CASIS research set for launch aboard SpaceX mission to space station

The Bone Densitometer developed by Techshot, Inc. will enable X-ray testing for research studies aboard the International Space Station. Credit: CASIS

This fall marks another commercial cargo flight to the International Space Station. In September, SpaceX's Dragon spacecraft is scheduled to blast off to the orbital laboratory carrying supplies and investigations as part of the company's fourth contracted mission to the complex.

Included in the cargo will be the third suite of research investigations sponsored by the Center for the Advancement of Science in Space (CASIS). With the role of managing the U.S. National Laboratory on the space station, CASIS is responsible for brokering and facilitating research investigations on the station with clear Earth applications and benefits.

The latest collection of CASIS-sponsored research, termed Advancing Research Knowledge (ARK)-2, centers heavily on life sciences. Studies include those focused on drug development, disease understanding and validation testing. Each investigation will use the unique conditions aboard the space station to advance researchers' understanding in those areas of study.

Additionally, CASIS and NASA have partnered with Techshot Inc., of Greenville, Indiana, to develop a new hardware device capable of assisting with research that may improve understandings of muscle wasting and diseases like osteoporosis.

The CASIS-sponsored hardware and life science investigations destined for the space station's national laboratory include the Bone Densitometer, which will be the first X-ray machine installed on the space station. A joint project between CASIS, NASA and Techshot, the facility will be instrumental in conducting rodent research on station. The Bone 

Densitometer will allow astronauts to examine bone density of model organisms in space through the use of Dual-Energy X-ray Absorptiometry (DEXA) technology. In short, researchers will be able to assess bone density loss by measuring energy levels absorbed by bones via the device.

The Rodent Research-1 investigation kicks off a series of NASA and CASIS-sponsored investigations focused on rodent research aboard the space station. The study will be the first to use the Bone Densitometer in an effort to help scientists examine the effects of long duration spaceflight. There are numerous applications to these investigations including studying bone loss, muscle atrophy and cardiovascular anomalies. However, the primary focus of this inaugural mission will be to assess the operational capabilities of the new hardware designed for these investigations.

The Drug Metabolism study will assist researchers in the area of drug development and human biology. This investigation is led by a scientist from the U.S. Department of Veteran Affairs, Dr. Timothy Hammond, who is looking to study yeast cells in microgravity. The goal of this investigation is to explore the changes in these cells in space to improve drug development for various diseases, including cancer therapeutics.

The Protein Crystal Optimization study is an investigation aiming to leverage the unique location of the space station to examine the internal structure of three medically important proteins. The space environment should allow researchers to grow the selected protein crystals to an optimal size and quality to allow for closer examination via neutron diffraction. This protein crystal growth in microgravity may reveal new characteristics that are masked by gravity on Earth. By studying these three proteins, medically relevant to salmonella infection, peptic ulcer disease, and biomarkers for heart attack and liver disease, researchers can apply insights towards improved treatments.

A New Era In Commercial Use of the Space Station

The space station's national laboratory affords researchers the ability to conduct experiments in a distinctive environment with factors and variables that are near impossible to replicate on the ground. With access to our nation's only orbiting laboratory, CASIS works with new and non-traditional users to take advantage of this resource. A great example of novel commercial research heading to station is the Cobra Puma Golf investigation.

The Cobra Puma Golf-electroplating investigation, also launching aboard SpaceX, is a materials science investigation sponsored by CASIS in collaboration with COBRA PUMA Golf (CPG). The CPG research and development team will examine the impacts of microgravity on electroplating -- the process of coating a metallic surface using an electric current. The study will test a variety of coating substances on materials used in golf equipment manufacturing. The insight gained from this investigation will aid CPG in identifying improved material development techniques.

CPG's project is another example of a commercial user leveraging the capabilities of the ISS National Lab to advance ground research. Through brokering research investigations with commercial companies, CASIS hopes to demonstrate the space station is not only a test-bed for groundbreaking research and development, but a unique laboratory that can help differentiate investigations initiatives from ground-based studies.

