среда, 31 октября 2018 г.

Paleontologists discovered six new species in the East African…

Paleontologists discovered six new species in the East African Rift http://www.geologypage.com/2018/10/paleontologists-discovered-six-new-species-in-the-east-african-rift.html

Most Detailed Observations of Material Orbiting close to a Black Hole

 PR Image eso1835a

Simulation of Material Orbiting close to a Black Hole

PR Image eso1835b

Sagittarius A* in the constellation of Sagittarius

PR Image eso1835c

Wide-field view of the centre of the Milky Way

PR Image eso1835d

The centre of the Milky Way*


ESOcast 181 Light: Most Detailed Observations of Material Orbiting close to a Black Hole (4K UHD)

ESOcast 181 Light: Most Detailed Observations of Material Orbiting close to a Black Hole (4K UHD)

Simulation of Material Orbiting close to a Black Hole

Simulation of Material Orbiting close to a Black Hole

Zooming into Sagittarius A*

Zooming into Sagittarius A*

Simulation of the orbits of stars around the black hole at the centre of the Milky Way

Simulation of the orbits of stars around the black hole at the centre of the Milky Way

ESO’s GRAVITY instrument confirms black hole status of the Milky Way centre

ESO’s exquisitely sensitive GRAVITY instrument has added further evidence to the long-standing assumption that a supermassive black hole lurks in the centre of the Milky Way. New observations show clumps of gas swirling around at about 30% of the speed of light on a circular orbit just outside its event horizon — the first time material has been observed orbiting close to the point of no return, and the most detailed observations yet of material orbiting this close to a black hole.

ESO’s GRAVITY instrument on the Very Large Telescope (VLT) Interferometer has been used by scientists from a consortium of European institutions, including ESO [1], to observe flares of infrared radiation coming from the accretion disc around Sagittarius A*, the massive object at the heart of the Milky Way. The observed flares provide long-awaited confirmation that the object in the centre of our galaxy is, as has long been assumed, a supermassive black hole. The flares originate from material orbiting very close to the black hole’s event horizon — making these the most detailed observations yet of material orbiting this close to a black hole.

While some matter in the accretion disc — the belt of gas orbiting Sagittarius A* at relativistic speeds [2] — can orbit the black hole safely, anything that gets too close is doomed to be pulled beyond the event horizon. The closest point to a black hole that material can orbit without being irresistibly drawn inwards by the immense mass is known as the innermost stable orbit, and it is from here that the observed flares originate.

It’s mind-boggling to actually witness material orbiting a massive black hole at 30% of the speed of light,” marvelled Oliver Pfuhl, a scientist at the MPE. “GRAVITY’s tremendous sensitivity has allowed us to observe the accretion processes in real time in unprecedented detail.

These measurements were only possible thanks to international collaboration and state-of-the-art instrumentation [3]. The GRAVITY instrument which made this work possible combines the light from four telescopes of ESO’s VLT to create a virtual super-telescope 130 metres in diameter, and has already been used to probe the nature of Sagittarius A*.

Earlier this year, GRAVITY and SINFONI, another instrument on the VLT, allowed the same team to accurately measure the close fly-by of the star S2 as it passed through the extreme gravitational field near Sagittarius A*, and for the first time revealed the effects predicted by Einstein’s general relativity in such an extreme environment. During S2’s close fly-by, strong infrared emission was also observed.

We were closely monitoring S2, and of course we always keep an eye on Sagittarius A*,”  explained Pfuhl. “During our observations, we were lucky enough to notice three bright flares from around the black hole — it was a lucky coincidence!

This emission, from highly energetic electrons very close to the black hole, was visible as three prominent bright flares, and exactly matches theoretical predictions for hot spots orbiting close to a black hole of four million solar masses [4]. The flares are thought to originate from magnetic interactions in the very hot gas orbiting very close to Sagittarius A*.

Reinhard Genzel, of the Max Planck Institute for Extraterrestrial Physics (MPE) in Garching, Germany, who led the study, explained: “This always was one of our dream projects but we did not dare to hope that it would become possible so soon.” Referring to the long-standing assumption that Sagittarius A* is a supermassive black hole, Genzel concluded that “the result is a resounding confirmation of the massive black hole paradigm.


[2] Relativistic speeds are those which are so great that the effects of Einstein’s Theory of Relativity become significant. In the case of the accretion disc around Sagittarius A*, the gas is moving at roughly 30% of the speed of light.

[3] GRAVITY was developed by a collaboration consisting of the Max Planck Institute for Extraterrestrial Physics (Germany), LESIA of Paris Observatory–PSL/CNRS/Sorbonne Université/Univ. Paris Diderot and IPAG of Université Grenoble Alpes/CNRS (France), the Max Planck Institute for Astronomy (Germany), the University of Cologne (Germany), the CENTRA–Centro de Astrofísica e Gravitação (Portugal) and ESO.

