough for sunlight to strike its rim.

Such perpetually lit areas would be good places to start our exploration of the moon. If you didn’t want to rely on complex power systems, you could install solar power stations at the peaks and use the energy to run small rovers and landers. Such systems are easier to design than electrical and mechanical systems that must withstand the extreme variation of temperature between lunar day and night. Branching out from there, you could build a spider web of facilities and habitats, with the core feeding energy to surrounding areas.

A peak of eternal light would be a good place to retreat to in winter, where we could maintain low level operations. In the spring and summer, we could reach out to other parts of the moon, extending hundreds of kilometers from the core.

The peaks provide some temperature stability. On the moon’s equator, the temperature can vary from minus 170 degrees C to plus 110 degrees C. The peaks have less variation, and an average temperature of minus 30 degrees C. A solar collector placed on a peak could provide enough energy to maintain a habitat with a very comfortable temperature of 20 degrees C.

With such a stable environment, you could do life science experiments to test how life adapts on another world. We could see how bacteria withstand the radiation environment. We could develop plant growth experiments in preparation for human bases.

But we also want to know if different organisms can survive and proliferate in the extreme conditions of the moon. By experimenting with different temperatures, artificial pressure, and other factors, we could figure out whether we even needed to develop lunar greenhouses. Do we need to recreate an exact copy of Earth conditions, or can we just adapt aspects of lunar conditions and make use of local resources?

Some astronomers are interested in the peaks of eternal light. You could build a very large observatory, at some distance from a peak of eternal light, that could observe the universe unattended. Because there’s no atmosphere on the moon, sunlight does not get scattered, so you can make observations even during part of the daytime.

Finally, just as the moon’s axis of rotation produces peaks of eternal light, there are also places, like the bottoms of some craters near the poles, that are in permanent shadow. We are very interested in such craters because they may contain water ice. That could be a valuable resource for future bases on the moon.

So a peak of eternal light would be a good central base from which to begin our lunar activities. It could provide a source of solar power for exploration, astronomical observations, life science experiments, and the investigation of possible water in the dark craters.

To extend beyond a few hundred kilometers from the peaks, however, we would need to develop nuclear power systems. That would provide enough energy to allow us to grow from a little refuge to a global village on the moon.

Original Source: NASA Astrobiology

Why is Moondust So Clingy?

A single grain of moondust hangs suspended in Abba’s vacuum chamber. Image credit: NASA Click to enlarge
Each morning, Mian Abbas enters his laboratory and sits down to examine–a single mote of dust. Zen-like, he studies the same speck suspended inside a basketball-sized vacuum chamber for as long as 10 to 12 days.

The microscopic object of his rapt attention is not just any old dust particle. It’s moondust. One by one, Abbas is measuring properties of individual dust grains returned by Apollo 17 astronauts in 1972 and the Russian Luna-24 sample-return spacecraft that landed on the Moon in 1976.

“Experiments on single grains are helping us understand some of the strange and complex properties of moondust,” says Abbas. This knowledge is important. According to NASA’s Vision for Space Exploration, astronauts will be back on the moon by 2018–and they’ll have to deal with lots of moondust.

The dozen Apollo astronauts who walked on the moon between 1969 and 1972 were all surprised by how “sticky” moondust was. Dust got on everything, fouling tools and spacesuits. Equipment blackened by dust absorbed sunlight and tended to overheat. It was a real problem.

Many researchers believe that moondust has a severe case of static cling: it’s electrically charged. In the lunar daytime, intense ultraviolet (UV) light from the sun knocks electrons out of the powdery grit. Dust grains on the moon’s daylit surface thus become positively charged.

Eventually, the repulsive charges become so strong that grains are launched off the surface “like cannonballs,” says Abbas, arcing kilometers above the moon until gravity makes them fall back again to the ground. The moon may have a virtual atmosphere of this flying dust, sticking to astronauts from above and below.

Or so the theory goes.

But do grains of lunar dust truly become positively charged when illuminated by ultraviolet light? If so, which grains are most affected–big grains or little grains? And what does moondust do when it’s charged?

These are questions Abbas is investigating in his “Dusty Plasma Laboratory” at the National Space Science and Technology Center in Huntsville, Alabama. Along with colleagues Paul Craven and doctoral student Dragana Tankosic, Abbas injects a single grain of lunar dust into a chamber and “catches” it using electric force fields. (The injector gives the grain a slight charge, allowing it to be handled by electric fields.) With the grain held suspended literally in mid-air, they “pump the chamber down to 10-5 torr to simulate lunar vacuum.”

