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Did Researchers Find The Missing Link To Life

November 20, 2017 by  
Filed under Around The Net

Four billion years ago, Earth was covered in a watery sludge swarming with primordial molecules, gases, and minerals — nothing that biologists would recognize as alive. Then somehow, out of that prebiotic stew emerged the first critical building blocks — proteins, sugars, amino acids, cell walls — that would combine over the next billion years to form the first specks of life on the planet.

A subset of chemists have devoted their careers to puzzling out the early chemical and environmental conditions that gave rise to the origins of life. With scant clues from the geological record, they synthesize simple molecules that may have existed billions of years ago and test if these ancient enzymes had the skills to turn prebiotic raw material into the stuff of life.

A team of such chemists from the Scripps Research Institute reported Nov. 6 in the journal Nature Chemistry that they identified a single, primitive enzyme that could have reacted with early Earth catalysts to produce some of the key precursors to life: the short chains of amino acids that power cells, the lipids that form cell walls, and the strands of nucleotides that store genetic information.

Ramanarayanan Krishnamurthy is an associate professor of chemistry at Scripps and lead author of the origins of life paper. For a number of years, his lab has been experimenting with a synthetic enzyme called diamidophosphate (DAP) that’s been shown to drive a critical chemical process called phosphorylation. Without phosphorylation — which is simply the process of adding a phosphate molecule to another molecule — life wouldn’t exist.

“If you look at life today, and how it probably was at least three billion years ago, it was based on a lot of phosphorylation chemistry,” Krishnamurthy told Seeker. “Your RNA, DNA, and a lot of your biomolecules are phosphorylated. So are sugars, amino acids, and proteins.”

The enzymes that trigger phosphorylation are called kinases. They use phosphorylation to send signals instructing cells to divide, to make more of one protein than another, to tell DNA strands to separate, or RNA to form. DAP may have been one of the first primordial kinases to get the phosphorylation ball rolling, Krishnamurthy believed.

To test his theory, Krishnamurthy and his colleagues simulated early Earth conditions in the lab, using both a water base and a muddy paste set to varying pH levels. They combined DAP with different concentrations of magnesium, zinc, and a compound called imidazole that acted as a catalyst to speed the reactions, which still took weeks or sometimes months to complete.

For DAP to pass the test, it had to successfully trigger phosphorylation events that resulted in simple nucleotides, peptides, and cell wall structures under similar conditions. Past candidates for origin-of-life enzymes could only phosphorylate certain structures under wildly different chemical and environmental conditions. DAP, Krishnamurthy found, could do it all, phosphorylating the four nucleoside building blocks of RNA, then short RNA-like strands, then fatty acids, lipids, and peptide chains.

Does that mean that DAP is the pixie dust that transformed random matter into life? Not quite, said Krishnamurthy.

“The best we can do is try to demonstrate that simple chemicals under the right conditions could give rise to further chemistry which may lead to life-like behavior. We can’t make a claim that this is the way that life formed on the early Earth.”

For one thing, Krishnamurthy has no proof that DAP even existed four billion years ago. He synthesized the molecule in his lab as a way to solve one of the fundamental challenges to phosphorylating in wet, early Earth conditions. For most phosphorylation reactions to work, they need to remove a molecule of water in the process.

“How do you remove water from a molecule when you are surrounded by a pool of water?” asked Krishnamurthy. “That’s thermodynamically an uphill task.”

DAP gets around that problem by removing a molecule of ammonia instead of water.

Krishnamurthy is working with geochemists to identify potential sources of DAP in the distant geological past. Phosphate-rich lava flows may have reacted with ammonia in the air to create DAP, or it could have been leached out of phosphate-containing minerals. Or maybe it even arrived on the back of a meteorite forged by a far-off star.

One thing is clear, without DAP or something like it, Earth might still be a lifeless mud puddle.

Courtesy-Space

Did Life Start With A Cosmic Splash

October 30, 2017 by  
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A new study bolsters the theory that the chemical origins of life on Earth were midwifed by meteorites that delivered essential building blocks from space.

Meteorites slamming into warm, small ponds on the planet’s rising land surfaces more than 4 billion years ago could have delivered those building blocks into an environment where they could grow and combine into ribonucleic acid, or RNA, said Ben K.D. Pearce, an astrobiologist at Canada’s McMaster University.

The study, produced by researchers at McMaster and Germany’s Max Planck Institute for Astronomy and published in the journal Proceedings of the National Academy of Sciences, is the latest in a debate over the origins of life. Did it come from Earth itself — forming around hot undersea vents in the crust — or from small ponds on land, as Darwin theorized, with material deposited from the cosmos around it? Pearce and his colleagues come down on the “warm little pond” side, arguing that the oceans were too harsh an environment for the building blocks of life.

RNA can reproduce itself and evolve. In its current form, it takes the genetic code contained in DNA and forms proteins.

“At one time, it was the dominant life form on Earth, and likely the first life form on Earth,” Pearce told Seeker. But it’s made up of a family of molecules known as nucleobases, which stem from a reactive type of nitrogen that wouldn’t have formed on a lifeless early Earth.

Nitrogen compounds like ammonia and hydrogen cyanide likely collected on bits of dust and rock floating around the sun, snowballing into larger bodies where they could react to produce nucleobases.

“You have get these molecules from space,” he said. And when those space rocks fell to Earth, the nucleobases they held could have landed in ponds of water and reacted with other chemicals that produced RNA.

Previous studies have put forth that theory, but what Pearce and his colleagues have done is to use computer models to gauge how probable that would have been. Nucleotides would have to survive in an environment bombarded with ultraviolet light, since there was no protective ozone layer at the time, and in water that could have broken them up.

While other scientists, including the famous astronomer Carl Sagan, have theorized that cosmic dust may have delivered those precursors, Pearce said any nucleotides riding in on dust particles were likely to have been too small to survive in their new home.

But by entering data “from all facets of science,” including biology, geophysics, and astrophysics, they’ve calculated that meteorites would have been a frequent and durable enough vehicle to deliver the building blocks of life, and wet and dry cycles could have helped them bond into larger chains that formed RNA.

“There were thousands of opportunities for this to emerge from thousands of different pond environments,” Pearce said.

Pearce said the next step will be to try to test that theory in a laboratory. Researchers at McMaster, located at the western end of Lake Ontario, are building a “planet simulator” in which they hope to reproduce the conditions of a primeval Earth and see whether they can get the same results.

Courtesy-Space

Does The Asteroid Belt Hold Key To The Building Blocks Of Planets

September 27, 2017 by  
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The asteroid belt may have started out empty, later becoming a “cosmic refugee camp” taking on leftovers of planetary formation from across the solar system, a new study finds.

The main asteroid belt, located between the orbits of Mars and Jupiter, makes up 0.05 percent the mass of Earth. The asteroids there can range greatly in mass, with the four largest ones — Ceres, Vesta, Pallas and Hygiea — holding more than half the belt’s mass.

To explain the dramatic range of sizes in the asteroid belt, previous models suggested that the primordial asteroid belt originally possessed a mass equal to at least that of Earth, and that its members had less disparity in mass. The gravitational pulls of the planets later helped whittle down this primordial belt, depleting asteroids of certain sizes more than others.  

However, these prior models of asteroid formation raised a question: how the belt could have lost more than 99.9 percent of its mass without losing all of it, said study lead author Sean Raymond, an astronomer at the University of Bordeaux in France.