[4] The solar mass is a unit used in astronomy. It is equal to the mass of our closest star, the Sun, and has a value of 1.989 × 1030 kg. This means that Sgr A* has a mass 1.3 trillion times greater than the Earth.

More Information

This research was presented in a paper entitled “Detection of Orbital Motions Near the Last Stable Circular Orbit of the Massive Black Hole SgrA*”, by the GRAVITY Collaboration, published in the journal Astronomy & Astrophysics on 31 October 2018.

The GRAVITY Collaboration team is composed of: R. Abuter (ESO, Garching, Germany), A. Amorim (Universidade de Lisboa, Lisbon, Portugal), M. Bauböck (Max Planck Institute for Extraterrestrial Physics, Garching, Germany [MPE]), J.P. Berger (Univ. Grenoble Alpes, CNRS, IPAG, Grenoble, France [IPAG]; ESO, Garching, Germany), H. Bonnet (ESO, Garching, Germany), W. Brandner (Max Planck Institute for Astronomy, Heidelberg, Germany [MPIA]), Y. Clénet (LESIA, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Universités, UPMC Univ. Paris 06, Univ. Paris Diderot, Meudon, France [LESIA])), V. Coudé du Foresto (LESIA), P. T. de Zeeuw (Sterrewacht Leiden, Leiden University, Leiden, The Netherlands; MPE), C. Deen (MPE), J. Dexter (MPE), G. Duvert (IPAG), A. Eckart (University of Cologne, Cologne, Germany; Max Planck Institute for Radio Astronomy, Bonn, Germany), F. Eisenhauer (MPE), N.M. Förster Schreiber (MPE), P. Garcia (Universidade do Porto, Porto, Portugal; Universidade de Lisboa Lisboa, Portugal), F. Gao (MPE), E. Gendron (LESIA), R. Genzel (MPE; University of California, Berkeley, California, USA), S. Gillessen (MPE), P. Guajardo (ESO, Santiago, Chile), M. Habibi (MPE), X. Haubois (ESO, Santiago, Chile), Th. Henning (MPIA), S. Hippler (MPIA), M. Horrobin (University of Cologne, Cologne, Germany), A. Huber (MPIA), A. Jimenez Rosales (MPE), L. Jocou (IPAG), P. Kervella (LESIA; MPIA), S. Lacour (LESIA), V. Lapeyrère (LESIA), B. Lazareff (IPAG), J.-B. Le Bouquin (IPAG), P. Léna (LESIA), M. Lippa (MPE), T. Ott (MPE), J. Panduro (MPIA), T. Paumard (LESIA), K. Perraut (IPAG), G. Perrin (LESIA), O. Pfuhl (MPE), P.M. Plewa (MPE), S. Rabien (MPE), G. Rodríguez-Coira (LESIA), G. Rousset (LESIA), A. Sternberg (School of Physics and Astronomy, Tel Aviv University, Tel Aviv, Israel, Center for Computational Astrophysics, Flatiron Institute, New York, USA), O. Straub (LESIA), C. Straubmeier (University of Cologne, Cologne, Germany), E. Sturm (MPE), L.J. Tacconi (MPE), F. Vincent (LESIA), S. von Fellenberg (MPE), I. Waisberg (MPE), F. Widmann (MPE), E. Wieprecht (MPE), E. Wiezorrek (MPE), J. Woillez (ESO, Garching, Germany), S. Yazici (MPE; University of Cologne, Cologne, Germany).

ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It has 16 Member States: Austria, Belgium, the Czech Republic, Denmark, France, Finland, Germany, Ireland, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom, along with the host state of Chile and with Australia as a Strategic Partner. 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 and its world-leading Very Large Telescope Interferometer as well as two survey telescopes, VISTA working in the infrared and the visible-light VLT Survey Telescope. ESO is also a major partner in two facilities on Chajnantor, APEX and ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre Extremely Large Telescope, the ELT, which will become “the world’s biggest eye on the sky”.



