Curiosity Finds Evidence of Mars Crust Contributing to Atmosphere

NASA - Mars Science Laboratory (MSL) logo.

Sept. 29, 2016

Image above: This low-angle self-portrait of NASA's Curiosity Mars rover shows the vehicle at the site from which it reached down to drill into a rock target called "Buckskin." The MAHLI camera on Curiosity's robotic arm took multiple images on Aug. 5, 2015, that were stitched together into this selfie. Image Credits: NASA/JPL-Caltech/MSSS.

NASA's Curiosity rover has found evidence that chemistry in the surface material on Mars contributed dynamically to the makeup of its atmosphere over time. It’s another clue that the history of the Red Planet’s atmosphere is more complex and interesting than a simple legacy of loss.

The findings come from the rover’s Sample Analysis at Mars, or SAM, instrument suite, which studied the gases xenon and krypton in Mars’ atmosphere. The two gases can be used as tracers to help scientists investigate the evolution and erosion of the Martian atmosphere. A lot of information about xenon and krypton in Mars’ atmosphere came from analyses of Martian meteorites and measurements made by the Viking mission.

Image above: Chemistry that takes place in the surface material on Mars can explain why particular xenon (Xe) and krypton (Kr) isotopes are more abundant in the Martian atmosphere than expected. The isotopes – variants that have different numbers of neutrons – are formed in the loose rocks and material that make up the regolith. The chemistry begins when cosmic rays penetrate into the surface material. If the cosmic rays strike an atom of barium (Ba), the barium can lose one or more of its neutrons (n⁰). Atoms of xenon can pick up some of those neutrons – a process called neutron capture – to form the isotopes xenon-124 and xenon-126. In the same way, atoms of bromine (Br) can lose some of their neutrons to krypton, leading to the formation of krypton-80 and krypton-82 isotopes. These isotopes can enter the atmosphere when the regolith is disturbed by impacts and abrasion and gas escapes from the regolith. Image Credits: NASA's Goddard Space Flight Center.

“What we found is that earlier studies of xenon and krypton only told part of the story,” said Pamela Conrad, lead author of the report and SAM’s deputy principal investigator at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “SAM is now giving us the first complete in situ benchmark against which to compare meteorite measurements.”

Of particular interest to scientists are the ratios of certain isotopes – or chemical variants – of xenon and krypton. The SAM team ran a series of first-of-a-kind experiments to measure all the isotopes of xenon and krypton in the Martian atmosphere. The experiments are described in a paper published in Earth and Planetary Science Letters.

The team’s method is called static mass spectrometry, and it’s good for detecting gases or isotopes that are present only in trace amounts. Although static mass spectrometry isn’t a new technique, its use on the surface of another planet is something only SAM has done.

Overall, the analysis agreed with earlier studies, but some isotope ratios were a bit different than expected. When working on an explanation for those subtle but important differences, the researchers realized that neutrons might have gotten transferred from one chemical element to another within the surface material on Mars. The process is called neutron capture, and it would explain why a few selected isotopes were more abundant than previously thought possible.

In particular, it looks as if some of the barium surrendered neutrons that got picked up by xenon to produce higher-than-expected levels of the isotopes xenon-124 and 126. Likewise, bromine might have surrendered some of its neutrons to produce unusual levels of krypton-80 and krypton-82.

Image above: The Sample Analysis at Mars instrument suite on NASA’s Curiosity rover. Image Credits: NASA's Goddard Space Flight Center.

These isotopes could have been released into the atmosphere by impacts on the surface and by gas escaping from the regolith, which is the soil and broken rocks of the surface.

“SAM’s measurements provide evidence of a really interesting process in which the rock and unconsolidated material at the planet’s surface have contributed to the xenon and krypton isotopic composition of the atmosphere in a dynamic way,” said Conrad.

The atmospheres of Earth and Mars exhibit very different patterns of xenon and krypton isotopes, particularly for xenon-129. Mars has much more of it in the atmosphere than does Earth.

“The unique capability to measure in situ the six and nine different isotopes of krypton and xenon allows scientists to delve into the complex interactions between the Martian atmosphere and crust,” said Michael Meyer, lead scientist for the Mars Exploration Program at NASA Headquarters in Washington. “Discovering these interactions through time allows us to gain a greater understanding of planetary evolution.”