“Our approach is the opposite. We asked the question, ‘Could the asteroid belt have been born empty?’,” Raymond told Space.com. “The answer is yes, effortlessly.”

The scientists developed computer models of an empty primordial asteroid belt to see whether leftovers from planetary formation could explain the belt’s current composition. The inner belt is dominated by dry S-type, or silicaceous, asteroids, which appear to be made of silicate materials and nickel iron and account for about 17 percent of known asteroids. The outer belt is dominated by water-rich C-type, or carbonaceous, asteroids, which consist of clay and stony silicate rocks and make up more than 75 percent of known asteroids.

The researchers found that an empty primordial asteroid belt could explain the mass and compositions of the current members of the asteroid belt. This model suggests that this zone between Mars and Jupiter is a repository of planetary leftovers, “a refugee camp housing objects that were kicked out of their homes and left to brave interplanetary space, finally settling onto stable orbits in the asteroid belt,” Raymond told Space.com. 

In this new model, the inner belt consists largely of rocky leftovers from the formation of the terrestrial planets — Earth, Mars, Venus and Mercury. In contrast, the outer belt is made up of remnants of the formation of the gas giant planets, such as Jupiter and Saturn.

“In terms of composition, Jupiter and Saturn grew in a region that was much colder than where the rocky planets grew,” Raymond said. “Being colder, their cores could incorporate ice and other volatiles. The C-types are about 10 percent water, whereas the S-types are much drier, having started off in the much hotter terrestrial planet zone.”

These findings suggest that the asteroid belt “is a treasure trove — it must contain relics of the building blocks of all the planets,” Raymond said. “There must be pieces of terrestrial building blocks out in the asteroid belt, as well as leftovers from building the giant planets’ cores.”

Future research can further test how well the various models of asteroid-belt formation match reality. Raymond hopes the team’s new concept “will help keep people’s minds open to potentially drastically different origins stories for the solar system, and for extra-solar planets, too.”

Raymond and his colleague Andre Izidoro at the University of Bordeaux detailed their findings online Sept. 13 in the journal Science Advances.

Courtesy-Space

Is NASA Planning Another Mission To Saturn

September 26, 2017 by  
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Humanity’s light at Saturn has gone out.

NASA’s robotic Cassini spacecraft burned up in the ringed planet’s atmosphere Friday morning (Sept. 15), ending a remarkable 13-year run at Saturn that has revolutionized scientists’ understanding of the outer solar system and its potential to host life.

For example, Cassini discovered methane seas on Saturn’s huge moon Titan and geysers of water vapor blasting from fellow moon Enceladus. Both of these moons are worthy of much further study, as is the ringed planet itself and the diverse Saturn system as a whole, Cassini team members said. 

“We left the world informed, but still wondering, and I couldn’t ask for more,” Cassini project manager Earl Maize, of NASA’s Jet Propulsion Laboratory in Pasadena, California, said during a news conference Wednesday (Sept. 13). “We’ve got to go back — we know it.”

And various research teams are indeed working on plans to return to Saturn. In fact, five such concepts are in the running for NASA’s next New Frontiers mission — the same type flown by the agency’s New Horizons Pluto probe, Juno Jupiter orbiter and OSIRIS-REx asteroid sample-return craft.

During its intentional death dive Friday, Cassini briefly became the first-ever Saturn atmospheric probe. One of the proposed New Frontiers missions would pick up on, and greatly extend, the last measurements Cassini ever made.

The SPRITE (Saturn Probe Interior and Atmosphere Explorer) spacecraft would plunge into Saturn’s thick atmosphere, characterizing its composition and structure for about 90 minutes before breaking apart and burning up. (Cassini, which was not built for such work, lasted just a minute or two during its dive.)

“Fundamental measurements of the interior structure and noble-gas abundances of Saturn are needed to better constrain models of solar system formation, as well as to provide an improved context for exoplanet systems,” principal investigator Amy Simon, of NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and her colleagues wrote in a mission description last year.

SPRITE would make such measurements, and its data would help “ground-truth” data Cassini gathered about Saturn from afar over the years, the scientists added

Cassini studied Titan closely over the course of 127 targeted flybys. The Saturn orbiter also carried a piggyback European lander called Huygens, which touched down on the 3,200-mile-wide (5,150 kilometers) moon in January 2005. In the process, it became the first probe ever to pull off a soft landing on a body in the outer solar system.

Observations by both Cassini and Huygens revealed Titan in all its otherworldly glory. Hydrocarbon rain falls from the huge moon’s sky, pooling in lakes and seas of methane, some of which are as big as Earth’s Black Sea. Complex organic chemicals — the carbon-containing building blocks of life as we know it — waft about in Titan’s thick, nitrogen-dominated atmosphere and eventually drift down to the moon’s surface.

It’s possible that this bizarre landscape could harbor life, astrobiologists say. And Cassini’s work suggests that the big moon may have another potentially habitable environment as well: a salty ocean of liquid water buried beneath the crust. (Indeed, Cassini was directed to its doom primarily to ensure that it would never contaminate Titan or Enceladus with microbes from Earth.)

A proposed New Frontiers mission called Oceanus would investigate both of these environments, taking a variety of measurements from its perch in orbit around Titan. For example, the probe would characterize the organics in the moon’s atmosphere and help researchers determine how thick and rigid Titan’s crust is, and whether it is convecting internal heat to the surface.

Oceanus “would follow up on Cassini’s amazing discoveries and assess Titan’s habitability by following the organics through the methanologic cycle and assessing exchange processes between the atmosphere, surface and subsurface,” the concept mission’s planners wrote in a description of the project, which they presented earlier this year at the 48th Lunar and Planetary Science Conference in The Woodlands, Texas.

Also in the New Frontiers running is Titan Dragonfly, which would send a drone to study the moon from the air and the ground.

“Heavier-than-air flight is substantially easier [on Titan]” than on Earth, Dragonfly principal investigator Elizabeth Turtle, a planetary scientist at the Johns Hopkins University Applied Research Laboratory in Maryland, told Space.com earlier this year. (Titan’s atmosphere is considerably thicker than that of Earth, but the moon’s gravity is just 14 percent as strong as our planet’s.)

“That means we can take a really capable lander and move it by a few tens of kilometers in a single flight, and hundreds of kilometers over the time of the mission,” Turtle added.

The drone would study the composition of Titan’s organics in detail, at a variety of different locations.

“Dragonflyis a truly revolutionary concept providing the capability to explore diverse locations to characterize the habitability of Titan’s environment, investigate how far prebiotic chemistry has progressed, and search for chemical signatures indicative of water-based and/or hydrocarbon-based life,” Turtle and her colleagues wrote about the potential mission in their presentation at the 48th Lunar and Planetary Science Conference.

The other two Saturn-oriented New Frontiers proposals target 313-mile-wide (504 km) Enceladus, whose geysers were a revelation to the Cassini team, NASA officials and space scientists in general.

“When we observed the southern hemisphere [of Enceladus] and geysers of water spewing out into the Saturn system, it amazed us and began changing the way we view the habitability — or potential habitability — of moons in the outer part of our solar system,” Jim Green, chief of NASA’s Planetary Science Division at the agency’s headquarters in Washington, D.C., said at Wednesday’s news conference.

