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A New Biodiversity Metric

The Brazilian Atlantic rainforest.  Image Source: Wikipedia

The Brazilian Atlantic rainforest. Image Source: Wikipedia

To understand how the repeated climatic shifts over the last 120,000 years may have influenced today’s patterns of genetic diversity, a team of researchers led by City College of New York biologist Dr. Ana Carnaval developed a new biodiversity metric called “phylogeographic endemism.”

It quantifies the degree to which the genetic variation within species is restricted in geographical space.

Dr. Carnaval, an assistant professor of biology, and 14 other researchers from institutions in Brazil, Australia and the United States, analyzed the effects of current and past climatic variation on the genetic diversity of 25 vertebrates in the highly diverse yet much threatened Brazilian Atlantic rainforest.

“We discovered that the climatic regimes of the northern and southern portions of the Atlantic forest are strikingly different. While past climate dynamics predicted phylogeographic endemism in the northern forests, contemporary climatic heterogeneity explains endemism in the south,” she said. “Studying these forest domains in isolation helped us to identify those areas holding most unique and small-ranged genetic variation, guiding research and conservation.”

The research findings appear in a paper entitled, “Prediction of phylogeographic endemism in an environmentally complex biome,” in the latest edition of the British journal “Proceedings of the Royal Society B.” The latter is the Royal Society’s flagship biological research journal, dedicated to the rapid publication and broad dissemination of high-quality research papers.

The shores of the Dead Sea, which borders Jordan, Palestine and Israel. As the lowest and saltiest lake in the world, it is home to some extreme creatures. Image Credit: Aaron L. Gronstal

DNA May Have Had Humble Beginnings As Nutrient Carrier

An artist's impression of a DNA molecule. Credit: FBI

An artist’s impression of a DNA molecule. Credit: FBI

New research intriguingly suggests that DNA, the genetic information carrier for humans and other complex life, might have had a rather humbler origin. In some microbes, a study shows, DNA pulls double duty as a storage site for phosphate. This all-important biomolecule contains phosphorus, a sometimes hard-to-get nutrient.

Maintaining an in-house source of phosphate is a newfound tactic for enabling microorganisms to eke out a living in harsh environments, according to a new study published in the open-access, peer reviewed scientific journal PLOS ONE. The finding bodes well for life finding a way, as it were, in extreme conditions on worlds less hospitable than Earth.

The results also support a second insight: DNA might have come onto the biological scene merely as a means of keeping phosphate handy. Only later on in evolutionary history did the mighty molecule perhaps take on the more advanced role of genetic carrier.

“DNA might have initially evolved for the purpose of storing phosphate, and the various genetic benefits evolved later,” said Joerg Soppa, senior author of the paper and a molecular biologist at Goethe University in Frankfurt, Germany.

Unraveling life’s origins

Scientists continue to investigate the development of self-replicating, intricate sets of chemistry — in other words, life — from the chemical compounds thought available on early Earth. Out of this mixture of prebiotic chemicals, two nucleic acids — RNA and DNA — emerged as champions.

Early Earth, in an artist's impression, where somehow complex, self-replicating chemistry (in other words, life) emerged. Credit: Peter Sawyer / Smithsonian Institution

Early Earth, in an artist’s impression, where somehow complex, self-replicating chemistry (in other words, life) emerged. Credit: Peter Sawyer / Smithsonian Institution

Today, these two types of biomolecules serve as the genetic information carriers for all Earthly biota. RNA on its own suffices for the business of life for simpler creatures, such as some viruses. Complex life, like humans, however, relies on DNA as its genetic carrier.

Astrobiologists want to understand the origin of DNA and its genetic cousin, RNA, because figuring out how life got started here on Earth is key for gauging if it might ever develop on alien planets.

Many researchers think RNA must have preceded DNA as the genetic molecule of choice. RNA is more versatile, acting as both genetic code and a catalyst for chemical reactions. Explicating the rise of DNA as a genetic material directly from RNA, however, is tricky. Compared to RNA, DNA needs significantly more supporting players for it to work well in a biological setting.

“The switch from RNA to DNA is not easy because many additional enzymes are required for DNA genomes,” said Soppa.

This unclear transition from RNA to DNA opens the door for a precursor to DNA possibly having a more mundane job. The new study offers an attractive explanation: that DNA was a fancy way to store nutrients in cells.

Phosphate depot?

DNA is chock-full of phosphate. Cells depend on phosphate to form not only DNA and RNA, but also related genetic machinery, such as the ribosome. Phosphate, furthermore, is a must for building the molecule ATP, life’s energy carrier, as well as fatty membrane molecules, certain phospho-proteins and phospho-sugars, and more.

The shores of the Dead Sea, which borders Jordan, Palestine and Israel. As the lowest and saltiest lake in the world, it is home to some extreme creatures. Image Credit: Aaron L. Gronstal

The shores of the Dead Sea, which borders Jordan, Palestine and Israel. As the lowest and saltiest lake in the world, it is home to some extreme creatures. Image Credit: Aaron L. Gronstal

“Phosphate is important for an immense set of biomolecules,” said Soppa.

Unfortunately for some microbes, ample phosphate is not always available. For example, in salty, nutrient-poor habitats, such as the Dead Sea in the Middle East, an organism called Haloferax volcanii must regularly “eat” ambient DNA to obtain phosphate (plus some other nutritional goodies, such as nitrogen).

Notably, H. volcanii can still survive and reproduce when phosphorus, the element needed to make phosphate, is lacking. Somehow, then, the microbe must turn to an inner source of phosphate, for otherwise it should cease to grow.

In their study, Soppa and colleagues from Germany, the United States and Israel sought out this source. The nature of H. volcanii provided some clues. The organism is classified as archaea, one of the three domains of life, in addition to bacteria and eukarya, the latter encompassing all multicellular organisms, from fungi to fruit flies. Many archaea and bacteria — collectively, “prokaryotes”— have just one, circular chromosome. Eukaryotes, like us, on the other hand, can have any number of the chunky pieces of DNA, RNA and proteins. (Humans have 23 pairs of different chromosomes, for the record.) H. volcanii is unusual. It has 20 copies of the same chromosome when it’s growing happily under favorable conditions, and 10 when nutrients are exhausted and it reaches a stationary phase.

Strength in numbers

Lots of chromosome copies are good to have in a pinch. So-called polyploidal organisms like H. volcanii use their copious chromosomes to tough it out through bad situations, such as high radiation exposure or total dry-outs, called desiccation. Either scenario causes the strands in chromosomal DNA to break. For single-chromosome species, only a few breaks lead to death because it is impossible to repair a chromosome scattered into fragments.

But if there are multiple copies of the cracked chromosomes, fragments can fortuitously line up. Rather like how a jigsaw puzzle is easier to put together if there are numerous duplicates of each necessary piece, the chromosome shards can sync up and restore a functional chromosome.

H. Volcanii grown in culture. Credit: Yejineun/Wikipedia

H. Volcanii grown in culture. Credit: Yejineun/Wikipedia

“In polyploid species, the fragments generated from different copies of the chromosome overlap, and it is possible to regenerate an intact chromosome from overlapping fragments,” said Soppa.

Desperate times, desperate measures

To investigate if H. volcanii‘s extra chromosomes might help the archaeon survive low phosphate conditions, Soppa and colleagues starved the organism in the lab of the critical substance. The microbe continued to reproduce by splitting one cell apart into two. Interestingly, chromosome counts diminished in the “parent” and the “daughter” cells.

“From quantifying the number of chromosomes prior to and after growth in the absence of phosphate, we have found that about 30 percent of the chromosomes are ‘missing’ afterwards,” said Soppa.

The numbers for another potential in-house source of phosphate, H. volcanii‘s ribosomes, however, remained steady. The most likely explanation, then, of the microorganism’s hardiness when facing a phosphate nutrient shortage: H. volcanii simply cannibalizes some of its own chromosomes.

As further verification, Soppa and colleagues tested the survival skills of H. volcanii cells that contained varying numbers of chromosome copies. Those archaea with just two copies of their chromosome turned out to be more than five times as sensitive to desiccation as those H. volcanii with a hefty complement of 20 chromosomes.

Life, undaunted

This newly described benefit of polyploidy in H. volcanii is a fresh demonstration of how life can make do in severe environments. So-called extremophiles have been discovered in recent decades thriving in strongly acidic hot springs, within liquid asphalt, and in other eyebrow-raising niches. Salt-tolerant bacteria and archaea, like H. volcanii, have been found to survive in deserts, simulated Mars conditions, and even the rigors of a space flight. We should not be surprised, perhaps, if life has managed to take hold on formidable worlds.