NASA’s Mars Science Laboratory Project is using Curiosity to determine if life was possible on Mars and study major changes in Martian environmental conditions. NASA studies Mars to learn more about our own planet, and in preparation for future human missions to Mars. NASA’s Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the project for NASA’s Science Mission Directorate in Washington.

For more information about SAM, visit: http://ssed.gsfc.nasa.gov/sam/

SAM experiment data are archived in the Planetary Data System, online at: http://pds.nasa.gov/

For more information about Curiosity, visit: http://www.nasa.gov/msl

The research paper is available at: http://dx.doi.org/10.1016/j.epsl.2016.08.028

Images (mentioned), Text, Credits: NASA’s Goddard Space Flight Center, written by Elizabeth Zubritsky/JPL/Guy Webster/Karl Hille.

Greetings, Orbiter.ch

ALMA Catches Stellar Cocoon with Curious Chemistry

ALMA - Atacama Large Millimeter/submillimeter Array logo.

29 September 2016

The first of its kind to be found outside the Milky Way

Artist's impression of the hot molecular core discovered in the Large Magellanic Cloud

A hot and dense mass of complex molecules, cocooning a newborn star, has been discovered by a Japanese team of astronomers using ALMA. This unique hot molecular core is the first of its kind to have been detected outside the Milky Way galaxy. It has a very different molecular composition from similar objects in our own galaxy — a tantalising hint that the chemistry taking place across the Universe could be much more diverse than expected.

A team of Japanese researchers have used the power of the Atacama Large Millimeter/submillimeter Array (ALMA) to observe a massive star known as ST11 [1] in our neighbouring dwarf galaxy, the Large Magellanic Cloud (LMC). Emission from a number of molecular gases was detected. These indicated that the team had discovered a concentrated region of comparatively hot and dense molecular gas around the newly ignited star ST11. This was evidence that they had found something never before seen outside of the Milky Way — a hot molecular core [2].

Takashi Shimonishi, an astronomer at Tohoku University, Japan, and the paper's lead author enthused: "This is the first detection of an extragalactic hot molecular core, and it demonstrates the great capability of new generation telescopes to study astrochemical phenomena beyond the Milky Way."

The ALMA observations revealed that this newly discovered core in the LMC has a very different composition to similar objects found in the Milky Way. The most prominent chemical signatures in the LMC core include familiar molecules such as sulfur dioxide, nitric oxide, and formaldehyde — alongside the ubiquitous dust. But several organic compounds, including methanol (the simplest alcohol molecule), had remarkably low abundance in the newly detected hot molecular core. In contrast, cores in the Milky Way have been observed to contain a wide assortment of complex organic molecules, including methanol and ethanol.

ALMA results and the region seen in infrared light

Takashi Shimonishi explains: “The observations suggest that the molecular compositions of materials that form stars and planets are much more diverse than we expected.”

The LMC has a low abundance of elements other than hydrogen or helium [3]. The research team suggests that this very different galactic environment has affected the molecule-forming processes taking place surrounding the newborn star ST11. This could account for the observed differences in chemical compositions.

It is not yet clear if the large, complex molecules detected in the Milky Way exist in hot molecular cores in other galaxies. Complex organic molecules are of very special interest because some are connected to prebiotic molecules formed in space. This newly discovered object in one of our nearest galactic neighbours is an excellent target to help astronomers address this issue. It also raises another question: how could the chemical diversity of galaxies affect the development of extragalactic life?

Notes:

[1] ST11’s full name is 2MASS J05264658-6848469. This catchily-named young massive star is defined as a Young Stellar Object. Although it currently appears to be a single star, it is possible that it will prove to be a tight cluster of stars, or possibly a multiple star system. It was the target of the science team’s observations and their results led them to realise that ST11 is enveloped by a hot molecular core.

[2] Hot molecular cores must be: (relatively) small, with a diameter of less than 0.3 light-years; have a density over a thousand billion (1012) molecules per cubic metre (far lower than the Earth's atmosphere, but high for an interstellar environment); warm in temperature, at over –173 degrees Celsius. This makes them at least 80 degrees Celsius warmer than a standard molecular cloud, despite being of similar density. These hot cores form early on in the evolution of massive stars and they play a key role in the formation of complex chemicals in space.

