среда, 5 декабря 2018 г.

Around the World 100,000 Times

The International Space Station is a microgravity laboratory in which an international crew of six people live and work while traveling at a speed of five miles per second (or 17,500 miles per hour), orbiting Earth every 90 minutes.


Monday, May 16, marks the International Space Station’s 100,000th orbit!


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That’s more than 2,643,342,240 miles traveled! Which is also like 10 round trips to Mars, OR nearly the distance to Neptune!


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The space station has been in orbit for over 17 years, and during that time, over 1,922 research investigations have been performed. More than 1,200 scientific results publications have been produced as a result. 


Important studies like the VEGGIE experiment, which is working to grow plants in microgravity, and the Twin’s Study, which is studying the impacts of microgravity on the human body, are helping us on our journey to Mars. Using this unique orbiting laboratory as a place to conduct research is helping us learn important things for future deep space missions. 


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There have even been 222 different people that have visited the space station. This includes the current crew that is working and living on orbit. 


Did you know that the space station is the third brightest object in the sky? If you know when and where to look up, you can spot it on your own! Find out when and where to look up HERE


On Snapchat? Watch today’s Live Story to discover more about the orbiting laboratory and get a tour of the station! You can also add ‘nasa’ on Snapchat to get a regular dose of space. 


Make sure to follow us on Tumblr for your regular dose of space: http://nasa.tumblr.com


2018 December 5 Highlights of the North Winter Sky Image Credit…


2018 December 5


Highlights of the North Winter Sky
Image Credit & Copyright: Universe2go.com


Explanation: What can you see in the night sky this season? The featured graphic gives a few highlights for Earth’s northern hemisphere. Viewed as a clock face centered at the bottom, early (northern) winter sky events fan out toward the left, while late winter events are projected toward the right. Objects relatively close to Earth are illustrated, in general, as nearer to the cartoon figure with the telescope at the bottom center – although almost everything pictured can be seen without a telescope. As happens during any season, constellations appear the same year to year, and, as usual, the Geminids meteor shower will peak in mid-December. Also as usual, the International Space Station (ISS) can be seen, at times, as a bright spot drifting across the sky after sunset. Less usual, the Moon is expected to pass nearly in front of several planets in early January. A treat this winter is Comet 46P/Wirtanen, already bright, will pass only 36 lunar distances from the Earth in mid-December, potentially making it easily visible to the unaided eye.


∞ Source: apod.nasa.gov/apod/ap181205.html


The hominins of Sima de los Huesos are drawing ever closer to the Neanderthals

The Dental Anthropology Group of the Centro Nacional de Investigación sobre la Evolución Humana (CENIEH) has just published a paper on dental histology in the journal Comptes Rendus PALEVOL, in which a comparison is made for the first time between the sample from the Sima de los Huesos site, in Atapuerca (Burgos), and dental samples from the Neanderthal site of Krapina, in Croatia, as well as with different modern human populations.











The hominins of Sima de los Huesos are drawing ever closer to the Neanderthals
The Dental Anthropology Group of the CENIEH has published the first dental histology study of Sima de los Huesos,
which reinforces the close relationship between this European Middle Pleistocene population
 and the species Homo neanderthalensis [Credit: CENIEH]

This is a comparative study centering on the canines, in which certain dental pieces from Homo antecessor were included, whose results make it clear that the Pleistocene populations at Atapuerca already showed the pattern considered typically Neanderthal in their enamel and dentine volumes.
“The teeth from Sima de los Huesos exhibit large coronal and root dentine dimensions, as well as thin enamel. This histological pattern has traditionally been considered a distinctive trait of the Neanderthals, and it has allowed them to be distinguished both from other groups and from modern humans”, according to Cecilia García Campos, lead author of the paper.


Further, the results of this study might support an early appearance of this highly characteristic dental trait, which had been observed as early as 800,000 years ago in Homo antecessor, and maintained in later groups during the Middle Pleistocene.


The fossils found at Sima de los Huesos were initially considered to belong to the taxon Homo heidelbergensis, a species which populated Europe before the Neanderthals, so named from the mandible found in the locality of Heidelberg (Germany).


Nevertheless, a study led by Juan Luis Arsuaga, Centro Mixto UCM-ISCIII de Evolución y Comportamiento Humanos de Madrid, published in 2014 in the journal Science, raised doubts about this assignment, and suggested removing the population at Sima from this taxon because of its evident similarities to Homo neanderthalensis.


Later, two genetic studies of Sima de los Huesos, published in the journal Nature in 2014 and 2016, underpinned this decision by showing that these hominins belonged to the Neanderthal evolutionary lineage because of their close relationship to the ancestors of the Neanderthals.


“The dental histology results obtained for the individuals at la Sima de los Huesos support the close relationship there must have been between the Middle Pleistocene hominins at Atapuerca and the later Neanderthal groups living in Europe”, adds García Campos.


Source: CENIEH – Centro Nacional de Investigación sobre la Evolución Humana [December 01, 2018]



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Combination of space-based and ground-based telescopes reveals more than 100 exoplanets

An international team of astronomers using a combination of ground and space based telescopes have reported more than 100 extrasolar planets (here after, exoplanets) in only three months. These planets are quite diverse and expected to play a large role in developing the research field of exoplanets and life in the Universe.











Combination of space-based and ground-based telescopes reveals more than 100 exoplanets
This is an artist’s impression of the planets orbiting K2-187 [Credit: NASA/JPL-Caltech/
R. Hurt, T. Pyle (IPAC), UTokyo/J. Livingston]

Exoplanets, planets that revolve around stars other than the Sun, have been actively researched in recent years. One of the reasons is the success of the Kepler Space Telescope, which launched in 2009 to search for exoplanets. If a planet crosses (transits) in front of its parent star, then the observed brightness of the star drops by a small amount. The Kepler Space Telescope detected many exoplanets using this method.
However, such dimming phenomena could be caused by other reasons. Therefore, confirmation that the phenomena are really caused by exoplanets is very important. The Kepler space telescope experienced mechanical trouble in 2013, which led to a successor mission called K2. Astronomers around the world are competing to confirm exoplanets suggested by the K2 data.



Distribution of discovered exoplanet orbits. Small exoplanets are Mercury sized, large ones are Jupiter sized. 


