Software Development Life Cycle

The Software Development Life Cycle (SDLC) refers to a methodology with clearly defined processes for creating high-quality software. in detail, the SDLC methodology focuses on the following phases of software development:

1. Requirement analysis
2. Planning
3. Software design such as architectural design
4. Software development
5. Testing
6. Deployment

This article will explain how SDLC works, dive deeper in each of the phases, and provide you with examples to get a better understanding of each phase.

Definition of SDLC

SDLC or the Software Development Life Cycle is a process that produces software with the highest quality and lowest cost in the shortest time possible. SDLC provides a well-structured flow of phases that help an organization to quickly produce high-quality software which is well-tested and ready for production use.

The SDLC involves six phases as explained in the introduction. Popular SDLC models include the waterfall model, spiral model, and Agile model.

So, how does the Software Development Life Cycle work?

How SDLC Works

SDLC works by lowering the cost of software development while simultaneously improving quality and shortening production time. SDLC achieves these apparently divergent goals by following a plan that removes the typical pitfalls of software development projects. That plan starts by evaluating existing systems for deficiencies.

Next, it defines the requirements of the new system. It then creates the software through the stages of analysis, planning, design, development, testing, and deployment. By anticipating costly mistakes like failing to ask the end-user or client for feedback, SLDC can eliminate redundant rework and after-the-fact fixes.

It’s also important to know that there is a strong focus on the testing phase. As the SDLC is a repetitive methodology, you have to ensure code quality at every cycle. Many organizations tend to spend few efforts on testing while a stronger focus on testing can save them a lot of rework, time, and money. Be smart and write the right types of tests.
https://stackify.com/

sQuba, world’s first swimming car !!!

The Island

நடிகை சுஜாதாவின் வாழ்க்கை வரலாறு

நடிகை சுஜாதாவின் மறைவு தென்னிந்திய திரைப்படத்துறைக்குப் பேரிழப்பாகும் என்பதை திரைப்படத்துறை ரசிகர்கள் நிச்சயம் ஏற்றுக் கொள்வார்கள்.58 வயதான சுஜாதா 06-‍‍‍04-௨011 அன்று சென்னையில் உள்ள அவரது இல்லத்தில் காலமானார்.

இனி அவரது வாழ்க்கை வரலாறு பற்றிப் பார்ப்போம்.

1950 களில் கேரளாவில் இருந்து யாழ்ப்பாணம் வந்த  மலையாள ஆசிரியர் சுஜாதாவின் தந்தையான மேனன் ஆவார்.இவரது தந்தையான ஆசிரியர் மேனன் அவர்கள் சிறந்த  விலங்கியல் ஆசிரியராகத் திகழ்ந்தார். இவர் யாழ்ப்பாணத்தில் உள்ள தெல்லிப்பளை மகாஜனாக் கல்லூரியில் கல்வி கற்பித்தார்.இவர் தனது குடும்பத்தினரோடு தெல்லிப்பளையில் வசித்தார்.

இவரது மகளான நடிகை சுஜாதா 1952ம் ஆண்டு மார்கழி மாதம் 10ம் திகதி யாழ்ப்பாணம் தெல்லிப்பளையில் பிறந்தார்.

சுஜாதா தனது 14ம் வயதில் பெற்றோருடன் கேரளாவிற்குத் திரும்பிச் சென்று அங்கே தனது கல்வியைத் தொடர்ந்தார்.

