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Scientists probe Neptune’s depths to reveal secrets of icy planets

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Scientists have helped solve the mystery of what lies beneath the surface of Neptune  the most distant planet in our solar system.

A new study sheds light on the chemical make-up of the planet, which lies around 4.5 billion kilometres from the sun.

Extremely low temperatures on planets like Neptune — called ice giants — mean that chemicals on these distant worlds exist in a frozen state, researchers say.

Frozen mixtures of water, ammonia and methane make up a thick layer between the planets’ atmosphere and core — known as the mantle. However, the form in which these chemicals are stored is poorly understood.

Using laboratory experiments to study these conditions is difficult, as it is very hard to recreate the extreme pressures and temperatures found on ice giants, researchers say.

Instead, scientists at the University of Edinburgh ran large-scale computer simulations of conditions in the mantle. By looking at how the chemicals there react with each other at very high pressures and low temperatures, they were able to predict which compounds are formed in the mantle.

The team found that frozen mixtures of water and ammonia inside Neptune — and other ice giants, including Uranus — are likely to form a little-studied compound called ammonia hemihydrate.

The findings will influence how ice giants are studied in future and could help astronomers classify newly discovered planets as they look deeper into space.

Dr Andreas Hermann, of the University of Edinburgh’s Centre for Science at Extreme Conditions, said: “This study helps us better predict what is inside icy planets like Neptune. Our findings suggest that ammonia hemihydrate could be an important component of the mantle in ice giants, and will help improve our understanding of these frozen worlds. Computer models are a great tool to study these extreme places, and we are now building on this study to get an even more complete picture of what goes on there.”

Lunar dynamo’s lifetime extended by at least 1 billion years

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New evidence from ancient lunar rocks suggests that an active dynamo once churned within the molten metallic core of the moon, generating a magnetic field that lasted at least 1 billion years longer than previously thought. Dynamos are natural generators of magnetic fields around terrestrial bodies, and are powered by the churning of conducting fluids within many stars and planets. Researchers from MIT and Rutgers University report that a lunar rock collected by NASA’s Apollo 15 mission exhibits signs that it formed 1 to 2.5 billion years ago in the presence of a relatively weak magnetic field of about 5 microtesla. That’s around 10 times weaker than Earth’s current magnetic field but still 1,000 times larger than fields in interplanetary space today.

Several years ago, the same researchers identified 4-billion-year-old lunar rocks that formed under a much stronger field of about 100 microtesla, and they determined that the strength of this field dropped off precipitously around 3 billion years ago. At the time, the researchers were unsure whether the moon’s dynamo — the related magnetic field — died out shortly thereafter or lingered in a weakened state before dissipating completely.

The results reported today support the latter scenario: After the moon’s magnetic field dwindled, it nonetheless persisted for at least another billion years, existing for a total of at least 2 billion years.

Study co-author Benjamin Weiss, professor of planetary sciences in MIT’s Department of Earth, Atmospheric and Planetary Sciences (EAPS), says this new extended lifetime helps to pinpoint the phenomena that powered the moon’s dynamo. Specifically, the results raise the possibility of two different mechanisms — one that may have driven an earlier, much stronger dynamo, and a second that kept the moon’s core simmering at a much slower boil toward the end of its lifetime.

“The concept of a planetary magnetic field produced by moving liquid metal is an idea that is really only a few decades old,” Weiss says. “What powers this motion on Earth and other bodies, particularly on the moon, is not well-understood. We can figure this out by knowing the lifetime of the lunar dynamo.”

Weiss’ co-authors are lead author Sonia Tikoo, a former MIT graduate student who is now an assistant professor at Rutgers; David Shuster of the University of California at Berkeley; Clément Suavet and Huapei Wang of EAPS; and Timothy Grove, the R.R. Schrock Professor of Geology and associate head of EAPS.

Apollo’s glassy recorders

Since NASA’s Apollo astronauts brought back samples from the lunar surface, scientists have found some of these rocks to be accurate “recorders” of the moon’s ancient magnetic field. Such rocks contain thousands of tiny grains that, like compass needles, aligned in the direction of ancient fields when the rocks crystallized eons ago. Such grains can give scientists a measure of the moon’s ancient field strength.

Until recently, Weiss and others had been unable to find samples much younger than 3.2 billion years old that could accurately record magnetic fields. As a result, they had only been able to gauge the strength of the moon’s magnetic field between 3.2 and 4.2 billion years ago.