That’s because the water in Enceladus’ geysers is apparently coming from an ocean of liquid water that sloshes beneath the frigid moon’s icy crust. Cassini observations suggest that this ocean may even have a chemical energy source that could support life as we know it.

But researchers want to learn more about the ocean, and the geysers’ plume provides a great way of doing so. One of the New Frontiers candidates, known as Enceladus Life Finder (ELF), would zoom through this plume repeatedly, collecting and analyzing molecules. ELF would look for complex organic compounds that could be a sign of prebiotic chemistry — or perhaps even of life itself.

“It’s free samples,” principal investigator Jonathan Lunine, of Cornell University, told Space.com in 2015, when ELF was competing for a slot in NASA’s Discovery program of low-cost, extremely focused missions. (In January of this year, NASA chose the asteroid-studying Lucy and Psyche missions as its next Discovery projects.) “We don’t need to land, drill, melt or do anything like that.” 

Cassini did some plume sampling of its own, but ELF would sport more-sensitive mass spectrometers than its predecessor did, ELF team members have said. (Cassini’s handlers didn’t know about Enceladus’ geysers before launch, so they didn’t put any life-hunting gear aboard the craft.)

Not much has been publicly revealed about the final Saturn-oriented New Frontiers proposal. But its name — Enceladus Life Signatures and Habitability — suggests that it would also be a plume-sampling mission.

You can learn more about all 12 New Frontiers candidates — the other seven of which would target Venus, a comet or Earth’s moon — in this excellent synopsis by The Planetary Society’s Van Kane.

NASA is expected to cull the New Frontiers proposals to a handful of finalists before the end of the year and announce the selected mission sometime in 2019. (That mission will have a cost cap of $850 million, excluding launch, and will lift off by 2025.)

So, it’s too soon to say if any of the Saturn-centric missions will ever get off the ground. But fans of the ringed planet may be heartened by one of Green’s comments at Wednesday’s news conference.

Cassini’s discoveries “will live on for many decades afterwards, and already they’re beckoning us to go back,” Green said. Between NASA’s Voyager mission, which visited Saturn with back-to-back flybys in 1980 and 1981, “and Cassini was 30 years,” he said, “and I believe that will be much shorter the next time around.”   

 

Courtesy-Space

Astronomers Gain Insight Into Black Hole With Powerful Space Explosion

August 2, 2017 by  
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An ultrapowerful, superfast explosion in space is providing new insight into how dying stars turn into black holes.

An international team of researchers looked at a gamma-ray explosion called GRB 160625B that brightened the sky in June 2016. Gamma-ray bursts are among the most powerful explosions in the universe, but they are typically tough to track because they are very short-lived (sometimes lasting just a few milliseconds). 

“Gamma-ray bursts are catastrophic events, related to the explosion of massive stars 50 times the size of our sun,” said Eleonora Troja, lead author of the new study and an assistant research scientist in astronomy at University of Maryland. “If you ranked all the explosions in the universe based on their power, gamma-ray bursts would be right behind the Big Bang.” [Record Breaking Gamma-Ray Burst Captured By Fermi (Video)]

“In a matter of seconds, the process can emit as much energy as a star the size of our sun would in its entire lifetime,” Troja said in a statement. “We are very interested to learn how this is possible.”

Two key findings emerged from the observations, gathered using several ground- and space-based telescopes. The first step was better model what happens as the dying star collapses. The data suggests that the black hole creates a strong magnetic field that initially overwhelms jets of matter and energy formed because of the explosion. Then, the magnetic field breaks down, the study authors said.

In the next phase, the magnetic field diminishes, allowing matter to dominate the jets. Before, scientists thought that jets could be dominated only by the magnetic field or matter — not both.

Another insight concerns what kind of radiation is responsible for the bright phase at the beginning of the burst, which astronomers call the “prompt” phase. Before, several types of radiation were considered, including so-called blackbody radiation (heat emission from an object) and inverse Compton radiation (which happens when accelerated particles transfer energy to photons), according to the statement. 

It turns out that a phenomenon called synchrotron radiation is behind the prompt phase. This kind of radiation happens when electrons accelerate in a curved or spiral pathway, propelled along by an organized magnetic field.

“Synchrotron radiation is the only emission mechanism that can create the same degree of polarization and the same spectrum we observed early in the burst,” Troja said. 

The fading afterglow of GRB 160625B, a gamma-ray burst recorded in June 2016. Here, data from Arizona State University’s Reionization And Transients Infrared (RATIR) camera, on a telescope at Mexico’s National Astronomical Observatory in Baja California, shows the burst from June 26 to Aug. 20, 2016.

“Our study provides convincing evidence that the prompt gamma-ray burst emission is driven by synchrotron radiation,” she added. “This is an important achievement because, despite decades of investigation, the physical mechanism that drives gamma-ray bursts had not yet been unambiguously identified.”

Gathering information about GRB 160625B required many telescopes to work together quickly. NASA’s Fermi Gamma-ray Space Telescope first saw the explosion, and the ground-based Russia’s MASTER-IAC telescope, which is located at the Teide Observatory in Spain’s Canary Islands, quickly joined with observations in optical light.

MASTER-IAC’s observations were key to understanding the evolution of GRB 160625B’s magnetic field, the research team said. The magnetic field can influence polarized light (light waves that vibrate in a single plane) emanating from the burst. In a rare achievement, the telescope measured the proportion of polarized light to total light through almost the entire explosion.

“There is very little data on polarized emission from gamma-ray bursts. This burst was unique because we caught the polarization state at an early stage,” said study co-author Alexander Kutyrev, an associate astronomy research scientist at the University of Maryland and an associate scientist at NASA’s Goddard Space Flight Center.

“This is hard to do because it requires a very fast reaction time, and there are relatively few telescopes with this capability,” Kutyrev added. “This paper shows how much can be done, but to get results like this consistently, we will need new rapid-response facilities for observing gamma-ray bursts.”

Other participating telescopes included NASA’s Swift Gamma-ray Burst Mission (X-ray and ultraviolet), the multi-institution Reionization and Transient Infrared/Optical Project camera (at Mexico’s National Astronomical Observatory in Baja California), the National Radio Astronomy Observatory’s Very Large Array in New Mexico, and the Commonwealth Scientific Industrial Research Organisation’s Australia Telescope Compact Array.

The new research was detailed today (July 26) in the journal Nature.

Courtesy-Space

Does An Asteroid Start Off As A Giant Mud Rock

July 21, 2017 by  
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The most common asteroids in the solar system may have started out as giant balls of mud, rather than as rocks, as scientists previously thought, a new study finds.

Such mud balls could still exist today in the heart of the largest asteroids, according to the study.

More than 75 percent of known asteroids are carbonaceous in composition; these grayish asteroids probably consist of clay and stony rocks, and inhabit the main belt’s outer regions

One key reason scientists investigate carbonaceous asteroids is that they were probably the building blocks of the rocky planets of the solar system, said study lead author Philip Bland, a planetary scientist at the Curtin University of Technology in Australia. Analyzing these giant rocks could shed light on the origins of Earth, Mars and the other terrestrial planets.

However, the way carbonaceous asteroids formed in the early days of the solar system is still mysterious. “There have probably been about a dozen different models to explain the origins of these primitive objects over the years, and they’ve all been limited in one way or another,” Bland told Space.com.