நடிகை சுஜாதாவை ஜோசி பிரகாஷ் என்பவர் தான் முதன் முதலாக மேடை நாடகமான பொலிஸ் ஸ்டேசனில் நடிக்க வைத்தது மட்டுமல்ல, திரையுலகத்திற்கும் அறிமுகப்படுத்தினார்.இவரது கணவரின் பெயர் ஜெயகர்.சஜித் என்ற  மகனுக்கும்  திவ்யா என்ற  மகளுக்கும் இவர் தாயாவார்.டூ கல்யான் (1968) என்ற இந்திப்படத்திலும், தபாஷ்வினி என்ற மலையாளப் படத்திலும் இவர் முதலில் தோன்றினாலும் ஏர்ணாம்குளம் ஜங்சன் என்ற மலையாளப்படத்தில் நடித்த பொது தான் கே.பாலசந்தரின் கண்களில் பட்டார்.1974 இல் பிரபல இயக்குனரான கே.பாலசந்தர் எடுத்த அவள் ஒரு தொடர்கதை என்ற படம் தான் சுஜாதாவை சிறந்த ஒரு நடிகையாகத் தமிழ் திரையுலகில் இனம் காட்டியது. எம்.எஸ்.விஸ்வநாதனின் இசையமைப்பில் வெளிவந்த இந்தப்படத்தில் சுஜாதாவுடன் கமல்ஹாசன், சிறி பிரியா , விஜயகுமார் ஆகியோர் நடித்திருந்தனர்.1976 இல் வெளிவந்த இளையராஜாவின் பாடல் மூலம் மேலும் இவரது புகழ் ஓங்கியது. மீண்டும் இவர் 1977 இல் கே.பாலசந்தரின் அவர்கள் படத்தில் ரஜினிகாந்த்,கமல்ஹாசன் ஆகியோரோடு அணு என்ற பாத்திரமேற்று நடித்துப் புகழ் பெற்றார்.

அன்றைய பிரபல தமிழ் திரைப்படத்துறை நடிகர்களான சிவாஜி கணேசன் ,ரஜினிகாந்த்,கமல்ஹாசன் ஆகியோரோடு கதாநாயகியாக நடித்த பெருமை இவருக்கு உரியது.இவர் தமிழ்,மலையாளம், தெலுங்கு, கன்னடம், இந்திப்படங்களிலும்

நடித்திருக்கிறார். அக்னி நாகேஸ்வரராவ்,சோபன் பாபு,சிரஞ்சீவி ,கிருஷ்ணா,மோகன்பாபு, போன்றவர்களோடும் வேற்று மொழிப் படங்களில் நடித்திருக்கின்றார்.

அமரர் நடிகை சுஜாதா அவர்கள் சுமார் 150 படங்கள் நடித் திருப்பதாகத் தெரிய வருகின்றது.இதில் சுமார் 50இற்கு மேற்பட்ட தமிழ்ப் படங்களும் அடங்கும்.இவர் நடித்த கடல் மீன்,அந்தமான் காதலி,விதி,கோசில் காளை, புனர் ஜென்மம்,உன்னை நான் சந்தித்தேன் போன்ற படங்கள் பலராலும் பாராட்டப் பட்டன.

இவர்   நடித்த கடைசி ப்படம் தெலுங்கில் வெளிவந்த நாகர் யுனாவின் படமான ஸ்ரீ ராம ராசு(2006) என்பதாகும்.இவரது கடைசி தமிழ்ப் படம் வரலாறு (2004) ஆகும்.இவர் தனது சிறந்த நடிப்பிற்காக தமிழக அரசின் கலைமாமணி,மற்றும் நந்தி விருது போன்றவற்றைப் பெற்றவர் என்பதும் குறிப்பிடத்தக்கது.

Light from Galaxy Clusters Confirms General Theory of Relativity

Until now, the gravitational redshift has only been tested with experiments and observations in relation to distances here on Earth and about the solar system. With the new research, the theory has been tested on a cosmological scale for the first time by analyzing galaxies in galaxy clusters in the distant universe. It is a huge scale, which is 1,022 times greater (ten thousand billion times larger than the laboratory test). The observed data confirm Einstein's general theory of relativity. (Credit: Dark Cosmology Centre, Niels Bohr Institute)

Science Daily  — All observations in astronomy are based on light (electromagnetic radiation) emitted from stars and galaxies and, according to the general theory of relativity, the light will be affected by gravity. At the same time all interpretations in astronomy are based on the correctness of the theory of relatively. Still, it has been difficult to accurately test Einstein's theory of gravity on scales larger than the solar system. Now astrophysicists at the Dark Cosmology Centre at the Niels Bohr Institute have managed to measure how the light is affected by gravity on its way out of galaxy clusters. The observations confirm the theoretical predictions.