“The problem is, there are very few lunar rocks that are younger than about 3 billion years old, because right around then, the moon cooled off, volcanism largely ceased and, along with it, formation of new igneous rocks on the lunar surface,” Weiss explains. “So there were no young samples we could measure to see if there was a field after 3 billion years.”

There is, however, a small class of rocks brought back from the Apollo missions that formed not from ancient lunar eruptions but from asteroid impacts later in the moon’s history. These rocks melted from the heat of such impacts and recrystallized in orientations determined by the moon’s magnetic field.

Weiss and his colleagues analyzed one such rock, known as Apollo 15 sample 15498, which was originally collected on Aug. 1, 1971, from the southern rim of the moon’s Dune Crater. The sample is a mix of minerals and rock fragments, welded together by a glassy matrix, the grains of which preserve records of the moon’s magnetic field at the time the rock was assembled.

“We found that this glassy material that welds things together has excellent magnetic recording properties,” Weiss says.

Baking rocks

The team determined that the rock sample was about 1 to 2.5 billion years old — much younger than the samples they previously analyzed. They developed a technique to decipher the ancient magnetic field recorded in the rock’s glassy matrix by first measuring the rock’s natural magnetic properties using a very sensitive magnetometer.

They then exposed the rock to a known magnetic field in the lab, and heated the rock to close to the extreme temperatures in which it originally formed. They measured how the rock’s magnetization changed as they increased the surrounding temperature.

“You see how magnetized it gets from getting heated in that known magnetic field, then you compare that field to the natural magnetic field you measured beforehand, and from that you can figure out what the ancient field strength was,” Weiss explains.

The researchers did have to make one significant adjustment to the experiment to better simulate the original lunar environment, and in particular, its atmosphere. While the Earth’s atmosphere contains around 20 percent oxygen, the moon has only imperceptible traces of the gas. In collaboration with Grove, Suavet built a customized, oxygen-deprived oven in which to heat the rocks, preventing them from rusting while at the same time simulating the oxygen-free environment in which the rocks were originally magnetized.

“In this way, we finally have gotten an accurate measurement of the lunar field,” Weiss says.

From ice cream makers to lava lamps

From their experiments, the researchers determined that, around 1 to 2.5 billion years ago, the moon harbored a relatively weak magnetic field, with a strength of about 5 microtesla — two orders of magnitude weaker than the moon’s field around 3 to 4 billion years ago. Such a dramatic dip suggests to Weiss and his colleagues that the moon’s dynamo may have been driven by two distinct mechanisms.

Scientists have proposed that the moon’s dynamo may have been powered by the Earth’s gravitational pull. Early in its history, the moon orbited much closer to the Earth, and the Earth’s gravity, in such close proximity, may have been strong enough to pull on and rotate the rocky exterior of the moon. The moon’s liquid center may have been dragged along with the moon’s outer shell, generating a very strong magnetic field in the process.

It’s thought that the moon may have moved sufficiently far away from the Earth by about 3 billion years ago, such that the power available for the dynamo by this mechanism became insufficient. This happens to be right around the time the moon’s magnetic field strength dropped. A different mechanism may have then kicked in to sustain this weakened field. As the moon moved away from the Earth, its core likely sustained a low boil via a slow process of cooling over at least 1 billion years.

“As the moon cools, its core acts like a lava lamp — low-density stuff rises because it’s hot or because its composition is different from that of the surrounding fluid,” Weiss says. “That’s how we think the Earth’s dynamo works, and that’s what we suggest the late lunar dynamo was doing as well.”

The researchers are planning to analyze even younger lunar rocks to determine when the dynamo died off completely.

Arrival of modern humans in Southeast Asia questioned

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Humans may have exited out of Africa and arrived in Southeast Asia 20,000 years earlier than previously thought, a new study involving University of Queensland researchers suggests.

Findings from the Macquarie University-led study also suggest humans could have potentially made the crossing to Australia even earlier than the accepted 60,000 to 65,000 years ago.

Dr Gilbert Price of UQ School of Earth and Environmental Sciences said the dating of a cave site in West Sumatra, called Lida Ajer, provided first evidence for rainforest use of modern humans.

“Rainforests aren’t the easiest place to make a living, especially for a savannah-adapted primate, so it suggests that these people were ahead of the curve in terms of intelligence, planning and technological adaptation,” Dr Price said.