The mission is another milestone for the space community, showcasing how commercial endeavors can work hand-in-hand with research goals. The studies of ARK-2 exemplify the diverse possibilities for the space station and users of the research platform. From commercial launch providers that transport investigations to space, to commercial researchers looking to use the national laboratory, science in space is good for life on Earth.

Source: NASA

Rosetta and Philae separation confirmed

Artist impression showing Philae separating from Rosetta and descending to the surface of comet 67P/Churyumov-Gerasimenko. Credit: Image courtesy of European Space Agency

The Philae lander has separated from the Rosetta orbiter, and is now on its way to becoming the first spacecraft to touch down on a comet.

Separation was confirmed at ESA's Space Operation Centre, ESOC, in Darmstadt, Germany at 09:03 GMT / 10:03 CET. It takes the radio signals from the transmitter on Rosetta 28 minutes and 20 seconds to reach Earth, so separation actually occurred in space at 08:35 GMT / 09:35 CET.

The first signal from Philae is expected in around two hours, when the lander establishes a communication link with Rosetta. Philae cannot send its data to Earth directly -- it must do it via Rosetta.

Once the link has been established, the lander will relay via Rosetta a status report of its health, along with the first science data. This will include images taken of the orbiter shortly after separation.

The descent to the surface of Comet 67P/Churyumov-Gerasimenko will take around seven hours, during which the lander will take measurements of the environment around the comet. It will also take images of the final moments of descent.

Confirmation of a successful touchdown is expected in a one-hour window centred on 16:02 GMT / 17:02 CET. The first image from the surface is expected some two hours later.

Source: European Space Agency

Cassini spacecraft reveals 101 geysers and more on icy Saturn moon

This graphic shows a 3-D model of 98 geysers whose source locations and tilts were found in a Cassini imaging survey of Enceladus' south polar terrain by the method of triangulation.
Credit: NASA/JPL-Caltech/Space Science Institute

Scientists using mission data from NASA's Cassini spacecraft have identified 101 distinct geysers erupting on Saturn's icy moon Enceladus. Their analysis suggests it is possible for liquid water to reach from the moon's underground sea all the way to its surface.

These findings, and clues to what powers the geyser eruptions, are presented in two articles published in the current online edition of the Astronomical Journal.

Over a period of almost seven years, Cassini's cameras surveyed the south polar terrain of the small moon, a unique geological basin renowned for its four prominent "tiger stripe" fractures and the geysers of tiny icy particles and water vapor first sighted there nearly 10 years ago. The result of the survey is a map of 101 geysers, each erupting from one of the tiger stripe fractures, and the discovery that individual geysers are coincident with small hot spots. These relationships pointed the way to the geysers' origin.

After the first sighting of the geysers in 2005, scientists suspected that repeated flexing of Enceladus by Saturn's tides as the moon orbits the planet had something to do with their behavior. One suggestion included the back-and-forth rubbing of opposing walls of the fractures generating frictional heat that turned ice into geyser-forming vapor and liquid.

Alternate views held that the opening and closing of the fractures allowed water vapor from below to reach the surface. Before this new study, it was not clear which process was the dominating influence. Nor was it certain whether excess heat emitted by Enceladus was everywhere correlated with geyser activity.

To determine the surface locations of the geysers, researchers employed the same process of triangulation used historically to survey geological features on Earth, such as mountains. When the researchers compared the geysers' locations with low-resolution maps of thermal emission, it became apparent the greatest geyser activity coincided with the greatest thermal radiation. Comparisons between the geysers and tidal stresses revealed similar connections. However, these correlations alone were insufficient to answer the question, "What produces what?"

The answer to this mystery came from comparison of the survey results with high-resolution data collected in 2010 by Cassini's heat-sensing instruments. Individual geysers were found to coincide with small-scale hot spots, only a few dozen feet (or tens of meters) across, which were too small to be produced by frictional heating, but the right size to be the result of condensation of vapor on the near-surface walls of the fractures. This immediately implicated the hot spots as the signature of the geysering process.

