Earth’s Moon Wandered Off Axis Billions Of Years Ago

A new study published in Nature reports discovery of a rare event — that Earth’s moon slowly moved from its original axis roughly 3 billion years ago. Ancient lunar ice indicates the moon’s axis slowly shifted by 125 miles, or 6 degrees, over 1 billion years. Earth’s moon now a member of solar system’s exclusive ‘true polar wander’ club, which includes just a handful of other planetary bodies.

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Planetary scientist Matt Siegler at Southern Methodist University, Dallas, and colleagues made the discovery while examining NASA data known to indicate lunar polar hydrogen. The hydrogen, detected by orbital instruments, is presumed to be in the form of ice hidden from the sun in craters surrounding the moon’s north and south poles. Exposure to direct sunlight causes ice to boil off into space, so this ice — perhaps billions of years old — is a very sensitive marker of the moon’s past orientation.

An odd offset of the ice from the moon’s current north and south poles was a tell-tale indicator to Siegler and prompted him to assemble a team of experts to take a closer look at the data from NASA’s Lunar Prospector and Lunar Reconnaissance Orbiter missions. Statistical analysis and modeling revealed the ice is offset at each pole by the same distance, but in exactly opposite directions.

This precise opposition indicates the moon’s axis — the imaginary pole that runs north to south through it’s middle, and around which the moon rotates — shifted at least six degrees, likely over the course of 1 billion years, said Siegler.

“This was such a surprising discovery. We tend to think that objects in the sky have always been the way we view them, but in this case the face that is so familiar to us — the Man on the Moon — changed,” said Siegler, who also is a scientist at the Planetary Science Institute, Tucson, Ariz.

“Billions of years ago, heating within the Moon’s interior caused the face we see to shift upward as the pole physically changed positions,” he said. “It would be as if Earth’s axis relocated from Antarctica to Australia. As the pole moved, the Man on the Moon turned his nose up at the Earth.”

The discovery is reported today in an article in the scientific journal Nature, “Lunar true polar wander inferred from polar hydrogen.” Siegler’s primary co-authors are astrophysicist Richard S. Miller, a professor at the University of Alabama Huntsville, and planetary dynamicist James T. Keane, a graduate student at the University of Arizona.

Very few planetary bodies known to permanently shift their axis

Planetary bodies settle into their axis based on their mass: A planet’s heavier spots lean it toward its equator, lighter spots toward the pole. On the rare occasion mass shifts and causes a planet to relocate on its axis, scientists refer to the phenomenon as “true polar wander.”

Discovery of lunar polar wander gains the moon entry into an extremely exclusive club. The only other planetary bodies theorized to have permanently shifted location of their axis are Earth, Mars, Saturn’s moon Enceladus and Jupiter’s moon Europa.

What sets the moon apart is its polar ice, which appears to effectively “paint out” the path along which its poles moved.

Moon’s axis likely started relocating about 3 billion years ago

On Earth, polar wander is believed to have happened due to movement of the continental plates. Polar wander on Mars resulted from a heavy volcanic region. The moon’s change in mass was internal — the shift of a large, single mantle “plume.” Ancient volcanic activity some 3.5 billion years ago melted a portion of the moon’s mantle, causing it to bubble up toward its surface, like goo drifting upward in a lava lamp.

“The moon has a single region of the crust, a large basaltic plain called Procellarum, where radioactive elements ended up as the moon was forming,” Siegler said. “This radioactive crust acted like an oven broiler heating the mantle below.”

Some of the material melted, forming the dark patches we see at night, which are ancient lava, he said.

“This giant blob of hot mantle was lighter than cold mantle elsewhere,” Siegler said. “This change in mass caused Procellarum — and the whole moon — to move.”

The moon likely relocated its axis starting about 3 billion years ago or more, slowly moving over the course of a billion years, Siegler said, etching a path in its ice.

Over time, the axis shifted 125 miles or 200 kilometers — about half the distance from Dallas to Houston, or equal the distance from Washington D.C. to Philadelphia.

Neutrons can indicate the presence of water or ice

Polar wander explains why the moon appears to have lost much of its ice.

Siegler compares true polar wander to holding a glass filled with water. Most planets are like a steady hand holding a glass, their axis doesn’t shift and the water stays put. A planet whose mass is changing is like a wobbly hand, causing its axis to shift and the water to spill out. Similarly, as Earth’s moon changed its axis, much of its ice ceased to be hidden from the sun and was lost.