Researchers have observed carbonaceous asteroids and analyzed meteorites thought to come from them to glean details about their composition. However, scientists had trouble devising a model that could explain all of these features of the asteroids, Bland said.

“For instance, one model might find there is a lot of water getting circulated around inside the asteroids, so they could lose heat — which would explain why meteorites from these asteroids appear to have experienced alterations at relatively low temperatures,” Bland said. “However, if you have a lot of water circulating inside asteroids, it would strip elements from the rock, and you would get a very different chemical composition than what we see in the meteorites.”

“If there wasn’t water inside the asteroids, you wouldn’t mess up the chemistry we see, but the asteroids would not lose heat as easily,” Bland added. “One way around that is to have the asteroids be smaller so they would cool down more easily, but we don’t see that today.”

All of these previous models assumed the asteroids had lithified — that is, had become rock. “Most people look at meteorites, and they’re rocks. So the natural thing to assume would be that the asteroids they came from were rocks, too,” Bland said. “We were interested in seeing what happened if we deleted that assumption.”

Prior work suggested that carbonaceous asteroids formed from round, porous mineral pellets known as chondrules, as well as fine-grained dust, and ice. When pockets of these materials got pulled together by their own gravity, they would not have become rock, the researchers suggested. Instead, when radioactive materials inside the dust and chondrules melted the ice, the result would have been a sludgy mud, they said.

“When you stop to think about it, there’s no reason that asteroids would be rocks right at the beginning,” Bland said.

The scientists devised computer models that simulated how pockets of dust, chondrules and ice might act with different concentrations of these various ingredients and the density at which these materials were packed together. They found that not only could asteroids emerge from these building blocks without lithification, but the way in which mud churned in these mud balls could help explain the chemical and thermal details seen from carbonaceous asteroids.

“I feel like this helps plug a gap in knowledge when it comes to the question of what happened inside what are amongst the most important objects in the history of our solar system,” Bland said.

After the mud balls formed, they could have lithified in various ways. For instance, if these mud balls hit each other, the force of the impacts would have generated heat that could have welded the components of these mud balls together into rock, Bland said.

As for whether the mud balls might still exist in the solar system, when the researchers modeled Ceres, the largest asteroid, they “found there was a reasonable chance of temperatures above freezing in its interior, so there could still be quite a bit of a mud ball inside Ceres,” Bland said.

Future research could explore how the other kinds of asteroids in the solar system were born, and how asteroids in other star systems might arise and, in turn, influence the formation of alien planets, Bland said.

Bland and his colleague Bryan Travis at the Planetary Science Institute in Tucson, Arizona, detailed their findings online July 14 in the journal Science Advances.

Courtesy-Space

Did Comets Bring The Building Blocks Of Life To Earth

June 20, 2017 by  
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Life on Earth may not have been possible without comet strikes.

A new study suggests that about 20 percent of the noble gas xenon in Earth’s atmosphere was delivered by comets long ago. And these icy wanderers likely brought lots of other stuff to our planet as well, researchers said. 

The “cometary contribution could have been significant for organic matter, especially prebiotic material, and could have contributed to shape the cradle of life on Earth,” said study lead author Bernard Marty, a geochemist at the University of Lorraine and the Centre de Recherches Pétrographiques et Géochimiques in France.  

Marty and his colleagues studied measurements made by the European Space Agency’s (ESA) Rosetta spacecraft, which orbited the 2.5-mile-wide (4 kilometers) Comet 67P/Churyumov-Gerasimenko from August 2014 through September of last year.

Specifically, they analyzed xenon-isotope data that Rosetta gathered during a series of low-altitude orbits of Comet 67P between May 14 and May 31, 2016. (Isotopes are versions of an element that contain different numbers of neutrons in their nuclei. “Heavy” isotopes have more neutrons compared to “lighter” ones.)

Rosetta’s observations revealed that 67P is deficient in heavy xenon. Furthermore, the team determined that the comet’s xenon isotope composition matches a signature of Earth xenon whose origin had been a mystery.

Scientists think asteroids delivered the vast majority of the water in Earth’s oceans, and these space rocks have been regarded as the chief suppliers of the planet’s other “volatiles” — substances with low boiling points, such as nitrogen, carbon dioxide and noble gases — as well. (Models suggest that Earth was extremely hot shortly after its formation about 4.5 billion years ago, so it probably lost its primordial volatiles early on.) 

This inference is drawn partly from the isotopic similarity of hydrogen, nitrogen and other materials on Earth to that of certain asteroids known as carbonaceous chondrites, as measured in meteorite samples, Marty said.

“There was also a dynamical argument: Jupiter and the other giant planets formed early, and the outer solar system (from which comets originate) was isolated early from the inner solar system by the giant planets’ gravitational fields,” he said. “Now our finding calls for a revision of such models.”

Comets are especially enriched in noble gases, explaining how their contribution of xenon (and perhaps other materials) to the early Earth can be outsized compared to the proportion of water these icy wanderers delivered, Marty added.

The newly analyzed Rosetta data also indicate that 67P’s xenon predates the solar system — that is, the comet contains samples of interstellar matter. That’s an exciting result that argues for further, more detailed study of pristine cometary material, Marty said. 

“Returning a cometary sample on Earth should be the highest priority, because it will permit analyses with unprecedented precision of such exotic material and could respond to questions such as: How long interstellar material can survive, which stars contributed to shape the cradle of the solar system, what is the origin(s) of the large isotopic variations of some of the elements (e.g., N, H, O), what was the role of irradiation of early solar system material, etc.,” he said. (N, H and O are nitrogen, hydrogen and oxygen, respectively.)

Rosetta launched in March 2004. A decade later, it became the first mission ever to orbit a comet and the first to touch down softly on one of these bodies. (The Rosetta orbiter dropped a lander called Philae onto 67P in November 2014.)

The mission ended when Rosetta intentionally crash-landed on 67P’s surface on Sept. 30, 2016.

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Can Companies Mine The Moon AT A Profit

May 25, 2017 by  
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The first-ever private mining operation on the moon is scheduled to kick off in 2020, when a landing craft sent by Florida-based Moon Express will ferry a single scoop of lunar dirt and rocks back to Earth.

Unlike the three governments that have led lunar missions — the United States, the Soviet Union, and China — the owners of this private firm have something history-making in mind for that little ball of extraterrestrial soil: They plan to sell it.

“It will instantly become the most valuable and scarcest material on Earth,” says Bob Richards, the CEO of Moon Express. “We’ll make some of it available to scientific research. But we also plan to commoditize it ourselves.”

Moon Express is gearing up to become the first company to ever transport a commercial asset from space back to Earth. But it’s not alone.

Several ambitious startups are busily developing plans to launch mining operations on both the moon and asteroids, with initial proof-of-concept missions set to kick off over the next few years and more robust operations within a decade. China is a key player, too, along with a tiny, unlikely European upstart: the Grand Duchy of Luxembourg.

Those seeking to conquer celestial commodity markets are beckoned by the glittering wealth that could await them in space.

“We believe that the first trillionaires will be made from space resources,” says Richards.

Exactly which minerals will drive those fortunes remains to be seen.

The moon holds significant amounts of a special type of a futuristic fuel source called helium-3 — enough, some say, to meet all of Earth’s power demand for thousands of years providing scientists can master the fusion power technology to utilize it.