"Once we had these results in hand, we knew right away heat was not causing the geysers, but vice versa," said Carolyn Porco, leader of the Cassini imaging team from the Space Science Institute in Boulder, Colorado, and lead author of the first paper. "It also told us the geysers are not a near-surface phenomenon, but have much deeper roots."

Thanks to recent analysis of Cassini gravity data, the researchers concluded the only plausible source of the material forming the geysers is the sea now known to exist beneath the ice shell. They also found that narrow pathways through the ice shell can remain open from the sea all the way to the surface, if filled with liquid water.

In the companion paper, the authors report the brightness of the plume formed by all the geysers, as seen with Cassini's high-resolution cameras, changes periodically as Enceladus orbits Saturn. Armed with the conclusion that the opening and closing of the fractures modulates the venting, the authors compared the observations with the expected venting schedule due to tides.

They found the simplest model of tidal flexing provides a good match for the brightness variations Cassini observes, but it does not predict the time when the plume begins to brighten. Some other important effect is present and the authors considered several in the course of their work.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory (JPL) in Pasadena, California, manages the mission for NASA's Science Mission Directorate in Washington. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging team consists of scientists from the United States, England, France and Germany. The imaging team is based at the Space Science Institute.

Source: NASA/Jet Propulsion Laboratory

Looking for Earths by looking for Jupiters

Montage of Jupiter and the Galilean satellites, Io, Europa, Ganymede, and Callisto.
Credit: NASA/Jet Propulsion Laboratory

In the search for Earth-like planets, it is helpful to look for clues and patterns that can help scientist narrow down the types of systems where potentially habitable planets are likely to be discovered. New research from a team including Carnegie's Alan Boss narrows down the search for Earth-like planets near Jupiter-like planets. Their work indicates that the early post-formation movements of hot-Jupiter planets probably disrupt the formation of Earth-like planets.

Their work is published the week of May 7 by Proceedings of the National Academy of Sciences.

The team, led by Jason Steffen of the Fermilab Center for particle Astrophysics, used data from NASA's Kepler mission to look at so-called "hot Jupiter" planets -- those roughly Jupiter-sized planets with orbital periods of about three days. If a Jupiter-like planet has been discovered by a slight dimming of brightness in the star it orbits as it passes between the star and Earth, it is then possible -- within certain parameters -- to determine whether the hot-Jupiter has any companion planets.

Of the 63 candidate hot Jupiter systems identified by Kepler, the research team did not find any evidence for nearby companion planets. There are several possible explanations. One is that there are no companion planets for any of these hot Jupiters. Another is that the companions are too small in either size or mass to be detected using these methods. Lastly it is possible that there are companion planets, but that the configuration of their orbits makes them undetectable using these methods.

However, when expanding the search to include systems with either Neptune-like planets (known as "hot Neptunes"), or "warm Jupiters" (Jupiter-sized planets with slightly larger orbits than hot Jupiters), the team found some potential companions. Of the 222 hot Neptunes, there were two with possible companions, and of the 31 warm Jupiters, there were three with possible companions.

"The implications of these findings are that systems with Earth-like planets formed differently than systems with hot Jupiters," Boss said. "Since we believe that hot Jupiters formed farther out, and then migrated inward toward their stars, the inward migration disrupted the formation of Earth-like planets. If our sun had a hot Jupiter, we would not be here."

Source: Carnegie Institution

Solving the mystery of the 'Man in the Moon': Volcanic plume, not an asteroid, likely created the moon's largest basin

The moon as observed in visible light (left), topography (center, where red is high and blue is low), and the GRAIL gravity gradients (right). The Procellarum region is a broad region of low topography covered in dark mare basalt. The gravity gradients reveal a giant rectangular pattern of structures surrounding the region. Credit: NASA/Colorado School of Mines/MIT/JPL/Goddard Space Flight Center

New data obtained by NASA's GRAIL mission reveals that the Procellarum region on the near side of the moon -- a giant basin often referred to as the "man in the moon" -- likely arose not from a massive asteroid strike, but from a large plume of magma deep within the moon's interior.