[3] The nuclear fusion reactions that take place when a star has stopped fusing hydrogen to helium generate heavier elements. These heavier elements get blasted into space when massive dying stars explode as supernovae. Therefore, as our Universe has aged, the abundance of heavier elements has increased. Thanks to its low abundance of heavier elements, the LMC provides insight into the chemical processes that were taking place in the earlier Universe.

More information:

This research was presented in a paper published in the Astrophysical Journal on August 9, 2016, entitled The Detection of a Hot Molecular Core in the Large Magellanic Cloud with ALMA: http://dx.doi.org/10.3847/0004-637X/827/1/72

The team is composed of Takashi Shimonishi (Frontier Research Institute for Interdisciplinary Sciences & Astronomical Institute, Tohoku University, Japan), Takashi Onaka (Department of Astronomy, The University of Tokyo, Japan), Akiko Kawamura (National Astronomical Observatory of Japan, Japan) and Yuri Aikawa (Center for Computational Sciences, The University of Tsukuba, Japan)

The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of the European Organisation for Astronomical Research in the Southern Hemisphere (ESO), the U.S. National Science Foundation (NSF) and the National Institutes of Natural Sciences (NINS) of Japan in cooperation with the Republic of Chile. ALMA is funded by ESO on behalf of its Member States, by NSF in cooperation with the National Research Council of Canada (NRC) and the National Science Council of Taiwan (NSC) and by NINS in cooperation with the Academia Sinica (AS) in Taiwan and the Korea Astronomy and Space Science Institute (KASI).

ALMA construction and operations are led by ESO on behalf of its Member States; by the National Radio Astronomy Observatory (NRAO), managed by Associated Universities, Inc. (AUI), on behalf of North America; and by the National Astronomical Observatory of Japan (NAOJ) on behalf of East Asia. The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA.

ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It is supported by 16 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom, along with the host state of Chile. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world’s largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is a major partner in ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre European Extremely Large Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.

Links:

Research paper: http://www.eso.org/public/archives/releases/sciencepapers/eso1634/eso1634a.pdf

Photos of ALMA: http://www.eso.org/public/images/archive/category/alma/

Atacama Large Millimeter/submillimeter Array (ALMA): http://www.eso.org/public/teles-instr/alma/

Images, Text, Credits: ESO/M. Kornmesser; NASA, ESA, and S. Beckwith (STScI) and the HUDF Team; NASA/ESA and the Hubble Heritage Team (AURA/STScI)/HEI/FRIS/Tohoku University/T. Shimonishi/Tohoku University, ALMA (ESO/NAOJ/NRAO).

Best regards, Orbiter.ch

CERN - Looking for charming asymmetries

CERN - European Organization for Nuclear Research logo.

29 Sep 2016

One of the biggest challenges in physics is to understand why everything we see in our universe seems to be formed only of matter, whereas the Big Bang should have created equal amounts of matter and antimatter.

CERN’s LHCb experiment is one of the best hopes for physicists looking to solve this longstanding mystery.

At the VIII International Workshop on Charm Physics, which took place in Bologna earlier this month, the LHCb Collaboration presented the most precise measurement to date of a phenomenon called Charge-Parity (CP) violation among particles that contain a charm quark.

CP symmetry states that laws of physics are the same if a particle is interchanged with its anti-particle (the “C” part) and if its spatial coordinates are inverted (P). The violation of this symmetry in the first few moments of the universe is one of the fundamental ingredients to explain the apparent cosmic imbalance in favour of matter.

Until now, the amount of CP violation detected among elementary particles can only explain a tiny fraction of the observed matter-antimatter asymmetry. Physicists are therefore extending their search in the quest to identify the source of the missing anti-matter.

A view of the LHCb experimental cavern. (Image: Maximilien Brice/CERN)

The LHCb collaboration made a precise comparison between the decay lifetime of a particle called a D⁰ meson (formed by a charm quark and an up antiquark) and its anti-matter counterpart  D⁰ (formed by an charm antiquark and up quark), when decaying either to a pair of pions or a pair of kaons. Any difference in these lifetimes would provide strong evidence that an additional source of CP violation is at work. Although CP violation has been observed in processes involving numerous particles that contain b and s quarks, the effect is still unobserved in the charm-quark sector and its magnitude is predicted to be very small in the Standard Model.

