Russians 'Close' to Drilling Into Antarctica's Lake Vostok
|10:17:26 PM, Monday, February 06, 2012|
“(National Geographic News) Russian scientists are "very, very close" to reaching the surface of afreshwater lake 2.3 miles (3,768) meters under the Antarctic ice, news reports say. It would be the first time anyone has penetrated a subglacial lake on the frozen continent.
The Russian news agency RIA Novosti reported today that the team has in fact breached the Lake Vostok.
However Mahlon C. Kennicutt II, a professor of oceanography at Texas A&M University who leads several Antarctic research groups, said the report should be viewed with skepticism until an official announcement is made.
"I would be surprised if it was announced officially this quiet. Also, the one source [in the article] is unnamed, so it is hard to tell," he said.
Montana State ecologist John Priscu echoed Kennicutt's caution. "There are a lot of rumors going around about penetrating the lake, and we need the Russian program to make the official announcement," Priscu told National Geographic News via email.
Scientists have been drilling this shaft toward Lake Vostok—one of the world's largest freshwater lakes—since the lake was discovered in 1996. This field season, the Russian team has been drilling since the beginning of January.
As of February 6, the team was within 16 to 32 feet (5 to 10 meters) of reaching the under-ice lake, Priscu told BBC News.
With the Antarctic summer rapidly coming to a close, it's now or next year for the scientists, who are hoping to probe the Great Lake-size water body for the first time in 25 million years.
Once it happens, "it'll be a big splash, and I mean that metaphorically," Texas A&M's Kennicutt said.
Race to the Lake
Lake Vostok is the largest of more than 145 subglacial lakes—most of them several kilometers long—that have been discovered under the Antarctic ice in past decades.
These subglacial lakes may open a new window onto our planet, for example by offering new insights into climate history or revealing unknown life-forms.
Montana State's Priscu, for instance, has found evidence that microbes could live in the subglacial lake, deriving energy from minerals—"eating rocks," as he told National Geographic News in 2007.
Regardless of what they find, if the Russian team succeeds, "their efforts will transform the way we do science in Antarctica and provide us with an entirely new view of what exists under the vast Antarctic ice sheet," Priscu said Monday…”
The Naked and Famous – Punching In A Dream
|4:18:51 PM, Saturday, February 04, 2012|
Two New Moons Found Orbiting Jupiter
|1:17:38 PM, Saturday, February 04, 2012|
“(National Geographic News) Two new moons have been found orbiting Jupiter, bringing the Jovian family count up to 66 natural satellites, astronomers revealed this week.
Currently known as S/2011 J1 and S/2011 J2, the new moons were first identified in images acquired with the Magellan-Baade Telescope at the Las Campanas Observatory in Chile on September 27, 2011.
The objects are among the smallest moons yet discovered in the solar system, each measuring only about a kilometer (0.62 mile) wide.
Unlike Jupiter's four large Galilean moons, which are visible from Earth with even small backyard telescopes, both new moons are dim and very distant from the planet, taking about 580 and 726 days to complete their orbits.
Scientists had previously discovered new Jovian satellites in 2010, and astronomers think there may be more—lots more.
"The satellites are part of the outer retrograde swarm of objects around Jupiter," said Scott Sheppard, of the Department of Terrestrial Magnetism at the Carnegie Institute for Science in Washington, D.C., who reported the discovery.
Retrograde satellites are moons that orbit "backward"—in the opposite direction of a planet's axial rotation. Including the two new moons, the Jupiter swarm features 52 known retrograde satellites, which are all relatively tiny.
"It is likely there are about a hundred satellites of this size" in the swarm, Sheppard said.
New Moons Are Likely Captured Bodies
Like most of Jupiter's other retrograde satellites, S/2011 J1 and J2 are also classified as irregular moons, because they orbit far from the planet and have highly eccentric and inclined orbits.
Due to their odd orbits, the moons are likely asteroid or comet pieces that were long ago captured by Jupiter's gravity rather than developing in place during the formation of the planet itself.
"Because these outer irregular satellites were captured during the solar system's early years, they can give us insight into the planet's formation and evolution process," Sheppard added.
As far as more imaginative names are concerned, that will require more time and more data.
By established convention, satellites in the Jovian system are named for lovers and descendants of the Roman god Jupiter or his Greek counterpart, Zeus.
But "satellites in general are not given Roman or Greek mythological names until they have at least one year of observations," Sheppard said.
The new Jupiter moons were announced this week in the International Astronomical Union's Central Bureau for Astronomical Telegrams.”