A fortune could be made by anyone able to capture and exploit one of the mountain-sized asteroids made of platinum or other precious metals thought to be orbiting the sun, or deposits of rare earth elements on the moon.

Others point to the potential for zero-gravity construction of super-massive colonizing spacecraft and mammoth floating structures using raw materials sourced from asteroids.

Most, however, are focused on a resource that’s commonplace on Earth: water.

Water, space entrepreneurs say, will be the key space commodity for an economy expanding into the solar system — both because it can sustain life as drinking water and breathable air, and because it can be broken down into hydrogen and oxygen to make rocket fuel.

Sourcing water from space could, for example, turn the moon into a depot for more ambitious missions.

“Water is like the oil of the solar system,” said Richards. “The moon could become a gas station in the sky.”

In the near term, Moon Express is focused on providing relatively low-cost transport to the surface of the moon for commercial, private, academic, and government customers.

One client that’s already signed up is the moon-burial company Celestis, which offers to send cremated human remains to the surface of the moon for a starting price of $12,500.

In 2016 Moon Express became the first private company in history to receive permission from the US Federal Aviation Administration to travel beyond Earth’s orbit and land a craft on the moon.

The company is planning three lunar missions by the time it brings back the small scoop of lunar soil, between the size of a baseball and basketball, in 2020.

Selling part of that scoop to private interests — for example, as moon gems for jewelry for the ultra-rich — will set an important precedent. The international Outer Space Treaty of 1967 says no country can claim sovereignty over extraterrestrial territory. But in 2015 President Barack Obama signed a law granting private citizens the rights to resources recovered from space.

The company’s first mission, slated for this year, will be in part an attempt to win the Google Lunar XPrize. The competition offers $20 million to the first private company able to land a rover on the moon’s surface, travel 500 meters, and then broadcast hi-definition images back to Earth.

Another company fielding a team for the XPrize, which also plans to eventually tap moon water, is Japan’s ispace Inc.

In December, ispace signed a memorandum of understanding with Japan’s national space agency, JAXA, for the “mining, transport, and use of resources on the moon,” according to a company statement.

During an initial phase of operations, from 2018 through 2023, ispace will go prospecting on the moonscape, sending exploratory robots into lunar craters and caves to check for water. Production is planned to begin in 2024.

China is also eyeing moon resources — especially helium-3.

As an energy source, helium-3 is as alluring as it is elusive: a non-radioactive agent that wouldn’t produce dangerous waste. The isotope is released by the sun and carried through the cosmos on solar winds that are blocked by Earth’s atmosphere, but collect on the surface of the moon.

As a result, the moon is “so rich” in helium-3, it could “solve human beings’ energy demand for around 10,000 years at least,” a top Chinese scientific advisor to the country’s moon exploration program, Professor Ouyang Ziyuan, told the BBC.

 

One of the top proponents of lunar helium-3 is Harrison Schmitt, a geologist who walked on the moon during NASA’s Apollo 17 mission and wrote a 2006 book advocating lunar helium-3 mining called Return to the Moon.

Others, however, are deeply skeptical — even if the necessary fusion technology, which has long eluded researchers, is mastered.

“I do not see this as being an economic solution to Earth’s energy needs,” Ian Crawford of the Department of Earth and Planetary Sciences at Birkbeck College, University of London, said in an email. “The problem is that the abundance is very low, of the order 10 parts per billion by mass in even the most abundant regions.”

Another potentially attractive lunar resource is the platinum group of metals, including iridium, palladium and platinum, which have special qualities that make them highly useful in electronic devices. Such elements, rare on earth, are thought to be bountiful on the moon.

Richards of Moon Express said it’s too soon to specify the most valuable resource on the moon.

“It would be speculative and predictive to say which specific element is going to be the game-changer,” he said. “Pick your favorite spice.”

For now, he says, the key target is water — which, to be sure, can be found on frozen asteroids circling the sun as well.

Two US companies, Planetary Resources and Deep Space Industries, are leading the charge into asteroid mining, largely with the aim of providing resources that other types of space missions will need.

Rick Tumlinson, chairman of Deep Space Industries, said his company plans to land its first prospector on an asteroid by 2020.

The company will use tiny scouts to explore and study prospective targets. When a prime asteroid has been located, a larger robot will land on it, bite out a chunk, and then use solar power to evaporate and capture water from the sample.

“Water, we believe, is relatively easy to harvest from asteroid materials,” said Tumlinson.

If all goes according to plan, “by the middle-20s, we’d be producing serious quantities of resources,” he said.

Planetary Resources is also focused on water.

“You can concentrate that solar energy and heat up the surface of the asteroid and literally bake off the water in the same way you’d bake a clay pot,” says CEO Chris Lewicki.

 

Both Lewicki and Tumlinson also point to the potential for supplying building materials in space, which could allow for the construction of super-massive floating structures that would be ungainly to launch from Earth.

In space, “you can build these huge structures we see in movies and science fiction,” said Lewicki. “The resource that will allow us to do that is the metal that’s on asteroids. We can use technology like 3D printing. We can print up a structure in space that never has to hold itself up on Earth, never has to take a violent rocket ride.”

As billionaires Elon Musk and Jeff Bezos explore ideas for colonizing space and Mars, someone, advocates of space mining say, will need to provide the raw materials, water and fuel the colonizers will need.

And while space mining might sound like science fiction, serious backers with deep pockets are taking notice.

A total of $1.8 billion was invested in space ventures in 2015 — more than in the prior 15 years combined, according to the Tauri Group consultancy. More than 50 venture capital firms invested in space deals in 2015, the most of any year, the group found.

The tiny European nation of Luxembourg has invested 25 million euros in Planetary Resources, and collaborated on the development of Prospector-X, the first spacecraft from Deep Space Industries.

The moon, said Richards, is like Earth’s 8th continent, and it’s largely unexplored.

“We’re like early pioneers,” he said, “looking at a whole new world.”

 

Courtesy-Fud

 

 

Astronomers Find The Building Blocks Of Life On Ceres

February 23, 2017 by  
Filed under Around The Net

The dwarf planet Ceres keeps looking better and better as a possible home for alien life.

NASA’s Dawn spacecraft has spotted organic molecules — the carbon-containing building blocks of life as we know it — on Ceres for the first time, a study published today (Feb. 16) in the journal Science reports.

And these organics appear to be native, likely forming on Ceres rather than arriving via asteroid or comet strikes, study team members said.

“Because Ceres is a dwarf planet that may still preserve internal heat from its formation period and may even contain a subsurface ocean, this opens the possibility that primitive life could have developed on Ceres itself,” Michael Küppers, a planetary scientist based at the European Space Astronomy Centre just outside Madrid, said in an accompanying “News and Views” article in the same issue of Science.

“It joins Mars and several satellites of the giant planets in the list of locations in the solar system that may harbor life,” added Küppers, who was not involved in the organics discovery.

The $467 million Dawn mission launched in September 2007 to study Vesta and Ceres, the two largest objects in the main asteroid belt between Mars and Jupiter. 

Dawn circled the 330-mile-wide (530 kilometers) Vesta from July 2011 through September 2012, when it departed for Ceres, which is 590 miles (950 km) across. Dawn arrived at the dwarf planet in March 2015, becoming the first spacecraft ever to orbit two different bodies beyond the Earth-moon system.