Oliver Pfuhl

Max Planck Institute for Extraterrestrial Physics

Garching bei München, Germany

Tel: +49 89 30 000 3295

Jason Dexter

Max Planck Institute for Extraterrestrial Physics

Garching bei München, Germany

Tel: +49 89 30 000 3324

Thibaut Paumard

CNRS Researcher

Observatoire de Paris, France

Tel: +33 145 077 5451

Xavier Haubois

ESO Astronomer

Santiago, Chile

Tel: +56 2 2463 3055

IR Group Secretariat

Max Planck Institute for Extraterrestrial Physics

Garching bei München, Germany

Tel: +49 89 30000 3880

Source: ESO/News

Archive link

2018 October 31 R Leporis: A Vampire’s Star Image Credit…

2018 October 31

R Leporis: A Vampire’s Star
Image Credit & Copyright: Martin Pugh

Explanation: Better known as Hind’s Crimson Star, R Leporis is a rare star in planet Earth’s night sky. It’s also a shocking shade of red. The star’s discoverer, 19th century English astronomer John Russell Hind, reported that it appeared in a telescope “… like a drop of blood on a black field.” Located 1,360 light-years away in the constellation Lepus the star is a Mira-type variable, changing its brightness over a period of about 14 months. R Leporis is now recognized as a carbon star, a very cool and highly evolved red giant with an extreme abundance of carbon. Extra carbon in carbon stars is created by helium fusion near the dying stellar core and dredged up into the stars’ outer layers. The dredge-up results in an overabundance of simple carbon molecules, like CO, CH, CN, and C2. While it’s true that cool stars radiate most of their energy in red and infrared light, the carbon molecules strongly absorb what little blue light is left and give carbon stars an exceptionally deep red color. R Leporis is losing its carbon-rich atmosphere into the surrounding interstellar material through a strong stellar wind though, and could be near the transition to a planetary nebula. Oh, and Happy Halloween from the folks at APOD.

∞ Source: apod.nasa.gov/apod/ap181031.html

Trefignath Prehistoric Burial Chambers, Anglesey, North Wales, 20.10.18.A series of...

Trefignath Prehistoric Burial Chambers, Anglesey, North Wales, 20.10.18.

A series of chambers on a single site in use over an extended period of time, likely over a thousand years.

Source link

Evolution does repeat itself after all: How evolution lets stripes come and go

A team of evolutionary biologists from the University of Konstanz, headed by Prof. Dr. Axel Meyer, discovers the genetic basis for the repeated evolution of colour patterns. The findings about the stripes of the especially diverse species of East-African cichlid fishes explain how evolution can repeat itself at record speed. The study is published in Science magazine.

Evolution does repeat itself after all: How evolution lets stripes come and go
Pundamilia nyererei fish from Lake Victoria that has been altered using CRISPR-Cas as ‘gene scissors’.
The fish demonstrates horizontal stripes on its flank as a result of the genetic alteration
[Credit: Claudius Kratochwil]

Why does evolution repeat itself? What happens genetically during these repetitions? Do the same or other genes and mechanisms produce organisms that look similar? Professor Axel Meyer and his team from Konstanz University have come closer to answering this question that is as old as it is important. The answer is quite astonishing. They studied a special colour pattern that is omnipresent among all kinds of animals: horizontal stripes. The researchers were able to identify the basis of the repeated evolution of these stripes with modern methods in genomics and molecular biology and verified them with a CRISPR-Cas mutant fish that added a stripe.
More than 1200 types of colourful cichlid can be found in the large African lakes Malawi, Victoria and Tanganjika. Not only are they very diverse in colours, they also have numerous colour patterns such as horizontal or vertical stripes. “But that’s not all” explains Axel Meyer, “cichlids are prime examples of evolution. They are extremely diverse in terms of social behaviour, body shape, colour pattern and many other biological aspects, but at the same time certain features repeatedly evolved independently in the different lakes.”

This principle of repeated evolution — biologists term it convergent evolution — makes cichlids the perfect target to study the genetic basis of this phenomenon. If similar colours and body shapes have emerged in several evolutionary lines independently from each other this means that evolution reacted to similar environmental conditions in the same way. The question now is: When evolution repeats itself, how does this work genetically?

Evolution does repeat itself after all: How evolution lets stripes come and go
Colourful cichlids with horizontal stripes living in the large African lakes Malawi, Victoria and Tanganjika
illustrate the repeating (convergent) process of evolution [Credit: Claudius Kratochwil]

Which gene and which genetic mechanism are responsible for the cichlids’ stripes to come and go has now been reconstructed in the laboratory through genome analyses, breeding and experiments, including CRISPR-Cas as “gene scissors.” Dr Claudius Kratochwil, early career researcher in Professor Meyers team and first author of the study in Science, explains: “In breeding experiments we can exactly determine on which of the 22 chromosomes, even on which area of the chromosome of the fish, the genetic instruction for stripes is located.”
The relevant gene on this chromosome part is called agrp2. This “stripe gene,” its origin and distribution in other African lakes was described in comparative molecular studies. From an evolutionary point of view, the cichlids’ stripes are rather unstable. Over the course of a few million years, they have been lost and re-emerged in the African lakes many times over. As these species (with and without stripes) are so young, they can be interbred in aquaria. Breeding and examining the cichlids with and without stripes in the laboratory shows that all cichlids carry the “stripes gene,” but the switches (regulatory elements) of this gene differ.