The colors indicate those planets’ temperatures; blue indicates roughly Earth’s temperature; white shows


 temperatures similar to the surface of Venus; and red shows lava like temperatures 


[Credit: John H. Livingston]


An international research team involving researchers at the University of Tokyo and Astrobiology Center of the National Institutes of Natural Sciences investigated 227 K2 exoplanet candidates using other space telescopes and ground-based telescopes. They confirmed that 104 of them are really exoplanets. Seven of the confirmed exoplanets have ultra-short orbital periods less than 24 hours.
The formation process of exoplanets with such short orbital periods is still unclear. Further study of these ultra-short period planets will help to advance research into the processes behind their formation. They also confirmed many low-mass rocky exoplanets with masses less than twice that of the Earth as well as some planetary systems with multiple exoplanets.


Mr. John Livingston, a Ph.D. student at the University of Tokyo and lead author of the papers reporting the exoplanets, explains, “Although the Kepler Space Telescope has been officially retired by NASA, its successor space telescope, called TESS, has already started collecting data. In just the first month of operations, TESS has already found many new exoplanets, and it will continue to discover many more. We can look forward to many new exciting discoveries in the coming years.”


The findings are published in The Astronomical Journal.


Source: National Institutes of Natural Sciences [December 03, 2018]




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Space Station Science Highlights: Week of November 26, 2018


ISS – Expedition 57 Mission patch.


Dec. 4, 2018


After a day off for Thanksgiving, the Expedition 57 crew members headed into a busy week. They continued conducting science investigations aboard the International Space Station and prepared for arrival of SpX-16 Dragon, scheduled for launch December 4 and arrival December 6.



International Space Station (ISS). Animation Credit: NASA

A planned December 3 launch brings to the space station Expedition 58, NASA astronaut Anne McClain, Canadian Space Agency astronaut David Saint-Jacques and Oleg Kononenko of the Russian space agency Roscosmos.


Here’s a look at some of the science conducted last week aboard the orbiting lab:


Taking advantage of microgravity for crystal growth



Image above: ESA astronaut Alexander Gerst uses a uses a pipette to transfer a protein solution into the Protein Crystal Growth Card for an experiment observing protein crystals associated with Parkinson’s disease to potentially improve treatments on Earth. Image Credit: NASA.


The crew began Crystallization of Leucine-Rich Repeat Kinase 2 (LRRK2) Under Microgravity Conditions-2 (CASIS PCG 16), setting up hardware and filling card wells. CASIS PCG 16 evaluates growth of LRRK2 protein crystals in microgravity. LRRK2 is implicated in Parkinson’s disease, but crystals of the protein grown on Earth are too small and compact to study. Detailed analysis of larger, space-grown crystals can help define the protein’s exact shape and morphology and give scientists a better understanding of the disease’s pathology.


Better membranes for capturing CO2


To support the Design of Scalable Gas Separation Membranes via Synthesis Under Microgravity (Cemsica) investigation, crew members installed the Solidification Using a Baffle in Sealed Ampoules (SUBSA) in the space station’s Microgravity Science Glovebox (MSG). SUBSA offers a gradient freeze furnace that can reach 850°C for materials science investigations.


The crew finished calibrating the SUBSA facility and began processing the first Cemsica cartridge.



Image above: NASA astronaut Serena Auñón-Chancellor prepares to insert modules containing samples for the MICS experiment into the MVP platform. Image Credit: NASA.


Cemsica tests using particles of calcium-silicate (C-S) to synthesize nanoporous membranes (those with pores 100 nanometers or smaller) that can separate carbon dioxide (CO2) molecules from air or other gases. Synthesizing these materials in microgravity may resolve existing challenges in membrane manufacturing and lead to development of lower-cost, better-performing membranes.


Analyzing biofilms in spacecraft


In preparation for its return to the ground, the crew removed a Microbial Aerosol Tethering on Innovative Surfaces in the International Space Station (MATISS) sample holder. MATISS investigates the antibacterial properties of materials in space and is expected to provide insight into the mechanisms for attachment of biofilms in microgravity conditions. Bacteria tend to build up in the constantly-recycled atmosphere of the space station, and this insight has applications for future space missions.


Other work was done on these investigations:



Image above: NASA astronaut Serena Auñón-Chancellor harvests Dragoon lettuce and Red Russian Kale plants that have been growing since Oct. 25 in the Veggie plant growth facility. Part of the harvest was packed for return for ground analysis, and the rest of the harvest was made available for crew consumption. Image Credit: NASA.


– Food Acceptability examines changes in how food appeals to crew members during their time aboard the station. Acceptability of food – whether crew members like and actually eat something – may directly affect crew caloric intake and associated nutritional benefits: https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Investigation.html?#id=7562


– The Life Sciences Glovebox (LSG) is a sealed work area that accommodates life science and technology investigations in a workbench-type environment. Due to its larger size, two crew members can work in the LSG simultaneously: https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Facility.html?#id=7676


– VECTION determines to what extent an astronaut’s ability to visually interpret motion, orientation, and distance may be disrupted in a microgravity environment, and how it may adapt and be changed upon return to Earth. Multiple tests inflight and post-flight allow for investigation of the adaptation and recovery process: https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Investigation.html?#id=7484


– MVP Cell-05 investigates the complex process of cement solidification at various levels of gravity (lunar, Mars and 0.7 g). The MVP facility, used to conduct research in space with a wide variety of sample types, includes internal carousels that simultaneously can produce up to 2 g of artificial gravity: https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Investigation.html?#id=7874


– The Veg-03 investigation expands on previous validation tests of the new Veggie hardware, which crew members used to grow fresh vegetables in space. Crew members harvested Dragoon lettuce and Red Russian Kale plants growing since October 25: https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Investigation.html?#id=1159



Space to Ground: Constructive Ideas: 11/30/2018

Related links:


Expedition 57: https://www.nasa.gov/mission_pages/station/expeditions/expedition57/index.html


Expedition 58: https://www.nasa.gov/mission_pages/station/expeditions/expedition58/index.html


SpX-16 Dragon: https://www.nasa.gov/feature/space-life-and-physical-sciences-research-and-applications-spacex-16-experimentspayloads


CASIS PCG 16: https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Investigation.html?#id=7855


Cemsica: https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Investigation.html?#id=7721


SUBSA: https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Investigation.html?#id=308


MSG: https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Facility.html?#id=341


MATISS: https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Investigation.html?#id=7333


Veggie: https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Facility.html?#id=374


Spot the Station: https://spotthestation.nasa.gov/


Space Station Research and Technology: https://www.nasa.gov/mission_pages/station/research/index.html


International Space Station (ISS): https://www.nasa.gov/mission_pages/station/main/index.html


Images (mentioned), Animation (mentioned), Video (NASA), Text, Credits: NASA/Michael Johnson/Vic Cooley, Lead Increment Scientist Expeditions 57/58.


Greetings, Orbiter.chArchive link


Flight VA246: Ariane 5 lifts off from French Guiana


ARIANESPACE – Flight VA246 Mission poster.