Observations of large distances in the universe are based on redshift measurements. In this phenomenon, the wavelength of the light from distant galaxies is shifted more and more towards the red with greater distance. The redshift indicates how much the universe has expanded from when the light left until it was measured on Earth. Furthermore, according to Einstein's general theory of relativity, the light and thus the redshift is also affected by the gravity from large masses like galaxy clusters and causes a gravitational redshift of the light. But the gravitational influence on light has never been measured on a cosmological scale.

The results have been published in the scientific journal, Nature.

"It is really wonderful. We live in an era with the technological ability to actually measure such phenomena as cosmological gravitational redshift," says astrophysicist Radek Wojtak, Dark Cosmology Centre under the Niels Bohr Institute at the University of Copenhagen.

Galaxy clusters in the searchlight

Radek Wojtak and colleagues Steen Hansen and Jens Hjorth have analysed light measurements from galaxies in approximately 8,000 galaxy clusters. Galaxy clusters are accumulations of thousands of galaxies, held together by their own gravity. This gravity affects the light being sent out into space from the galaxies.

The researchers have studied the galaxies lying in the middle of the galaxy clusters and those lying on the periphery and measured the wavelengths of the light.

"We could measure small differences in the redshift of the galaxies and see that the light from galaxies in the middle of a cluster had to 'crawl' out through the gravitational field, while it was easier for the light from the outlying galaxies to emerge," explains Radek Wojtak.

Then he measured the entire galaxy cluster's total mass and with that got the gravitational potential. By using the general theory of relativity he could now calculate the gravitational redshift for the different locations of the galaxies.

"It turned out that the theoretical calculations of the gravitational redshift based on the general theory of relativity was in complete agreement with the astronomical observations. Our analysis of observations of galaxy clusters show that the redshift of the light is proportionally offset in relation to the gravitational influence from the galaxy cluster's gravity. In that way our observations confirm the theory of relativity," explains Radek Wojtak.

New light on the dark universe

The discovery has significance for the phenomena in the universe that researchers are working to unravel. It is the mysterious dark universe -- dark matter and dark energy.

In addition to the visible celestial bodies like stars, planets and galaxies, the universe consists of a large amount of matter, which researchers can work out that it must be there, but which cannot be observed as it neither emits nor reflects light. It is invisible and is therefore called dark matter. No one knows what dark matter is, but they know what the mass and thus the gravity must be. The new results for gravitational redshift do not change the researchers' modelling for the presence of dark matter.

Another of the main components of the universe is dark energy, which according to the theoretical models acts like a kind of vacuum that causes the expansion of the universe to accelerate. According to the calculations, which are based on Einstein's theory of relativity, dark energy constitutes 72 percent of the structure of the universe. Many alternative theories try to explain the accelerating expansion without dark energy.

Theory tested on a large scale

"Now the general theory of relativity has been tested on a cosmological scale and this confirms that the general theory of relativity works and that means that there is a strong indication for the presence of dark energy," explains Radek Wojtak.

The new gravitation results thus contribute a new piece of insight to the understanding of the hidden, dark universe and provide a greater understanding of the nature of the visible universe.

Hide-And-Seek: Altered HIV Can't Evade Immune System

Science Daily  — Researchers at Johns Hopkins have modified HIV in a way that makes it no longer able to suppress the immune system. Their work, they say in a report published online September 19 in the journal Blood, could remove a significant hurdle in HIV vaccine development and lead to new treatments.

Typically, when the body's immune system cells encounter a virus, they send out an alarm by releasing chemicals called interferons to alert the rest of the body to the presence of a viral infection. When the immune cells encounter HIV, however, they release too many interferons, become overwhelmed and shut down the subsequent virus-fighting response.

"Something about the HIV virus turns down the immune response, rather than triggering it, making it a tough target for vaccine development," says David Graham, PhD, assistant professor of molecular and comparative pathobiology and medicine. "We now seem to have a way to sidestep this barrier," he adds.