He said the study stood on the shoulders of brilliant Dutch paleo-anthropologist Eugene Dubois, famed for his discovery of ‘Java Man’.

“He visited a series of caves in Sumatra in the late 1800s, and in one in particular, recovered some human teeth, which is quite interesting in itself, but no one had spent much time trying to determine their significance,” Dr Price said.

“Fast forward over 100 years later, both the team of lead author Dr Kira Westaway of Macquarie University and my crew (separately) were lucky enough to re-discover and visit the caves.

“It was quite an adventure. We ended up sharing notes and the collaboration was born.”

As a result of thorough documentation of the cave, reanalysis of the specimens, and a new dating program, it was confirmed the teeth were modern humans, Homo sapiens, but dated to as old as 73,000 years ago.

A barrage of dating techniques were applied to the sediment around the fossils, to overlying and underlying rock deposits in the cave and to associated mammal teeth, indicating that the deposit and fossils were laid down between 63,000 to 73,000 years ago.

“This cave has been shrouded in doubt since it was first excavated,” Dr Westaway said.

“We employed a range of dating techniques from different institutions to establish a robust chronology that would, after 120 years, finally put an end to the uncertainty associated with the age and significance of these teeth.”

Advanced equipment at UQ’s Centre for Geoanalytical Mass Spectrometry, a hub backed by researchers from Queensland’s major research institutions, was used in the analysis.

“We were lucky to have some of the best dating facilities in the world at our disposal, including the same pieces of equipment at UQ that had earlier dated the famous ‘Hobbit’ fossils of Southeast Asia,” Dr Price said.

Dr Westaway said the hardest part was trying to find the site again, with only a sketch of the cave and a rough map from a copy of Dubois’s original field notebook to guide them.

Southeast Asia is a key region in the path of human dispersal from Africa round to Australia, as all hominins would have had to pass through this region en route to Australia.

 

Dawn of the cosmos: Seeing galaxies that appeared soon after the Big Bang

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Arizona State University astronomers Sangeeta Malhotra and James Rhoads, working with international teams in Chile and China, have discovered 23 young galaxies, seen as they were 800 million years after the Big Bang.

Long ago, about 300,000 years after the beginning of the universe (the Big Bang), the universe was dark. There were no stars or galaxies, and the universe was filled with neutral hydrogen gas. In the next half billion years or so the first galaxies and stars appeared. Their energetic radiation ionized their surroundings, illuminating and transforming the universe.

This dramatic transformation, known as re-ionization, occurred sometime in the interval between 300 million years and one billion years after the Big Bang. Astronomers are trying to pinpoint this milestone more precisely and the galaxies found in this study help in this determination.

“Before re-ionization, these galaxies were very hard to see, because their light is scattered by gas between galaxies, like a car’s headlights in fog,” says Malhotra. “As enough galaxies turn on and ‘burn off the fog’ they become easier to see. By doing so, they help provide a diagnostic to see how much of the ‘fog’ remains at any time in the early universe.”

The Dark Energy Camera

To detect these galaxies, Malhotra and Rhoads have been using the Dark Energy Camera (DECam), one of the new powerful instruments in the astronomy field. DECam is installed at the National Optical Astronomy Observatory (NOAO)’s 4-meter Blanco Telescope, located at the Cerro Tololo Inter-American Observatory (CTIO), in northern Chile, at an altitude of 7,200 feet.

“Several years ago, we carried out a similar study using a 64-megapixel camera that covers the same amount of sky as the full moon,” says Rhoads. “DECam, by comparison, is a 570-megapixel camera and covers 15 times the area of the full moon in a single image.”

DECam was recently made even more powerful when it was equipped with a special narrowband filter, designed at ASU’s School of Earth and Space Exploration (SESE), primarily by Rhoads and Zheng (who was a SESE postdoctoral fellow and is currently at the Shanghai Astronomical Observatory in China), with assistance from Alistair Walker of NOAO.

“We spent several months refining the design of the filter profile, optimizing the design to get maximum sensitivity in our search” says Zheng, the lead author of this study.

Touching the Cosmic Dawn

The galaxy search using the ASU-designed filter and DECam is part of the ongoing “Lyman Alpha Galaxies in the Epoch of Reionization” project (LAGER). It is the largest uniformly selected sample that goes far enough back in the history of the universe to reach cosmic dawn.