December 4, 2018


Ariane 5 delivers for two special Arianespace partners: the space agencies of India and South Korea



Flight VA246 lift off

Arianespace’s 10th mission of 2018 orbited satellite payloads today for the Indian Space Research Organisation (ISRO) and the Korea Aerospace Research Institute (KARI), using the workhorse Ariane 5 ECA launch vehicle from Ariane Launch Complex No. 3 (ELA 3) at Guiana Space Centre in Kourou, French Guiana, on 4 December 2018, at 20:37 UTC (17:37 Guiana time).



Successful Mission Arianespace Flight VA246– GSAT-11 and GEO-KOMPSAT-2A

Designated Flight VA246 in Arianespace’s launcher family numbering system, it delivered the ISRO GSAT-11 relay platform for Ku- and Ka-band communications, along with KARI’s GEO-KOMPSAT-2A – which is to provide meteorological and space weather monitoring data.


“I want to express my deepest gratitude to two very special partners since the beginning of their space ambitions: ISRO and KARI,” said Arianespace CEO Stéphane Israël in post-launch comments from the Spaceport.


Continuing the long relationship with India’s ISRO



GSAT-11

Israël noted that GSAT-11 was the 22nd ISRO satellite orbited by Arianespace and Ariane-series launchers, tracing the relationship back to India’s APPLE small experimental communications spacecraft, which had a liftoff mass of 670-kg. and was lofted in 1981 by an Ariane 1 version. On today’s Ariane 5 mission, GSAT-11 weighed in at 5,854.6 kg. – the largest and heaviest satellite ever built by the Indian space agency.



GSAT-11 and GEO-KOMPSAT-2A satellites separation

Deployed first during Ariane 5’s 33-minute mission to geostationary transfer orbit, GSAT-11 will be positioned at 74 deg. East, providing communications services in Ku- and Ka-bands in both forward and return links. The satellite was designed and manufactured by ISRO, with its multi-spot beam coverage over the Indian mainland and nearby islands to bring significant advantages to users when compared with existing India’s INSAT/GSAT satellite systems. GSAT-11’s design lifetime is more than 15 years.


South Korea’s seventh satellite orbited by Arianespace


GEO-KOMPSAT-2A was carried in Ariane 5’s lower payload position and released second in the sequence for Flight VA246. Developed by KARI at its South Korean facility in Daejeon, this 3,507.2-kg. satellite will deliver meteorological and space weather monitoring from an orbital position of 128.2 deg. East as part of a Korean government national program.



GEO-KOMPSAT-2A

“Arianespace is proud to maintain such a close bond with South Korea,” Israël stated, adding that Flight VA246 marked the seventh time South Korea’s flag has appeared on the fairing of an Arianespace launch vehicle.



Image above: This close-up photo shows the Ariane 5 payload fairing logos for Flight VA246’s GSAT-11 and GEO-KOMPSAT-2A passengers, along with a decal for the Community of Ariane Cities and Les Mureaux.


In addition to the Ariane 5’s payload fairing logos representing Flight VA246’s two satellite passengers, also included was a decal recognizing the French city of Les Mureaux – home to the ArianeGroup site responsible for integration of Ariane 5 cryogenic main stages today, and for Ariane 6 launchers in the future. Les Mureaux is completing its year-long presidency for the Community of Ariane Cities, a non-profit association that brings together cities and their industrial companies involved in the Ariane program.


For more information about Arianespace, visit: http://www.arianespace.com/


For more information about ISRO, visit: https://www.isro.gov.in/


For more information about KARI, visit: https://www.kari.re.kr/eng.do


Images, Videos, Text, Credits: ARIANESPACE/ISRO/KARI/SciNews.


Best regards, Orbiter.chArchive link


Skeletal muscle cells – revisited – Image of the Week – August…


Skeletal muscle cells – revisited – Image of the Week – August 24, 2015


CIL:48104 – http://www.cellimagelibrary.org/images/48104


Description: Cryopreserved rabbit skeletal muscle cells were revived and stained for actin (in red) to reveal cytoskeleton and DAPI (in blue) to label nuclei.


Author: Natalie Prigozhina


Licensing: Attribution Only: This image is licensed under a Creative Commons Attribution License


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The water in Saturn’s rings and satellites is like that on Earth except for moon...

By developing a new method for measuring isotopic ratios of water and carbon dioxide remotely, scientists have found that the water in Saturn’s rings and satellites is unexpectedly like water on the Earth, except on Saturn’s moon Phoebe, where the water is more unusual than on any other object so far studied in the Solar System.











The water in Saturn's rings and satellites is like that on Earth except for moon Phoebe, which is out of this world
Above image lower left: Cassini VIMS infrared view of Saturn. Blue is infrared light where water ice reflects relatively
 brightly. Red is longer wavelength thermal emission showing heat from deep inside the planet. Green is infrared
wavelengths where aurora emit light. Above image upper right: Phoebe in visible light. Phoebe is very dark,
like charcoal whereas the rings are very bright in visible light like slightly dirty snow. Phoebe is not
 to scale relative to Saturn [Credit: NASA, JPL, VIMS Team, ISS Team,
U. Arizona, D. Machacek, U. Leicester]

The results, found in the Icarus paper “Isotopic Ratios of Saturn’s Rings and Satellites: Implications for the Origin of Water and Phoebe” by Planetary Science Institute Senior Scientist Roger N. Clark, also mean we need to change models of the formation of the Solar System because the new results are in conflict with existing models. Robert H. Brown (U. Arizona), Dale P. Cruikshank (NASA), and Gregg A. Swayze (USGS) are co-authors.
Isotopes are different forms of elements but with differing numbers of neutrons. Adding a neutron adds mass to the element, and that can change processes of how a planet, comet, or moon is formed. Water is composed of two hydrogen (H) atoms and one oxygen atom, H2O. Adding a neutron to one hydrogen atom, then called deuterium (D), increases the mass of a water molecule (HDO) by about 5 percent, and that small change results in isotopic differences in the formation of a planet, moon, or comet, and changes the evaporation of water after formation. The deuterium to hydrogen ratio (D/H) is a fingerprint of the formation conditions, including temperature and evolution over time. Evaporating water enriches deuterium in the remaining surface.


Models for the formation of the Solar System indicate that the D/H should be much higher in the colder outer Solar System than in the hotter inner system where the Earth formed. Deuterium is more abundant in cold molecular clouds. Some models predict the D/H should be 10 times higher for the Saturn system than on Earth. But the new measurements show this is not the case for Saturn’s rings and satellites except Saturn’s moon Phoebe.