Space Pictures This Week: Sun Loops, Blue Marble, More
|5:02:26 PM, Saturday, January 28, 2012|
"Huge loops of plasma?superheated, charged gas?rise from an active region on the sun in a newly released picture from NASA's Solar Dynamics Observatory. Each loop is as tall as several Earths stacked on top of each other.
The plasma loops trace the sun's otherwise invisible magnetic field lines, which rise from the star's magnetically active regions?the starting points for huge eruptions of radiation known as solar flares..."
-- Been neglecting the page a bit, but I'm trying to get back into at least making somewhat regular updates.
Phobos-Grunt: Failed Probe 'Falls Over Pacific'
|5:20:27 PM, Sunday, January 15, 2012|
“Orbital tracking reports suggest Russia's failed Mars probe, Phobos-Grunt, fell back to Earth on Sunday, to be destroyed over the Pacific.
Both Russian and US military sources announced the demise of the craft within minutes of each other.
It brings to an end the sorry story of this mission, which promised to return rocky samples from Mars' biggest moon.
Instead, after its launch in November, Phobos-Grunt could not get more than 345km from Earth before stalling.
Once it became clear that controllers could not establish contact with the probe and diagnose its faults, a fiery dive back to Earth became inevitable.
This is the third high-profile spacecraft re-entry in four months, following the return in September of the American UARS satellite and the German Rosat telescope in October. Both fell over the ocean.
With so much of the Earth's surface covered by water, there was every chance Phobos-Grunt would do the same.
The Russians have had a torrid run of space failures recently, leading the head of the country's space agency to wonder even if saboteurs were at work.
Western countries, which use Russian rockets to launch their satellites, are just worried though that some systematic failures have started to appear in what has traditionally been a highly regarded space industry.
With their own opportunity to go to Mars now lost, the Russians may decide to put their future interplanetary efforts into joint ventures with the Americans and the Europeans. The Russians have an offer from the US and Europe to join the ExoMars missions to the Red Planet in 2016 and 2018…”
Doomed Phobos-Grunt, Russian Mars Probe to Crash Sunday
|12:47:40 AM, Sunday, January 15, 2012|
(Nat. Geo.) After circling Earth for more than two months, the failed Russian Mars probe Phobos-Grunt will make a kamikaze dive into Earth's atmosphere sometime around Sunday, experts say.
The Russian space agency, Roscosmos, which has given up hope of recovering the spacecraft, is now concentrating on figuring out what will happen to the pieces that fall to Earth.
The agency expects about 20 to 30 fragments totaling about 440 pounds (200 kilograms) to reach the ground, with very low risk to people.
"Due to its predominantly low-melting construction materials, Phobos-Grunt will largely burn up during its reentry, so the corresponding risk to the population on ground is low," said Heiner Klinkrad, head of the space-debris office at the European Space Agency's space operations center in Darmstadt, Germany.
Phobos-Grunt is also carrying 11 tons of toxic fuel propellants, all of which should be consumed by the massive fireball at reentry.
"Roscosmos does not expect any environmental contamination—neither for an impact on ground nor at sea," Kilnkrad noted.
Predicting Mars Probe's Reentry Is Tricky
Phobos-Grunt was meant to go to Phobos—one of the red planet's two moons—where it would have scooped up soil samples and sent them back to Earth in 2014.
But the Russian probe was doomed soon after reaching orbit on November 8, 2011, when the spacecraft failed to fire its rockets and got stuck in Earth's orbit.
As the probe circles about 120 miles (200 kilometers) above Earth, Phobos-Grunt's orbit is rapidly lowering due to drag from Earth's outer atmosphere, Klinkrad said.
Predicting the probe's precise reentry time and location have been tricky, since it will depend on how the probe behaves in its final days and hours in orbit.
"When the 14-ton spacecraft completes its last orbits, at altitudes below 120 kilometers [75 miles], aerodynamic forces can break off parts of the appendices, like solar arrays," Klinkrad said.
In addition, "short-term changes in solar and geomagnetic activity can [have] a strong influence on the ambient atmospheric air density and affect the orbit lifetime," he said.
Meanwhile, before it meets its demise, Phobos-Grunt can be spotted in the night sky without any optical aid whatsoever—if you know what to look for.
"Under favorable conditions, Phobos-Grunt is readily visible to the unaided-eye as a bright, rapidly moving, starlike object," said veteran satellite tracker Ted Molczan of Toronto, Canada.