The researchers had learned from other studies that when human immune cells (white blood cells) are depleted of cholesterol, HIV can no longer infect them. It turns out the coat that surrounds and protects the HIV viral genome is also rich in cholesterol, leading the Johns Hopkins team to test whether viruses lacking cholesterol could still infect cells.

The researchers treated HIV with a chemical to remove cholesterol from the viral coat. Then they introduced the cholesterol-diminished or regular HIV to human immune cells growing in culture dishes and measured how the cells responded. The cells exposed to cholesterol-diminished HIV didn't release any initial-response interferons, whereas those exposed to regular HIV did.

"The altered HIV doesn't overwhelm the system and instead triggers the innate immune response to kick in like with any first virus encounter," says Graham.

Next, the researchers checked to see if cholesterol-diminished HIV activates so-called adaptive immune responses -- the responses that help the body remember specific pathogens long-term so the body develops immunity and counters future infections. To do this, they put regular HIV or cholesterol-diminished HIV into blood samples containing all the cells needed for an adaptive immune response.

More specifically, they tested blood samples from people with previous exposure to HIV to see if their blood could mount an adaptive immune response. Blood samples were used from 10 HIV-positive people and 10 people repeatedly exposed to HIV who weren't infected. The researchers didn't expect the HIV-positive blood to respond to either version of HIV because of the severely damaged immune systems of HIV patients. However, when cholesterol-diminished HIV was introduced to the non-infected HIV blood in a tube, the adaptive immune response cells reacted against the virus. By altering the virus, explains Graham, the researchers were able to reawaken the immune system's response against HIV and negate HIV's immunosuppressive properties.

"In addition to vaccine applications, this study opens the door to developing drugs that attack the HIV viral coat as an adjunct therapy to promote immune system detection of the virus," says Graham.

This research was supported by funds from the Wellcome Trust and the National Institutes of Health.

Contributors to the research include David Graham and Veronica Aquino of The Johns Hopkins University; Adriano Boasso, Caroline Royle and Spyridon Doumazos of Imperial College; Mara Biasin, Luca Piacentini, Barbara Tavano and Mario Clerici of Università degli Studi di Milano; Dietmar Fuchs of Innsbruck Medical University; Francesco Mazzotta and Sergio Lo Caputo of Ospedale S. M. Annunziata and Gene Shearer of the National Cancer Institute.

Pigeon 'Milk' Contains Antioxidants and Immune-Enhancing Proteins

Pigeon and chick. (Credit: Dr. Tamsyn Crowley)

Science Daily — Production of crop milk, a secretion from the crops of parent birds, is rare among birds and, apart from pigeons, is only found in flamingos and male emperor penguins. Essential for the growth and development of the young pigeon squab, pigeon 'milk' is produced by both parents from fluid-filled cells lining the crop that are rich in fat and protein.

Researchers from CSIRO Livestock Industries and Deakin University, Australia, compared the global gene expression profiles of the crops of four 'lactating' and four 'non-lactating' female pigeons. As the pigeon genome has not yet been sequenced, they used a chicken microarray to find the genes involved. Genes predominantly over-expressed in 'lactating' birds were those involved in stimulating cell growth, producing antioxidants and in immune response. They also found genes associated with triglyceride fat production, suggesting the fat in the 'milk' is derived from the pigeon's liver.

Research published in BioMed Central's open access journal BMC Genomics uses new technology to study the genes and proteins involved in pigeon 'milk' production and shows that pigeon 'milk' contains antioxidants and immune-enhancing proteins.

Lead author, Meagan Gillespie, says, "It is possible that if antioxidant and immune proteins are present in pigeon 'milk', they are directly enhancing the immune system of the developing squab as well as protecting the parental crop tissue." She continues, "This study has provided a snap-shot view of some of the processes occurring when 'lactation' in the pigeon crop is well established. Due to the unusual nature of 'lactation' in the pigeon it would be interesting to investigate the early stages of the differentiation and development of the crop in preparation for 'milk' production to further ascertain gene expression patterns that characterize crop development and 'lactation' in the pigeon."