The Procellarum region is a roughly circular, volcanic terrain some 1,800 miles in diameter -- nearly as wide as the United States. One hypothesis suggested that it was formed by a massive impact, in which case it would have been the largest impact basin on the moon. Subsequent asteroid collisions overprinted the region with smaller -- although still large -- basins.

Now researchers from MIT, the Colorado School of Mines, and other institutions have created a high-resolution map of the Procellarum, and found that its border is not circular, but polygonal, composed of sharp angles that could not have been created by a massive asteroid. Instead, researchers believe that the angular outline was produced by giant tension cracks in the moon's crust as it cooled around an upwelling plume of hot material from the deep interior.

Maria Zuber, the E.A. Griswold Professor of Geophysics and also MIT's vice president for research, says that as cracks occurred, they formed a "plumbing system" in the moon's crust through which magma could meander to the surface. Magma eventually filled the region's smaller basins, creating what we see today as dark spots on the near side of the moon -- features that have inspired the popular notion of a "man in the moon."

"A lot of things in science are really complicated, but I've always loved to answer simple questions," says Zuber, who is principal investigator for the GRAIL (Gravity Recovery and Interior Laboratory) mission. "How many people have looked up at the moon and wondered what produced the pattern we see -- let me tell you, I've wanted to solve that one!"

Zuber and her colleagues publish their results this week in the journal Nature.

Making Less of an Impact

The team mapped the Procellarum region using data obtained by GRAIL -- twin probes that orbited the moon from January to December 2012. Researchers measured the distance between the probes as they chased each other around the moon. As the leading probe passed over a region of lower density, it briefly slowed, caught by that region's gravitational pull. As the probes circled the moon, they moved in accordion fashion, the distance between them stretching and contracting in response to varying gravitational attraction due to the mass variations in the lunar interior.

From the variable distance between the probes, Zuber and her team determined the strength of gravity across the moon's surface, creating a highly detailed map, which they then used to determine where the lunar crust thickens and thins.

From this mapping, the researchers observed that the rim of the Procellarum region is composed of edges that abut at 120-degree angles. As asteroid impacts tend to produce circular or elliptical craters, Zuber says the Procellarum's angular shape could not have been caused by an impact.

Instead, the team explored an alternative scenario: Some time after the moon formed and cooled, a large plume of molten material rose from the lunar interior, around where the Procellarum region is today. The steep difference in temperature between the magma plume and the surrounding crust caused the surface to contract over time, creating a pattern of fractures that provided a conduit for molten material to rise to the surface.

To test the hypothesis, the researchers modeled the region's gravitational signal if it were to contain volcanic intrusions -- magma that seeped up to just beneath the moon's surface and, over time, cooled and crystallized. The resulting simulation matched the gravity signal recorded by GRAIL, supporting the idea that the Procellarum was caused by a magma plume, and not an asteroid.

"How such a plume arose remains a mystery," Zuber says. "It could be due to radioactive decay of heat-producing elements in the deep interior. Or, conceivably, a very early large impact triggered the plume. But in the latter case, all evidence for such an impact has been completely erased. People who thought that all this volcanism was related to a gigantic impact need to go back and think some more about that."

Source: Nasa

Martian meteorite yields more evidence of the possibility of life on Mars

Is there, or was there once, life on Mars? Credit: NASA/JPL/MSSS

A tiny fragment of Martian meteorite 1.3 billion years old is helping to make the case for the possibility of life on Mars, say scientists.

The finding of a 'cell-like' structure, which investigators now know once held water, came about as a result of collaboration between scientists in the UK and Greece. Their findings are published in the latest edition of the journal Astrobiology.

While investigating the Martian meteorite, known as Nakhla, Dr Elias Chatzitheodoridis of the National Technical University of Athens found an unusual feature embedded deep within the rock. In a bid to understand what it might be, he teamed up with long-time friend and collaborator Professor Ian Lyon at the University of Manchester.

Professor Lyon, based in Manchester's School of Earth, Atmospheric and Environmental Sciences explains: "In many ways it resembled a fossilized biological cell from Earth but it was intriguing because it was undoubtedly from Mars. Our research found that it probably wasn't a cell but that it did once hold water, water that had been heated, probably as a result of an asteroid impact."