Thanks to the excellent performance of CERN’s Large Hadron Collider, for the first time the LHCb collaboration is accumulating a dataset large enough to access the required level of precision on CP-violating effects in charm-meson decays. The latest results indicate that the lifetimes of the D⁰ and D⁰  particles, measured using their decays to pions or kaons, are still consistent, thereby demonstrating that any CP violation effect that is present must indeed be at a tiny level.

However, with many more analyses and data to come, LHCb is looking forward to delving even deeper into the possibility of CP violation in the charm sector and thus closing in on the universe’s missing antimatter. “The unique capabilities of our experiment, and the huge production rate of charm mesons at the LHC, allow us to perform measurements that are far beyond the sensitivity of any previous facility,” says Guy Wilkinson, spokesperson for the LHCb collaboration. “However, nature demands that we dig even deeper in order to uncover an effect. With the data still to come, we are confident of responding to this challenge,” he adds.

More information is available on the LHCb website: http://lhcb-public.web.cern.ch/lhcb-public/Welcome.html#Charm2016

Note:

CERN, the European Organization for Nuclear Research, is one of the world’s largest and most respected centres for scientific research. Its business is fundamental physics, finding out what the Universe is made of and how it works. At CERN, the world’s largest and most complex scientific instruments are used to study the basic constituents of matter — the fundamental particles. By studying what happens when these particles collide, physicists learn about the laws of Nature.

The instruments used at CERN are particle accelerators and detectors. Accelerators boost beams of particles to high energies before they are made to collide with each other or with stationary targets. Detectors observe and record the results of these collisions.

Founded in 1954, the CERN Laboratory sits astride the Franco–Swiss border near Geneva. It was one of Europe’s first joint ventures and now has 22 Member States.

Related links:

VIII International Workshop on Charm Physics: http://charm2016.bo.infn.it/

For more information about European Organization for Nuclear Research (CERN), Visit: http://home.cern/

Image (mentioned), Text, Credits: CERN/Stefania Pandolfi.

Best regards, Orbiter.ch

NASA’s Van Allen Probes Spot Electron Rainfall in Atmosphere

NASA - Van Allen Probes Mission logo.

Sept. 28, 2016

Our planet is nestled in the center of two doughnut-shaped regions of powerful, dynamic radiation: the Van Allen belts, where high-energy particles are trapped by Earth’s magnetic field. Depending on incoming radiation from the sun, they can gain energetic particles. On the other hand, the belts can lose energized particles too.

NASA Explores High-Energy Rainfall in the Atmosphere

Video above: This video illustrates the complexity of Earth’s magnetic environment, from the radiation belts encircling Earth to the magnetic field lines, depicted as blue ribbons, extending far out into space. During a drop-out, ultra-relativistic electrons stream down along powerful electromagnetic waves, as if they are raining into the atmosphere. Video Credits: NASA Goddard/Joy Ng/Martin Rother/GFZ-Potsdam.

We are familiar with rapid changes in weather, and the radiation belts can experience these too – particles can be depleted by a thousand-fold in mere hours. These dramatic loss events are called drop-outs, and they can happen when intense bouts of solar radiation disturb Earth’s magnetic environment. There have been many theories on how this happens, but scientists have not had the data to pinpoint which one is correct.

Artist's view of Van Allen Probes in orbit. Image Credit: NASA

However, on Jan. 17, 2013, NASA's Van Allen Probes were in just the right position to watch a drop-out in progress and resolve a long-standing question as to how the lower region of the belts close to Earth loses high-energy electrons – known as ultra-relativistic electrons for their near-light speeds. During a drop-out, a certain class of powerful electromagnetic waves in the radiation belts can scatter ultra-relativistic electrons. The electrons stream down along these waves, as if they are raining into the atmosphere. A team led by Yuri Shprits of University of California in Los Angeles published a paper summarizing these findings in Nature Communications on Sept. 28, 2016: http://www.nature.com/articles/ncomms12883

Such information helps illustrate the complexity of Earth's magnetic surroundings.  Understanding changes within the belts is crucial for protecting the satellites and astronauts travelling through this sometimes harsh space environment.

Related Links:

Van Allen Probes Mission Overview: http://www.nasa.gov/mission_pages/rbsp/mission/index.html

Van Allen Probes Catch Rare Glimpse of Supercharged Radiation Belt: https://www.nasa.gov/feature/goddard/2016/nasas-van-allen-probes-catch-rare-glimpse-of-supercharged-radiation-belt

For more information about Van Allen Probes, visit: https://www.nasa.gov/mission_pages/rbsp/main/index.html

Image (mentioned), Video (mentioned), Text, Credits: NASA's Goddard Space Flight Center, by Lina Tran/Rob Garner.