Red waters of the Rio Tinto in Spain. Image credit: Leslie Mullen

Extremophile microbes have been found that can survive in the polluted Rio Tinto River in Spain. Mining in the river’s vicinity has led to its waters having a high heavy metal content and very low pH, though the bacteria themselves, through their metabolism, also likely contribute to the intense acidity. Image credit: Leslie Mullen

“The understanding of how harsh the conditions can be that can be survived by some archaea and bacteria helps us to be more optimistic that life could have evolved at very rough and unsuitable places on early Earth or on other planets,” said Soppa.

The new role ascribed to DNA, as phosphate storage, might help to explain how a completely RNA-dominated primordial era began sharing genetic duties with DNA. Life did not leap from RNA to DNA. Rather, DNA, slowly but surely, learned new tricks.

“The hypothesis that DNA might have evolved as a storage polymer and became genetic material later, makes the step from RNA to DNA as genetic material easier, because it then would be a two-step and not a one-step process,” said Soppa. “DNA would have been around, and during long time spans additional roles could have been evolved.”

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NASA’s Spitzer Telescope Witnesses Asteroid Smashup

This artist’s concept shows the immediate aftermath of a large asteroid impact around NGC 2547-ID8, a 35-million-year-old sun-like star. NASA's Spitzer Space Telescope witnessed a giant surge in dust around the star, likely the result of two asteroids colliding. Image Credit:  NASA/JPL-Caltech

This artist’s concept shows the immediate aftermath of a large asteroid impact around NGC 2547-ID8, a 35-million-year-old sun-like star. NASA’s Spitzer Space Telescope witnessed a giant surge in dust around the star, likely the result of two asteroids colliding. Image Credit: NASA/JPL-Caltech

NASA’s Spitzer Space Telescope has spotted an eruption of dust around a young star, possibly the result of a smashup between large asteroids. This type of collision can eventually lead to the formation of planets.

Scientists had been regularly tracking the star, called NGC 2547-ID8, when it surged with a huge amount of fresh dust between August 2012 and January 2013.

“We think two big asteroids crashed into each other, creating a huge cloud of grains the size of very fine sand, which are now smashing themselves into smithereens and slowly leaking away from the star,” said lead author and graduate student Huan Meng of the University of Arizona, Tucson.

While dusty aftermaths of suspected asteroid collisions have been observed by Spitzer before, this is the first time scientists have collected data before and after a planetary system smashup. The viewing offers a glimpse into the violent process of making rocky planets like ours.

Rocky planets begin life as dusty material circling around young stars. The material clumps together to form asteroids that ram into each other. Although the asteroids often are destroyed, some grow over time and transform into proto-planets. After about 100 million years, the objects mature into full-grown, terrestrial planets. Our moon is thought to have formed from a giant impact between proto-Earth and a Mars-size object.

In the new study, Spitzer set its heat-seeking infrared eyes on the dusty star NGC 2547-ID8, which is about 35 million years old and lies 1,200 light-years away in the Vela constellation. Previous observations had already recorded variations in the amount of dust around the star, hinting at possible ongoing asteroid collisions.

Astronomers were surprised to see these data from NASA's Spitzer Space Telescope in January 2013, showing a huge eruption of dust around a star called NGC 2547-ID8. In this plot, infrared brightness is represented on the vertical axis, and time on the horizontal axis. Image Credit: NASA/JPL-Caltech/University of Arizona

Astronomers were surprised to see these data from NASA’s Spitzer Space Telescope in January 2013, showing a huge eruption of dust around a star called NGC 2547-ID8. In this plot, infrared brightness is represented on the vertical axis, and time on the horizontal axis. Image Credit: NASA/JPL-Caltech/University of Arizona

In hope of witnessing an even larger impact, which is a key step in the birth of a terrestrial planet, the astronomers turned to Spitzer to observe the star regularly. Beginning in May 2012, the telescope began watching the star, sometimes daily.

A dramatic change in the star came during a time when Spitzer had to point away from NGC 2547-ID8 because our sun was in the way. When Spitzer started observing the star again five months later, the team was shocked by the data they received.

“We not only witnessed what appears to be the wreckage of a huge smashup, but have been able to track how it is changing — the signal is fading as the cloud destroys itself by grinding its grains down so they escape from the star,” said Kate Su of the University of Arizona and co-author on the study. “Spitzer is the best telescope for monitoring stars regularly and precisely for small changes in infrared light over months and even years.”

A very thick cloud of dusty debris now orbits the star in the zone where rocky planets form. As the scientists observe the star system, the infrared signal from this cloud varies based on what is visible from Earth. For example, when the elongated cloud is facing us, more of its surface area is exposed and the signal is greater. When the head or the tail of the cloud is in view, less infrared light is observed. By studying the infrared oscillations, the team is gathering first-of-its-kind data on the detailed process and outcome of collisions that create rocky planets like Earth.

“We are watching rocky planet formation happen right in front of us,” said George Rieke, a University of Arizona co-author of the new study. “This is a unique chance to study this process in near real-time.”

The team is continuing to keep an eye on the star with Spitzer. They will see how long the elevated dust levels persist, which will help them calculate how often such events happen around this and other stars, and they might see another smashup while Spitzer looks on.

The results of this study are posted online Thursday in the journal Science.

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How Can We Find Tiny Particles In Exoplanet Atmospheres?

Image credit: NASA/ESA

Image credit: NASA/ESA

It may seem like magic, but astronomers have worked out a scheme that will allow them to detect and measure particles ten times smaller than the width of a human hair, even at many light-years distance.  They can do this by observing a blue tint in the light from far-off objects caused by the way in which small particles, no more than a micron in size (one-thousandth of a millimeter) scatter light.

In a recent study conducted by Adrian Brown of the SETI Institute, the broad outlines of this process have been worked out.  “The effect is related to a familiar phenomenon known as Rayleigh scattering,” says Brown.  “And that’s something everyone has seen: it makes the sky blue.”

By analyzing spectroscopic data from the Cassini orbiter, the Mars Reconnaissance Orbiter, and ground-based telescopes, Brown has managed to document this blue enhancement in many nearby objects, including the rings of Saturn, its moons Dione and Epimetheus, Mars, the moon, and the tail of Comet 17P/Holmes.

Brown’s theoretical study of the phenomenon showed that the spectral bluing occurs any time sufficiently small objects are in our field of view.  In his studies, he considered particles between 0.1 and 1.0 microns in size.  A human hair is roughly 17 microns in diameter.

So why isn’t the ground beneath our feet blue?  Brown’s research suggests that the effect is quickly damped by other objects that, despite being of the same type, have different size distributions.   The effect depends on having many particles within a narrow range of size.  In addition, too many tiny particles might turn objects white.  As an example of the latter, a glass of milk appears white because of multiple scattering from fat globules, and clouds appear white due to multiple scattering from water aerosols (droplets).

Consequently, the bluing effect requires some process that forms lots of particles of almost identical size.  Simply establishing that such a process is present can give researchers clues to the history and conditions on extraterrestrial bodies.

“This technique would, in principle, allow us to find extremely tiny particles in the atmospheres or on the surfaces of exoplanets that are tens or thousands of light-years away,” Brown says.

The research was published in the September 1 issue of Icarus.

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What lit up the universe?

A computer model shows one scenario for how light is spread through the early universe on vast scales (more than 50 million light years across). Astronomers will soon know whether or not these kinds of computer models give an accurate portrayal of light in the real cosmos. Credit: Andrew Pontzen/Fabio Governato

A computer model shows one scenario for how light is spread through the early universe on vast scales (more than 50 million light years across). Astronomers will soon know whether or not these kinds of computer models give an accurate portrayal of light in the real cosmos.
Credit: Andrew Pontzen/Fabio Governato

New research shows we will soon uncover the origin of the ultraviolet light that bathes the cosmos, helping scientists understand how galaxies were built.

The study published this month in The Astrophysical Journal Letters by UCL cosmologists Dr Andrew Pontzen and Dr Hiranya Peiris (both UCL Physics & Astronomy), together with collaborators at Princeton and Barcelona Universities, shows how forthcoming astronomical surveys will reveal what lit up the cosmos.

“Which produces more light? A country’s biggest cities or its many tiny towns?” asked Dr Pontzen, lead author of the study. “Cities are brighter, but towns are far more numerous. Understanding the balance would tell you something about the organisation of the country. We’re posing a similar question about the universe: does ultraviolet light come from numerous but faint galaxies, or from a smaller number of quasars?”