These findings are significant because they add to increasing evidence that beneath the surface, Mars does provide all the conditions for life to have formed and evolved. It also adds to a body of evidence suggesting that large asteroids hit Mars in the past and produce long-lasting hydrothermal fields that could sustain life on Mars, even in later epochs, if life ever emerged there.

As part of the research, the feature was imaged in unprecedented detail by Dr Sarah Haigh of The University of Manchester whose work usually involves high resolution imaging for next generation electronic devices ,which are made by stacking together single atomic layers of graphene and other materials with the aim of making faster, lighter and bendable mobile phones and tablets. A similar imaging approach was able to reveal the atomic layers of materials inside the meteorite.

Together their combined experimental approach has revealed new insights into the geological origins of this fascinating structure.

Professor Lyon said: "We have been able to show the setting is there to provide life. It's not too cold, it's not too harsh. Life as we know it, in the form of bacteria, for example, could be there, although we haven't found it yet. It's about piecing together the case for life on Mars -- it may have existed and in some form could exist still."

Now, the team is using these and other state-of-the-art techniques to investigate new secondary materials in this meteorite and search for possible bio signatures which provide scientific evidence of life, past or present. Professor Lyon concluded: "Before we return samples from Mars, we must examine them further, but in more delicate ways. We must carefully search for further evidence."

Source: Manchester University

Water vapor on Rosetta's target comet significantly different from that found on Earth

First measurements of comet’s water ratio. Credit: Copyright Spacecraft: ESA/ATG medialab; Comet: ESA/Rosetta/NavCam; Data: Altwegg et al. 2014

ESA's Rosetta spacecraft has found the water vapour from its target comet to be significantly different to that found on Earth. The discovery fuels the debate on the origin of our planet's oceans.

The measurements were made in the month following the spacecraft's arrival at Comet 67P/Churyumov-Gerasimenko on 6 August. It is one of the most anticipated early results of the mission, because the origin of Earth's water is still an open question.

One of the leading hypotheses on Earth's formation is that it was so hot when it formed 4.6 billion years ago that any original water content should have boiled off. But, today, two thirds of the surface is covered in water, so where did it come from?
In this scenario, it should have been delivered after our planet had cooled down, most likely from collisions with comets and asteroids. The relative contribution of each class of object to our planet's water supply is, however, still debated.

The key to determining where the water originated is in its 'flavour', in this case the proportion of deuterium -- a form of hydrogen with an additional neutron -- to normal hydrogen.

This proportion is an important indicator of the formation and early evolution of the Solar System, with theoretical simulations showing that it should change with distance from the Sun and with time in the first few million years.

One key goal is to compare the value for different kinds of object with that measured for Earth's oceans, in order to determine how much each type of object may have contributed to Earth's water.

Comets in particular are unique tools for probing the early Solar System: they harbour material left over from the protoplanetary disc out of which the planets formed, and therefore should reflect the primordial composition of their places of origin.

But thanks to the dynamics of the early Solar System, this is not a straightforward process. Long-period comets that hail from the distant Oort cloud originally formed in Uranus-Neptune region, far enough from the Sun that water ice could survive.

They were later scattered to the Solar System's far outer reaches as a result of gravitational interactions with the gas giant planets as they settled in their orbits.

Conversely, Jupiter-family comets like Rosetta's comet were thought to have formed further out, in the Kuiper Belt beyond Neptune. Occasionally these bodies are disrupted from this location and sent towards the inner Solar System, where their orbits become controlled by the gravitational influence of Jupiter.

Indeed, Rosetta's comet now travels around the Sun between the orbits of Earth and Mars at its closest and just beyond Jupiter at its furthest, with a period of about 6.5 years.

Previous measurements of the deuterium/hydrogen (D/H) ratio in other comets have shown a wide range of values. Of the 11 comets for which measurements have been made, it is only the Jupiter-family Comet 103P/Hartley 2 that was found to match the composition of Earth's water, in observations made by ESA's Herschel mission in 2011.