"Observers have noted a pronounced orange hue, which results from the gold-colored thermal blanket that covers most of its surface."
But the real sky show will occur when the dead probe burns up in the atmosphere.
As it sinks into the denser layers of Earth's atmosphere, the probe will heat up and begin to glow brightly, forming a long plasma tail and resembling "a surreal-looking comet," Molczan said.
"Eventually, the combination of extreme heat and rapid deceleration will cause it to fragment into many pieces that will spread out along the path of descent," he said.
"The debris trail will move rapidly across the sky, visible for perhaps one to two minutes, assuming [a viewer has a] reasonably unobstructed view of the sky."
If any pieces do make it to the ground, the European Space Agency's Klinkrad warns people not to take them as souvenirs.
"If someone finds a fragment, it should be turned in to national authorities, because they remain the property of Russia."”
Super-Cool Planck Mission Begins to Warm
|3:50:16 PM, Friday, January 13, 2012|
“ (BBC) One of Europe's great astronomical ventures is coming to a close.
The Planck telescope, put in space to map the oldest light in the Universe, has run out of the helium coolant that keeps it in full working order.
Engineers expect the observatory's systems to start to warm from their ultra-frigid state in the coming days, blinding one of its two instruments.
Nonetheless, Planck has gathered more than enough data since its launch in 2009 to complete its mission goals.
"We have had a flood of data - much more data than originally anticipated, and now we are in the frantic phase," revealed Jan Tauber, the European Space Agency's (Esa) Planck project scientist.
"In a year's time we have promised to deliver our maps and scientific papers, so we are feeling some pressure," he told BBC News.
Planck's quest has been to survey the Cosmic Microwave Background (CMB) - the "first light" to sweep out across space once a post-Big-Bang Universe had cooled sufficiently to permit the formation of hydrogen atoms.
Before that time, scientists say, the cosmos would have been so hot that matter and radiation would have been "coupled" - the Universe would have been opaque.
The CMB pervades the entire sky, and scientists can measure tiny temperature variations in it to glean information about the age, contents and shape of the cosmos.
Two American satellites have already done this, but Planck is much more sensitive and can make much more detailed maps, with higher resolution.
To do this, some of its light detectors have had to operate at the astonishingly low temperature of minus 273.05C - just a tenth of a degree above "absolute zero", the lowest temperature theoretically possible in the Universe…”
Pentagon-Backed 'Time Cloak' Stops the Clock
|3:13:41 AM, Friday, January 13, 2012|
“Pentagon-supported physicists on Wednesday said they had devised a "time cloak" that briefly makes an event undetectable.
It's one thing to make an object invisible, like Harry Potter's mythical cloak. But scientists have made an entire event impossible to see. They have invented a time masker.
Think of it as an art heist that takes place before your eyes and surveillance cameras. You don't see the thief strolling into the museum, taking the painting down or walking away, but he did. It's not just that the thief is invisible - his whole activity is.
What scientists at Cornell University did was on a much smaller scale, both in terms of events and time. It happened so quickly that it's not even a blink of an eye. Their time cloak lasts an incredibly tiny fraction of a fraction of a second. They hid an event for 40 picoseconds (trillionths of a second), according to a study appearing in Thursday's edition of the journal Nature.
We see events happening as light from them reaches our eyes. Usually it's a continuous flow of light. In the new research, however, scientists were able to interrupt that flow for just an instant.
Other newly created invisibility cloaks fashioned by scientists move the light beams away in the traditional three dimensions. The Cornell team alters not where the light flows but how fast it moves, changing in the dimension of time, not space.
They tinkered with the speed of beams of light in a way that would make it appear to surveillance cameras or laser security beams that an event, such as an art heist, isn't happening.
Another way to think of it is as if scientists edited or erased a split second of history. It's as if you are watching a movie with a scene inserted that you don't see or notice. It's there in the movie, but it's not something you saw, said study co-author Moti Fridman, a physics researcher at Cornell.
The scientists created a lens of not just light, but time. Their method splits light, speeding up one part of light and slowing down another. It creates a gap and that gap is where an event is masked.
"You kind of create a hole in time where an event takes place," said study co-author Alexander Gaeta, director of Cornell's School of Applied and Engineering Physics. "You just don't know that anything ever happened."