Quasars are the brightest objects in the Universe; their intense light is generated by gas as it falls towards a black hole. Galaxies can contain millions or billions of stars, but are still dim by comparison. Understanding whether the numerous small galaxies outshine the rare, bright quasars will provide insight into the way the universe built up today’s populations of stars and planets. It will also help scientists properly calibrate their measurements of dark energy, the agent thought to be accelerating the universe’s expansion and determining its far future.

The new method proposed by the team builds on a technique already used by astronomers in which quasars act as beacons to understand space. The intense light from quasars makes them easy to spot even at extreme distances, up to 95% of the way across the observable universe. The team think that studying how this light interacts with hydrogen gas on its journey to Earth will reveal the main sources of illumination in the universe, even if those sources are not themselves quasars.

Two types of hydrogen gas are found in the universe – a plain, neutral form and a second charged form which results from bombardment by UV light. These two forms can be distinguished by studying a particular wavelength of light called ‘Lyman-alpha’ which is only absorbed by the neutral type of hydrogen. Scientists can see where in the universe this ‘Lyman-alpha’ light has been absorbed to map the neutral hydrogen.

Since the quasars being studied are billions of light years away, they act as a time capsule: looking at the light shows us what the universe looked like in the distant past. The resulting map will reveal where neutral hydrogen was located billions of years ago as the universe was vigorously building its galaxies.

An even distribution of neutral hydrogen gas would suggest numerous galaxies as the source of most light, whereas a much less uniform pattern, showing a patchwork of charged and neutral hydrogen gas, would indicate that rare quasars were the primary origin of light.

Current samples of quasars aren’t quite big enough for a robust analysis of the differences between the two scenarios; however, a number of surveys currently being planned should help scientists find the answer.

Chief among these is the DESI (Dark Energy Spectroscopic Instrument) survey which will include detailed measurements of about a million distant quasars. Although these measurements are designed to reveal how the expansion of the universe is accelerating due to dark energy, the new research shows that results from DESI will also determine whether the intervening gas is uniformly illuminated. In turn, the measurement of patchiness will reveal whether light in our universe is generated by ‘a few cities’ (quasars) or by ‘many small towns’ (galaxies).

Co-author Dr Hiranya Peiris, said: “It’s amazing how little is known about the objects that bathed the universe in ultraviolet radiation while galaxies assembled into their present form. This technique gives us a novel handle on the intergalactic environment during this critical time in the universe’s history.”

Dr Pontzen, said: “It’s good news all round. DESI is going to give us invaluable information about what was going on in early galaxies, objects that are so faint and distant we would never see them individually. And once that’s understood in the data, the team can take account of it and still get accurate measurements of how the universe is expanding, telling us about dark energy. It illustrates how these big, ambitious projects are going to deliver astonishingly rich maps to explore. We’re now working to understand what other unexpected bonuses might be pulled out from the data.”

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Walking fish reveal how our ancestors evolved onto land

About 400 million years ago a group of fish began exploring land and evolved into tetrapods – today’s amphibians, reptiles, birds, and mammals. But just how these ancient fish used their fishy bodies and fins in a terrestrial environment and what evolutionary processes were at play remain scientific mysteries.

Researchers at McGill University published in the journal Nature, turned to a living fish, called Polypterus, to help show what might have happened when fish first attempted to walk out of the water.

Polypterus senegalus walks across a sandy substrate. Credit: E.M. Standen and T.Y. Du, H. Larsson

Polypterus is an African fish that can breathe air, ‘walk’ on land, and looks much like those ancient fishes that evolved into tetrapods. The team of researchers raised juvenile Polypterus on land for nearly a year, with an aim to revealing how these ‘terrestrialized’ fish looked and moved differently.

“Stressful environmental conditions can often reveal otherwise cryptic anatomical and behavioural variation, a form of developmental plasticity”, says Emily Standen, a former McGill post-doctoral student who led the project, now at the University of Ottawa. “We wanted to use this mechanism to see what new anatomies and behaviours we could trigger in these fish and see if they match what we know of the fossil record.”

Remarkable anatomical changes

Polypterus senegalus. Credit: A. Morin, E.M. Standen, T.Y. Du, H. Larsson

Polypterus senegalus. Credit: A. Morin, E.M. Standen, T.Y. Du, H. Larsson

The fish showed significant anatomical and behavioural changes. The terrestrialized fish walked more effectively by placing their fins closer to their bodies, lifted their heads higher, and kept their fins from slipping as much as fish that were raised in water.

“Anatomically, their pectoral skeleton changed to became more elongate with stronger attachments across their chest, possibly to increase support during walking, and a reduced contact with the skull to potentially allow greater head/neck motion,” says Trina Du, a McGill Ph.D. student and study collaborator.

“Because many of the anatomical changes mirror the fossil record, we can hypothesize that the behavioural changes we see also reflect what may have occurred when fossil fish first walked with their fins on land”, says Hans Larsson, Canada Research Chair in Macroevolution at McGill and an Associate Professor at the Redpath Museum.

Unique experiment

Polypterus senegalus.  Credit: A. Morin, E.M. Standen, T.Y. Du, H. Larsson

Polypterus senegalus.
Credit: A. Morin, E.M. Standen, T.Y. Du, H. Larsson

The terrestrialized Polypterus experiment is unique and provides new ideas for how fossil fishes may have used their fins in a terrestrial environment and what evolutionary processes were at play.

Larsson adds, “This is the first example we know of that demonstrates developmental plasticity may have facilitated a large-scale evolutionary transition, by first accessing new anatomies and behaviours that could later be genetically fixed by natural selection“.

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Scientist uncovers Red Planet’s climate history in unique meteorite

(Illustration: NASA/Greg Shirah)

Mars may have once been a warm, wet planet. (Illustration: NASA/Greg Shirah)

Was Mars — now a cold, dry place — once a warm, wet planet that sustained life? And if so, how long has it been cold and dry?

Research underway at the National High Magnetic Field Laboratory may one day answer those questions — and perhaps even help pave the way for future colonization of the Red Planet. By analyzing the chemical clues locked inside an ancient Martian meteorite known as Black Beauty, Florida State University Professor Munir Humayun and an international research team are revealing the story of Mars’ ancient, and sometimes startling, climate history.

The team’s most recent finding of a dramatic climate change appeared in Nature Geoscience, in the paper “Record of the ancient Martian hydrosphere and atmosphere preserved in zircon from a Martian meteorite.”

Martian meteorite known as "Black Beauty." Image credit: NASA

Martian meteorite known as “Black Beauty.” Image credit: NASA

The scientists found evidence for the climate shift in minerals called zircons embedded inside the dark, glossy meteorite. Zircons, which are also abundant in the Earth’s crust, form when lava cools. Among their intriguing properties, Humayun says, is that “they stick around forever.”

“When you find a zircon, it’s like finding a watch,” Humayun said. “A zircon begins keeping track of time from the moment it’s born.”

Last year, Humayun’s team correctly determined that the zircons in its Black Beauty sample were an astonishing 4.4 billion years old. That means, Humayun says, it formed during the Red Planet’s infancy and during a time when the planet might have been able to sustain life.

“First we learned that, about 4.5 billion years ago, water was more abundant on Mars, and now we’ve learned that something dramatically changed that,” said Humayun, a professor of geochemistry. “Now we can conclude that the conditions that we see today on Mars, this dry Martian desert, must have persisted for at least the past 1.7 billion years. We know now that Mars has been dry for a very long time.”

The secret to Mars’ climate lies in the fact that zircons (ZrSiO4) contain oxygen, an element with three isotopes. Isotopes are atoms of the same element that have the same number of protons but a different number of neutrons — sort of like members of a family who share the same last name but have different first names.

On Mars, oxygen is distributed in the atmosphere (as carbon dioxide, molecular oxygen and ozone), in the hydrosphere (as water) and in rocks. In the thin, dry Martian atmosphere, the sun’s ultraviolet light causes unique shifts in the proportions in which the three isotopes of oxygen occur in the different atmospheric gases.

Munir Humayun, professor of geoscience at Florida State.

Munir Humayun, professor of geoscience at Florida State.

So when water vapor that has cycled through the Martian atmosphere condenses into the Martian soil, it can interact with and exchange oxygen isotopes with zircons in the soil, effectively writing a climate record into the rocks. A warm, wet Mars requires a dense atmosphere that filters out the ultraviolet light making the unique isotope shifts disappear.