Greetings, Orbiter.ch

'Pandora's Cluster' Seen by Spitzer

NASA - Spitzer Space Telescope patch.

Sept. 28, 2016

This image of galaxy cluster Abell 2744, also called Pandora's Cluster, was taken by the Spitzer Space Telescope. The gravity of this galaxy cluster is strong enough that it acts as a lens to magnify images of more distant background galaxies. This technique is called gravitational lensing.

The fuzzy blobs in this Spitzer image are the massive galaxies at the core of this cluster, but astronomers will be poring over the images in search of the faint streaks of light created where the cluster magnifies a distant background galaxy.

The cluster is also being studied by NASA's Hubble Space Telescope and Chandra X-Ray Observatory in a collaboration called the Frontier Fields project. Hubble's image of Abell 2744 can be seen here: http://www.nasa.gov/content/hubble-frontier-field-abell-2744

In this image, light from Spitzer's infrared channels is colored blue at 3.6 microns and green at 4.5 microns.

JPL manages the Spitzer Space Telescope mission for NASA's Science Mission Directorate, Washington. Science operations are conducted at the Spitzer Science Center at Caltech in Pasadena, California. Spacecraft operations are based at Lockheed Martin Space Systems Company, Littleton, Colorado. Data are archived at the Infrared Science Archive housed at the Infrared Processing and Analysis Center at Caltech. Caltech manages JPL for NASA.

For more information about Spitzer, visit: http://spitzer.caltech.edu

Image, Text, Credits: NASA/JPL-Caltech/Martin Perez.

Greetings, Orbiter.ch

Rosetta measures production of water at comet over two years

ESA - Rosetta Mission patch.

28 September 2016

Over the past two years, Rosetta has kept a close eye on many properties of Comet 67P/Churyumov-Gerasimenko, tracking how these changed along the comet's orbit. A very crucial aspect concerns how much water vapour a comet releases into space, and how the water production rate varies at different distances from the Sun. For the first time, Rosetta enabled scientists to monitor this quantity and its evolution in situ over two years.

In a new study led by Kenneth C. Hansen of the University of Michigan, in the US, measurements of water production rate based on data from ROSINA, the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis, are compared with water measurements from other Rosetta instruments.

Image above: Comet 67P/C-G on 11 September 2015 - NavCam. Image Credits: ESA/Rosetta/NAVCAM, CC BY-SA IGO 3.0.

The combination of all instruments shows an overall increase of the production of water, from a few tens of thousands of kg per day when Rosetta first reached the comet, in August 2014, to almost 100 000 000 kg per day around perihelion, the closest point to the Sun along the comet's orbit, in August 2015. In addition, ROSINA data show that the peak in water production is followed by a rather steep decrease in the months following perihelion.

"We were pleasantly surprised to find such a good agreement between the data collected by all the various instruments in this unprecedented study of the water production rate's evolution for a Jupiter-family comet," says Hansen.

The scientists analysed almost two years' worth of data from ROSINA, which detects neutral water molecules with its Double-Focussing Mass Spectrometer (DFMS).

Graphic above: Water production rate measured by different instruments at Comet 67P/C-G. Image adapted from Hansen et al. (2016).

"This is by no means trivial: ROSINA performs measurements locally, at specific points around the comet, and we need a model to extend them to the entire atmosphere," adds Hansen.

The simplest model would be a spherical distribution of the outgassing centred around the nucleus but, given the complex shape and season cycle of Comet 67P/C-G, this would be a very crude approximation. For this reason, the ROSINA team developed a series of numerical simulations to accurately describe the comet's production of water, which are presented in a separate study led by Nicolas Fougere also of the University of Michigan.

From these simulations, which showed that the water production rate at a comet like 67P/C-G is highly inhomogeneous, Hansen and his colleagues derived an empirical model, which they then used to transform the local ROSINA measurements into estimates of the overall water production rate.

The results revealed that, during the first several months of observations, when the comet was at distances between 3.5 and 1.7 astronomical units (au) from the Sun, water was predominantly produced in the comet's northern hemisphere.