The discovery of an unusual deuterium to hydrogen isotopic ratio (D/H) for Saturn’s moon Phoebe means it was formed in and comes from a far part of the Solar System, Clark said. “Phoebe’s D/H ratio is the highest value yet measured in the Solar System, implying an origin in the cold outer Solar System far beyond Saturn.”


The team also measured the carbon-13 to carbon-12 (13C/12C) ratio on Saturn’s moon Iapetus and Phoebe. Iapetus, which also has D/H similar to Earth, also has 13C/12C close to Earth’s values, but Phoebe is almost five times higher in the carbon isotope. The carbon dioxide presence places limits on how much of Phoebe could have evaporated to space after formation, leaving the only possibility that Phoebe formed in the very cold outer reaches of the Solar System, much further out than Saturn, and was subsequently perturbed into an orbit where it was captured by Saturn. Exactly how far out Phoebe originated is unknown. There are currently no measurements of D/H or 13C/12C for the icy surfaces on Pluto or Kuiper Belt objects beyond Pluto, but this new methodology will enable us to make such measurements of the surface ices.


The measurements were made from the NASA Cassini spacecraft using the Visual and Infrared Mapping Spectrometer (VIMS) over the course of the mission. An improved calibration of the instrument, completed early in 2018, enabled the precision needed for these measurements of reflected light from the rings and satellites. The new method of measuring isotopic ratios on solids like water ice and carbon dioxide ice using reflectance spectroscopy remotely will enable measurements of isotopic ratios for other objects throughout the Solar System, putting further constraints on models of Solar System formation.


The Saturn system D/H values close to the Earth’s values imply a similar water source for the inner and outer Solar System, and new models need to be developed where the change from inner to outer Solar System is less.


The NASA Europa Clipper mission could be used to measure isotopic ratios on the icy Galilean satellites around Jupiter, and Clark is a Co-Investigator on the mission and hopes to make such measurements.


Source: Planetary Science Institute [December 03, 2018]




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Billions of nanoparticles accumulate in marine organisms within six hours

The research, led by the University of Plymouth, examined the uptake of nanoparticles by a commercially important mollusc, the great scallop (Pecten maximus). After six hours exposure in the laboratory, billions of particles measuring 250nm (around 0.00025mm) had accumulated within the scallop’s intestines. However, considerably more even smaller particles measuring 20nm (0.00002mm) had become dispersed throughout the body including the kidney, gill, muscle and other organs.











Billions of nanoparticles accumulate in marine organisms within six hours
These are some of the scallops used as part of the current research
[Credit: University of Plymouth]

The study is the first to quantify the uptake of nanoparticles at predicted environmentally relevant conditions, with previous research having been conducted at far higher concentrations than scientists believe are found in our oceans.
Dr Maya Al Sid Cheikh, Postdoctoral Research Fellow at the University of Plymouth, led the study. She said: “For this experiment, we needed to develop an entirely novel scientific approach. We made nanoparticles of plastic in our laboratories and incorporated a label so that we could trace the particles in the body of the scallop at environmentally relevant concentrations. The results of the study show for the first time that nanoparticles can be rapidly taken up by a marine organism, and that in just a few hours they become distributed across most of the major organs.”


Professor Richard Thompson OBE, Head of the University’s International Marine Litter Research Unit, added: “This is a ground breaking study, in terms of both the scientific approach and the findings. We only exposed the scallops to nanoparticles for a few hours and, despite them being transferred to clean conditions, traces were still present several weeks later. Understanding the dynamics of nanoparticle uptake and release, as well as their distribution in body tissues, is essential if we are to understand any potential effects on organisms. A key next step will be to use this approach to guide research investigating any potential effects of nanoparticles and in particular to consider the consequences of longer term exposures.”











Billions of nanoparticles accumulate in marine organisms within six hours
A scan showing particles accumulated within the scallop’s gills (GI), kidney (K),
gonad (GO), intestine (I), hepatopancreas (HP) and muscle (M)
[Credit: University of Plymouth]

Accepted for publication in the Environmental Science and Technology journal, the study also involved scientists from the Charles River Laboratories in Elphinstone, Scotland; the Institute Maurice la Montagne in Canada; and Heriot-Watt University.


It was conducted as part of RealRiskNano, a £1.1million project funded by the Natural Environment Research Council (NERC). Led by Heriot-Watt and Plymouth, it is exploring the effects which microscopic plastic particles can have on the marine environment.


In this study, the scallops were exposed to quantities of carbon-radiolabeled nanopolystyrene and after six hours, autoradiography was used to show the number of particles present in organs and tissue.


It was also used to demonstrate that the 20nm particles were no longer detectable after 14 days, whereas 250nm particles took 48 days to disappear.


Ted Henry, Professor of Environmental Toxicology at Heriot-Watt University, said: “Understanding whether plastic particles are absorbed across biological membranes and accumulate within internal organs is critical for assessing the risk these particles pose to both organism and human health. The novel use of radiolabelled plastic particles pioneered in Plymouth provides the most compelling evidence to date on the level of absorption of plastic particles in a marine organism.”


Source: University of Plymouth [December 03, 2018]



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First jellyfish genome reveals ancient beginnings of complex body plan

Jellyfish undergo an amazing metamorphosis, from tiny polyps growing on the seafloor to swimming medusae with stinging tentacles. This shape-shifting has served them well, shepherding jellyfish through more than 500 million years of mass extinctions on Earth.











First jellyfish genome reveals ancient beginnings of complex body plan
Jellyfish are an ancient and successful group of animals. An in-depth look at the genome of the moon jelly, Aurita
aurelia, shows that early jellyfish likely repurposed an existing set of genes to transition between polyp
and swimming life stages [Credit: Alexander Vasenin/WikiCommons]

“Whatever they’re doing has really worked for them,” said David Gold, an assistant professor of paleobiology in the UC Davis College of Letters and Science.


The first in-depth look at the genome of a jellyfish — the moon jelly Aurelia aurita — reveals the origins of this successful survival strategy. The Aurelia genome, published online in the journal Nature Ecology and Evolution, indicates early jellyfish recycled existing genes to morph from polyp to medusa. The results suggest animals can radiate into new niches and forms fairly easily.


“These findings provide further evidence that evolution doesn’t necessarily make the genetic code more complex,” said Gold, a lead researcher on the genome study. “Jellyfish can build a big, complex life history using many of the same genes found in simpler animals.”


The research team was led equally by Gold, who performed much of the work as a postdoctoral fellow at the California Institute of Technology, and by Takeo Katsuki, a project scientist at the Kavli Institute for Brain and Mind at UC San Diego.