In order to measure the proportions of the oxygen isotopes in the zircons, the team, led by scientist Alexander Nemchin, used a device called an ion microprobe. The instrument is in the NordSIMS facility at the Swedish Museum of Natural History, directed by team member Martin Whitehouse.

Because of these precise measurements, said Humayun, “we now have an isotopic record of how the atmosphere changed, with dates on it.”

The Black Beauty meteorite Humayun’s team is studying was discovered in the Sahara Desert in 2011. It’s also known as NWA 7533, which stands for Northwest Africa, the location where it was found.

In all, more than five pieces of Black Beauty were found by Bedouin tribesmen, who make a living scouring the Sahara for meteorites and fossils that they can sell. The zircons analyzed by Humayun’s team were from Black Beauty samples kept in Paris.

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A touching story: The ancient conversation between plants, fungi and bacteria

Rhizobia are soil bacteria that fix nitrogen after becoming established inside root nodules of legumes. Image credit: Wikipedia

Rhizobia are soil bacteria that fix nitrogen after becoming established inside root nodules of legumes. Image credit: Wikipedia

The mechanical force that a single fungal cell or bacterial colony exerts on a plant cell may seem vanishingly small, but it plays a heavy role in setting up some of the most fundamental symbiotic relationships in biology.

In fact, it may not be too much of a stretch to say that plants may have never moved onto land without the ability to respond to the touch of beneficial fungi, according to a new study led by Jean-Michel Ané, a professor of agronomy at the University of Wisconsin-Madison.

“Many people have studied how roots progress through the soil, when fairly strong stimuli are applied to the entire growing root,” says Ané, who just published a review of touch in the interaction between plants and microbes in the journal Current Opinion in Plant Biology. “We are looking at much more localized, tiny stimuli on a single cell that is applied by microbes.”

Jean-Michel Ané

Jean-Michel Ané

Specifically, Ané, Dhileepkumar Jayaraman, a postdoctoral researcher in agronomy, and Simon Gilroy, a professor of botany, studied how such a slight mechanical stimulus starts round one of a symbiotic relationship — that is, a win-win relationship between two organisms.

It’s known that disease-causing fungi build a structure to break through the plant cell wall, “but there is growing evidence that fungi and also bacteria in symbiotic associations use a mechanical stimulation to indicate their presence,” says Ané. “They are knocking on the door, but not breaking it down.”

After the fungus announces its arrival, the plant builds a tube in which the fungus can grow. “There is clearly a mutual exchange of signals between the plant and the fungus,” says Ané. “It’s only when the path is completed that the fungus starts to penetrate.”

Mycorrhizae are the beneficial fungi that help virtually all land plants absorb the essential nutrients — phosphorus and nitrogen — from the soil. Biologists believe this ubiquitous mechanism began about 450 million years ago, when plants first moved onto land.

Mechanical signaling is only part of the story — microbes and plants also communicate with chemicals, says Ané. “So this is comparable not to breaking the door or even just knocking on the door, but to knocking on the door while wearing cologne. Clearly the plant is much more active than we thought; it can process signals, prepare the path and accept the symbiont.”

Beyond fungi, some plants engage in symbiosis with bacteria called rhizobia that “fix” nitrogen from the atmosphere, making it available to the plant.

Legumes like soybean plants, pictured in Jean-Michel Ané’s lab, can grow without nitrogen fertilizer when engaged with rhizobia. Photo: Jean-Michel Ané

Legumes like soybean plants, pictured in Jean-Michel Ané’s lab, can grow without nitrogen fertilizer when engaged with rhizobia. Photo: Jean-Michel Ané

Rhizobia enable legumes like soybeans and alfalfa to grow without nitrogen fertilizer.

When Ané and his colleagues looked closer, they found that rhizobium symbiosis also employs mechanical stimulation. When the bacterium first contacts a root hair, the hair curls around the bacterium, trapping it.

The phenomenon of curling has been known for almost 100 years. “But why would nature develop such a complicated mechanism to entrap a bacterial colony?” Ané asks. “We propose the purpose is to apply mechanical stimulation” so the plant will start building a home for the rhizobium — for mutual benefit. “We have preliminary evidence that when the entrapment is not complete, the process of colonization does not happen,” he says.

Again, the two-step communication system is at work, Ané adds. “The curling process itself can only begin when the plant gets a chemical signal from the bacterium — but the growing tube inside the root hair that accepts the bacteria requires something else, and nobody knew what. We propose it’s a mechanical stimulation created by entrapping, which gives the bacterial colony a way to push against the root.”

In many respects, this symbiosis parallels the older one between plants and beneficial fungi, Ané says. Indeed, he says legumes have “hijacked” the mycorrhizae system. “Plants used the symbiosis toolkit to develop this relationship with mycorrhizae, and then used it again for bacteria. This dual requirement for chemical and mechanical signals is present in both associations, even though the association between rhizobia and legumes is only 60 million years old.”

A Salty, Martian Meteorite Offers Clues to Habitability

Artist's conception of the Mars Phoenix lander, which found perchlorate on the Red Planet in 2008. Credit: NASA/JPL-Caltech

Artist’s conception of the Mars Phoenix lander, which found perchlorate on the Red Planet in 2008. Credit: NASA/JPL-Caltech

Life as we know it requires energy of some sort to survive and thrive. For plants, that source of energy is the Sun. But there are some microbes that can survive using energy from chemical reactions. Some of them even eat salts, such as perchlorates.

Perchlorate (ClO4-) is a highly oxidized form of chlorine. Perchlorate salts are found not only on Earth, but also on Mars. They’re highly toxic to humans but are useful for components such as rocket fuel.

It was good news for future Martian explorers when in 2008 an instrument on the Mars Phoenix polar lander discovered evidence of perchlorate in a flat valley informally called “Green Valley.” Four years later, the new NASA Curiosity rover uncovered more of the substance near the equator.

Now, there’s stronger evidence that the salt is widespread. New research shows that a martian meteorite recovered on Earth has perchlorate in it as well as other salts, namely chlorate and nitrate.

“We analyzed it and didn’t know what to expect,” said lead author Samuel Kounaves, a chemistry professor at Tufts University in Massachusetts. “We found perchlorate, not so high as on Mars, but at a well detectable level.”

Learning about salts on Mars also leads to related questions about organic materials and habitability on the Red Planet in general. While it’s a harsh environment for microbes today, it’s possible that they could survive in protected areas (such as underground), or that they were there in the past when climate conditions may have been warmer and wetter.

Scoop marks made by the Mars Science Laboratory Curiosity rover at a site called "Rocksnest" in 2012. After analyzing the sample inside the rover, scientists found a compound with chlorine and oxygen that likely is from chlorate or perchlorate. Credit: NASA/JPL-Caltech/MSSS

Scoop marks made by the Mars Science Laboratory Curiosity rover at a site called “Rocksnest” in 2012. After analyzing the sample inside the rover, scientists found a compound with chlorine and oxygen that likely is from chlorate or perchlorate. Credit: NASA/JPL-Caltech/MSSS

The results of the study, called “Evidence of martian perchlorate, chlorate, and nitrate in Mars meteorite EETA79001: Implications for oxidants and organics,” was recently published in the journal Icarus.

Checking for contamination

Kounaves led the Phoenix team that discovered perchlorate on Mars, so he is familiar with what the substance looks like on the Red Planet. With this new discovery, his team took pains to make sure that this meteorite was not contaminated in any way from the surrounding environment.

This meteorite, EETA79001, a basalt lava rock nearly indistinguishable from many Earth rocks, provided the first strong proof that meteorites could come from Mars. Originally weighing nearly 8 kilograms (17.6 pounds), it was collected in 1979 in the Elephant Moraine area of Antarctica. Credit: NASA/JSC/JPL/Lunar Planetary Institutef

This meteorite, EETA79001, a basalt lava rock nearly indistinguishable from many Earth rocks, provided the first strong proof that meteorites could come from Mars. Originally weighing nearly 8 kilograms (17.6 pounds), it was collected in 1979 in the Elephant Moraine area of Antarctica. Credit: NASA/JSC/JPL/Lunar Planetary Institute

“We said that if this is terrestrial contamination it should match the material where the meteorite was found in Antarctica,” Kounaves said.

The team used samples from a meteorite that was recovered in Antarctica during the 1979 field season. It is estimated to be 170 million years old (give or take 20 million years), was ejected from Mars about 65 million years ago, and is believed to have arrived on Earth roughly 12,000 years ago.