Co-author Richard Miller mapped the moon’s remaining ice by using data from NASA’s Lunar Prospector mission, which orbited the moon from 1998 to 1999. The presence of ice is inferred by measuring the energy of neutrons emitted from the lunar surface. Instruments on NASA’s satellite, including a neutron spectrometer, measured neutrons liberated from the moon by a rain of stellar particles scientists call cosmic rays. Low energy neutrons indicate the presence of hydrogen, the dominant molecule in water and ice.

“The maps show four key features,” said Siegler and his colleagues. “First, the largest quantity of hydrogen is offset from the current rotation axis of the moon by roughly 5.5 degrees. Second, the hydrogen enhancements are of similar magnitude at both poles. Third, the asymmetric enhancements do not correlate with expectations from the current thermal or permanently shadowed environment. And lastly, and most significantly, the spatial distributions of polar hydrogen appear to be nearly antipodal.”

Lunar ice is ancient time capsule; may hold answers to deep mysteries

Siegler’s discovery opens the door to further discoveries around an even deeper question — the mystery of why there is water on the moon and on Earth. Scientific theory surrounding the formation of the solar system postulates water could not have formed much closer to the sun than Jupiter, Siegel said.

“We don’t know where the Earth’s water came from. It appears to have come from the outer solar system well after the Earth and moon formed,” he said. “Ice on other bodies, like the moon or Mercury, might give us a clue to its origin.”

The fact lunar ice correlates so well with true polar wander implies that it predates this motion, Siegler said, making the ice very ancient.

“The ice may be a time capsule from the same source that supplied the original water to Earth,” he said. “This is a record we don’t have on Earth. Earth has reworked itself so many times, there’s nothing that old left here. Ancient ice from the moon could provide answers to this deep mystery.”

Other co-authors on the scientific paper include Matthieu Laneuville, David A. Paige, Isamu Matsuyama, David J. Lawrence, Arlin Crotts and Michael J. Poston.

Tales of a Tilting Moon Hidden in Its Polar Ice

A new study published Wednesday in Nature reports that the moon may not have always had the same face pointed toward the Earth. Instead, the “Man in the Moon” nodded up and down, because of heating and volcanic eruptions on the Earth-facing side of the moon.

erupting volcanoes on moon

An international team including University of Arizona planetary scientists James Keane and Isamu Matsuyama made this discovery while trying to explain maps of lunar polar hydrogen. This hydrogen, which was discovered by NASA’s Lunar Prospector mission in the 1990s, is believed to represent water ice, protected from the Sun’s rays in cold, permanently shadowed craters near the moon’s north and south poles. If ice were exposed to direct sunlight on the moon, it would boil off into space, so it is a very sensitive tracer of the moon’s orientation with time.

“Weirdly, the moon’s ice isn’t exactly at the coldest spots on the north or south poles of the moon,” said Matt Siegler, a scientist with the Planetary Science Institute in Tucson and the paper’s first author.

Instead, the polar ice is shifted off the poles by about six degrees, and in exact opposite directions at either pole. (On the Earth, six degrees is about equal to the distance from Tucson to Los Angeles.) This precisely opposite (“antipodal”) relationship indicates that the moon’s spin axis – the imaginary line that runs from the north pole, through the center of the moon, to the south pole, and around which the moon rotates – shifted over the last few billion years. As the moon reoriented, it left behind a trail of water ice, effectively “painting out” the path that the poles took with time.

When the research team realized that the moon’s ice might be telling a story of reorientation, it turned to UA experts in planetary dynamics, Keane and Matsuyama.
“Usually we think of planets as ‘spinning on’ in the same unchanging way with time, but that’s not true,” said Keane, a graduate student at the UA’s Lunar and Planetary Laboratory. “We know that the Earth and a handful of other planetary bodies have changed their spin axes with time.”

On the Earth, this reorientation can be measured with GPS and techniques that we don’t have on other planets. This forces scientists to look for clues in other, more unusual datasets. For example, Matsuyama, a professor of planetary science at LPL and Keane’s doctoral advisor, recently used gravity measurements and observations of ancient valley networks on Mars to infer reorientation on that planet. This study is the first to use lunar ice to infer the change in the spin of the moon.

The spins of planetary bodies are set by how mass is distributed within the planet: A planet’s denser spots try to drag the planet toward its equator, less dense spots toward the pole. On the moon, tidal forces from the Earth also can drag dense spots toward – or away from – the Earth-facing side of the moon. Scientists refer to this reorientation phenomenon as “true polar wander.”

Using this idea that the moon’s ice traces an earlier spin pole, Keane used a combination of theoretical models and measurements of the moon’s mass distribution from NASA missions to identify what could physically cause this polar wander.