She concludes, "This mechanism is an interesting example of the evolution of a system with analogies to mammalian lactation, as pigeon 'milk' fulfills a similar function to mammalian milk."

Women Have Stronger Immune Systems Than Men -- And It's All Down to X-Chromosome Related microRNA

Science Daily  — As anyone familiar with the phrase 'man-flu' will know women consider themselves to be the more robust side of the species when it comes to health and illness. Now new research published in BioEssays, seems to support the idea. The research focuses on the role of MicroRNAs encoded on the X chromosome to explain why women have stronger immune systems to men and are less likely to develop cancer.

"Statistics show that in humans, as with other mammals, females live longer than males and are more able to fight off shock episodes from sepsis, infection or trauma," said Libert. "We believe this is due to the X chromosome, which in humans contains 10% of all micro RNAs detected so far in the genome. The roles of many remain unknown, but several X chromosome-located strands of microRNA have important functions in immunity and cancer."

The research, led by Dr Claude Libert from Ghent University in Belgium, focused on MicroRNA, tiny strains of ribonucleic acid which alongside DNA and proteins, make up the three major macromolecules that are essential for all known forms of life.

Dr Libert's team proposes that the biological mechanisms of the X chromosome have a strong impact on an individual's genes, known as genetic imprinting, which gives an immunological advantage to females. To develop their hypothesis the team produced a detailed map of all described microRNAs which have a role in immune functions and cancer in both human and mouse X chromosomes.

"We believe this immunological advantage is due to the silencing of X-linked genes by these microRNAs," said Libert. "Gene silencing and inactivation skewing are known mechanisms which affect X-linked genes and may influence X-linked microRNAs in the same way."

This genetic silencing leaves males at an immunological disadvantage as a male has only one X-chromosome. The Y-Chomosone contains fewer genes so if the genes involved in immunity are silenced maternally the male is left with no compensating genetic information.

"How this unique form of genetic inheritance influences X-chromosone linked microRNAs will be a challenge for researchers for years to come," concluded Libert, "not only from an evolutionary point of view, but also for scientists investigating the causes and cures of disease.

New Technique Maps Twin Faces of Smallest Janus Nanoparticles

A Janus nanoparticle. (Credit: Deborah Brewington / Vanderbilt University)

Science Daily  — New drug delivery systems, solar cells, industrial catalysts and video displays are among the potential applications of special particles that possess two chemically distinct sides. These particles are named after the two-faced Roman god Janus and their twin chemical faces allow them to form novel structures and new materials.

Now, a team of Vanderbilt chemists has overcome this obstacle by developing the first method that can rapidly and accurately map the chemical properties of the smallest of these Janus nanoparticles.
However, as scientists have reduced the size of Janus particles down to a few nanometers in diameter -- about the size of individual proteins, which has the greatest potential for drug therapy -- their efforts have been hampered because they haven't had a way to accurately map the surfaces of the particles that they produce. This uncertainty has made it difficult to evaluate the effectiveness of these particles for various applications and to improve the methods researchers are using to produce them.

The results, published online this month in the German chemistry journal Angewandte Chemie, address a major obstacle that has slowed the development and application of the smallest Janus nanoparticles.

The fact that Janus particles have two chemically distinct faces makes them potentially more valuable than chemically uniform particles. For example, one face can hold onto drug molecules while the other is coated with linker molecules that bind to the target cells. This advantage is greater when the different surfaces are cleanly separated into hemispheres than when the two types of surfaces are intermixed.

For larger nanoparticles (with sizes above 10 nanometers), researchers can use existing methods, such as scanning electron microscopy, to map their surface composition. This has helped researchers improve their manufacturing methods so they can produce cleanly segregated Janus particles. However, conventional methods do not work at sizes below 10 nanometers.

The Vanderbilt chemists -- Associate Professor David Cliffel, Assistant Professor John McLean, graduate student Kellen Harkness and Lecturer Andrzej Balinski -- took advantage of the capabilities of a state-of-the-art instrument called an ion mobility-mass spectrometer (IM-MS) that can simultaneously identify thousands of individual particles.