Researchers are sure the meteorite came from Mars because of the noble gases trapped inside of it, which are generally nonreactive gases such as helium, neon and argon. These gases have been analyzed on Earth, Mars and Venus in past missions and the match was closest to that of Mars.

To check for contamination, Kounaves’ group examined the ratios of types (isotopes) of nitrogen and oxygen, and discovered that the isotope ratios were different in the meteorite than in the ice where it was recovered, or in the nearby Antarctic Dry Valley soils. Similar results were also found for the ratios of chlorate and perchlorate to nitrate.

The perchlorate and other salts Kounaves was interested in was embedded in the very center of the 17 pound meteorite, three inches from the closest surface.

“It’s hard to believe that in the short period of time it laid in the ice in Antarctica it would have picked up that much perchlorate, nitrate and chlorate,” he said.

Artist's conception of the Mars 2020 rover, which will include instruments to search for organic materials on the Red Planet. Credit: NASA/JPL-Caltech

Artist’s conception of the Mars 2020 rover, which will include instruments to search for organic materials on the Red Planet. Credit: NASA/JPL-Caltech

Looking for life

The presence of perchlorate on Mars has some astrobiological implications. On Earth, perchlorate is typically used for making fuel, explosives and matches, but it is a health hazard to humans. Terrestrial microbes, however, can use it as a source of energy.

Perchlorate can also lower the freezing point of water to approximately -70 degrees Celsius (-94 degrees Fahrenheit.) On the cold Martian surface, where water exists in frozen polar ice caps and in frost, perchlorate makes it possible to keep water as a liquid. Microbes, however, could have a tough time living in such a brine because it lowers the availability of water molecules for life, Kounaves cautioned, similar to how ocean salts are harsh for certain types of organisms.

Concentrations of perchlorate on Mars are only about 1 percent, too low to be easily detected by any instruments on orbiting spacecraft, such as NASA’s Mars Reconnaissance Orbiter. That said, there are features on the Red Planet that are visible from orbit, such as gullies, that suggest flowing water. There are other explanations as well for these features, however, such as frozen carbon dioxide.

The links between perchlorate and water and life are not a given, but Kounaves said examining the relationship helps him better understand the potential for life on Mars. Figuring out the boundaries of habitability helps answer that question.

Mars is a harsh environment. It is very cold and dry. The surface is baked by radiation, and disturbed by occasional global dust storms. For microbial life to survive under such extreme conditions is highly improbable, but Kounaves said that life may find protection deep underground, and the search for life should, perhaps, begin there.

“It’s possible that if you go deep enough — maybe a kilometer underground, who knows how deep — there may be areas on Mars that may have allowed life to survive after having emerged billions of years ago.” he said.

Looking for organics

A related question to searching for salts on Mars is finding organic materials. Searching for organics has been a point of contention over the years, particularly with regard to some famous experiments on NASA’s Viking 1 and 2 landers in the 1970s.

At first blush, the Viking experiments seemed to show evidence of life. A gas exchanger detected oxygen from a sample of Mars soil that was treated with organic and inorganic compounds. Another experiment with Earth organic compounds inside Mars soil showed evidence of carbon dioxide, and another experiment detected organic residues in a sample of heated Mars soil.

Tracks from the Mars Science Laboratory Curiosity rover after crossing a dune on the Red Planet. Scientists are interested in learning what resources are available on the Red Planet for possible fuel sources, among other things. Credit: NASA/JPL-Caltech/MSSS

Tracks from the Mars Science Laboratory Curiosity rover after crossing a dune on the Red Planet. Scientists are interested in learning what resources are available on the Red Planet for possible fuel sources, among other things. Credit: NASA/JPL-Caltech/MSSS

Critics, however, pointed out that microbes don’t necessarily release oxygen and it was unclear if the organic compounds that were detected were, indeed, from Mars.

The Curiosity rover did find organics while heating up a portion of martian soil, but it was unclear if those organics were due to terrestrial contamination, as NASA acknowledged in results released in December 2012. The only thing that was clearly martian in this sample was evidence of water, sulphur and substances containing chlorine.

“We have no definitive detection of martian organics at this point, but we will keep looking in the diverse environments of Gale Crater,” said NASA Goddard’s Paul Mahaffy, the principal investigator of the Curiosity instrument that found the results at that time.

However, it’s also possible that the act of heating up or altering the soil could destroy any organics that would have been present in the first place, and that’s leaving aside the question of how radiation would damage organics on the surface.

“Maybe it’s in rocks, ancient rocks, where the organics may be protected,” Kounaves added.

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Orion Rocks! Pebble-Size Particles May Jump-Start Planet Formation

Radio/optical composite of the Orion Molecular Cloud Complex showing the OMC-2/3 star-forming filament. GBT data is shown in orange. Uncommonly large dust grains there may kick-start planet formation. Credit: S. Schnee, et al.; B. Saxton, B. Kent (NRAO/AUI/NSF); We acknowledge the use of NASA's SkyView Facility located at NASA Goddard Space Flight Center.

Radio/optical composite of the Orion Molecular Cloud Complex showing the OMC-2/3 star-forming filament. Credit: S. Schnee, et al.; B. Saxton, B. Kent (NRAO/AUI/NSF)

Rocky planets like Earth start out as microscopic bits of dust tinier than a grain of sand, or so theories predict.

Astronomers using the National Science Foundation’s (NSF) Green Bank Telescope (GBT) have discovered that filaments of star-forming gas near the Orion Nebula may be brimming with pebble-size particles — planetary building blocks 100 to 1,000 times larger than the dust grains typically found around protostars. If confirmed, these dense ribbons of rocky material may well represent a new, mid-size class of interstellar particles that could help jump-start planet formation.

“The large dust grains seen by the GBT would suggest that at least some protostars may arise in a more nurturing environment for planets,” said Scott Schnee, an astronomer with the National Radio Astronomy Observatory (NRAO) in Charlottesville, Virginia. “After all, if you want to build a house, it’s best to start with bricks rather than gravel, and something similar can be said for planet formation.”

The new GBT observations extend across the northern portion of the Orion Molecular Cloud Complex, a star-forming region that includes the famed Orion Nebula. The star-forming material in the section studied by the GBT, called OMC-2/3, has condensed into long, dust-rich filaments. The filaments are dotted with many dense knots known as cores. Some of the cores are just starting to coalesce while others have begun to form protostars — the first early concentrations of dust and gas along the path to star formation.

Astronomers speculate that in the next 100,000 to 1 million years, this area will likely evolve into a new star cluster. The OMC-2/3 region is located approximately 1,500 light-years from Earth and is roughly 10 light-years long.

Zoom in of the OMC-2/3 region. Credit: S. Schnee, et al.; B. Saxton, B. Kent (NRAO/AUI/NSF); We acknowledge the use of NASA's SkyView Facility located at NASA Goddard Space Flight Center.

Zoom in of the OMC-2/3 region. Credit: S. Schnee, et al.; B. Saxton, B. Kent (NRAO/AUI/NSF); We acknowledge the use of NASA’s SkyView Facility located at NASA Goddard Space Flight Center.

Based on earlier maps of this region made with the IRAM 30 meter radio telescope in Spain, the astronomers expected to find a certain brightness to the dust emission when they observed the filaments at slightly longer wavelengths with the GBT.

Instead, the GBT discovered that the area was shining much brighter than expected in millimeter-wavelength light.

“This means that the material in this region has different properties than would be expected for normal interstellar dust,” noted Schnee. “In particular, since the particles are more efficient than expected at emitting at millimeter wavelengths, the grains are very likely to be at least a millimeter, and possibly as large as a centimeter across, or roughly the size of a small Lego-style building block.”

Though incredibly small compared to even the most modest of asteroids, dust grains on the order of a few millimeters to a centimeter are incredibly large for such young star-forming regions. Due to the unique environment in the Orion Molecular Cloud Complex, the researchers propose two intriguing theories for their origin.

The first is that the filaments themselves helped the dust grains grow to such unusual proportions. These regions, compared to molecular clouds in general, have lower temperatures, higher densities, and lower velocities — all of which would encourage grain growth.

The second scenario is that the rocky particles originally grew inside a previous generation of cores or perhaps even protoplanetary disks. The material could then have escaped back into the surrounding molecular cloud rather than becoming part of the original newly forming star system.

“Rather than typical interstellar dust, these researchers appear to have detected vast streamers of gravel — essentially a long and winding road in space,” said NRAO astronomer Jay Lockman, who was not involved in these observations. “We’ve known about dust specks and we have known that there are things the size of asteroids and planets, but if we can confirm these results it would add a new population of rocky particles to interstellar space.”