“This genetic switch causes the gene in species without stripes to be more activated. As a result, a lot of protein is produced. The “stripes gene” agrp2 works as a “stripes inhibitor”: if gene production is high, stripes will be suppressed, if production is low, they will remain. The researchers were able to demonstrate this by using modern genetic methods. “If we use CRISPR-Cas to remove the gene from the genome of a species without stripes,” Kratochwil explains, “then even a “stripeless” fish will suddenly develop stripes, as we showed with a CRISPR-Cas mutant fish. This proves that the stripes gene is the decisive genetic factor.”

Evolution does repeat itself after all: How evolution lets stripes come and go
The especially colourful Haplochromis chilotes fish from Lake Victoria exhibits both horizontal
and vertical stripes [Credit: Claudius Kratochwil]

The latest findings on this genetic mechanism, the activation or deactivation of stripes by the “stripes gene,” were published in the current issue of Science magazine. Interestingly, the cichlid’s agrp2 gene is a copy of the agouti gene in mammals, which is responsible for the different coat colours of cats, dogs, horses and striped baby birds.
“The world of animals might be much less colourful without the agouti gene family,” reflects Claudius Kratochwil. The mechanism of the “stripes gene” in cichlids clearly makes repeated evolution possible within the briefest of times, relatively speaking. If characteristics are lost during evolution, usually this loss is forever, as the Belgian palaeontologist Louis Dollo already realized exactly 125 years ago, and wrote up his conclusions in “Dolls Law” in 1893.

The special aspect of the stripes gene agrp2 is that it makes repeated evolution of a characteristic possible in a simple way. If a cichlid loses its stripes that does not mean they will never return or vice versa. These molecular-biological studies also show that palaeontological rules and evolutionary rules have to be questioned once again.

Source: University of Konstanz [October 25, 2018]



A single genetic switch changes butterfly wing colour

Heliconius butterflies are a diverse and colorful group of species that live throughout tropical regions of Central and South America. Many of them have wing patterns and colors that mimic other species to protect themselves from predators, and new research by scientists from the University of Chicago shows that in one species, Heliconius cydno, just one gene controls whether the butterfly has white or yellow spots on its wings.

A single genetic switch changes butterfly wing colour
Heliconius cydno butterflies have either white or yellow markings on their wings,
which is controlled by a single gene [Credit: Kat Carlton, UChicago]

To conduct the study, published Current Biology, the researchers developed a genetic map using white and yellow H. cydno butterflies. They then studied genome sequences to identify a single gene called aristaless1 (al1) that acted as a switch for yellow and white coloration.
Most Heliconius species closely related to H. cydno have yellow spots on their wings; H. cydno has subspecies that are either yellow or white. The researchers saw that the butterflies with white spots have elevated expression of al1 (i.e. it’s switched “on”), meaning that it may play a role in repressing yellow pigmentation from being produced. Using CRISPR/Cas9 gene editing tools, the scientists confirmed this function of al1. When they knocked it out (or switched it off) in embryos of butterflies that should be white, those butterflies developed yellow spots instead.

“For decades people have been cross-breeding these butterflies and they knew that this white vs. yellow switch was in one spot in the genome. They just weren’t able to trace it to the actions of a single gene,” said Marcus Kronforst, Ph.D., associate professor of ecology and evolution and senior author of the study.

A single genetic switch changes butterfly wing colour
Heliconius cydno butterflies have either white or yellow markings on their wings,
which is controlled by a single gene [Credit: Kat Carlton, UChicago]

“Now with CRISPR we can knock the gene out and see what happens. It turns out the evolutionary innovation here is not one species gaining a pigment, but instead turning on a gene to repress an ancestrally present pigment,” he said.
Kronforst and his team also traced the evolutionary history this color patterning by comparing genetic differences in the H. cydno version of al1 to those of other, closely-related Heliconius species. The white version of the gene appears to be a relatively new development. While H. cydno was the first species to develop white forms, there are signs of cross-breeding that introduced the white color into other species at a later time.

There is also evidence that the same gene may be linked to mating preferences for color. White H. cydno males prefer females with white spots; yellow males likewise prefer yellow females. Scientists have long known that genes for both color patterning and mate preference in H. cydno are located in the same area of the genome.

“Now that we know the molecular basis of the color, we can start asking how preference is linked to it,” Kronforst said. “Are they two genes near one another or is it somehow the same gene doing both jobs?”
While Kronforst and his team don’t yet know if mate preference is controlled by al1 or another gene nearby, the close proximity could account for the diversity of Heliconius species.