Animations above: Simulation of comet 67P's water production rate during northern summer. Images adapted from Hansen et al. (2016); animations courtesy of K.C. Hansen.

Then, in May 2015, the equinox marked the end of the 5.5-year long northern summer and the beginning of the short and intense southern summer. At that time, the comet was about 1.7 au from the Sun, and scientists expected that the peak of water production would drift slowly from the northern to the southern hemisphere; instead, this transition happened more abruptly than predicted. This was likely due to the complex shape of the nucleus, which causes highly variable illumination conditions including self-shadowing effects.

As expected, the production of water peaked between the end of August and early September 2015, about three weeks after the comet's perihelion, which took place on 13 August, 1.24 au from the Sun. The data hint at possible variations in the water production rate at this epoch: these might be due to the spacecraft's motion relative to the comet, but could also be an indication of actual changes to the outgassing dynamics, and will be subject of future in-depth investigation.

Animations above: Simulation of comet 67P's water production rate around perihelion. Images adapted from Hansen et al. (2016); animations courtesy of K.C. Hansen.

In addition to the ROSINA measurements, Hansen and his colleagues collated a series of previously published measurements of the water production rate at 67P/C-G. These include observations performed with the Microwave Instrument for the Rosetta Orbiter (MIRO) shortly before and after Rosetta had reached the comet, data from the Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) obtained between November 2014 and January 2015, and measurements from the Ion Composition Analyser, part of the Rosetta Plasma Consortium (RPC) suite of instruments, obtained between October 2014 and April 2015.

RPC-ICA does not detect water directly, but rather measures the ratio of differently ionised Helium ions; since He+ ions arise mainly from collisions between alpha particles (He2+) from the solar wind and neutral molecules, such as water, found in the comet's atmosphere, this ratio can be used to estimate the amount of water produced at the comet.

Hansen and his collaborators have found some small discrepancies between the various data sets: for example, the measurements from ROSINA yield systematically higher values than those from VIRTIS. One possible reason for this is the different nature of the two experiments: ROSINA samples the gas in the coma at the spacecraft's position, while VIRTIS tends to observe closer to the nucleus, where the water production activity is potentially more confined than it is further out in the coma. The difference in measurements techniques and the discrepancy could potentially indicate an extended source of water in the coma itself, for example icy grains that are lifted into the coma and turn into gas a few kilometers above the surface.

Another difference was found between the MIRO measurements, which indicate a rising trend in the water production rate from June to September 2014, and the first months of ROSINA data, starting in August, pointing to an almost constant rate in the same period.

"This could be explained if a sudden surge in the water production happened around the time of the first MIRO measurement, a few weeks before Rosetta's rendezvous with 67P/C-G, and the beginning of ROSINA observations," says Hansen.

The scientists also compared the comet's production rate of water to that of dust, which can be measured via ground-based observations and was recently reported in a study led by Colin Snodgrass of the Open University, UK. These observations were performed with a number of robotic telescopes across the globe, from Chile to Hawaii and the Canary Islands.

"The correlation between the production rate of water and dust, both before and after perihelion, is impressive, suggesting that the gas-to-dust ratio remained constant over this long period," explains Hansen.

Based on the water production rate, the team estimated that the comet lost some 6.4 billion kg of water to space over the period monitored by Rosetta, with the most intense mass loss happening near perihelion. The total mass loss, taking into account other gas molecules and in particular the dust, could be roughly 10 times larger than that and, if distributed uniformly across the comet nucleus, it would translate into a reduction of 2 to 4 metres.

"This study shows how cross comparison between different instruments and simulations is beginning to reveal the comet further," says Matt Taylor, Rosetta project scientist at ESA.

"Connecting in-situ measurements from Rosetta with ground-based observations was a major science goal for the mission and it is wonderful to see this cooperation in action," concludes Kathrin Altwegg, ROSINA principal investigator.

Notes for Editors:

"Evolution of water production of 67P/Churyumov-Gerasimenko: An empirical model and a multi-instrument study" by K.C. Hansen et al. is published in the special issue of Monthly Notices of the Royal Astronomical Society, "The ESLAB 50 Symposium - spacecraft at comets from 1P/Halley to 67P/Churyumov-Gerasimenko".