Next comes the mesmerizing part: Abbas shines a UV laser on the grain. As expected, the dust gets “charged up” and it starts to move. By adjusting the chamber’s electric fields with painstaking care, Abbas can keep the grain centered; he can measure its changing charge and explore its fascinating characteristics.

Like the Apollo astronauts, Abbas has already discovered some surprises–even though his experiment is not yet half done.

“We’ve found two things,” says Abbas. “First, ultraviolet light charges moondust 10 times more than theory predicts. Second, bigger grains (1 to 2 micrometers across) charge up more than smaller grains (0.5 micrometer), just the opposite of what theory predicts.”

Clearly, there’s much to learn. For instance, what happens at night, when the sun sets and the UV light goes away?

That’s the second half of Abbas’s experiment, which he hopes to run in early 2006. Instead of shining a UV laser onto an individual lunar particle, he plans to bombard dust with a beam of electrons from an electron gun. Why electrons? Theory predicts that lunar dust may acquire negative charge at night, because it is bombarded by free electrons in the solar wind–that is, particles streaming from the sun that curve around behind the moon and hit the night-dark soil.

When Apollo astronauts visited the Moon 30+ years ago, they landed in daylight and departed before sunset. They never stayed the night, so what happened to moondust after dark didn’t matter. This will change: The next generation of explorers will remain much longer than Apollo astronauts did, eventually setting up a permanant outpost. They’ll need to know, how does moondust behave around the clock?

Stay tuned for answers from the Dusty Plasma Lab.

Original Source: NASA News Release

Lunar Lawn Mower

Lunar surface from Apollo 17. Image credit: NASA. Click to enlarge.
“If you can’t lick ’em, join ’em,” goes a cliché that essentially means “figure out how to live with whatever you can’t get rid of.”

That may be superb advice for living and working on the moon.

Scientists and engineers figuring out how to return astronauts to the moon, set up habitats, and mine lunar soil to produce anything from building materials to rocket fuels have been scratching their heads over what to do about moondust. It’s everywhere! The powdery grit gets into everything, jamming seals and abrading spacesuit fabric. It also readily picks up electrostatic charge, so it floats or levitates off the lunar surface and sticks to faceplates and camera lenses. It might even be toxic.

So what do you do with all this troublesome dust? Larry Taylor, Distinguished Professor of Planetary Sciences at the University of Tennessee has an idea:

Don’t try to get rid of it–melt it into something useful!

“I’m one of those weird people who like to stick things in ordinary kitchen microwave ovens to see what happens,” Taylor confessed to several hundred scientists at the Lunar Exploration Advisory Group (LEAG) conference at NASA’s Johnson Space Center last month.

At home in Tennessee, his most famous experiment involves a bar of Irish Spring soap, which quickly turns into “an abominable monster” when you hit the microwave’s Start button. But that’s not the one he told about at LEAG.

Apropos to the moon, he once put a small pile of lunar soil brought back by the Apollo astronauts into a microwave oven. And he found that it melted “lickety-split,” he said, within 30 seconds at only 250 watts.

The reason has to do with its composition. The lunar regolith, or soil, is produced when micrometeorites plow into lunar rocks and sand at tens of kilometers per second, melting it into glass. The glass contains nanometer-scale beads of pure iron – so called “nanophase” iron. It is those tiny iron beads that so efficiently concentrate microwave energy that they “sinter” or fuse the loose soils into large clumps.

This observation has inspired Taylor to imagine all kinds of machinery for sending to the moon that could fuse lunar dust into useful solids.

“Picture a buggy pulled behind a rover that is outfitted with a set of magnetrons,” that is, the same gizmo at the guts of a microwave oven. “With the right power and microwave frequency, an astronaut could drive along, sintering the soil as he goes, making continuous brick down half a meter deep–and then change the power settings to melt the top inch or two to make a glass road,” he suggested.

“Or say that you want a radio telescope,” he continued. “Find a round crater and run a little microwave ‘lawnmower’ up and down the crater’s sides to sinter a smooth surface. Hang an antenna from the middle–voila, instant Arecibo!” he exclaimed, referring to the giant 305-meter-diameter radio telescope in Puerto Rico formed out of a natural circular valley.

Technical challenges remain. Sintering moondust in a microwave oven on Earth isn’t the same as doing it on the airless moon. Researchers still need to work out details of a process to produce strong, uniformly sintered material in the harsh lunar environment.

But the idea has promise: Sintered rocket landing pads, roads, bricks for habitats, radiation shielding–useful products and dust abatement, all at once.

“The only limit,” says Taylor, “is imagination.”

Original Source: [email protected] News Release