During its time at Ceres, Dawn has found bizarre bright spots on crater floors, discovered a likely ice volcano 2.5 miles (4 km) tall and helped scientists determine that water ice is common just beneath the surface, especially near the dwarf planet’s poles.

The newly announced organics discovery adds to this list of achievements. The carbon-containing molecules — which Dawn spotted using its visible and infrared mapping spectrometer instrument — are concentrated in a 385-square-mile (1,000 square km) area near Ceres’ 33-mile-wide (53 km) Ernutet crater, though there’s also a much smaller patch about 250 miles (400 km) away, in a crater called Inamahari. 

And there could be more such areas; the team surveyed only Ceres’ middle latitudes, between 60 degrees north and 60 degrees south. 

“We cannot exclude that there are other locations rich in organics not sampled by the survey, or below the detection limit,” study lead author Maria Cristina De Sanctis, of the Institute for Space Astrophysics and Space Planetology in Rome, told Space.com via email.

Dawn’s measurements aren’t precise enough to nail down exactly what the newfound organics are, but their signatures are consistent with tar-like substances such as kerite and asphaltite, study team members said.

“The organic-rich areas include carbonate and ammoniated species, which are clearly Ceres’ endogenous material, making it unlikely that the organics arrived via an external impactor,” co-author Simone Marchi, a senior research scientist at the Southwest Research Institute in Boulder, Colorado, said in a statement. 

In addition, the intense heat generated by an asteroid or comet strike likely would have destroyed the organics, further suggesting that the molecules are native to Ceres, study team members said.

The organics might have formed via reactions involving hot water, De Sanctis and her colleagues said. Indeed, “Ceres shows clear signatures of pervasive hydrothermal activity and aqueous alteration,” they wrote in the new study.

Such activity likely would have taken place underground. Dawn mission scientists aren’t sure yet how organics generated in the interior could make it up to the surface and leave the signatures observed by the spacecraft.

“The geological and morphological settings of Ernutet are still under investigation with the high-resolution data acquired in the last months, and we do not have a definitive answer for why Ernutet is so special,” De Sanctis said.

It’s already clear, however, that Ceres is a complex and intriguing world — one that astrobiologists are getting more and more excited about.

“In some ways, it is very similar to Europa and Enceladus,” De Sanctis said, referring to ocean-harboring moons of Jupiter and Saturn, respectively. 

“We see compounds on the surface of Ceres like the ones detected in the plume of Enceladus,” she added. “Ceres’ surface can be considered warmer with respect to the Saturnian and Jovian satellites, due to [its] distance from the sun. However, we do not have evidence of a subsurface ocean now on Ceres, but there are hints of subsurface recent fluids.” 

Courtesy-Fud

Will The U.S. And Russia Team Up For A Venus Mission?

January 19, 2017 by  
Filed under Around The Net

Russia’s space program and NASA are working together on a mission to Venus that would investigate some of the scorching-hot planet’s biggest mysteries, including, perhaps, whether it harbors life.

An international team of scientists tasked with fleshing out the main goals of the mission, which is known as Venera-D, is wrapping up its work and will deliver its final report to NASA and the Russian Academy of Sciences’ Space Research Institute by the end of the month, said David Senske, of NASA’s Jet Propulsion Laboratory in Pasadena, California.

“Is this the mission that’s going to fly? No, but we’re getting there,” Senske, the U.S. co-chair of this “joint science-definition team,” told Space.com last month at the annual fall meeting of the American Geophysical Union, in San Francisco.

Venera-D is led by Russia, which has been developing the project for more than a decade. The mission would mark a return to once-familiar territory for the nation; Russia’s forerunner state, the Soviet Union, launched a number of probes to Venus from the early 1960s through the mid-1980s, as part of its Venera and Vega programs. (“Venera” is the Russian name for Venus.)

“Russia has always been interested in going back to Venus,” Senske said.

NASA got involved about three years ago, when Russia asked if the U.S. space agency would be interested in collaborating on the mission, Senske added.

The joint science-definition team arose out of those initial discussions. The team stood down shortly thereafter; Russia’s March 2014 annexation of Crimea prompted NASA to suspend most cooperation with Roscosmos, Russia’s federal space agency (with activities involving the International Space Station being the most prominent exception).

But the collaboration was up and running again by August 2015, Senske said, and the team met in Moscow that October. More meetings are planned, including a workshop this May that will inform decisions about the mission’s scientific instruments, he added.

Venera-D is a large-scale mission, comparable in scope to NASA “flagship” efforts such as the $2.5 billion Curiosity Mars rover, Senske said. The baseline concept calls for an orbiter that will study Venus from above for at least three years, plus a lander that will operate for a few hours on the planet’s surface.

Mission planners said they had originally hoped the lander could survive for 30 days; the “D” in Venera-D stands for “dolgozhivushaya,” which means “long lasting” in Russian. But this goal was ultimately deemed too difficult and costly, given the blistering temperatures on Venus’ surface, according to RussianSpaceWeb.com (which outlines the mission’s tortuous history in rich detail).

Data gathered by the orbiter should help scientists better understand the composition, structure and dynamics of Venus’ atmosphere, including why the planet’s air rotates so much faster than the surface does, a mysterious phenomenon known as super-rotation, Senske said.

The lander will collect further atmospheric information while descending, then study the composition and morphology of the Venusian surface after touching down.

Venera-D could incorporate additional components as well. Some ideas on the drawing board include a handful of small, relatively simple ground stations that would gather surface data for a month or so (putting the “D” back in Venera-D) and a solar-powered, uncrewed aerial vehicle that would ply the Venusian skies.

The surface of Venus is far too hot to support life as we know it, but temperatures are much more hospitable at an altitude of 31 miles (50 kilometers) or so. Furthermore, the planet’s atmosphere sports mysterious dark streaks that some astronomers have speculated might be signs of microbial life. The UAV could hypothetically investigate this possibility, sampling the air while cruising along.

Engineers have already been thinking about how to build such an aircraft. For example, the U.S. aerospace company Northrop Grumman and partner L’Garde Inc. have been researching a concept vehicle called the Venus Atmospheric Maneuverable Platform (VAMP) for several years now.

It’s still too early to know exactly what Venera-D will look like, what it will do or when the mission will launch. A liftoff in 2025 or 2026 is possible under an “aggressive” time line, Senske said. “It depends when the Russians can get this into their federal space budget,” he said.

Some things are known, however. For instance, Russia will build the orbiter and the lander, and Venera-D will launch atop Russia’s in-development Angara A5 rocket, Senske said. If NASA remains involved in the mission — which is far from a given at this point — the U.S. space agency will likely contribute smaller items, such as individual scientific instruments.

“Russia is definitely in the driver’s seat,” Senske said. “NASA is the junior partner.”

Courtesy-Space

Did Astronomers Find Water On Psyche?

November 3, 2016 by  
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0-0-0-0-0-0-0-0-0-0-0-0-0-0-0-0-0-0-0-0-0-0-0-0-0-pysche-mission-conceptThe largest metallic asteroid in the solar system may have water on its surface, astronomers have found. 

The asteroid, called 16 Psyche, is one of the most massive in the asteroid belt. Researchers think the 186-mile-wide (300 kilometers) body, made of almost pure nickel-iron, might be the core of a world whose outer layers were blasted off by impacts billions of years ago. 