"Direct Simulation Monte-Carlo Modeling of the Major Species in the Coma of Comet 67P/Churyumov-Gerasimenko" by N. Fougere et al., and "The perihelion activity of comet 67P/Churyumov-Gerasimenko as seen by robotic telescopes" by C. Snodgrass et al. are also published in the same special issue.

Published studies:

http://dx.doi.org/10.1093/mnras/stw2413

http://mnras.oxfordjournals.org/content/early/2016/09/20/mnras.stw2388.abstract

https://mnras.oxfordjournals.org/content/early/2016/09/12/mnras.stw2300.abstract?cited-by=yes&legid=mnras;stw2300v1

http://mnras.oxfordjournals.org/content/462/Suppl_1.toc

http://mnras.oxfordjournals.org/content/early/2016/09/20/mnras.stw2388.abstract

Related links:

Comet viewer tool: http://sci.esa.int/comet-viewer/

Where is Rosetta?: http://sci.esa.int/where_is_rosetta/

For more information about Rosetta mission, visit: http://www.esa.int/Our_Activities/Space_Science/Rosetta

Rosetta overview: http://www.esa.int/Our_Activities/Space_Science/Rosetta_overview

Rosetta in depth: http://sci.esa.int/rosetta

Image (mentioned), Graphic (mentioned), Animations (mentioned), Text, Credit: European Space Agency (ESA).

Best regards, Orbiter.ch

NASA Develops Satellite Concept to Exploit Rideshare Opportunities

NASA - Goddard Space Flight Center logo.

Sept. 27, 2016

Each time a rocket blasts off to deliver a primary payload into space, it typically does so with room to spare — a reality that got NASA engineer Joe Burt thinking.

Why not exploit that unused capacity and create a sealed, pressurized, thermally controlled capsule that could take advantage of rideshare opportunities while accommodating less-expensive, off-the-shelf instrument components typically used in laboratory-like settings? Several years in the making, Burt and his team at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, now are ready to validate portions of such a system.

Called the Capsulation Satellite, or CapSat for short, the system is a hockey puck-shaped structure that measures roughly 40 inches wide and 18 inches tall. Purposely designed as either a stand-alone system or stacked depending on payload needs, each capsule is capable of carrying about 661 pounds of payload into orbit — a microsatellite-class weight not accommodated by the increasingly popular CubeSat platform whose instruments typically weigh two to six pounds.

Image above: Goddard engineer Joe Burt now is developing a satellite system that would take advantage of unused capacity on launch vehicles, while accommodating less-expensive, off-the-shelf instrument components typically used in laboratory-like settings. Image Credits: NASA/W. Hrybyk.

With funding from NASA’s Earth Science Technology Office, or ESTO, Burt and his team will validate CapSat’s all-important thermal-control system in a thermal-vacuum chamber test in late September. The system uses thermostatically controlled fans — much like those used to cool electronic equipment on Earth — to circulate air over hot and cold plates located inside the craft. This maintains a constant temperature where instruments would experience little, if any, thermal degradation while on orbit, Burt said.

Under the ESTO-funded effort, Burt and Goddard detector expert Murzy Jhabvala also are conducting a study to scope out the specifics of flying a next-generation photodetector camera on a CapSat. The idea is that NASA could fly the detector on a constellation of CapSats to gather multiple, simultaneous measurements.

To show the concept’s feasibility, Jhabvala successfully installed in late July a laboratory version of his Strained-Layer Superlattice Infrared Detector Camera inside the CapSat model. “The main purpose of the camera demonstration was to show how easily a laboratory-based instrument could become a flight instrument, complete with flyable electronics and software connecting it all the way back to the ground data display and analysis,” Burt said.

Nothing New Under the Sun

Burt is the first to admit that pressurized spacecraft are not new, and aside from its thermal-control system, CapSat is not in the technological vanguard. “Flying a mission with pressurized volume goes back to Sputnik,” he said. “There is nothing magical here. Terrestrial pressure in space is a tried-and-true approach,” Burt added. “It happens on the ISS (International Space Station) where scores of laptops are running every day. This is not a new idea.”

CapSat’s Distinguishing Attributes

What distinguishes CapSat is the fact that the capsule can accommodate heavier payloads. Perhaps more important, Burt specifically designed it to take advantage of a U.S. Air Force-developed secondary-payload carrier called the Evolved Expendable Launch Vehicle Secondary Payload Adaptor, or ESPA ring. Working with Moog CSA Engineering, of Mountain View, California, the Air Force created the ring to accommodate as many as six payloads beneath the primary spacecraft, exploiting the thousands of pounds of unused cargo space on many rockets.