“I was shocked when the models outlined Oceanus Procellarum as the only possible geologic feature that could have done this,” Keane said.

Oceanus Procellarum is a vast, volcanic province on the Earth-facing side of the moon. It contains all of the dark splotches we see forming the “face” of the moon, which is actually a giant field of ancient lava flows. When the moon formed, many of the body’s radioactive elements ended up in the Procellarum.
“This radioactive crust acted liked an oven broiler heating and melting the mantle below,” Siegler said.

The giant Procellarum hot spot was less dense than the rest of the moon and caused the whole moon to move. As the moon slowly moved over billions of years, it etched a path into the polar ice.

The paper shows that the moon may have once had much more ice near its poles and the ice we see today is the tiny portion, which has survived this polar migration. Large amounts of ice could have been brought to the moon by comets and icy asteroids early in the moon’s history or potentially outgassed from the lunar mare themselves. Figuring out the origin of this ancient lunar water might also help scientists understand how water was delivered to the early Earth.

“This gives us a way to model exactly where the ice should be, which tells us about its origin and where astronauts might find a drink on future missions to the moon,” Siegler said.

“Up until this work, most researchers thought that the moon’s water was just recently deposited, as a late veneer,” Keane said. “Since we’ve shown that the moon’s water is linked to volcanic activity on the moon several billion years ago, this means it might be a time capsule of primordial water. Directly sampling this ancient ice will allow us to investigate many still unanswered questions around the origin of the Earth’s water.”

This project was supported in part by NASA’s SSERVI VORTICES node, the Lunar Reconnaissance Orbiter and the NASA Lunar Advanced Science and Exploration Research, or LASER, program.

First Observed Evidence of Galactic Wind Phenomenon

Research led by Johns Hopkins University scientists has found new persuasive evidence that could help solve a longstanding mystery in astrophysics. A paper published in the Monthly Notices of the Royal Astronomical Society, finds evidence supporting the argument that intense radiation and galaxy-scale winds emitted by quasars heats up clouds of dust and gas preventing material from cooling and forming more dense clouds, and eventually stars.

star-formation-prevention

“I would argue that this is the first convincing observational evidence of the presence of quasar feedback,” said Tobias Marriage, an assistant professor in the university’s Henry A. Rowland Department of Physics and Astronomy.

cosmic microwave background

Specifically, investigators looked at information on 17,468 galaxies and found a tracer of energy when high-energy electrons disturb the Cosmic Microwave Background. This phenomenon is known as the Sunyaev-Zel’dovich Effect. The phenomenon, named for two Russian physicists who predicted it nearly 50 years ago.

Information gathered in the Sloan Digital Sky Survey by an optical telescope at the Apache Point Observatory in New Mexico was used to find the quasars. Thermal energy and evidence of the SZ Effect were found using information from the Atacama Cosmology Telescope, an instrument designed to study the CMB that stands in the Atacama Desert in northern Chile. To focus on the dust, investigators used data from the SPIRE, or Spectral and Photometric Imaging Receiver, on the Herschel Space Observatory.

Astronomers Report Most ‘Outrageously’ Luminous Galaxies Ever Observed

Astronomers at the University of Massachusetts Amherst report that they have observed the most luminous galaxies ever seen in the Universe, objects so bright that established descriptors such as “ultra-” and “hyper-luminous” used to describe previously brightest known galaxies don’t even come close. Lead author and undergraduate Kevin Harrington says, “We’ve taken to calling them ‘outrageously luminous’ among ourselves, because there is no scientific term to apply.”

astronomers

Details appear in the current early online edition of Monthly Notices of the Royal Astronomical Society.

Harrington is a senior undergraduate in astronomy professor Min Yun’s group, which uses the 50-meter diameter Large Millimeter Telescope (LMT), the largest, most sensitive single-aperture instrument in the world for studying star formation. It is operated jointly by UMass Amherst and Mexico’s Instituto Nacional de Astrofísica, Óptica y Electrónica and is located on the summit of Sierra Negra, a 15,000-foot extinct volcano in the central state of Puebla, a companion peak to Mexico’s highest mountain.

Yun, Harrington and colleagues also used the latest generation of satellite telescope and a cosmology experiment on the NASA/ESA collaboration Planck satellite that detects the glow of the Big Bang and microwave background for this work. They estimate that the newly observed galaxies they identified are about 10 billion years old and were formed only about 4 billion years after the Big Bang.