The team coated the surfaces of gold nanoparticles ranging in size from two to four nanometers with two different chemical compounds. Then they broke the nanoparticles down into clusters of four gold atoms and ran these fragments through the IM-MS.

Molecules from the two coatings were still attached to the clusters. So, by analyzing the resulting pattern, the chemists showed that they could distinguish between original nanoparticles where the two surface compounds were completely separated, those where they were randomly mixed and those that had an intermediate degree of separation.

"There is no other way to analyze structure at this scale except X-ray crystallography," said Cliffel, "and X-ray crystallography is extremely difficult and can take months to get a single structure."

"IM-MS isn't quite as precise as X-ray crystallography but it is extremely practical," added McLean, who has helped pioneer the new instrument's development. "It can provide structural information in a few seconds. Two years ago a commercial version became available so people who want to use it no longer have to build one for themselves."

The research was funded in part by a grant from the National Institutes of Health.

How global warming could cause animals to shrink

 Biomechanism 

The way in which global warming causes many of the world’s organisms to shrink has been revealed by new research from Queen Mary, University of London.

Almost all cold-blooded organisms are affected by a phenomenon known as the ‘temperature-size rule’, which describes how individuals of the same species reach a smaller adult size when reared at warmer temperatures. But until now, scientists have not fully understood how these size changes take place.

Writing in the journal The American Naturalist, Dr Andrew Hirst and colleagues from Queen Mary’s School of Biological and Chemical Sciences explore this unusual shrinking effect in more detail, and show conclusively how it occurs.

Funded by the Natural Environment Research Council, the study was carried out using data on marine planktonic copepods. These tiny crustaceans are the main animal plankton in the world’s oceans and are important grazers of smaller plankton and a food source for larger fish, birds and marine mammals.

By gathering together more than 40 years of research studying the effect of temperature on these organisms, their results show that growth rate (how fast mass is accumulated) and development rate (how fast an individual passes through its life stages) are consistently decoupled in a range of species, with development being more sensitive to temperature than growth.

Dr Hirst explains: “We’ve shown that growth and development increase at different rates as temperatures warm. The consequences are that at warmer temperatures a species grows faster but matures even faster still, resulting in them achieving a smaller adult size.

“Decoupling of these rates could have important consequences for individual species and ecosystems,” he added.

The team’s findings suggest that rates fundamental to all organisms (such as mortality, reproduction and feeding), may not change in synch with one another in a warming world. This could have profound implications for understanding how organisms work, and impact on entire food webs and the world’s ecosystems.

Although the team’s findings disagree with earlier assertions of many macro-ecologists, they clearly explain the smaller sizes associated with the ‘temperature-size rule’. They hope their work will help those investigating the potential impacts of climate change on the natural world.