“Whether it was natural selection driving it or it was just chance that these two things are linked, that might be part of the reason why we have such a diverse group of butterflies,” he said. “When the color and preference for the color are linked together, it causes these things to evolve together very rapidly.”

Source: University of Chicago Medical Center [October 25, 2018]



Antarctic Ocean carbon dioxide helped end the Ice Age

A team of scientists, led by the University of St Andrews, has shown that rapid CO2 release from the ocean around Antarctica helped end the last ice age.

Antarctic Ocean carbon dioxide helped end the Ice Age
Deep sea coral – data was generated on deep sea corals from 1000m below the sea surface
 in the Antarctic Ocean [Credit: University of Bristol]

The findings published in Nature, found that CO2 was stored in the deep Southern Ocean during the last ice age and then released into the atmosphere as the ice age ended, linked to pulses of rapid climate change and melting sea ice.

The new study, led by Dr. James Rae from the School of Earth and Environmental Sciences at the University of St Andrews, provides crucial evidence of the processes that controlled CO2 and climate during ice ages. Although scientists have long-known that CO2 rise helped end the last ice age, its cause has remained a mystery.

Lead researcher Dr. Rae said: “Many scientists suspected that the ocean round Antarctica was responsible for changing CO2 levels during ice ages, but there’s not previously been data that directly proved this.”

Using samples of fossil deep sea corals, brought up from 1000 metres below the sea surface, Dr. Rae and his team made chemical measurements that allowed them to reconstruct the CO2 content of the deep ocean. The researchers found that the deep ocean CO2 record was the “mirror image” of CO2 in the atmosphere, with the ocean storing CO2 during an ice age and releasing it back to the atmosphere during deglaciation.

Antarctic Ocean carbon dioxide helped end the Ice Age
New data on the pH of the deep ocean in the past allow scientists to track
CO2 loss from the ocean to the atmosphere at the end of the last ice age
[Credit: University of Bristol]

“CO2 rise during the last ice age occurs in a series of steps and jumps associated with intervals of rapid climate change,” explained Professor Laura Robinson from the University of Bristol, who collected the samples from the Southern Ocean. “Deep sea corals capture information about these climate changes in the chemistry of their skeletons but are hard to find.”

To bring back these important samples, the team spent months in the freezing waters of the Drake Passage, between South America and Antarctica. “Most people think of corals as tropical creatures, but they also live deep beneath the waves in some of the world’s most extreme deep-sea environments,” said Dr. Andrea Burke from the University of St Andrews, who was part of the mission.

As well as helping scientists better understand the ice ages, the new findings also provide context to current CO2 rise and climate change. “Although the CO2 rise that helped end the last ice age was dramatic in geological terms, CO2 rise due to human activity over the last 100 years is even larger and about 100 times faster”, said Dr. Rae.

“CO2 rise at the end of the ice age helped drive major melting of ice sheets and sea level rise of over 100 metres. If we want to prevent dangerous levels of global warming and sea level rise in the future, we need to reduce CO2 emissions as quickly as possible.”

Source: University of St Andrews [October 25, 2018]



HiPOD (30 October 2018): At the Edge of a Polar Sea   – This…

HiPOD (30 October 2018): At the Edge of a Polar Sea

   – This striking image is of an ice mound in Louth Crater. Louth ice is an outlier and potentially growing/shrinking in the current climate. (337 km above the surface. Black and white is less than 5 km across; enhanced color is less than 1 km.)

NASA/JPL/University of Arizona

An ExoMars Landing SiteHiRISE plays an important role in finding…

An ExoMars Landing Site

HiRISE plays an important role in finding suitable landing sites for future rover missions. Scientists have narrowed down the candidate landing sites for the upcoming European ExoMars rover mission to two regions: the plains of Oxia and Mawrth Vallis.

Images covering these areas aid scientists in picking a location that will be both scientifically interesting and a safe place to land and operate. HiRISE pictures help to assess the risk for each particular location so that a final landing site can be selected.

If you look very closely, the image may appear hazy. This is due to additional dust lingering in the atmosphere from the massive summer global dust storm at the time we acquired this observation. ExoMars is due to launch to Mars in 2020.

NASA/JPL/University of Arizona

The Kepler space telescope has shown us our galaxy is teeming with planets — and other...


The Kepler space telescope has taught us there are so many planets out there, they outnumber even

the stars. Here is a sample of these wondrous, weird and unexpected worlds (and

other spectacular objects in space) that Kepler has spotted with its “eye” opened to the heavens.

Kepler has found that double sunsets

really do exist.