The most recent data were taken with the Green Bank Telescope’s high frequency imaging camera, MUSTANG. These data were compared with earlier studies as well as temperature estimates obtain from observations of ammonia molecules in the clouds.

“Though our results suggest the presence of unexpectedly large dust grains, measuring the mass of dust is not a straightforward process and there could be other explanations for the bright signature we detected in the emission from the Orion Molecular Cloud,” concluded Brian Mason, an astronomer at the NRAO and co-author on the paper. “Our team continues to study this fascinating area. Since it contains one of the highest concentrations of protostars of any nearby molecular cloud it will continue to excite the curiosity of astronomers.”

A paper detailing these results is accepted for publication in the Monthly Notices of the Royal Astronomical Society.

The GBT is the world’s largest fully steerable radio telescope. Its location in the National Radio Quiet Zone and the West Virginia Radio Astronomy Zone protects the incredibly sensitive telescope from unwanted radio interference.

Later this year, the GBT will receive two new, more advanced high frequency cameras: MUSTANG-1.5, the even-more-sensitive successor to MUSTANG, and ARGUS, a camera designed for mapping the distribution of organic molecules in space.

The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.

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NASA Telescopes Uncover Early Construction of Giant Galaxy

Artist impression of a firestorm of star birth deep inside core of young, growing elliptical galaxy. Image Credit:  NASA, Z. Levay, G. Bacon (STScI)

Artist impression of a firestorm of star birth deep inside core of young, growing elliptical galaxy.
Image Credit: NASA, Z. Levay, G. Bacon (STScI)

Astronomers have for the first time caught a glimpse of the earliest stages of massive galaxy construction. The building site, dubbed “Sparky,” is a dense galactic core blazing with the light of millions of newborn stars that are forming at a ferocious rate.

The discovery was made possible through combined observations from NASA’s Hubble and Spitzer space telescopes, the W.M. Keck Observatory in Mauna Kea, Hawaii, and the European Space Agency’s Herschel space observatory, in which NASA plays an important role.

A fully developed elliptical galaxy is a gas-deficient gathering of ancient stars theorized to develop from the inside out, with a compact core marking its beginnings. Because the galactic core is so far away, the light of the forming galaxy that is observable from Earth was actually created 11 billion years ago, just 3 billion years after the Big Bang.

This illustration shows the NASA/ESA Hubble Space Telescope in its high orbit 600 kilometres above Earth. Credit: European Space Agency

This illustration shows the NASA/ESA Hubble Space Telescope in its high orbit 600 kilometres above Earth. Credit: European Space Agency

Although only a fraction of the size of the Milky Way, the tiny powerhouse galactic core already contains about twice as many stars as our own galaxy, all crammed into a region only 6,000 light-years across. The Milky Way is about 100,000 light-years across.

“We really hadn’t seen a formation process that could create things that are this dense,” explained Erica Nelson of Yale University in New Haven, Connecticut, lead author of the study. “We suspect that this core-formation process is a phenomenon unique to the early universe because the early universe, as a whole, was more compact. Today, the universe is so diffuse that it cannot create such objects anymore.”

In addition to determining the galaxy’s size from the Hubble images, the team dug into archival far-infrared images from Spitzer and Herschel. This allowed them to see how fast the galaxy core is creating stars. Sparky produced roughly 300 stars per year, compared to the 10 stars per year produced by our Milky Way.

“They’re very extreme environments,” Nelson said. “It’s like a medieval cauldron forging stars. There’s a lot of turbulence, and it’s bubbling. If you were in there, the night sky would be bright with young stars, and there would be a lot of dust, gas, and remnants of exploding stars. To actually see this happening is fascinating.”

W.M. Keck Observatory in Hawaii. Credit: Pablo McLoud/WMKO

W.M. Keck Observatory in Hawaii. Credit: Pablo McLoud/WMKO

Astronomers theorize that this frenzied star birth was sparked by a torrent of gas flowing into the galaxy’s core while it formed deep inside a gravitational well of dark matter, invisible cosmic material that acts as the scaffolding of the universe for galaxy construction.

Observations indicate that the galaxy had been furiously making stars for more than a billion years. It is likely that this frenzy eventually will slow to a stop, and that over the next 10 billion years other smaller galaxies may merge with Sparky, causing it to expand and become a mammoth, sedate elliptical galaxy.

“I think our discovery settles the question of whether this mode of building galaxies actually happened or not,” said team-member Pieter van Dokkum of Yale University. “The question now is, how often did this occur? We suspect there are other galaxies like this that are even fainter in near-infrared wavelengths. We think they’ll be brighter at longer wavelengths, and so it will really be up to future infrared telescopes such as NASA’s James Webb Space Telescope to find more of these objects.”

The paper appears in the Aug. 27 issue of the journal Nature.

For more information about Spitzer, visit:

http://www.nasa.gov/spitzer

For images and more information about Hubble, visit:

http://www.nasa.gov/hubble

Organisms cultured from the samples collected from Lake Whillans. Credit: LSU/Christner et. al. (2014)

Subglacial Life in Antarctica

Organisms cultured from the samples collected from Lake Whillans. Credit: LSU/Christner et. al. (2014)

Organisms cultured from the samples collected from Lake Whillans. Credit: LSU/Christner et. al. (2014)

Scientists have proven that microbial ecosystems exist in a subglacial lake in Antarctica. The researchers cultured microorganisms from samples of water and sediment that were collected from Lake Whillans, which lies 800 meters beneath the surface of the West Antarctic ice sheet.

Antarctica is thought to have more than 400 subglacial lakes and streams, potentially providing an extensive habitat for organisms like those found in Lake Whillans. The new study provides astrobiologists with a glimpse into these unique habitats for life, which have remained largely unexplored until now.

An image from the Whillans Ice Stream Subglacial Access Research Drilling project (WISSARD) borehole camera is shown. Credit: The Whillans Ice Stream Subglacial Access Research Drilling Project

An image from the Whillans Ice Stream Subglacial Access Research Drilling project (WISSARD) borehole camera is shown. Credit: The Whillans Ice Stream Subglacial Access Research Drilling Project

Astrobiologists have long been interested in Antarctica’s subglacial lakes as analog environments for icy worlds like Jupiter’s moon Europa. Beneath the icy surface of Europa lies a liquid water ocean, and studying ice covered lakes on Earth could provide clues about the potential for life beyond our planet.

Many of Antarctica’s lakes are thought to support habitats that are almost completely isolated from the surface environment. Organisms living in these lakes would have developed unique adaptations in order to survive in the dark, cold waters while being cut off from the rest of Earth’s biosphere for long periods of time. The evolution of these  ecosystems could serve as an example for how life might adapt to similarly isolated environments on other worlds in the Solar System.

Samples were collected during the Whillans Ice Stream Subglacial Access Research Drilling (WISSARD) project. The article, “A microbial ecosystem beneath the West Antarctic ice sheet,” was published in the journal Nature under lead author Brent C. Christner.

 

Support for the project was provided by the National Science Foundation (NSF), NASA’s Cryospheric Sciences Program, the National Oceanic and Atmospheric Administration (NOAA), and the private Gordon and Betty Moore Foundation.

To read more about the research, including other results from the WISSARD project, visit the journal Nature at: http://www.nature.com/news/lakes-under-the-ice-antarctica-s-secret-garden-1.15729

The Voyager 2 spacecraft flew by Triton, a moon of Neptune, in the summer of 1989. Paul Schenk, a scientist at the Lunar and Planetary Institute in Houston, used Voyager data to construct the best-ever global color map of Triton. This map has a resolution of 1,970 feet (600 meters) per pixel. Image Credit: NASA/JPL-Caltech/Lunar & Planetary Institute

Triton: Oceans of the Outer Solar System

The Voyager 2 spacecraft flew by Triton, a moon of Neptune, in the summer of 1989. Paul Schenk, a scientist at the Lunar and Planetary Institute in Houston, used Voyager data to construct the best-ever global color map of Triton. This map has a resolution of 1,970 feet (600 meters) per pixel. Image Credit: NASA/JPL-Caltech/Lunar & Planetary Institute

The Voyager 2 spacecraft flew by Triton, a moon of Neptune, in the summer of 1989. Paul Schenk, a scientist at the Lunar and Planetary Institute in Houston, used Voyager data to construct the best-ever global color map of Triton. This map has a resolution of 1,970 feet (600 meters) per pixel. Image Credit: NASA/JPL-Caltech/Lunar & Planetary Institute

NASA recently released a new and highly detailed map of Neptune’s moon Triton. The map has a resolution of 600 meters per pixel and was created using ‘restored’ data from the Voyager 2 spacecraft’s 1989 encounter with Neptune. It is a beautiful example of the longevity of good data, and the value of using new technology and techniques to re-analyze archived data from past missions

The map of Triton provides a wealth of new information for comparative planetology and planetary geology studies, and scientists will use it to better-understand the diverse nature of solid bodies in the Solar System. But Triton also has some interesting things to teach astrobiologists.