How immune cells lead to cancer

AGENCY FOR SCIENCE, TECHNOLOGY AND RESEARCH

The study prompts a re-think of cancer therapies that aim at boosting the immune system. Image: eraxion/iStockphoto Scientists at A*STAR’s Singapore Immunology Network (SIgN) have shown for the first time that PMN-MDSC body’s immune system to combat cancer, a type of immune cell in the body that suppresses the immune response, can actually accelerate the growth and spread of cancerous tumours directly. This finding explains how inflammation, the body's natural defence mechanism when a tissue or an organ becomes affected, is linked to cancer progression. It also highlights the need for a careful reassessment of current cancer therapies that target the body’s immune system to combat cancer. Using a mouse model of melanoma, one of the most aggressive types of skin cancer, Benjamin Toh, an A*STAR scholar working under the supervision of Professor Jean-Pierre Abastado, a Principal Investigator of SIgN, discovered that the primary tumour first produces a unique protein “CXCL5”. CXCL5 specifically attracts the PMN-MDSC immune cells to the primary tumour, accelerating its growth. These PMN-MDSC immune cells also reactivate an innate cellular programme in early skin growth, which causes the cancer cells to detach and spread from the primary tumour to other parts of the body. However, this migratory ability is transient; migrating cancer cells can spontaneously lose their migratory potential and form a new tumour in another site.  Said Prof Abastado, “We are really excited because our finding is a clear mechanistic explanation for the long-recognized link between inflammation and cancer progression. It may have significant and far-reaching clinical implications in the way we treat cancer. This study will certainly prompt us to re-think about cancer therapies that aim at boosting the immune system.” This latest finding on the cancer cells’ transient migratory ability also reinforced the team’s earlier studies which showed that cancer cells can in fact detach and migrate away from the primary tumour at a very early stage, often before the primary tumour is even detected. This challenges the current theory that cancer progression is a linear process, where the developing cancer cell sequentially accumulates mutations that give it the ability to metastasize i.e. to migrate from the primary tumour and settle in a new site to establish a new tumour.  Prof Paola Castagnoli, Scientific Director of SIgN added, “This study has definitely opened a new area in cancer research where more specific therapeutic targets might be uncovered within our body’s immune system. It is such new knowledge discovered through fundamental research that we are able to find new strategies to combat complex clinical conditions like cancer with a more holistic and effective approach.” The research findings described in this news release can be found in the 27 Sept 2011 issue of PLoS Biology under the title, "Mesenchymal Transition and Dissemination of Cancer Cells is driven by Myeloid-Derived Suppressor Cells infiltrating the Primary Tumour” by Benjamin Toh, Xiaojie Wang, Jo Keeble, Wen Jing Sim, Karen Khoo, Wing-Cheong Wong, Masashi Kato, Armelle Prevost-Blondel, Jean-Paul Thiery and Jean-Pierre Abastado. Editor's Note: Original news release can be found here.

Earth evolution “all about gas”

THE UNIVERSITY OF MELBOURNE

Image: da-kuk/iStockphoto An international team of scientists has provided new insights into the processes behind the evolution of the planet by demonstrating how salty water and gases transfer from the atmosphere into the Earth’s interior. The paper was published in Nature Geoscience. Scientists have long argued about how the Earth evolved from a primitive state in which it was covered by an ocean of molten rock, into the planet we live on today with a solid crust made of moving tectonic plates, oceans and an atmosphere.   Lead author Dr Mark Kendrick from the University of Melbourne’s School of Earth Sciences said inert gases trapped inside the Earth’s interior provide important clues into the processes responsible for the birth of our planet and the subsequent evolution of its oceans and atmosphere. “Our findings throw into uncertainty a recent conclusion that gases throughout the Earth were solely delivered by meteorites crashing into the planet,” he said. The study shows atmospheric gases are mixed into the mantle, inside the Earth’s interior, during the process called ‘subduction’, when tectonic plates collide and submerge beneath volcanoes in subduction zones.  “This finding is important because it was previously believed that inert gases inside the Earth had primordial origins and were trapped during the formation of the solar system,” Dr Kendrick said. Because the composition of neon in the Earth’s mantle is very similar to that in meteorites, it was recently suggested by scientists that most of the Earth’s gases were delivered by meteorites during a late meteorite bombardment that also generated visible craters on the Earth’s moon. “Our study suggests a more complex history in which gases were also dissolved into the Earth while it was still covered by a molten layer, during the birth of the solar system,” he said. It was previously assumed that gases could not sink with plates in tectonic subduction zones but escaped during eruption of overlying volcanoes. “The new study shows this is not entirely true and the gases released from Earth’s interior have not faithfully preserved the fingerprint of solar system formation.”  To undergo the study researchers collected serpentinite rocks from mountain belts in Italy and Spain. These rocks originally formed on the seafloor and were partially subducted into the Earth’s interior before they were uplifted into their present positions by collision of the European and African plates.  “The serpentinite rocks are special because they trap large amounts of seawater in their crystal structure and can be transported to great depths in the Earth’s mantle by subduction,” he said. By analysing the inert gases and halogens trapped in these rocks, the team was able to show gases are incompletely removed by the mineral transformations that affect serpentinites during the subduction process and hence provide new insights into the role of these trapped gases in the evolution of the planet.  The study was done in collaboration with researchers from the Australian National University, Canberra and The University of Genoa, Italy. Editor's Note: Original news release can be found here.