The genome: a multi-use tool


Jellyfish come from one of the oldest branches on the animal family tree, the phylum Cnidaria, which includes corals and anemones. Jellyfish were probably the first muscle-powered swimmers in the open ocean. They appeared in the late Precambrian Era, a period of major geologic and ecological changes that preceded the Cambrian explosion of animal life.


At some point in their evolution, jellyfish gained the ability to transition from a stationary polyp to a swimming medusa. The transition involves major changes in the jellyfish nervous system, muscles and weaponry, aka the stinging cells called cnidocytes. To accomplish this, the medusa life stage often co-opts existing developmental gene networks and cell types present in polyps, the researchers found. In addition, Aurelia appears to pattern its different life stages using many of the same genes found in animals such as fruit flies and humans, the study reports. (all of these animals share a common ancestor, albeit an ancient one.)


There is a second, more controversial explanation for what the scientists found in the jellyfish genome. Perhaps the similarities between the moon jellyfish genome and “higher” animals demonstrates that the Cnidaria originally had a medusa life stage, which animals like corals and sea anemones lost.


“Our results can’t distinguish between these two scenarios,” said Gold. If the second hypothesis turns out to be correct, “Swimming, carnivorous animals may be even older than we think.” In addition to questions of evolution, the Aurelia genome will prove valuable in many other areas of biology, Gold said. Aurelia is an important model for studying the development and function of nervous systems, and can offer insights into animal wound healing and regeneration. Moon jellies are also a major culprit in environmentally and economically damaging jellyfish blooms, which are becoming more common. For example, giant swarms of moon jellies have clogged water-intake pipes, forcing the shutdown of nuclear plants in Florida and Sweden. An improved understanding of Aurelia genetics could offer new ideas for controlling the blooms.


“In many ways, the ancient oceans in the late Precambrian are very much like what the modern oceans will look like in the near future,” Gold said “meaning studying how jellyfish evolved in the past can tell us about their potential impact on the future.”


Source: University of California – Davis [December 03, 2018]



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Not in the DNA: Evolution sans mutation discovered in single-celled archaea

University of Nebraska-Lincoln researchers have found revolutionary evidence that an evolutionary phenomenon at work in complex organisms is at play in their single-celled counterparts, too.











Not in the DNA: Evolution sans mutation discovered in single-celled archaea
The Grand Prismatic Spring of Yellowstone National Park houses heat- and acid-loving archaea
[Credit: Shutterstock]

Species most often evolve through DNA mutations inherited by successive generations. A few decades ago, researchers began discovering that multicellular species can also evolve through epigenetics: traits originating from the inheritance of cellular proteins that control access to an organism’s DNA, rather than genetic changes.


Because those proteins can respond to shifts in an organism’s environment, epigenetics resides on the ever-thin line between nature and nurture. Evidence for it had emerged only in eukaryotes, the multicellular domain of life that comprises animals, plants and several other kingdoms.


But a series of experiments from Nebraska’s Sophie Payne, Paul Blum and colleagues has shown that epigenetics can pass along extreme acid resistance in a species of archaea: microscopic, single-celled organisms that share features with both eukaryotes and bacteria.


“The surprise is that it’s in these relatively primitive organisms, which we know to be ancient,” said Blum, Charles Bessey Professor of Biological Sciences at Nebraska. “We’ve been thinking about this as something (evolutionarily) new. But epigenetics is not a newcomer to the planet.”


The team discovered the phenomenon in Sulfolobus solfataricus, a sulfur-eating species that thrives in the boiling, vinegar-acidic springs of Yellowstone National Park. By exposing the species to increasing levels of acidity over several years, the researchers evolved three strains that exhibited a resistance 178 times greater than that of their Yellowstone ancestors.


One of those strains evolved the resistance despite no mutations in its DNA, while the other two underwent mutations in mutually exclusive genes that do not contribute to acid resistance. And when the team disrupted the proteins thought to control the expression of resistance-relevant genes—leaving the DNA itself untouched—that resistance abruptly disappeared in subsequent generations.











Not in the DNA: Evolution sans mutation discovered in single-celled archaea
Sophie Payne, doctoral student in biological sciences, has co-authored a study showing that single-celled organisms known
as archaea can pass on traits even without changes in their DNA. This phenomenon, known as epigenetics, was found
in a species that eats crystalline sulfur (pictured at front) [Credit: Greg Nathan/University Communication]

“We predicted that they’d be mutated, and we’d follow the mutations, and that would teach us what caused the extreme acid resistance,” Blum said. “But that’s not what we found.”


Though epigenetics is essential to some of the most productive and destructive physiological processes in humans—the differentiation of cells into roughly 200 types, the occurrence of cancers—it remains difficult to study in eukaryotes.


The simplicity of archaea, combined with the fact that their cells resemble eukaryotes’ in some important ways, should allow researchers to investigate epigenetic questions much faster and more cheaply than was possible before, Blum said.


“We don’t know what flips the switch in humans that changes epigenetic traits,” Blum said. “And we sure don’t know how to reverse it very often. That’s the first thing we’ll go after: how to turn it on, how to turn it off, how to get it to switch. And that has benefits when you think about (managing) traits in us or traits in plants.”


Yet the discovery also raises questions, Payne said, especially about how both eukaryotes and archaea came to adopt epigenetics as a method of inheritance.


“Maybe both of them had it because they diverged from a common ancestor that had it,” said Payne, a doctoral student in biological sciences. “Or maybe it evolved twice. It’s a really interesting concept from an evolutionary perspective.”


Blum said the team is likewise curious about whether and how epigenetics might explain why no known archaea cause disease or wage antibiotic-armed warfare against their brethren, as bacteria do.


“There are no antibiotics going on in that world,” he said. “Why is that? We’re thinking (that) it’s got something to do with epigenetics, and so their interactions among each other are fundamentally different than bacteria.”


The research introduces an even broader question, Blum said.


“What was the benefit for them to have this? We don’t know.”


The team reported its findings in the journal Proceedings of the National Academy of Sciences.


Author: Scott Schrage | Source: University of Nebraska-Lincoln [December 03, 2018]



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Life has a new ingredient

Our prehistoric Earth, bombarded with asteroids and lightening, rife with bubbling geothermal pools, may not seem hospitable today. But somewhere in the chemical chaos of our early planet, life did form. How? For decades, scientists have attempted to create miniature replicas of infant Earth in the lab. There, they hunt for the primordial ingredients that created the essential building blocks for life.