Yes, Star Wars fans, the double sunset on Tatooine could really exist.

Kepler discovered the first known planet around a double-star system, though Kepler-16b is probably a gas giant without a solid surface.

Kepler has gotten us closer to finding

planets like Earth.


Nope. Kepler hasn’t found Earth 2.0, and that wasn’t the job it set out

to do. But in its survey of hundreds of thousands of stars, Kepler found planets

near in size to Earth orbiting at a distance where liquid water could pool on

the surface. One of them, Kepler-62f, is about 40 percent bigger than Earth and

is likely rocky. Is there life on any of them? We still have a lot more to


This sizzling world is so hot iron would



One of Kepler’s early discoveries was the small, scorched world of Kepler-10b. With a year that lasts less than an Earth day and density high enough to

imply it’s probably made of iron and rock, this “lava world” gave us the first

solid evidence of a rocky planet outside our solar system. 

If it’s not an alien megastructure, what

is this oddly fluctuating star?


When Kepler detected the oddly fluctuating light from “Tabby’s

,” the internet lit up with speculation of an alien

megastructure. Astronomers have concluded it’s probably an orbiting dust


Kepler caught this dead

star cannibalizing its planet.


What happens when a solar system dies? Kepler discovered a white dwarf,

the compact corpse of a star in the process of vaporizing a


These Kepler planets are more than twice the age of our Sun!


The five small planets in Kepler-444 were born 11 billion years ago when our galaxy was in its youth. Imagine

what these ancient planets look like after all that time?

Kepler found a supernova exploding at

breakneck speed.


This premier planet hunter has also been watching stars explode. Kepler

recorded a sped-up version of a supernova called a “fast-evolving

luminescent transit
” that reached its peak brightness at breakneck

speed. It was caused by a star spewing out a dense shell of gas that lit up

when hit with the shockwave from the blast. 

* All images are artist illustrations.

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

Alterations to seabed raise fears for future

The ocean floor as we know it is dissolving rapidly as a result of human activity. Normally the deep sea bottom is a chalky white. It’s composed, to a large extent, of the mineral calcite (CaCO3) formed from the skeletons and shells of many planktonic organisms and corals. The seafloor plays a crucial role in controlling the degree of ocean acidification.

Alterations to seabed raise fears for future
Maps showing areas of the seafloor which have been affected, to varying degrees, by the increasing
acidification of the oceans as a result of human activities [Credit: McGill University]

The dissolution of calcite neutralizes the acidity of the CO2, and in the process prevents seawater from becoming too acidic. But these days, at least in certain hotspots such as the Northern Atlantic and the southern Oceans, the ocean’s chalky bed is becoming more of a murky brown. As a result of human activities the level of CO2 in the water is so high, and the water is so acidic, that the calcite is simply being dissolved.
The McGill-led research team who published their results this week in a study in Proceedings of the National Academy of Sciences believe that what they are seeing today is only a foretaste of the way that the ocean floor will most likely be affected in future.

Long-lasting repercussions

“Because it takes decades or even centuries for CO2 to drop down to the bottom of the ocean, almost all the CO2 created through human activity is still at the surface. But in the future, it will invade the deep-ocean, spread above the ocean floor and cause even more calcite particles at the seafloor to dissolve,” says lead author Olivier Sulpis who is working on his PhD in McGill’s Dept. of Earth and Planetary Sciences.

“The rate at which CO2 is currently being emitted into the atmosphere is exceptionally high in Earth’s history, faster than at any period since at least the extinction of the dinosaurs. And at a much faster rate than the natural mechanisms in the ocean can deal with, so it raises worries about the levels of ocean acidification in future.”

In future work, the researchers plan to look at how this deep ocean bed dissolution is likely to evolve over the coming centuries, under various potential future CO2 emission scenarios. They believe that it is critical for scientists and policy makers to develop accurate estimates of how marine ecosystems will be affected, over the long-term, by acidification caused by humans.

How the work was done

Because it is difficult and expensive to obtain measurements in the deep-sea, the researchers created a set of seafloor-like microenvironments in the laboratory, reproducing abyssal bottom currents, seawater temperature and chemistry as well as sediment compositions. These experiments helped them to understand what controls the dissolution of calcite in marine sediments and allowed them to quantify precisely its dissolution rate as a function of various environmental variables. By comparing pre-industrial and modern seafloor dissolution rates, they were able to extract the anthropogenic fraction of the total dissolution rates.

The speed estimates for ocean-bottom currents came from a high-resolution ocean model developed by University of Michigan physical oceanographer Brian Arbic and a former postdoctoral fellow in his laboratory, David Trossman, who is now a research associate at the University of Texas-Austin.