Previous observations of Psyche showed no water on the surface. But according to Vishnu Reddy, an assistant professor at the University of Arizona’s Lunar and Planetary Laboratory, new data from the NASA Infrared Telescope Facility show evidence for water or hydroxyl, a molecule with one hydrogen atom bound to one oxygen atom, on Psyche’s surface. Hydroxyl exists on Earth, but it is very reactive and tends to combine with other compounds — and in fact can remove those compounds from the air.

“We did not expect a metallic asteroid like Psyche to be covered by water and/or hydroxyl,” Reddy said in a statement. “Metal-rich asteroids like Psyche are thought to have formed under dry conditions without the presence of water or hydroxyl, so we were puzzled by our observations at first.”

Reddy presented his results Wednesday (Oct. 20) at the 48th meeting of the American Astronomical Society’s Division for Planetary Sciences and 11th European Planetary Science Congress in Pasadena, California.

The water could have reached Psyche via past impacts from smaller asteroids that contain volatiles such as carbon, hydrogen and water, Reddy said.

NASA is currently reviewing a proposed mission to Psyche, which could tell astronomers whether the signal from the surface comes from water or hydroxyl. 

The new research, co-authored by Reddy and led by Driss Takir at the U.S. Geological Survey, has been accepted to the Astronomical Journal, and can be read online here.

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Astronomers Find A Strange Planet Similar To Saturn

October 18, 2016 by  
Filed under Around The Net

0-0-0-0-0-0-0-0-0-0-0-0-0-0-0-0-0-0-0-0-0-0-0-0-bizarre-planetA strange and colossal ring system around an alien planet is apparently stuck in reverse, circling opposite to the planet’s own orbit around its parent star. While the arrangement appears unstable, new calculations show the rings could remain for at least 100,000 years.

These rings could account for bizarre eclipse behavior seen in 2007 for this star, called J1407, researchers on the new study suggested. Back then, astronomers observed an eclipse of the star last for several weeks, varying rapidly in brightness over the course of minutes. In 2015, the team suggested that there could be a planet orbiting this star with rings over a hundred times larger than the rings of Saturn.

In the new simulations conducted this year, the team calculated whether the planet could hang on to its ring system even as the gravitational effect of the star pulls on the rings. Because of the planet’s highly elliptical orbit, the star’s tug could potentially destabilize the rings when the planet approached closer, the researchers said.

According to the simulations, the system can stay stable for more than 10,000 orbits lasting 11 years each, with one stipulation, said lead author Steven Rieder, a postdoctoral fellow at the RIKEN Advanced Institute for Computational Science in Japan.

“The system is only stable when the rings rotate opposite to how the planet orbits the star,” Rieder said in a statement. “It might be far-fetched, massive rings that rotate in opposite direction,” he added, “but we now have calculated that a ‘normal’ ring system cannot survive.” More usually, a planet’s rings circle in the same direction as the planet is traveling, and the planet orbits in the same direction as the star turns.

It’s also possible that the stellar eclipses were created by a free-floating object passing between Earth and the star, but this would be true only if that object’s velocity as measured in the observations was not correct, Rieder said. He added that this would be a strange explanation, as the measurements the team obtained are “very accurate.”

The researchers said they next plan to examine how the ring structure was created, and how it evolves. A paper based on the research will appear shortly in the journal Astronomy and Astrophysics.

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Is Saturn’s Moon Dione Hiding Water?

October 12, 2016 by  
Filed under Around The Net

0-0-0-0-0-0-0-0-0-0-0-0-0-0-0-0-0-0-0-0-0-0-0-dioneThe icy Saturn moon Dione appears to have an underground ocean of liquid water, just like two of its more famous neighbors, a new study suggests.

This huge ocean is probably buried about 60 miles (100 kilometers) beneath Dione’s icy shell, according to the study. Intriguingly, Dione’s putative ocean is likely in contact with the moon’s rocky core, team members said.

“The contact between the ocean and the rocky core is crucial,” study co-author Attilio Rivoldini, of the Royal Observatory of Belgium in Brussels, said in a statement. “Rock-water interactions provide key nutrients and a source of energy, both being essential ingredients for life.”

If the researchers are correct, 700-mile-wide (1,120 kilometers) Dione would be the third Saturn moon known to harbor a subsurface ocean, after giant Titan and geyser-spouting Enceladus. Astronomers think the Jupiter moons Europa, Callisto and Ganymede also have buried oceans, and recent research indicates Pluto might as well.

The study team, led by Mikael Beuthe of the Royal Observatory of Belgium, modeled the icy shells of Dione and Enceladus using gravity data gathered by NASA’s Saturn-orbiting Cassini spacecraft during its various flybys of the satellites.

Similar simulations performed by other researchers in the past have suggested that Dione is sea-free and that Enceladus’ ocean is buried deep. But Beuthe and his colleagues added a new wrinkle into their models.

“As an additional principle, we assumed that the icy crust can stand only the minimum amount of tension or compression necessary to maintain surface landforms,” Beuthe said in the same statement. “More stress would break the crust down to pieces.”

The team’s results indicate that Enceladus’ ocean is close to the surface, especially near the moon’s south pole — which makes sense, because geysers blast water ice and other material deep into space from this region. 

The simulations also suggest Dione has a vast ocean tens of kilometers deep, buried under many miles of ice. This ocean has also probably existed for the moon’s entire history, meaning there has potentially been plenty of time for life to take root and evolve beneath Dione’s battered, icy shell, researchers said.

The new study was published online this week in the journal Geophysical Research Letters.

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Did Asteroids Help Deliver Building Blocks?

September 22, 2016 by  
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Meteorites that crashed onto Earth billions of years ago may have provided the phosphorous essential to the biological systems of terrestrial life. 

The meteorites are believed to have contained a phosphorus-bearing mineral called schreibersite, and scientists have recently developed a synthetic version that reacts chemically with organic molecules, showing its potential as a nutrient for life. 

Phosphorus is one of life’s most vital components, but it often goes unheralded. It helps form the backbone of the long chains of nucleotides that create RNA and DNA; it is part of the phospholipids in cell membranes; and is a building block of the coenzyme used as an energy carrier in cells, adenosine triphosphate (ATP).

Yet the majority of phosphorus on Earth is found in the form of inert phosphates that are insoluble in water and are generally unable to react with organic molecules. This appears at odds with phosphorus’ ubiquity in biochemistry, so how did phosphorus end up being critical to life?

In 2004, Matthew Pasek, an astrobiologist and geochemist from the University of South Florida, developed the idea that schreibersite [(Fe, Ni)3P], which is found in a range of meteorites from chondrites to stony-iron pallasites, could be the original source of life’s phosphorus. Because the phosphorus within schreibersite is a phosphide, which is a compound containing a phosphorus ion bonded to a metal, it behaves in a more reactive fashion than the phosphate typically found on Earth. 

Finding naturally formed schreibersite to use in laboratory experiments can be time-consuming when harvesting from newly fallen meteorites and expensive when buying from private collectors. Instead, it has become easier to produce schreibersite synthetically for use in the laboratory. 

Natural schreibersite is an alloy of iron, phosphorous and nickel, but the common form of synthetic schreibersite that has typically been used in experiments is made of just iron and phosphorus, and is easily obtainable as a natural byproduct of iron manufacturing. Previous experiments have indicated it reacts with organics to form chemical bonds with oxygen, the first step toward integrating phosphorous into biological systems. 