Life has a new ingredient
Somewhere in the hostile environment of early Earth, life was born
[Credit: Harvard University]

It’s attractive to chase our origin story. But this pursuit can bring more than just thrill. Knowledge of how Earth built its first cells could inform our search for extraterrestrial life. If we identify the ingredients and environment required to spark spontaneous life, we could search for similar conditions on planets across our universe.


Today, much of the origin-of-life research focuses on one specific building block: RNA. While some scientists believe that life formed from simpler molecules and only later evolved RNA, others look for evidence to prove (or disprove) that RNA formed first. A complex but versatile molecule, RNA stores and transmits genetic information and helps synthesize proteins, making it a capable candidate for the backbone of the first cells.


To verify this “RNA World Hypothesis,” researchers face two challenges. First, they need to identify which ingredients reacted to create RNA’s four nucleotides–adenine, guanine, cytosine, and uracil (A, G, C, and U). And, second, they need to determine how RNA stored and copied genetic information in order to replicate itself.


So far, scientists have made significant progress finding precursors to C and U. But A and G remain elusive. Now, in a paper published in the Proceedings of the National Academy of Sciences, Jack W. Szostak, Professor of Chemistry and Chemical Biology at Harvard University, along with first-author and graduate student Seohyun (Chris) Kim suggest that RNA could have started with a different set of nucleotide bases. In place of guanine, RNA could have relied on a surrogate–inosine.


“Our study suggests that the earliest forms of life (with A, U, C, and I) may have arisen from a different set of nucleobases than those found in modern life (A, U, C, and G),” said Kim. How did he and his team arrive at this conclusion? Lab attempts to craft A and G, purine-based nucleotides, produced too many undesired side products. Recently, however, researchers discovered a way to make versions of adenosine and inosine–8-oxo-adenosine and 8-oxo-inosine–from materials available on primeval Earth. So, Kim and his colleagues set out to investigate whether RNA constructed with these analogs could replicate efficiently.


But, the substitutes failed to perform. Like a cake baked with honey instead of sugar, the final product may look and taste similar, but it doesn’t function as well. The honey-cake burns and drowns in liquid. The 8-oxo-purine RNA still performs, but it loses both the speed and accuracy needed to copy itself. If it replicates too slowly, it falls apart before completing the process. If it makes too many errors, it cannot serve as a faithful tool for propagation and evolution.


Despite their inadequate performance, the 8-oxo-purines brought an unexpected surprise. As part of the test, the team compared 8-oxo-inosine’s abilities against a control, inosine. Unlike its 8-oxo counterpart, inosine enabled RNA to replicate with high speed and few errors. It “turns out to exhibit reasonable rates and fidelities in RNA copying reactions,” the team concluded. “We propose that inosine could have served as a surrogate for guanosine in the early emergence of life.”


Szostak and Kim’s discovery could help substantiate the RNA world hypothesis. In time, their work might confirm RNA’s primary role in our origin story. Or, scientists might find that early Earth offered multiple paths for life to grow. Eventually, armed with this knowledge, scientists could identify other planets that have the essential ingredients and determine whether we share this universe or are, indeed, alone.


Source: Harvard University [December 03, 2018]



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Artificial intelligence for studying the ancient human populations of Patagonia

Argentine and Spanish researchers have used statistical techniques of automatic learning to analyze mobility patterns and technology of the hunter-gatherer groups that inhabited the Southern Cone of America, from the time they arrived about 12,000 years ago until the end of the 19th century. Big data from archaeological sites located in the extreme south of Patagonia have been used for this study.











Artificial intelligence for studying the ancient human populations of Patagonia
Atlantic Coast of Isla Grande de Tierra del Fuego, Punta Torcida sector
[Credit: Ivan Briz i Godino]

The presence of humans on the American continent dates back to at least 14,500 years ago, according to datings made at archaeological sites such as Monte Verde, in Chile’s Los Lagos Region. But the first settlers continued moving towards the southernmost confines of America.
Now, researchers from Argentina’s National Council for Scientific and Technical Research (CONICET) and two Spanish institutions (the Spanish National Research Council and the University of Burgos) have analyzed the relationships between mobility and technology developed by those societies that originated in the far south of Patagonia.











Artificial intelligence for studying the ancient human populations of Patagonia
Selk’nam people, an example of a more pedestrian group, without nautical technology, although the marine resources
were intensely exploited by those who lived near the coast [Credit: C. W. Furlong (January 1908)/
End of the World Museum (Ushuaia, Argentina)]

The study, published in the Royal Society Open Science journal, is based on an extensive database of all available archaeological evidence of human presence in this region, from the time the first groups arrived in the early Holocene (12,000 years ago) until the end of the 19th century.
This was followed by the application of machine learning techniques, a statistical system that allows the computer to learn from many data (in this case, big data from characteristic technological elements of the sites) in order to carry out classifications and predictions.











Artificial intelligence for studying the ancient human populations of Patagonia
Example of a group with nautical technology: Yámana people in the Anglican mission of Bahía Tekenika (Tierra del Fuego),
 portrayed in the late 19th or early 20th century. Darwin lived with them during the second voyage of the Beagle
[Credit: Ivan Briz i Godino/Archives of the South American Missionary Society (United Kingdom)]

“It is by means of automatic classification algorithms that we have identified two technological packages or ‘landscapes’: one that characterizes pedestrian hunter-gatherer groups (with their own stone and bone tools) and the other characterizing those that had nautical technology, such as canoes, harpoons and mollusc shells used to make beads,” explains Ivan Briz i Godino, an archaeologist of the National Council for Scientific and Technical Research (CONICET) of Argentina and co-author of the work.
“In future excavations, when sets of technological elements such as those we have detected appear, we’ll be able to directly deduce the type of mobility of the group or the connections with other communities,” adds Briz.











Artificial intelligence for studying the ancient human populations of Patagonia
Technological landscapes of nautical mobility (red circles, with some blues that are less well classified by the algorithm)
and pedestrian mobility (orange and purple circles) in hunter-gatherer groups that lived
 in the extreme south of South America [Credit: Briz et al. 2018]

The results of the study have also made it possible to obtain maps with the settlements of the two communities, and this, in turn, has made it possible to locate large regions in which they interacted and shared their technological knowledge. In the case of groups with nautical technology, it has been confirmed that they arrived at around the beginning of the Mid-Holocene (some 6,000 years ago) from the channels and islands of the South Pacific, moving along the coast of what is now Chile.
“Traditional archaeology identifies sites, societies and their possible contacts on the basis of specific elements selected by specialists (such as designs of weapon tips or decorative elements), but here we show that it is more interesting to analyse sets of technological elements as a whole, using artificial intelligence techniques that allow us to work with large data volumes and without subjective prejudices,” concludes Briz.