“The combination of large survey size and sensitivity of this survey enables us to study galaxies that are common but faint, as well as those that are bright but rare, at this early stage in the universe,” says Malhotra.

Junxian Wang, a co-author on this study and the lead of the Chinese LAGER team, adds that “our findings in this survey imply that a large fraction of the first galaxies that ionized and illuminated the universe formed early, less than 800 million years after the Big Bang.”

The next steps for the team will be to build on these results. They plan to continue to search for distant star forming galaxies over a larger volume of the universe and to further investigate the nature of some of the first galaxies in the universe.

Diet choice, reproduction of fruit flies affected by gut bacteria

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Increasingly understood to be vital for wellbeing, gut microbiota are the trillion of microorganisms that live in the digestive tract of humans and other animals. Known to affect a range of physiological traits including development, immunity, nutrition and longevity, researchers are now investigating how manipulating gut microbiota might influence other aspects of health.

Two new studies  from the University of Sydney’s multidisciplinary Charles Perkins Centre and School of Life and Environmental Sciences (SOLES) in collaboration with Macquarie University’s Department of Biological Sciences  have discovered the gut microbiota of the common fruit fly has a significant effect on their foraging behaviour and reproductive success, and that its influence can be carried down to the next generation.

The study into foraging behaviour manipulated the type and timing of bacteria individual flies were exposed to, and examined their olfactory-guided preferences to food microbes and nutrients.

In addition to foraging for nutrients to achieve a balanced diet, the researchers found flies also forage for bacteria to populate a healthy gut flora. Responding to smells associated with particular bacteria in foods, the flies showed a distinct preference for more beneficial types of bacteria over less-beneficial types or food lacking the bacteria.

Lead author Dr Adam Wong, who conducted the research while at the University of Sydney and is now based at the University of Florida, said the findings warranted further investigation to determine how other animals interact with beneficial microbes in foraging.

“We knew animals foraged for nutrients, in ways that optimise their performance and physiology.” he said.

“Understanding they also forage for beneficial microbes opens up a whole new dimension for future research. The symbiotic relationship can shape how animals, including humans, may perceive and prefer different nutrients and microbes for better overall health.”

They found the reproductive investment and success of a mating pair was influenced by gut bacteria, as well as the body mass of offspring.

Lead author Dr Juliano Morimoto, now at Macquarie University, said the findings reveal the effect of gut microbiota on reproduction, but also suggest these effects can be carried over to the next generation.

“Given the importance of the gut microbiota in physiology and health, our findings reveal important and long-lasting effects of gut bacteria on reproduction and offspring traits,” he said.

“As understanding of the gut microbiome and its effect increases, the potential for breakthroughs in understanding broader health impacts increases too.”

Professor Stephen Simpson, Academic Director at the Charles Perkins Centre and a co-author on both papers, said the studies provided an exciting illustration of how microbes can influence the behaviour of host animals, which could be important for understanding gut microbiota and cognitive function in humans in the future.

“With the burgeoning interest in the role of the gut microbiome in health, and cross-talk between the gut and the brain, this demonstration that bacteria in the gut influences foraging and reproductive behaviour is of particular interest for further research,” he said.

Dr Fleur Ponton, last author on both studies and based at Macquarie University’s Department of Biological Sciences, said the success of this collaboration highlighted the importance of multidisciplinary and inter-institutional research.

“Beyond the biomedical significance of this research, there are potential interesting applications in the context of invasive and pest species control,” she added.

Holograms taken to new dimension

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Technology developed by a team of University of Utah electrical and computer engineers could make the holographic chess game R2-D2 and Chewbacca played in “Star Wars” a reality.

The team led by electrical and computer engineering associate professor Rajesh Menon has discovered a way to create inexpensive full-color 2-D and 3-D holograms that are far more realistic, brighter and can be viewed at wider angles than current holograms. The applications for this technology could be wide-ranging, from currency and identification badges to amusement rides and advertisements.

“You can have rich colors at high efficiency, with high brightness and at low cost. And you don’t need fancy lasers and complicated optics,” Menon says.

The paper, “Full Color, Large Area, Transmissive Holograms Enabled by Multi-Level Diffractive Optics,” was co-authored by University of Utah doctoral students Nabil Moham, Monjurul Meem and Xiaowen Wan.