Harrington explains that in categorizing luminous sources, astronomers call an infrared galaxy “ultra-luminous” when it has a rating of about 1 trillion solar luminosities, and that rises to about 10 trillion solar luminosities at the “hyper-luminous” level. Beyond that, for the 100 trillion solar luminosities range of the new objects, “we don’t even have a name,” he says.

Yun adds, “The galaxies we found were not predicted by theory to exist; they’re too big and too bright, so no one really looked for them before.” Discovering them will help astronomers understand more about the early Universe. “Knowing that they really do exist and how much they have grown in the first 4 billion years since the Big Bang helps us estimate how much material was there for them to work with. Their existence teaches us about the process of collecting matter and of galaxy formation. They suggest that this process is more complex than many people thought.”

The newly observed galaxies are not as large as they appear, the researchers point out. Follow-up studies suggest that their extreme brightness arises from a phenomenon called gravitational lensing that magnifies light passing near massive objects, as predicted by Einstein’s general relativity. As a result, from Earth they look about 10 times brighter than they really are. Even so, they are impressive, Yun says.

Gravitational lensing of a distant galaxy by another galaxy is quite rare, he adds, so finding as many as eight potential lensed objects as part of this investigation “is another potentially important discovery.” Harrington points out that discovering gravitational lensing is already like finding a needle in a haystack, because it requires a precise alignment from viewing on Earth. “On top of that, finding lensed sources this bright is as rare as finding the hole in the needle in the haystack.”

They also conducted analyses to show that the galaxies’ brightness is most likely due solely to their amazingly high rate of star formation. “The Milky Way produces a few solar masses of stars per year, and these objects look like they forming one star every hour,” Yun says. Harrington adds, “We still don’t know how many tens to hundreds of solar masses of gas can be converted into stars so efficiently in these objects, and studying these objects might help us to find out.”

For this work, the team used data from the most powerful international facilities available today to achieve these discoveries, the Planck Surveyor, the Herschel, and the LMT. As Yun explains, the all-sky coverage of the Planck is the only way to find these rare but exceptional objects, but the much higher resolutions of the Herschel and the LMT are needed to pinpoint their exact locations.

He suggests, “If the Planck says there’s an object of interest in Boston, the Herschel and LMT have the precision to say that the object is on which table in a particular bar next to Fenway Park.” With this information, another LMT instrument called “Redshift Search Receiver” can be deployed to determine how far away and how old these galaxies are and how much gas they contain to sustain their extreme luminosities.

One other aspect of this project is extraordinary, Yun says. “For an undergrad to do this kind of study is really impressive. In 15 years of teaching, I have seen only a few undergraduates who pushed a project to the point of publishing in a major journal article such as this. Kevin deserves a lot of credit for this work.”

For his part, Harrington, who will graduate in May with a double major in astronomy and neuroscience, says he plans to start his doctoral work in September at Germany’s Max Planck Institute for Astronomy and the University of Bonn, continuing this research on galaxy evolution.

This work was supported by the National Science Foundation, the UMass Amherst Commonwealth Honors College Research Fellowship and Honors Grants, and The William Bannick Student Travel Grant, without which Harrington’s two trips to the remote telescope in Mexico would not have been possible, Yun says.

New Finding Indicates Humans in Ireland 12,500 Years Ago

For decades, the earliest evidence of human life in Ireland dated from 8,000 BC. But radiocarbon dating of a bear’s knee bone indicated it had been butchered by a human in about 10,500 BC – some 12,500 years ago and far earlier than the previous date.

ireland palaeolithic period caves

“This find adds a new chapter to the human history of Ireland,” said Marion Dowd, an archaeologist at the Institute of Technology Sligo who made the discovery along with Ruth Carden, a research associate with the National Museum of Ireland.

The knee bone, which is marked by cuts from a sharp tool, was one of thousands of bones first found in 1903 in a cave in County Clare on the west coast of Ireland.

It was stored in the National Museum of Ireland since the 1920s, until Carden and Dowd re-examined it and applied for funding to have it radiocarbon dated – a technique developed in the 1940s – by Queen’s University Belfast.

The team sent a second sample to the University of Oxford to double-check the result. Both tests indicated the bear had been cut up by a human about 12,500 years ago.

The new date means there was human activity in Ireland in the Stone Age or Palaeolithic period, whereas previously, scientists only had evidence of humans in Ireland in the later Mesolithic period.

“Archaeologists have been searching for the Irish Palaeolithic since the 19th century, and now, finally, the first piece of the jigsaw has been revealed,” Dowd said.