This is all happening in beams of light that move too fast for the human eye to see. Using fiber optics, the hole in time is created as light moves along inside a fiber much thinner than a human hair. The scientists shoot the beam of light out, and then with other beams, they create a time lens that splits the light into two different speed beams that create the effect of invisibility by being too fast or too slow. The whole work is a mess of fibers on a long table and almost looks like a pile of spaghetti, Fridman said…”
The 5 Most Insane Original Uses of Famous Products
|2:40:16 AM, Friday, January 13, 2012|
"Plenty of products we use every day have interesting little back stories to them. For instance, we bet your fourth grade self could find no greater joy than discovering that Q-tips were originally called "Baby Gays."
But what is even more interesting than that is how some world-changing inventions were created for a completely different, and often stupid, purpose. For instance ..."
Bubble - Blowing Stars Seen in the Thousands by Public
|1:20:19 AM, Friday, January 13, 2012|
“A project to spot the "bubbles" that young, massive stars blow in the gas surrounding them has come up trumps, finding more than 5,000 of the objects.
That increases the known catalogue of bubbles by more than a factor of 10.
The discoveries were made by citizen scientists studying images from the Spitzer space telescope, as part of the Milky Way Project.
The much-improved catalogue has been submitted to the Monthly Notices of the Royal Astronomical Society.
One of the great remaining mysteries of how our Universe works is how stars themselves form in vast clouds of swirling gas.
Astronomers are keen to find star-forming regions, hoping to catch the process at various stages to better understand it.
Groups of stars form in clusters near particularly large stars, and one good hint of these stellar nurseries is the "bubble" that they blow into the surrounding gas - a bubble that can be seen in pictures taken by Spitzer's infrared camera.
But the task to find and list all the bubbles in existing high-resolution images taken by Spitzer is a daunting one.
The largest previous cataloguing effort was carried out in 2007 by a handful of US astronomers poring through the images with their own eyes; it came up with 269 bubbles.
Automating the process with a computer algorithm is not an option, said Eli Bressert of the European Southern Observatory.
"To have an algorithm that can identify that kind of structure, no one can do it a the moment - it's way too complex," he told BBC News.
"You need two things: pattern recognition and the ability to judge, based on the other data that you've seen, what's good and what's bad - and that's what humans are good at."
Enter the Milky Way Project, which grew from the riotously successful citizen science project to classify and describe types of galaxies, Galaxy Zoo…”
Old Genes Make New, Giant - Headed Ants
|2:33:20 AM, Thursday, January 12, 2012|
“Every animal carries a record of its past in its genes -- sometimes teeth show up in birds and vestigial limbs on snakes and whales. Ants are no exception. What if that potential could be tapped? And what brings it out?
That’s what a group of scientists at McGill University thought when they ran into a colony of ants on Long Island. A colony of ants known as Pheidole morrisi (more commonly called big-headed ants) had members we call soldiers with really outsized heads and bodies. These were called “super soldiers.”
Pheidole, like many other ant species, are divided into castes, such as workers, queens and soldiers. Different foods are given to them when they are larvae, which triggers hormones that determine which caste the ant grows up to be.
Super soldiers occur naturally in some species of Pheidole in the southwestern United States and Mexico. But those living in upstate New York aren’t supposed to have the big heads. Ants are a pretty diverse lot and there are more than 1,100 species within even the Pheidole genus. But only eight of them naturally produce the super soldiers.
Biology professor Ehab Abouheif and PhD student Rajee Rajakumar wondered if the genes that build super soldiers were present in the Long Island ants all along, but were just waiting for some environmental factor to bring them out. The scientists first went to Arizona and collected two other species of ant in the same genus, Pheidole rhea andPheidole obtusospinosa, which both have a subclass of super soldiers. They then observed how those two species developed their super soliders.
Next, the scientists gave the young Long Island ants juvenile hormones at certain specific points in their development. In the Pheidole morrisi they got the super-soldier ants, which showed that the potential was always there. It just needed something to bring it out. One interesting phenomenon was the super soldiers had wing buds, which their cousins from Arizona did not. Many ant species develop wings as part of their development and ants and wasps share a common ancestor. The procedure worked in three different species of Pheidole, even though all three were separated by thousands of miles and millions of years of evolution.
Previously, few biologists thought such ancestral traits were important. They were just leftovers like the stuff in your attic. This shows that when necessary, nature has a “tool kit” that it can use to create big morphological changes -- some of them new.”
'Tatooine' Planet With Two Suns Could Host Habitable Moon?
|3:11:13 AM, Wednesday, January 11, 2012|
“A new planet found last fall may be orbiting two stars, but it's far from a real-life Tatooine. Dubbed Kepler-16b, the world is a cold, Saturn-size gas giant with little chance of hosting desert farmers like the fictional Star Wars world.