By contrast, meteorites originally hailing from asteroids in the Asteroid Belt also match the composition of Earth's water. Thus, despite the fact that asteroids have a much lower overall water content, impacts by a large number of them could still have resulted in Earth's oceans.

It is against this backdrop that Rosetta's investigations are important. Interestingly, the D/H ratio measured by the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis, or ROSINA, is more than three times greater than for Earth's oceans and for its Jupiter-family companion, Comet Hartley 2. Indeed, it is even higher than measured for any Oort cloud comet as well.

"This surprising finding could indicate a diverse origin for the Jupiter-family comets -- perhaps they formed over a wider range of distances in the young Solar System than we previously thought," says Kathrin Altwegg, principal investigator for ROSINA and lead author of the paper reporting the results in the journal Science this week.

"Our finding also rules out the idea that Jupiter-family comets contain solely Earth ocean-like water, and adds weight to models that place more emphasis on asteroids as the main delivery mechanism for Earth's oceans."

"We knew that Rosetta's in situ analysis of this comet was always going to throw up surprises for the bigger picture of Solar System science, and this outstanding observation certainly adds fuel to the debate about the origin of Earth's water," says Matt Taylor, ESA's Rosetta project scientist.

"As Rosetta continues to follow the comet on its orbit around the Sun throughout next year, we'll be keeping a close watch on how it evolves and behaves, which will give us unique insight into the mysterious world of comets and their contribution to our understanding of the evolution of the Solar System."

Source: ESA

Dawn spacecraft begins approach to dwarf planet Ceres

This artist's concept shows NASA's Dawn spacecraft heading toward the dwarf planet Ceres. Credit: NASA/JPL-Caltech

NASA's Dawn spacecraft has entered an approach phase in which it will continue to close in on Ceres, a Texas-sized dwarf planet never before visited by a spacecraft. Dawn launched in 2007 and is scheduled to enter Ceres orbit in March 2015.

Dawn recently emerged from solar conjunction, in which the spacecraft is on the opposite side of the sun, limiting communication with antennas on Earth. Now that Dawn can reliably communicate with Earth again, mission controllers have programmed the maneuvers necessary for the next stage of the rendezvous, which they label the Ceres approach phase. Dawn is currently 400,000 miles (640,000 kilometers) from Ceres, approaching it at around 450 miles per hour (725 kilometers per hour).

The spacecraft's arrival at Ceres will mark the first time that a spacecraft has ever orbited two solar system targets. Dawn previously explored the protoplanet Vesta for 14 months, from 2011 to 2012, capturing detailed images and data about that body.

"Ceres is almost a complete mystery to us," said Christopher Russell, principal investigator for the Dawn mission, based at the University of California, Los Angeles. "Ceres, unlike Vesta, has no meteorites linked to it to help reveal its secrets. All we can predict with confidence is that we will be surprised."

The two planetary bodies are thought to be different in a few important ways. Ceres may have formed later than Vesta, and with a cooler interior. Current evidence suggests that Vesta only retained a small amount of water because it formed earlier, when radioactive material was more abundant, which would have produced more heat. Ceres, in contrast, has a thick ice mantle and may even have an ocean beneath its icy crust.

Ceres, with an average diameter of 590 miles (950 kilometers), is also the largest body in the asteroid belt, the strip of solar system real estate between Mars and Jupiter. By comparison, Vesta has an average diameter of 326 miles (525 kilometers), and is the second most massive body in the belt.

The spacecraft uses ion propulsion to traverse space far more efficiently than if it used chemical propulsion. In an ion propulsion engine, an electrical charge is applied to xenon gas, and charged metal grids accelerate the xenon particles out of the thruster. These particles push back on the thruster as they exit, creating a reaction force that propels the spacecraft. Dawn has now completed five years of accumulated thrust time, far more than any other spacecraft.

"Orbiting both Vesta and Ceres would be truly impossible with conventional propulsion. Thanks to ion propulsion, we're about to make history as the first spaceship ever to orbit two unexplored alien worlds," said Marc Rayman, Dawn's chief engineer and mission director, based at NASA's Jet Propulsion Laboratory in Pasadena, California.