Three experts further confirmed that the cut marks on the bone had been made when the bone was fresh, confirming they dated from the same time as the bone.

The results were revealed in a paper published in the journal Quaternary Science Reviews.

As well as pushing back the date of human history in Ireland, the find may have important implications for zoology, as scientists have not previously considered that humans could have influenced extinctions of species in Ireland so long ago.

“From a zoological point of view, this is very exciting,” Carden said. “This paper should generate a lot of discussion within the zoological research world and it’s time to start thinking outside the box… or even dismantling it entirely!”

The National Museum of Ireland noted that approximately two million more specimens are held in its collections and could reveal more secrets.

“All are available for research and we never know what may emerge,” said Nigel Monaghan, keeper of the natural history division of the National Museum of Ireland.

New Research Reveals Fastest Winds Ever Seen

New research led by astrophysicists at York University has revealed the fastest winds ever seen at ultraviolet wavelengths near a supermassive black hole. The team’s findings were published today in the print edition of the Monthly Notices of the Royal Astronomical Society.

High-energy-wind-from-Black-Holes
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Jesse Rogerson, Department of Physics and Astronomy at York University said; “We’re talking wind speeds of 20 per cent the speed of light, which is more than 200 million kilometers an hour. That’s equivalent to a category 77 hurricane – and we have reason to believe that there are quasar winds that are even faster.”

Astronomers have known about the existence of quasar winds since the late 1960s. At least one in four quasars have them. Quasars are the discs of hot gas that form around supermassive black holes at the center of massive galaxies – they are bigger than Earth’s orbit around the Sun and hotter than the surface of the Sun, generating enough light to be seen across the observable universe.

stellar_wind

“Black holes can have a mass that is billions of times larger than the Sun, mostly because they are messy eaters in a way, capturing any material that ventures too close,” says York University Associate Professor Patrick Hall, who is Rogerson’s supervisor. “But as matter spirals toward a black hole, some of it is blown away by the heat and light of the quasar. These are the winds that we are detecting.”

Rogerson and his team used data from a large survey of the sky known as the Sloan Digital Sky Survey to identify new outflows from quasars. After spotting about 300 examples, they selected about 100 for further exploration, collecting data with the Gemini Observatory’s twin telescopes in Hawaii and Chile, in which Canada has a major share.

“We not only confirmed this fastest-ever ultraviolet wind, but also discovered a new wind in the same quasar moving more slowly, at only 140 million kilometers an hour,” says Hall. “We plan to keep watching this quasar to see what happens next.”

Much of this research is aimed at better understanding outflows from quasars and why they happen.

“Quasar winds play an important role in galaxy formation,” says Rogerson. “When galaxies form, these winds fling material outwards and deter the creation of stars. If such winds didn’t exist or were less powerful, we would see far more stars in big galaxies than we actually do.”

Green Comet Approaches Earth

On March 21st, Comet 252P/LINEAR will make a close approach to Earth–only 0.036 AU (5.4 million km) away. This is the fifth closest cometary approach on record and, as a result, the normally dim comet has become an easy target for backyard telescopes. Indeed, it is brightening much faster than expected.

“Comet 252P/LINEAR has surpassed expectations and is now bordering on naked eye visibility for southern observers,” reports Michael Mattiazzo of Swan Hill, Australia. “At the moment it is near magnitude +6,” Observing from Brisbane, Australia, Tom Harradine didn’t even need a telescope to photograph 252P/LINEAR. On March 17th, he caught the green comet (circled) passing by the Tarantula Nebula using just a digital camera.

greencomet_strip

The comet is green because its vaporizing nucleus emits diatomic carbon, C2, a gas which glows green in the near-vacuum of space. The verdant color will become more intense in the nights ahead as 252P/LINEAR approaches Earth.

In recent days, astronomers have realized that Comet 252P/LINEAR might have a companion. A smaller and much dimmer comet named “P/2016 BA14” will buzz Earth even closer than 252P/LINEAR on March 22nd. P/2016 BA14 appears to be a fragment of 252P/LINEAR. Unlike its parent, however, P/2016 BA14 is “pitifully faint” and difficult to observe. Sky and Telescope has the full story.

There is a chance that the comet’s approach could cause a minor meteor shower. According to the International Meteor Organization, “[modeling by forecaster] Mikhail Maslov indicates that there might be a weak episode of faint, very slow meteors (15.5 km/s) on March 28–30 from a radiant near the star μ Leporis.” Little is known about meteors from this comet, so estimates of the meteor rate are very uncertain. Maslov’s models suggest no more than 5 to 10 per hour.