“When David and I developed these simulations, applications to the dissolution of geological material at the bottom of the oceans were far from our minds. It just goes to show you that scientific research can sometimes take unexpected detours and pay unexpected dividends,” said Arbic, an associate professor in the University of Michigan Department of Earth and Environmental Sciences.

Trossman adds: “Just as climate change isn’t just about polar bears, ocean acidification isn’t just about coral reefs. Our study shows that the effects of human activities have become evident all the way down to the seafloor in many regions, and the resulting increased acidification in these regions may impact our ability to understand Earth’s climate history.”

“This study shows that human activities are dissolving the geological record at the bottom of the ocean,” says Arbic. “This is important because the geological record provides evidence for natural and anthropogenic changes.”

Source: McGill University [October 29, 2018]



Mountain birds on ‘escalator to extinction’ as planet warms

A meticulous re-creation of a 3-decade-old study of birds on a mountainside in Peru has given scientists a rare chance to prove how the changing climate is pushing species out of the places they are best adapted to.

Mountain birds on 'escalator to extinction' as planet warms
A russet-crowned warbler in the Cerro de Pantiacolla mountain in Peru
[Credit: Graham Montgomery/AP]

Surveys of more than 400 species of birds in 1985 and then in 2017 have found that populations of almost all had declined, as many as eight had disappeared completely, and nearly all had moved to higher elevations in what scientists call “an escalator to extinction.”

“Once you move up as far as you can go, there’s nowhere else left,” said John W. Fitzpatrick, a study author and director of the Cornell Laboratory of Ornithology. “On this particular mountain, some ridgetop bird populations were literally wiped out.”

It’s not certain whether the birds shifted ranges because of temperature changes, or indirect impacts, such as shifts in the ranges of insects or seeds that they feed on.

These findings, published in the Proceedings of the National Academy of Sciences, confirm what biologists had long suspected, but had few opportunities to confirm. The existence of a 1985 survey of birds on the same mountain gave scientists a rare and useful baseline.

Past research has documented habitats of birds and other species moving up in elevation or latitude in response to warming temperatures. But Mark Urban, director of the Center of Biological Risk at the University of Connecticut, who was not involved in the study said it was the first to prove what climate change models predicted: that rising temperatures will lead to local extinctions.

Mountain birds on 'escalator to extinction' as planet warms
A deep-blue flowerpiercer in the Cerro de Pantiacolla mountain in Peru
[Credit: Graham Montgomery via AP]

“A study like this where you have historical data you can go back to and compare is very rare,” said Urban. “As long as the species can disperse, you will see species marching up the mountain, until that escalator becomes a stairway to heaven.”

In 1985, Fitzpatrick established a basecamp alongside a river running down a mountain slope in southeastern Peru, aiming to catalog the habitat ranges of tropical bird species that lived there. His team spent several weeks trekking up and down the Cerro de Pantiacolla, using fine nets called mist nets to catch and release birds, and keeping detailed journals of birds they caught, spotted or heard chirping in the forests.

Two years ago, Fitzpatrick passed his journals, photos and other records to Benjamin Freeman, a postdoctoral fellow at the Biodiversity Research Centre at the University of British Columbia. Freeman, who has been researching tropical birds for more than a decade, set out to recreate the journey in August and September of 2017. Using old photos of mountain views, his team located the same basecamp.

Freeman largely recreated Fitzpatrick’s path and methodology to see what had happened in the intervening years, a period when average mean temperatures on the mountain rose 0.76 degrees Fahrenheit (0.42 degrees Celsius). Because the mountain lies at the edge of a national park, the area hadn’t been disturbed.

In addition to unfurling 40-foot (12-meter) mist nets on the slopes, Freeman’s team placed 20 microphone boxes on the mountain to record the chirps of birds that might not easily be seen.

Mountain birds on 'escalator to extinction' as planet warms
A scarlet-breasted fruiteater in the Cerro de Pantiacolla mountain in Peru[Credit: Graham Montgomery via AP]

“We found that the bird communities were moving up the slope to reach the climate conditions to which they were originally adapted,” said Freeman, the lead author of the study. Near the top of the mountain the bird species moved higher by 321 feet (98 meters), on average.
“We think temperature is the master-switch in explaining why species live where they do on mountain slopes,” said Freeman. “A huge majority of species in our study were doing the same thing.”

Birds adapted to live within narrow temperature bands – in regions without wide seasonal variations – may be particularly vulnerable to climate change, Fitzpatrick said. “We should expect that what’s happening on this mountaintop is happening more generally in the Andes, and other tropical mountain ranges,” he said.