The next couple of months promise continually improving views of Ceres, prior to Dawn's arrival. By the end of January, the spacecraft's images and other data will be the best ever taken of the dwarf planet.

The Dawn mission to Vesta and Ceres is managed by JPL, a division of the California Institute of Technology in Pasadena, for NASA's Science Mission Directorate, Washington. 

UCLA is responsible for overall Dawn mission science.

Source: NASA/Jet Propulsion Laboratory

Nitrogen fingerprint in biomolecules could be from early sun

Ultraviolet light splits more readily splits molecules of nitrogen gas if one or both are the heavier isotope, nitrogen-15. Free nitrogen atoms combine with hydrogen to form ammonia molecules enriched in nitrogen-15. Credit: Image courtesy of University of California - San Diego

Chemical fingerprints of the element nitrogen vary by extremes in materials from the molecules of life to the solar wind to interstellar dust. Ideas for how this great variety came about have included alien molecules shuttled in by icy comets from beyond our solar system and complex chemical scenarios.

New experiments using a powerful source of ultraviolet light have shown that no extra-solar explanation is needed and the chemistry is straight forward, scientists from the University of California, San Diego, Hebrew University and UCLA report in the early online edition of the Proceedings of the National Academy of Sciences the week of September 29.

Nitrogen occurs in two stable forms. Nitrogen-14, with an equal number of protons and neutrons in its nucleus, is most abundant. Nitrogen-15, with an extra neutron, is far more rare, but biological molecules like proteins have larger proportions; they're enriched in nitrogen-15 relative to the nitrogen gas in Earth's atmosphere. And Earth's atmosphere itself has relatively more nitrogen-15 than other sources, such as the solar wind and Jupiter's atmosphere.

Samples from the icy comet Wild 2, retrieved by NASA's Stardust mission, and several kinds of meteorites also have relatively more nitrogen-15, and within the inhomogenous mix that makes up stony meteorites are inclusions, individual crystals that can have extremely high proportions of nitrogen-15. These observations led to the idea that the building blocks of life could have been 'seeded' on Earth, delivered perhaps by comet.

The new experiments render that hypothesis unnecessary. "We can generate this nitrogen enrichment inside the solar system. You can form all these building blocks of life inside our solar system. You don't have to bring the pieces in from outside," said Subrata Chakraborty, a project scientist in chemistry at UC San Diego and lead author of the report.

By shining a bright beam of very short wave ultraviolet light through nitrogen and hydrogen gas, Chakraborty and colleagues generated ammonia with drastically skewed ratios of nitrogen-15 relative to that found in the initial gas, which matched that of Earth's atmosphere. Pairs of nitrogen atoms -- the molecules of the gas -- were more likely to be split by UV photons if one or both atoms are the heavier version. Those freed nitrogen atoms recombined with hydrogen to form ammonia.

Ammonia molecules, a nitrogen atom bound to three hydrogen atoms, makes up a fundamental chemical group, the 'amines' the characterize amino acids, which link up in long chains to form proteins. They also join aromatic rings of carbon to form nitrogenous bases, the information carrying components of DNA and RNA. And RNA is how many think life got its start.

Light like this, with wavelengths this short, doesn't make it to Earth anymore. It's deflected by Earth's atmosphere. In fact, the experiments took place in a custom-engineered vacuum chamber aligned with the Lawrence Berkeley National Laboratory's Advanced Light Source synchrotron and were a challenge to pull off.

The chemical events that produced amines with extra nitrogen-15 would have happened long ago, probably in the icy outer reaches of the early solar nebula said Mark Thiemens, professor of chemistry at UC San Diego who directed the work. "It's the right time for this to have happened: before planets, before life."

Additional authors include Harel Muskatel of Hebrew University in Jerusalem, Teresa Jackson of UC San Diego, Musahid Ahmed of Lawrence Berkeley National Laboratory and R.D. Levine of Hebrew University and UCLA. NASA's Cosmochemistry and Origins of Solar System programs funded this work. The U.S. Department of Energy supports the operation of the Advanced Light Source.