But according to new computer simulations, the Kepler-16 stars may still shine on a world fit for life—a hypothetical Earthlike moon orbiting Kepler-16b.
Kepler-16b was discovered by NASA's Kepler spacecraft, which looks for dips in starlight as a planet transits—or passes in front of—a star, as seen from Earth.
For the new study, Billy Quarles, a doctoral student at the University of Texas at Arlington, and colleagues simulated several possible configurations for a theoretical Earth-mass world in the Kepler-16 system.
The team started by drawing up a "laundry list of parameters" for defining the habitable zone—the region around a star where a planet gets enough heat to host liquid water, essential for life as we know it—Quarles said Monday during ameeting of the American Astronomical Society in Austin, Texas.
The researchers assumed that the brighter of the two Kepler-16 stars is the main source of heat and light for any orbiting worlds.
Based on that star's size and temperature, the team determined that the main habitable zone possible around the Kepler-16 stars would extend from about 34 million to 66 million miles (55 to 106 million kilometers) out.
Capturing a Habitable Moon
With a roughly circular orbit about 65 million miles from the stars, the Saturn-like planet is on the outer edge of this main habitable zone. And while this "Tatooine" is uninhabitable, an Earthlike moon in Kepler-16b's orbit could sustain life, the researchers said.
The group isn't yet ready to say whether a moon could have formed alongside the planet. But their simulations suggest a moon could have arrived, fully formed, later in Kepler-16b's life.
According to the new models, a planet closer to the brighter star, squarely in the habitable zone, could have long ago been ejected from its orbit due to gravitational interactions with the other objects in the system.
Kepler-16b's gravitational pull could have attracted the Earthlike planet during its journey outward, turning the world from planet to moon.
Such a moon would technically be in the main habitable zone of the Kepler-16 system and—unlike Mars, on the outer edge of the habitable zone in our solar system—the moon would be massive enough to retain an Earthlike atmosphere, the team said.
First to Find an Alien Moon?
If astronomers were to discover an Earthlike satellite orbiting Kepler-16b—a bigif—it would be a major first.
More than 700 alien planets have been confirmed so far, and Kepler has identified more than 2,000 more potential planets.
As of yet, though, no moons have been detected outside our solar system.
With the new study, "we can say there are exomoons possible around Kepler-16b, and what's important about this is that they are detectable ... down to 0.2 Earth masses," Quarles said.
To do so would require looking for subtle irregularities in the gas giant's orbit that could be caused by a moon's gravitational pull—something Kepler is equipped to do…”
Worm-Eating Plant Found - Kills via Underground Leaves
|2:26:21 AM, Wednesday, January 11, 2012|
“Scientists have solved an underground mystery: Why does a plant that survives on sunlight grow leaves beneath the earth?
Flowering plants of the genusPhilcoxia are the only known plants with the "awkward" feature of subterranean leave, said Rafael Oliveira, a plant biologist at the State University of Campinas in Brazil.
Oliveira's new research sheds new light on the oddity, showing that the leaves act as traps for tiny roundworms, or nematodes. This worm food is vital for the plant's survival in the nutrient-deprived savannas of central Brazil.
Plants may seem "boring for some people, because they don't move or actively hunt for their food," Oliveira said by email.
But "they have evolved a number of fascinating solutions to solve common problems, such as the lack of readily available nutrients or water."
Feeding Worms to Plants
Oliveira and colleagues had suspected that Philcoxia plants may be carnivorous, because their sandy habitats and their physical features—such as poorly developed root systems—resemble those of known carnivorous plants. The team had also recently observed roundworms on the plants' subterranean leaves.
To test their hypothesis, the researchers bred nematodes in nitrogen, a marker that would allow the scientists to know if the plant indeed digests worms.
The team then "fed" the nematodes to plants in the lab, and harvested their leaves 24 and 48 days later. A chemical analysis revealed nitrogen from the worms had been incorporated into the plant's leaves.
The results add up to the first evidence of a carnivorous plant with specific adaptations for trapping and eating roundworms, he added.
More Killer Plants Out There?
Only 0.2 percent of flowering plant species are known to digest meat.
But "if we start to look closer at microorganisms [such as nematodes] as a prey type," Oliveira predicted, "we might find more carnivorous plants."
Many plant behaviors, he added, "operate hidden from our view."”