Computer-generated montage of Triton and Neptune, using images from the Voyager 2 flyby. Image Credit: NASA/JPL/USGS

Computer-generated montage of Triton and Neptune, using images from the Voyager 2 flyby. Image Credit: NASA/JPL/USGS

When studying life’s potential beyond Earth, Triton doesn’t immediately spring to mind as a promising location for biology. Earth, the only inhabited planet yet known, is roughly 149,600,000 kilometers away from the Sun and sits within our star’s habitable zone. In this region of space, the planet receives just the right amount of energy for liquid water to persist at the surface. Triton (and its host planet Neptune) are more than 4,503,443,600 kilometers away from the Sun’s warmth, orbiting in the dark depths of the outer Solar System.

But a star’s habitable zone is not the only measure of habitability in a solar system. With data from missions like Voyager, astrobiologists have identified cold, dark moons of giant planets that may still have the potential to support life.

In a 2012 paper in the journal Icarus, Jodi Gaeman and colleagues outlined a possible scenario for a subsurface ocean on Triton. They found that after Triton was drawn into Neptune’s orbit, the moon could have experienced tidal heating in a way similar to Jupiter’s moon Europa. Like Europa, energy from this heating could have melted areas of Triton’s subsurface, creating an ocean of liquid water beneath the moon’s icy shell.

The researchers determined that Triton could have a thin layer of liquid water rich in ammonia (NH3) today – but only if Triton started its life as a Neptunain moon with a highly eccentric orbit that slowly circularized over time.

An illustration of Voyager 2 setting its sights on Neptune and Triton in 1989 from Issue 4 of the Astrobiology Program's graphic history of astrobiology. Available at: http://www.astrobio.net/nasa-astrobio-graphic-novels/ Credit: NASA Astrobiology Program, Artwork by Aaron L. Gronstal

An illustration of Voyager 2 setting its sights on Neptune and Triton in 1989 from Issue 4 of the Astrobiology Program’s graphic history of astrobiology. Available at: http://www.astrobio.net/nasa-astrobio-graphic-novels/ Credit: NASA Astrobiology Program, Artwork by Aaron L. Gronstal

Astrobiology Magazine asked Dr. Saswata Hier-Majumder, co-author of the 2012 study and Senior Lecturer in the Department of Earth Sciences at Royal Holloway University of London, if the new map of Triton could provide further clues about the moon’s subsurface.

“This high resolution map will be helpful in studying, among other geological features on Triton’s surface, the system of ridges in the Cantaloupe terrain and the smooth planes,” said Hier-Majumder. “Both of these features can provide clues regarding the presence of a subsurface ocean, and potential estimates of the thickness of Triton’s crust.”

In the case of Europa, images of the moon’s surface have been essential for identifying features that provide insights into what lies beneath the moon’s ice. The new, detailed map of Triton could  have similar applications. Dr. Hier-Majumder gave an example of the types of features he would look for:

“Given the young age of Triton’s surface (~100 Ma), cryovolcanic features on the surface would imply recent extrusion of fluid from the subsurface ocean. The mechanism by which such extrusions occur, however,  are still not completely clear.”


The Voyager 2 spacecraft flew by Triton, a moon of Neptune, on August 25, 1989. Paul Schenk, a scientist at the Lunar and Planetary Institute in Houston, used Voyager data to construct this video recreating that exciting encounter. Image Credit: NASA/JPL-Caltech/Lunar & Planetary Institute

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Rosetta: Landing site search narrows

Philae candidate landing sites. Credits: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

Philae candidate landing sites. Credits: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

Using detailed information collected by ESA’s Rosetta spacecraft during its first two weeks at Comet 67P/Churyumov-Gerasimenko, five locations have been identified as candidate sites to set down the Philae lander in November – the first time a landing on a comet has ever been attempted.

Before arrival, Comet 67P/Churyumov-Gerasimenko had never been seen close up and so the race to find a suitable landing site for the 100 kg lander could only begin when Rosetta rendezvoused with the comet on 6 August.

The landing is expected to take place in mid-November when the comet is about 450 million km from the Sun, before activity on the comet reaches levels that might jeopardise the safe and accurate deployment of Philae to the comet’s surface, and before surface material is modified by this activity.

The comet is on a 6.5-year orbit around the Sun and today is 522 million km from it. At their closest approach on 13 August 2015, just under a year from now, the comet and Rosetta will be 185 million km from the Sun, meaning an eightfold increase in the light received from the Sun.

While Rosetta and its scientific instruments will watch how the comet evolves as heating by the Sun increases, observing how its coma develops and how the surface changes over time, the lander Philae and its instruments will be tasked with making complementary in situ measurements at the comet’s surface. The lander and orbiter will also work together using the CONSERT experiment to send and detect radio waves through the comet’s interior, in order to characterise its internal structure.

Philae on the comet. Credit: ESA/ATG medialab

Philae on the comet. Credit: ESA/ATG medialab

Choosing the right landing site is a complex process. That site must balance the technical needs of the orbiter and lander during all phases of the separation, descent, and landing, and during operations on the surface with the scientific requirements of the 10 instruments on board Philae.

A key issue is that uncertainties in the navigation of the orbiter close to the comet mean that it is only possible to specify any given landing zone in terms of an ellipse – covering up to one square kilometre – within which Philae might land.

For each possible zone, important questions must be asked: Will the lander be able to maintain regular communications with Rosetta? How common are surface hazards such as large boulders, deep crevasses or steep slopes? Is there sufficient illumination for scientific operations and enough sunlight to recharge the lander’s batteries beyond its initial 64-hour lifetime, while not so much as to cause overheating?

To answer these questions, data acquired by Rosetta from about 100 km distance have been used, including high-resolution images of the surface, measurements of the comet’s surface temperature, and the pressure and density of gas around the nucleus. In addition, measurements of the comet’s orientation with respect to the Sun, its rotation, mass and surface gravity have been determined. All of these factors influence the technical feasibility of landing at any specific location on the comet.

This weekend, the Landing Site Selection Group (comprising engineers and scientists from Philae’s Science, Operations and Navigation Centre at CNES, the Lander Control Centre at DLR, scientists representing the Philae Lander instruments and ESA’s Rosetta team) met at CNES, Toulouse, to consider the available data and determine a shortlist of five candidate sites.

“This is the first time landing sites on a comet have been considered,” says Stephan Ulamec, Lander Manager at DLR.

“Based on the particular shape and the global topography of Comet 67P/ Churyumov-Gerasimenko, it is probably no surprise that many locations had to be ruled out. The candidate sites that we want to follow up for further analysis are thought to be technically feasible on the basis of a preliminary analysis of flight dynamics and other key issues – for example they all provide at least six hours of daylight per comet rotation and offer some flat terrain. Of course, every site has the potential for unique scientific discoveries.”

“The comet is very different to anything we’ve seen before, and exhibits spectacular features still to be understood,” says Jean-Pierre Bibring, a lead lander scientist and principal investigator of the CIVA instrument.

“The five chosen sites offer us the best chance to land and study the composition, internal structure and activity of the comet with the ten lander experiments.”

The sites were assigned a letter from an original pre-selection of 10 possible sites, which does not signify any ranking. Three sites (B, I and J) are located on the smaller of the two lobes of the comet and two sites (A and C) are located on the larger lobe.

Summary of the five candidate sites

Rosetta_OSIRIS_NAC_comet_67P_20140816_SiteA_625

Candidate landing site A

Site A is an interesting region located on the larger lobe, but with a good view of the smaller lobe. The terrain between the two lobes is likely the source of some outgassing. Higher-resolution imaging is needed to study potential surface hazards such as small depressions and slopes, while the illumination conditions also need to be considered further.

Candidate landing site B

Candidate landing site B

Site B, within the crater-like structure on the smaller lobe, has a flat terrain and is thus considered relatively safe for landing, but illumination conditions may pose a problem when considering the longer-term science planning of Philae. Higher-resolution imaging will be needed to assess the boulder hazards in more detail. In addition, the boulders are also thought to represent more recently processed material and therefore this site may not be as pristine as some of the others.