Image above: CapSat is a pressurized platform designed to carry laboratory-style instruments into space. Image Credits: NASA/W. Hrybyk.

Goddard’s new Rideshare Office estimates that between 2015 and 2023, NASA will launch a number of missions whose total combined unused mass-to-orbit will exceed 46,300 pounds. “At an average launch cost of a million dollars-per-kilogram-to-orbit — even CubeSats cost about that — hundreds of millions of dollars in launch-vehicle costs are going unutilized,” said Bob Caffrey, who heads the Rideshare Office. “There really needs to be a paradigm shift,” he added.

In sharp contrast, Burt estimates that CapSat would reduce today’s launch costs of $1-million-per-kilogram-to-orbit to just $50,000-per-kilogram by using a pressurized volume to take advantage of the unused capacity.

Rideshare Opportunities Blossom

Also to consider, he added, is the fact that since its initial development in the early 2000s, the ESPA ring has become the de facto standard for secondary payload carriers, with a growing list of users and opportunities.

In 2009, NASA used the ESPA ring to deploy its Lunar Crater Observation and Sensing Satellite, which flew as a secondary payload on the Lunar Reconnaissance Orbiter. Private industry uses it, too. Late last year, SpaceX, of Hawthorne, California, used ESPA rings to mount 11 Orbcomm OG-2 communication satellites inside the Falcon 9 rocket, resulting in a successful deployment.

In the meantime, the U.S. Air Force has announced that it plans to fly the ESPA ring on all future launch vehicles. It also has developed a process for selecting potential rideshare payloads and is creating other versions of the carrier to accommodate a broader range of users. NASA, too, plans to take better advantage of the unused cargo capacity and will be providing rideshare opportunities on its future missions, Burt said.

“Secondary payloads are part of growing trend toward the increasing diversity of platforms used in pursuing space and Earth science,” said Greg Robinson, NASA Science Mission Directorate Deputy Associate Administrator for Programs. “Today, many U.S. government, academic, and industry partners are looking for ways to use secondary payloads as platforms to enable science, mature technologies, and enable workforce development,” he added.

Time is Ripe

Given this confluence of events, the time is ripe for NASA to develop a platform like CapSat, Burt said, adding that Goddard’s Strategic Partnerships Office now is pursuing a patent on the CapSat technology. Not only is it compatible with the ESPA ring, it also is capable of carrying heavier instruments, even those originally built for a terrestrially based laboratory testing. Such a platform, which Burt believes industry ultimately should manufacture and offer at competitive prices, would significantly reduce mission-development schedules and costs.

Image above: Goddard engineer Joe Burt is applied the CapSat concept to create a smaller pressurized platform, which he calls CapSIT. Image Credit: NASA.

Since CapSat’s roll out, a number of possible new missions have approached Burt about possibly using the platform. One of the more promising opportunities, he said, is flying a debris sensor called DRAGONS, which is short for Debris Resistive Acoustic Grid Orbital Navy-NASA Sensor, on as many as four CapSats. Furthermore, Burt also is developing a smaller CapSat-type platform, which he calls the CapSat Science Instrument Tube, or CapSIT. In this architecture, the pressurized volume for the CapSat science instrument is reduced to a tube about three feet long and one foot wide.

“The bottom line is that the CapSat concept has the potential to make science missions more affordable,” said Azita Valinia, an ESTO executive who awarded the ESTO study. “If proven successful, the CapSat architecture can change the cost paradigm for science missions.”

Robinson agrees. “It’s exciting to see what is being built by the Goddard team to provide researchers a capable and reliable platform for fast turn-around, lower-cost payloads,” he continued. “When combined with the wide array of launch opportunities for these secondary payloads, the opportunities for platforms like CapSat are showing real promise,” he said.

For more technology news, go to: http://gsfctechnology.gsfc.nasa.gov/newsletter/Current.pdf

Goddard Space Flight Center: http://www.nasa.gov/centers/goddard/home/index.html

Science Instruments: http://www.nasa.gov/topics/technology/science-instruments/index.html

Images (mentioned), Text, Credits: NASA’s Goddard Space Flight Center, by Lori Keesey/Lynn Jenner.

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