However, since natural schreibersite also incorporates nickel, some scientific criticism has pointed out that the nickel could potentially alter the chemistry of the mineral, rendering it non-reactive despite the presence of phosphides. If this were the case, it would mean that the experiments with the iron-phosphorous synthetic schreibersite would not represent the behavior of the mineral in nature. 

“There was always this criticism that if we did include nickel it might not react as much,” said Pasek. 

Pasek and his colleagues have addressed this criticism by developing a synthetic form of schreibersite that includes nickel.

In a recent paper published in the journal Physical Chemistry Chemical Physics, Pasek and lead author and geochemist Nikita La Cruz of the University of Michigan show how a form of synthetic schreibersite that includes nickel reacts when exposed to water. As the water evaporates, it creates phosphorus-oxygen (P-O) bonds on the surface of the schreibersite, making the phosphorus available to life. The findings seem to remove any doubts as to whether meteoritic schreibersite could stimulate organic reactions.

“Biological systems have a phosphorus atom surrounded by four oxygen atoms, so the first step is to put one oxygen atom and one phosphorous atom together in a single P-O bond,” Pasek explained.

Terry Kee, a geochemist at the University of Leeds and president of the Astrobiology Society of Britain, has conducted his own extensive work with schreibersite and, along with Pasek, is one of the original champions of the idea that it could be the source of life’s phosphorus.

“The bottom line of what [La Cruz and Pasek] have done is that it appears that this form of nickel-flavored synthetic schreibersite reacts pretty much the same as the previous synthetic form of schreibersite,” Kee said. 

Pasek described how meteors would have fallen into shallow pools of water on ancient Earth. The pools would then have undergone cycles of evaporation and rehydration, a crucial process for chemical reactions to take place. As the surface of the schreibersite dries, it allows molecules to join into longer chains. Then, when the water returns, these chains become mobile, bumping into other chains. When the pool dries out again, the chains bond and build ever larger structures.

“The reactions need to lose water in some way in order to build the molecules that make up life,” said Pasek. “If you have a long enough system with enough complex organics, then, hypothetically, you could build longer and longer polymers to make bigger pieces of RNA. The idea is that at some point you might have enough RNA to begin to catalyze other reactions, starting a chain reaction that builds up to some sort of primitive biochemistry, but there’s still a lot of steps we don’t understand.”

Demonstrating that nickel-flavored schreibersite, of the sort contained in meteorites, can produce phosphorus-based chemistry is exciting. However, Kee said further evidence is needed to show that the raw materials of life on Earth came from space

“I wouldn’t necessarily say that the meteoric origin of phosphorus is the strongest idea,” he said. “Although it’s certainly one of the more pre-biotically plausible routes.” [Fallen Stars: A Gallery of Famous Meteorites]

Despite having co-developed much of the theory behind schreibersite with Pasek, Kee pointed out that hydrothermal vents could rival the meteoritic model. Deep-sea volcanic vents are already known to produce iron-nickel alloys such as awaruite, and Kee says that the search is now on for the existence of awaruite’s phosphide equivalent in the vents: schreibersite.

“If it could be shown that schreibersite can be produced in the conditions found in vents — and I think those conditions are highly conducive to forming schreibersite — then you’ve got the potential for a lot of interesting phosphorylation chemistry to take place,” said Kee

Pasek agreed that hydrothermal vents could prove a good environment to promote phosphorus chemistry, with the heat driving off the water to allow the P-O bonds to form. “Essentially it’s this driving off of water that you’ve got to look for,” he added.

Pasek and Kee both agreed that it is possible that both mechanisms — the meteorites in the shallow pools and the deep-sea hydrothermal vents — could have been at work during the same time period and provided phosphorus for life on the young Earth. Meanwhile David Deamer, a biologist from the University of California, Santa Cruz, has gone one step further by merging the two models, describing schreibersite reacting in hydrothermal fields of bubbling shallow pools in volcanic locations similar to those found today in locations such as Iceland or Yellowstone National Park. 

Certainly, La Cruz and Pasek’s results indicate that schreibersite becomes more reactive as the environment in which it exists gets warmer.

“Although we see the reaction occurring at room temperature, if you increase the temperature to 60 or 80 degrees Celsius [140 or 176 degrees Fahrenheit], you get increased reactivity,” said Pasek. “So, hypothetically, if you have a warmer Earth, you should get more reactivity.”

One twist to the tale is the possibility that phosphorus could have bonded with oxygen in space, beginning the construction of life’s molecules before ever reaching Earth. Schreibersite-rich grains coated in ice and then heated by shocks in planet-forming disks of gas and dust could potentially have provided conditions suitable for simple biochemistry. While Pasek agreed with that idea in principle, he said he has “a hard time seeing bigger things like RNA or DNA forming in space without fluid to promote them.”

Courtesy-Space

Astronomers Solve Asteroid Mystery

February 24, 2016 by  
Filed under Computing

Near-Earth asteroids generally die a lingering death in the depths of space rather than plunging into the sun as previously thought, a new study suggests.

Researchers studied the properties of nearly 9,000 near-Earth objects (NEOs) — asteroids and other bodies that come within 1.3 Earth-sun distances of our planet — to build a model of the overall NEO population.

This model seemed to have a problem, however: It predicted that astronomers should be seeing 10 times more NEOs that closely approach the sun — come within 9 million miles (15 million kilometers) or so of the star — than they actually observe.

The research team spent a year puzzling over this outcome before coming to a surprising conclusion: The missing NEOs are actually being destroyed as they get close to the sun, but long before they actually dive into the star.

“The discovery that asteroids must be breaking up when they approach too close to the sun was surprising, and that’s why we spent so much time verifying our calculations,” study co-author Robert Jedicke, of the University of Hawaii Institute for Astronomy, said in a statement.

The team’s work should help scientists better understand the NEO population in a variety of ways. For example, many meteors that light up Earth’s night skies are pieces of debris shed by parent NEOs on their laps around the sun. Such debris clouds travel on the same orbits as their parent bodies, but astronomers generally have trouble finding these NEOs. The new study suggests that this is because the parent objects have already been destroyed, the researchers said.

In addition, study team members determined that darker NEOs die farther from the sun than brighter ones do, which helps explain something astronomers already knew: Asteroids that approach the sun closely tend to be quite bright.

This finding implies that dark and bright asteroids may differ significantly in structure and composition, the researchers said.

“Perhaps the most intriguing outcome of this study is that it is now possible to test models of asteroid interiors simply by keeping track of their orbits and sizes,” lead author Mikael Granvik, of the University of Helsinki in Finland, said in the same statement. “This is truly remarkable and was completely unexpected when we first started constructing the new NEO model.”

Granvik and his colleagues built their model by studying nearly 100,000 images of NEOs acquired by the Catalina Sky Survey in Arizona over an eight-year period.

To date, scientists have identified and tracked almost 14,000 NEOs, but the overall population is thought to number in the millions. Astronomers think that most of these bodies begin their lives in the main asteroid belt between Mars and Jupiter, and then veer inward after experiencing gravitational nudges by Jupiter and/or Saturn. The new study was published online today (Feb. 17) in the journal Nature.

Courtesy-Space

 

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