Source:  University of California - San Diego

Water vapor on Rosetta's target comet significantly different from that found on Earth

First measurements of comet’s water ratio. Credit: Copyright Spacecraft: ESA/ATG medialab; Comet: ESA/Rosetta/NavCam; Data: Altwegg et al. 2014

ESA's Rosetta spacecraft has found the water vapour from its target comet to be significantly different to that found on Earth. The discovery fuels the debate on the origin of our planet's oceans.

The measurements were made in the month following the spacecraft's arrival at Comet 67P/Churyumov-Gerasimenko on 6 August. It is one of the most anticipated early results of the mission, because the origin of Earth's water is still an open question.

One of the leading hypotheses on Earth's formation is that it was so hot when it formed 4.6 billion years ago that any original water content should have boiled off. But, today, two thirds of the surface is covered in water, so where did it come from?
In this scenario, it should have been delivered after our planet had cooled down, most likely from collisions with comets and asteroids. The relative contribution of each class of object to our planet's water supply is, however, still debated.

The key to determining where the water originated is in its 'flavour', in this case the proportion of deuterium -- a form of hydrogen with an additional neutron -- to normal hydrogen.

This proportion is an important indicator of the formation and early evolution of the Solar System, with theoretical simulations showing that it should change with distance from the Sun and with time in the first few million years.

One key goal is to compare the value for different kinds of object with that measured for Earth's oceans, in order to determine how much each type of object may have contributed to Earth's water.

Comets in particular are unique tools for probing the early Solar System: they harbour material left over from the protoplanetary disc out of which the planets formed, and therefore should reflect the primordial composition of their places of origin.

But thanks to the dynamics of the early Solar System, this is not a straightforward process. Long-period comets that hail from the distant Oort cloud originally formed in Uranus-Neptune region, far enough from the Sun that water ice could survive.

They were later scattered to the Solar System's far outer reaches as a result of gravitational interactions with the gas giant planets as they settled in their orbits.

Conversely, Jupiter-family comets like Rosetta's comet were thought to have formed further out, in the Kuiper Belt beyond Neptune. Occasionally these bodies are disrupted from this location and sent towards the inner Solar System, where their orbits become controlled by the gravitational influence of Jupiter.

Indeed, Rosetta's comet now travels around the Sun between the orbits of Earth and Mars at its closest and just beyond Jupiter at its furthest, with a period of about 6.5 years.
Previous measurements of the deuterium/hydrogen (D/H) ratio in other comets have shown a wide range of values. Of the 11 comets for which measurements have been made, it is only the Jupiter-family Comet 103P/Hartley 2 that was found to match the composition of Earth's water, in observations made by ESA's Herschel mission in 2011.

By contrast, meteorites originally hailing from asteroids in the Asteroid Belt also match the composition of Earth's water. Thus, despite the fact that asteroids have a much lower overall water content, impacts by a large number of them could still have resulted in Earth's oceans.
It is against this backdrop that Rosetta's investigations are important. Interestingly, the D/H ratio measured by the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis, or ROSINA, is more than three times greater than for Earth's oceans and for its Jupiter-family companion, Comet Hartley 2. Indeed, it is even higher than measured for any Oort cloud comet as well.

"This surprising finding could indicate a diverse origin for the Jupiter-family comets -- perhaps they formed over a wider range of distances in the young Solar System than we previously thought," says Kathrin Altwegg, principal investigator for ROSINA and lead author of the paper reporting the results in the journal Science this week.
"Our finding also rules out the idea that Jupiter-family comets contain solely Earth ocean-like water, and adds weight to models that place more emphasis on asteroids as the main delivery mechanism for Earth's oceans."

"We knew that Rosetta's in situ analysis of this comet was always going to throw up surprises for the bigger picture of Solar System science, and this outstanding observation certainly adds fuel to the debate about the origin of Earth's water," says Matt Taylor, ESA's Rosetta project scientist.

"As Rosetta continues to follow the comet on its orbit around the Sun throughout next year, we'll be keeping a close watch on how it evolves and behaves, which will give us unique insight into the mysterious world of comets and their contribution to our understanding of the evolution of the Solar System."

Source: ESA