Source: FECYT – Spanish Foundation for Science and Technology [December 03, 2018]



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Four Cool Facts About Our New Rocket’s Booster Test Firing

The

countdown to our last full-scale test firing of NASA’s Space Launch System (SLS) solid rocket boosters has begun

(mark your calendars: June 28, 8:05 a.m. MDT [local time] 10:05 a.m. EDT). SLS is NASA’s new rocket that

can go to deep space destinations, and this test is one more step on our

Journey to Mars. This test will be broadcast live on NASA TV

and our Facebook

page. For those watching at home or work, here are four cool things that might

not be so obvious on the screen.


1. So Hot, It Turns Sand Into

Glass


image

With

expanding gases and flames exiting the nozzle at speeds in excess of Mach 3 and

temperatures reaching 3,700 degrees Fahrenheit, say goodbye to some of the sand

at Orbital ATK’s test facility in the Utah desert because after the test, the

sand at the aft, or rear, end of the booster motor will be glass.


2. This Motor’s Chill



This

motor has been chilling — literally, down to 40 degrees — since the first week

in May in Orbital ATK’s “booster house,” a special building on rails that moves

to enclose the booster and rolls back so the motor can be test-fired. Even

though SLS will launch from the normally balmy Kennedy Space Center in Florida,

temperatures can vary there and engineers need to be sure the booster will

perform as expected whether the propellant inside the motor is 40 degrees or 90

degrees (the temperature of the propellant during the first full-scale test,

Qualification Motor 1 or QM-1).


3. This Booster’s on Lockdown


image

If you

happen to be near Promontory, Utah, on June 28, you can view the test for

yourself in the public viewing area off State Route 83. And don’t worry, this

booster’s not going anywhere — engineers have it locked down. The motor is held

securely in place by Orbital ATK’s T-97 test stand.  During the test, the motor will push against a

forward thrust block with more than three million pounds of force. Holding down

the rocket motor is more than 13 million pounds of concrete — most of which is

underground. The test stand contains a system of load cells that enable

engineers to measure the thrust the motor produces and verify their

predictions.


4. Next Time, It’s For Real


image

These

solid rocket boosters are the largest and most powerful ever built for flight.

They’ve been tested and retested in both full-scale and smaller subsystem-level

tests, and vital parts like the nozzle, insulation and avionics control systems

have been upgraded and revamped. Most of this work was necessary because,

plainly put, SLS needs bigger boosters. Bigger boosters mean bolder missions –

like around the moon during the first integrated mission of SLS and Orion. So

the next time we see these solid rocket motors fire, they will be propelling

SLS off the launch pad at Kennedy Space Center and on its first flight with NASA’s

Orion spacecraft.
For

real.


Marble Caves | #Geology #GeologyPage #Cave #MarbleCaves #Chile…


Marble Caves | #Geology #GeologyPage #Cave #MarbleCaves #Chile #Argentina


The Marble Caves is geological formation of unusual beauty. These caves have formed in a pure marble and are bathed in the deep blue water of General Carrera Lake


Read more & More Photos: http://www.geologypage.com/2016/06/marble-caves.html


Geology Page

www.geologypage.com

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Amethyst | #Geology #GeologyPage #Mineral Locality: Piedra…


Amethyst | #Geology #GeologyPage #Mineral


Locality: Piedra Parado, Veracruz, Mexico

Size: 2.5 × 1.7 × 1.7 cm


Photo Copyright © SystematicXX /e-rocks.com


Geology Page

www.geologypage.com

https://www.instagram.com/p/Bq-sBN8Fa_P/?utm_source=ig_tumblr_share&igshid=192nhnk1iauae


Rainbow Brain Rows Thousands of nerve cells (neurons)…


Rainbow Brain Rows



Thousands of nerve cells (neurons) waggling around behind our developing eyes somehow connect precisely with specific neurons in the brain. This amazing feat of wiring is challenging to untangle in humans. Thankfully, the nervous system of the fruit fly (partly pictured here) works in a similar way to our own, but is much easier to investigate. On the left, two different types of neuron in the fly’s imaginal disc (its developing eye) have been genetically-modified to glow as green and red blobs. They develop at different rates – each neuron’s age is vital information used to connect it to the correct area of the brain (blue, right). Sequoia, a protein inside each neuron, organises the neurons by age, producing neat curved layers of red and green connections. These layers will eventually ‘plug in’ to specific brain regions, bringing vision to the fly, and perhaps a glimpse into our own development.


Written by John Ankers




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Dragon Launch Slips One Day as New Crew Moves In


ISS – Expedition 57 Mission patch.


December 4, 2018


The launch of the SpaceX Dragon cargo vessel slipped one day to Wednesday at 1:16 p.m. EST with meteorologists forecasting 90% favorable weather for launch. Meanwhile, the newest crew members aboard the International Space Station are getting used to their new home in space.



Image above: Expedition 57 Commander Alexander Gerst of ESA (European Space Agency) peers out the International Space Station’s “window to the world,” the seven-windowed cupola. Just outside the cupola are two spacecraft including the Soyuz MS-09 crew craft and Northrop Grumman’s Cygnus cargo craft with one of its cymbal-shaped UltraFlex solar arrays featuring prominently in the frame. Image Credit: NASA.


Dragon’s 16th mission to the orbital lab will deliver almost 5,700 pounds of science, crew supplies and hardware. The commercial space freighter is due to arrive at the station Saturday when astronauts Alexander Gerst and Serena Auñón-Chancellor will command the Canadarm2 to grapple Dragon around 6 a.m.


New station crew members Oleg Kononenko, Anne McClain and David Saint-Jacques are in their second day aboard the station. The trio are familiarizing themselves with station systems and safety procedures today. They began their mission Monday when they launched aboard the Soyuz MS-11 spacecraft at 6:31 a.m. and docked just six hours and two minutes later to the Poisk module. The new crew will stay in space until June.



Image above: Sunrise over Austral Ocean, seen by EarthCam on ISS, speed: 27’558 Km/h, altitude: 404,19 Km, image captured by Roland Berga (on Earth in Switzerland) from International Space Station (ISS) using ISS-HD Live application with EarthCam’s from ISS on December 4, 2018 at 18:35 UTC. Image Credits: Orbiter.ch Aerospace/Roland Berga.


Expedition 57 Commander Alexander Gerst is getting for his return to Earth on Dec. 20 and began packing his personal items today. He’ll wrap up his mission with Flight Engineers Serena Auñón-Chancellor and Sergey Prokopyev and land in Kazakhstan inside the Soyuz MS-09 crew ship after six-and-a-half months in space.