Hackers Plot DIY Sputniks for Internet Freedom
|10:01:08 PM, Monday, January 02, 2012|
“(BBC) Computer hackers plan to take the internet beyond the reach of censors by putting their own communication satellites into orbit.
The scheme was outlined at the Chaos Communication Congress in Berlin.
The project's organisers said the Hackerspace Global Grid will also involve developing a grid of ground stations to track and communicate with the satellites.
Longer term they hope to help put an amateur astronaut on the moon.
Hobbyists have already put a few small satellites into orbit - usually only for brief periods of time - but tracking the devices has proved difficult for low-budget projects.
The hacker activist Nick Farr first put out calls for people to contribute to the project in August. He said that the increasing threat of internet censorship had motivated the project.
"The first goal is an uncensorable internet in space. Let's take the internet out of the control of terrestrial entities," Mr Farr said.
He cited the proposed Stop Online Piracy Act (Sopa) in the United States as an example of the kind of threat facing online freedom. If passed, the act would allow for some sites to be blocked on copyright grounds.
Whereas past space missions have almost all been the preserve of national agencies and large companies, amateur enthusiasts have in recent years sent a few payloads into orbit.
These devices have mostly been sent up using balloons and are tricky to pinpoint precisely from the ground.
According to Armin Bauer, a 26-year-old enthusiast from Stuttgart who is working on the Hackerspace Global Grid, this is largely due to lack of funding.
"Professionals can track satellites from ground stations, but usually they don't have to because, if you pay a large sum [to send the satellite up on a rocket], they put it in an exact place," Mr Bauer said.
In the long run, a wider hacker aerospace project aims to put an amateur astronaut onto the moon within the next 23 years.
"It is very ambitious so we said let's try something smaller first," Mr Bauer added.
The Berlin conference was the latest meeting held by the Chaos Computer Club, a decades-old German hacker group that has proven influential not only for those interested in exploiting or improving computer security, but also for people who enjoy tinkering with hardware and software.
When Mr Farr called for contributions to Hackerspace, Mr Bauer and others decided to concentrate on the communications infrastructure aspect of the scheme…”
Nasa's Gravity Twins Now Circling Moon
|9:51:47 PM, Monday, January 02, 2012|
“The US space agency (Nasa) has succeeded in placing two new satellites in orbit around the Moon.
Both spacecraft were put in elliptical paths around the lunar body over the weekend after performing braking manoeuvres following their more than 100-day journey from Earth.
The identical Grail twins are to map gravity variations across the lunar body in unprecedented detail.
This will help scientists refine our theories for how the Moon formed.
It will also enable them to test new ideas, such as the provocative suggestion made earlier this year that there were probably two moons in the sky above Earth billions of years ago.
Lead scientist Dr Maria Zuber is certainly hoping for some dramatic discoveries.
"Grail is a journey to the centre of the Moon and it will use exceedingly precise measurements of gravity to reveal what the inside of the Moon is like," the Massachusetts Institute of Technology (MIT) researcher said.
"This information will be combined with the plethora of remarkable observations of the Moon that have been taken by other satellites before, and together they will enable us to reconstruct the Moon's early evolution."
The 300kg Grail spacecraft were launched from Cape Canaveral, Florida, last September, and took a long spiral out to their destination.
This weekend, they approached the Moon over the south pole, 25 hours apart. Each satellite in turn fired its main engine to slow it and put it in an elliptical orbit around the lunar sphere.
This orbit has a period of 11.5 hours and must now gradually be reduced in size and circularised before any science can begin.
A series of further burns on each spacecraft should achieve this goal by March.
The twins will then map the small variations in gravity across the lunar surface from an altitude of 55km.
These gravity differences are the result of an uneven distribution of mass. Obvious examples at the Moon's surface include big mountain ranges or deep impact basins, but even inside the lunar body the rock will be arranged in an irregular fashion, with some regions being denser than others.
All this will have a subtle influence on the pull of gravity sensed by the over-flying spacecraft.
The Grail twins will make their measurements by carrying out a carefully calibrated pursuit of each other.
As the lead spacecraft flies through the uneven gravity field, it will experience small accelerations or decelerations. The second spacecraft, following some 100-200km behind, will detect these disturbances as very slight changes in the separation between the pair - deviations that are not much more than the width of a human red blood cell.
When the gravity map is combined with comparable-resolution topographical information showing the surface highs and lows, scientists should be able to deduce the Moon's probable internal structure and composition. This is fundamental knowledge that will play into theories of how the lunar body formed and how it has changed through time…”
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