Typically, the projection of any image, whether it is two or three dimensional, is inefficient because when white light shines on an object, we can only see the reflected color that bounces back to our eyes while the rest of the colors of the spectrum are absorbed. Therefore, there is a lot of wasted light. With a typical LCD projector, for example, you may only see as little as 5 percent of the total light at one time.

Menon and his team have discovered a better way that borrows from the same principle behind how wings of certain butterflies display their colors: Instead of reflecting only the colors you see while absorbing the rest, all of the white light is redirected so you see the wavelengths of the wing’s colors at different locations. None of the light is absorbed and therefore wasted.

Using sophisticated algorithms and a new fabrication method, the engineers can create holograms that do the same thing — redirect colors to appropriate locations — instead of absorbing most of it to project much brighter photographic images either in 2-D or 3-D and with full, natural colors. Currently, full-color holograms require lasers to not only make them, but also to view them. Menon’s holograms can be viewed with regular white light. Most importantly, these holograms can be viewed from any angle, and the image detail does not change, much like a real object.

“Projecting an image before was very inefficient, and you need a massive lamp,” Menon says. “Here, you can just do it with just a piece of plastic and a flashlight. It’s much simpler and more efficient this way.”

Such technology could be used on currency notes with security holograms that produce more lifelike images. Currently, the holograms on some foreign currency or on credit cards look like shimmering monochromatic images, but Menon’s holograms would be more like full-color photographs. It also could be used for identification badges, driver’s licenses and security documents like passports in which an officer could use just a flashlight to authenticate it instead of a special light such as an infrared scanner. And these holograms could be inexpensive to manufacture because they can stamp out each sticker like a compact disc or DVD.

While Menon and his team have only produced 2-D still images with their technology so far, he said it wouldn’t be difficult to take the next step to create full-color 3-D moving images similar to the holographic chess pieces in “Star Wars.” Therefore, the holograms could be utilized in entertainment, such as for virtual reality headsets, for movie theaters that wouldn’t require powerful projector lamps (and it could be an avenue for glasses-less 3-D movies) or for amusement rides that use high-tech special effects.

“Imagine going through a ride and you want a monster to jump out. This is a way to do that with much richer color, with higher efficiency and in a much more ubiquitous manner because it’s so cheap,” Menon says.

The technology can also be used to produce holographic photos or video for advertising for platforms like billboards or kiosks. Moving 3-D video could be possible in as little as two years, and his team is working toward that now, he said.

Menon launched a company called PointSpectrum that is researching this new technology and to commercialize its potential uses.

Gaining a few pounds may increase long-term heart failure risk

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Gaining even a little weight over time may alter the structure and function of heart muscle, affecting long-term risk of heart failure, the Open Access Journal of the American Heart Association/American Stroke Association.

Researchers followed 1,262 adults (average age 44, 57 percent women, 44 percent black, 36 percent obese) who were free from heart disease and other conditions that put them at high risk for heart disease for seven years. Participants had MRIs scans of their hearts and multiple body fat measurements at the start of the study and then seven years later.

Researchers found those who gained weight:

  • even as little as 5 percent, were more likely to have thickening and enlargement of the left ventricle, well-established indicators of future heart failure;
  • were more likely to exhibit subtle decreases in their hearts’ pumping ability; and
  • were more likely to exhibit changes in heart muscle appearance and function that persisted even after the researchers eliminated other factors that could affect heart muscle performance and appearance, including high blood pressure, diabetes, smoking and alcohol use.

Conversely, people who lost weight were more likely to exhibit decreases in heart muscle thickness.

Notably, how much a person weighed at the beginning of the study didn’t impact the changes, suggesting that even those of normal weight could experience adverse heart effects if they gain weight over time, researchers said.

“Any weight gain may lead to detrimental changes in the heart above and beyond the effects of baseline weight so that prevention should focus on weight loss or if meaningful weight loss cannot be achieved — the focus should be on weight stability,” said Ian Neeland, M.D., study senior author and a cardiologist and assistant professor of medicine at University of Texas Southwestern Medical Center in Dallas, Texas. “Counseling to maintain weight stability, even in the absence of weight loss, may be an important preventive strategy among high-risk individuals.”

The researchers caution that their study was relatively small and their findings do not mean that every person with weight gain will necessarily develop heart failure. The results do suggest that changes in weight may affect heart muscle in ways that can change the organ’s function.