Candidate landing site C

Candidate landing site C

Site C is located on the larger lobe and hosts a range of surface features including some brighter material, depressions, cliffs, hills and smooth plains, but higher-resolution imaging is needed to assess the risk of some of these features. It is also well illuminated, which would benefit the long-term scientific planning for Philae.

Candidate landing site I

Candidate landing site I

Site I is a relatively flat area on the smaller lobe that may contain some fresh material, but higher-resolution imaging is needed to assess the extent of the rough terrain. The illumination conditions should also allow for longer-term science planning.

Candidate landing site J

Candidate landing site J

Site J is similar to site I, and also on the smaller lobe, offering interesting surface features and good illumination. It offers advantages for the CONSERT experiment compared with Site I, but higher-resolution imaging is needed to determine the details of the terrain, which shows some boulders and terracing.

The next step is a comprehensive analysis of each of the candidate sites, to determine possible orbital and operational strategies that could be used for Rosetta to deliver the lander to any of them. At the same time, Rosetta will move to within 50 km of the comet, allowing a more detailed study of the proposed landing sites.

By 14 September, the five candidate sites will have been assessed and ranked, leading to the selection of a primary landing site, for which a fully detailed strategy for the landing operations will be developed, along with a backup.

During this phase, Rosetta will move to within 20–30 km of the comet, allowing even more detailed maps of the boulder distributions at the primary and backup landing sites to be made. This information could be important in deciding whether to switch from primary to backup.

The Rosetta mission team are working towards a nominal landing date of 11 November, but confirmation of the primary landing site and the date will likely only come on 12 October. This will be followed by a formal Go/No Go from ESA, in agreement with the lander team, after a comprehensive readiness review on 14 October.

“The process of selecting a landing site is extremely complex and dynamic; as we get closer to the comet, we will see more and more details, which will influence the final decision on where and when we can land,” says Fred Jansen, ESA Rosetta mission manager.

“We had to complete our preliminary analysis on candidate sites very quickly after arriving at the comet, and now we have just a few more weeks to determine the primary site. The clock is ticking and we now have to meet the challenge to pick the best possible landing site.”

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NASA’s New Horizons Spacecraft Crosses Neptune Orbit En Route to Historic Pluto Encounter

During August 16 and 17, 1989, the Voyager 2 narrow-angle camera was used to photograph Neptune almost continuously, recording approximately two and one-half rotations of the planet. Image credit: NASA/JPL

During August 16 and 17, 1989, the Voyager 2 narrow-angle camera was used to photograph Neptune almost continuously, recording approximately two and one-half rotations of the planet. Image credit: NASA/JPL

NASA’s Pluto-bound New Horizons spacecraft has traversed the orbit of Neptune. This is its last major crossing en route to becoming the first probe to make a close encounter with distant Pluto on July 14, 2015.

The sophisticated piano-sized spacecraft, which launched in January 2006, reached Neptune’s orbit — nearly 2.75 billion miles from Earth — in a record eight years and eight months. New Horizons’ milestone matches precisely the 25th anniversary of the historic encounter of NASA’s Voyager 2 spacecraft with Neptune on Aug. 25, 1989.

“It’s a cosmic coincidence that connects one of NASA’s iconic past outer solar system explorers, with our next outer solar system explorer,” said Jim Green, director of NASA’s Planetary Science Division, NASA Headquarters in Washington. “Exactly 25 years ago at Neptune, Voyager 2 delivered our ‘first’ look at an unexplored planet. Now it will be New Horizons’ turn to reveal the unexplored Pluto and its moons in stunning detail next summer on its way into the vast outer reaches of the solar system.”

New Horizons now is about 2.48 billion miles from Neptune — nearly 27 times the distance between the Earth and our sun — as it crosses the giant planet’s orbit at 10:04 p.m. EDT Monday. Although the spacecraft will be much farther from the planet than Voyager 2’s closest approach, New Horizons’ telescopic camera was able to obtain several long-distance “approach” shots of Neptune on July 10.

NASA's Pluto-bound New Horizons spacecraft captured this view of the giant planet Neptune and its large moon Triton on July 10, 2014, from a distance of about 2.45 billion miles (3.96 billion kilometers) - more than 26 times the distance between the Earth and sun. Image Credit:  NASA/Johns Hopkins University Applied Physics Laboratory

NASA’s Pluto-bound New Horizons spacecraft captured this view of the giant planet Neptune and its large moon Triton on July 10, 2014, from a distance of about 2.45 billion miles (3.96 billion kilometers) – more than 26 times the distance between the Earth and sun. Image Credit: NASA/Johns Hopkins University Applied Physics Laboratory

NASA’s Voyager 1 and 2 explored the entire middle zone of the solar system where the giant planets orbit,” said Alan Stern, New Horizons principal investigator at the Southwest Research Institute in Boulder, Colorado. “Now we stand on Voyager’s broad shoulders to explore the even more distant and mysterious Pluto system.”

Several senior members of the New Horizons science team were young members of Voyager’s science team in 1989. Many remember how Voyager 2’s approach images of Neptune and its planet-sized moon Triton fueled anticipation of the discoveries to come. They share a similar, growing excitement as New Horizons begins its approach to Pluto.

“The feeling 25 years ago was that this was really cool, because we’re going to see Neptune and Triton up-close for the first time,” said Ralph McNutt of the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Maryland, who leads the New Horizons energetic-particle investigation and served on the Voyager plasma-analysis team. “The same is happening for New Horizons. Even this summer, when we’re still a year out and our cameras can only spot Pluto and its largest moon as dots, we know we’re in for something incredible ahead.”

Voyager’s visit to the Neptune system revealed previously unseen features of Neptune itself, such as the Great Dark Spot, a massive storm similar to, but not as long-lived, as Jupiter’s Great Red Spot. Voyager also, for the first time, captured clear images of the ice giant’s ring system, too faint to be clearly viewed from Earth. “There were surprises at Neptune and there were surprises at Triton,” said Ed Stone, Voyager’s long-standing project scientist from the California Institute of Technology in Pasadena. “I’m sure that will continue at Pluto.”

Many researchers feel the 1989 Neptune flyby — Voyager’s final planetary encounter — might have offered a preview of what’s to come next summer. Scientists suggest that Triton, with its icy surface, bright poles, varied terrain and cryovolcanoes, is a Pluto-like object that Neptune pulled into orbit. Scientists recently restored Voyager’s footage of Triton and used it to construct the best global color map of that strange moon yet — further whetting appetites for a Pluto close-up.

“There is a lot of speculation over whether Pluto will look like Triton, and how well they’ll match up,” McNutt said. “That’s the great thing about first-time encounters like this — we don’t know exactly what we’ll see, but we know from decades of experience in first-time exploration of new planets that we will be very surprised.”

Similar to Voyager 1 and 2′s historic observations, New Horizons also is on a path toward potential discoveries in the Kuiper Belt, which is a disc-shaped region of icy objects past the orbit of Neptune, and other unexplored realms of the outer solar system and beyond.

“No country except the United States has the demonstrated capability to explore so far away,” said Stern. “The U.S. has led the exploration of the planets and space to a degree no other nation has, and continues to do so with New Horizons. We’re incredibly proud that New Horizons represents the nation again as NASA breaks records with its newest, farthest and very capable planetary exploration spacecraft.”

Voyager 1 and 2 were launched 16 days apart in 1977, and one of the spacecraft visited Jupiter, Saturn, Uranus and Neptune. Voyager 1 now is the most distant human-made object, about 12 billion miles (19 billion kilometers) away from the sun. In 2012, it became the first human-made object to venture into interstellar space. Voyager 2, the longest continuously operated spacecraft, is about 9 billion miles (15 billion kilometers) away from our sun.

New Horizons is the first mission in NASA’s New Frontiers program. APL manages the mission for NASA’s Science Mission Directorate at NASA Headquarters. APL also built and operates the New Horizons spacecraft.

The Voyager spacecraft were built and continue to be operated by NASA’s Jet Propulsion Laboratory in Pasadena, California. The Voyager missions are part of NASA’s Heliophysics System Observatory, sponsored by the Heliophysics Division of the Science Mission Directorate.

To view the Neptune images taken by New Horizons and learn more about the mission, visit:

http://www.nasa.gov/newhorizons

For more information about the Voyager spacecraft, visit:

http://www.nasa.gov/voyager