Related links:


Expedition 57: https://www.nasa.gov/mission_pages/station/expeditions/expedition57/index.html


SpaceX Dragon: https://www.nasa.gov/spacex


Space Station Research and Technology: https://www.nasa.gov/mission_pages/station/research/index.html


International Space Station (ISS): https://www.nasa.gov/mission_pages/station/main/index.html


Images (mentioned), Text, Credits: NASA/Marck Garcia/Orbiter.ch Aerospace/Roland Berga.


Best regards, Orbiter.chArchive link


Galileo satellites prove Einstein’s Relativity Theory to highest accuracy yet


ESA – Galileo Programme logo.


4 December 2018


Europe’s Galileo satellite navigation system – already serving users globally – has now provided a historic service to the physics community worldwide, enabling the most accurate measurement ever made of how shifts in gravity alter the passing of time, a key element of Einstein’s Theory of General Relativity.



Galileos measure Einsteinian time dilation

Two European fundamental physics teams working in parallel have independently achieved about a fivefold improvement in measuring accuracy of the gravity-driven time dilation effect known as ‘gravitational redshift’.


The prestigious Physical Review Letters journal has just published the independent results obtained from both consortiums, gathered from more than a thousand days of data obtained from the pair of Galileo satellites in elongated orbits.


 “It is hugely satisfying for ESA to see that our original expectation that such results might be theoretically possible have now been borne out in practical terms, providing the first reported improvement of the gravitational redshift test for more than 40 years,” comments Javier Ventura-Traveset, Head of ESA’s Galileo Navigation Science Office.



Time shift in billionths of a second

“These extraordinary results have been made possible thanks to the unique features of the Galileo satellites, notably the very high stabilities of their onboard atomic clocks, the accuracies attainable in their orbit determination and the presence of laser-retroreflectors, which allow for the performance of independent and very precise orbit measurements from the ground, key to disentangle clock and orbit errors.”


 These parallel research activities, known as GREAT (Galileo gravitational Redshift Experiment with eccentric sATellites), were led respectively by the SYRTE Observatoire de Paris in France and Germany’s ZARM Center of Applied Space Technology and Microgravity, coordinated by ESA’s Galileo Navigation Science Office and supported through its Basic Activities.


Happy results from an unhappy accident


These findings are the happy outcome of an unhappy accident: back in 2014 Galileo satellites 5 and 6 were stranded in incorrect orbits by a malfunctioning Soyuz upper stage, blocking their use for navigation. ESA flight controllers moved into action, performing a daring salvage in space to raise the low points of the satellites’ orbits and make them more circular.



Incorrect orbits

Once the satellites achieved views of the whole Earth disc their antennas could be locked on their homeworld and their navigation payloads could indeed be switched on. The satellites are today in use as part of Galileo search and rescue services while their integration as part of nominal Galileo operations is currently under final assessment by ESA and the European Commission.


However, their orbits remain elliptical, with each satellite climbing and falling some 8500 km twice per day. It was these regular shifts in height, and therefore gravity levels, which made the satellites so valuable to the research teams.


Reenacting Einstein’s prediction


Albert Einstein predicted a century ago that time would pass more slowly close to a massive object, a finding that has since been verified experimentally several times – most significantly in 1976 when a hydrogen maser atomic clock on the Gravity Probe-A suborbital rocket was launched 10 000 km into space, confirming Einstein’s prediction to within 140 parts per million.



Albert Einstein

In fact, atomic clocks aboard navigation satellites must already take into account the fact that they run faster up in orbit than down on the ground – amounting to a few tenths of a microsecond per day, which would result in navigation errors of around 10 km daily, if uncorrected.


The two teams relied upon the stable timekeeping of the passive hydrogen maser (PHM) clocks aboard each Galileo – stable to one second in three million years – and kept from drifting by the worldwide Galileo ground segment.


“The fact that the Galileo satellites carry passive hydrogen maser clocks, was essential for the attainable accuracy of these tests,” noted Sven Hermann at the University of Bremen’s ZARM Center of Applied Space Technology and Microgravity.



Gravity Probe A

“While every Galileo satellite carries two rubidium and two hydrogen maser clocks, only one of them is the active transmission clock. During our period of observation, we focus then on the periods of time when the satellites were transmitting with PHM clocks and assess the quality of these precious data very carefully. Ongoing improvements in the processing and in particular in the modelling of the clocks, might lead to tightened results in the future.”


Refining the results


A key challenge over three years of work was to refine the gravitational redshift measurements by eliminating systematic effects such as clock error and orbital drift due to factors such as Earth’s equatorial bulge, the influence of Earth’s magnetic field, temperature variations and even the subtle but persistent push of sunlight itself, known as ‘solar radiation pressure’.




Day of Galileo observations

“Careful and conservative modelling and control of these systematic errors has been essential, with stabilities down to four picoseconds over the 13 hours orbital period of the satellites; this is four millionth of one millionth of a second,” Pacôme Delva of SYRTE Observatoire de Paris.


“This required the support of many experts, with notably the expertise of ESA thanks to their knowledge of the Galileo system.”



Passive Hydrogen Maser atomic clock

Precise satellite tracking was enabled by the International Laser Ranging Service, shining lasers up to the Galileos’ retro-reflectors for centimetre-scale orbital checks.



Laser ranging station

Major support was also received from the Navigation Support Office based at ESA’s ESOC operations centre in Germany, whose experts generated the reference stable clock and orbit products for the two Galileo eccentric satellites and also determined the residual errors of the orbits after the laser measurements.


Related article:


Salvaged Galileos to help satnav specialists find their way
https://orbiterchspacenews.blogspot.com/2016/08/salvaged-galileos-to-help-satnav.html


Related links:


Physical Review Letters: https://journals.aps.org/prl/highlights


SYRTE Observatoire de Paris: https://syrte.obspm.fr/


ZARM Center of Applied Space Technology and Microgravity: https://zarm.uni-bremen.de/en/


International Laser Ranging Service: https://ilrs.cddis.eosdis.nasa.gov/


Navigation Support Office: http://www.esa.int/Our_Activities/Operations/gse/ESA_Navigation_Support_Office


Navigation: http://www.esa.int/Our_Activities/Navigation


Galileo: http://www.esa.int/Our_Activities/Navigation/Galileo


Images, Text, Credits: ESA/P. Carril/Wikimedia Commons/G. Porter/ESOC Navigation Support Office/Dr Erik Schoenemann/Dr Javier Ventura-Traveset/ZARM Center of Applied Space Technology and Microgravity/Dr Sven Hermann.


Best regards, Orbiter.chArchive link


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