Author: Christina Larson | Source: The Associated Press [October 29, 2018]



Synthetic microorganisms allow scientists to study ancient evolutionary mysteries

Scientists at Scripps Research and their collaborators have created microorganisms that may recapitulate key features of organisms thought to have lived billions of years ago, allowing them to explore questions about how life evolved from inanimate molecules to single-celled organisms to the complex, multicellular lifeforms we see today.

Synthetic microorganisms allow scientists to study ancient evolutionary mysteries
A genetically modified yeast containing an endosymbiotic bacterium
[Credit: Scripps Research]

By studying one of these engineered organisms-a bacterium whose genome consists of both ribonucleic acid (RNA) and deoxyribonucleic acid (DNA)-the scientists hope to shed light on the early evolution of genetic material, including the theorized transition from a world where most life relied solely on the genetic molecule RNA to one where DNA serves as the primary storehouse of genetic information.

Using a second engineered organism, a genetically modified yeast containing an endosymbiotic bacterium, they hope to better understand the origins of cellular power plants called mitochondria. Mitochondria provide essential energy for the cells of eukaryotes, a broad group of organisms-including humans-that possesses complex, nucleus-containing cells.

The researchers report engineering the microbes in two papers, one published in the Proceedings of the National Academy of Sciences and another published in Journal of the American Chemical Society.

“These engineered organisms will allow us to probe two key theories about major milestones in the evolution of living organisms-the transition from the RNA world to the DNA world and the transition from prokaryotes to eukaryotes with mitochondria,” says Peter Schultz, PhD, senior author on the papers and president of Scripps Research. “Access to readily manipulated laboratory models enables us to seek answers to questions about early evolution that were previously intractable.”

The origins of life on Earth have been a human fascination for millennia. Scientists have traced the arc of life back several billion years and concluded that the simplest forms of life emerged from Earth’s primordial chemical soup and subsequently evolved over the eons into organisms of greater and greater complexity. A monumental leap came with the emergence of DNA, a molecule that stores all of the information required to replicate life and directs cellular machinery to do its bidding primarily by generating RNA, which in turn directs the synthesis of proteins, the molecular workhorses in cells.

In the 1960s, Carl Woese and Leslie Orgel, along with DNA pioneer Francis Crick, proposed that before DNA, organisms relied on RNA to carry genetic information, a molecule similar to but far less stable than DNA, that can also catalyze chemical reactions like proteins. “In science class, students learn that DNA leads to RNA which in turn leads to proteins-that’s a central dogma of biology-but the RNA world hypothesis turns that on its head,” says Angad Mehta, PhD, first author of the new papers and a postdoctoral research associate at Scripps Research. “For the RNA world hypothesis to be true, you have to somehow get from RNA to a DNA genome, yet how that might have happened is still a very big question among scientists.”

One possibility is that the transition proceeded through a kind of microbial missing link, a replicating organism that stored genetic information as RNA. For the JACS study, the Scripps Research-led team created Escherichia coli bacteria that partially build their DNA with ribonucleotides, the molecular building blocks typically used to build RNA. These engineered genomes contained up to 50 percent RNA, thus simultaneously representing a new type of synthetic organism and possibly a throwback to billions of years ago.

Synthetic microorganisms allow scientists to study ancient evolutionary mysteries
A genetically modified yeast containing an endosymbiotic bacterium
[Credit: Scripps Research]

Mehta cautions that their work so far has focused on characterizing this chimeric RNA-DNA genome and its effect on bacterial growth and replication but hasn’t explicitly explored questions about the transition from the RNA world to the DNA world. But, he says, the fact that E. coli with half its genome comprised of RNA can survive and replicate is remarkable and seems to support the possibility of the existence of evolutionarily transitional organisms possessing hybrid RNA-DNA genomes. The Scripps Research team is now studying how the mixed genomes of their engineered E. coli function and plans to use the bacteria to explore a number of evolutionary questions.

For instance, one question is whether the presence of RNA leads to rapid genetic drift-large changes in gene sequence in a population over time. Scientists theorize that massive genetic drift occurred quickly during early evolution, and the presence in the genome of RNA could help explain how genetic change occurred so quickly.

In the paper published in PNAS, the researchers report engineering another laboratory model for an evolutionary milestone thought to have occurred more than 1.5 billion years ago. They created a yeast dependent for energy on bacteria living inside it as a beneficial parasite or “endosymbiont.” This composite organism will allow them to investigate the ancient origins of mitochondria-tiny, bacteria-like organelles that produce chemical energy within the cells of all higher organisms.

Mitochondria are widely thought to have evolved from ordinary bacteria that were captured by larger, single-celled organisms. They carry out several key functions in cells. Most importantly, they serve as oxygen reactors, using O2 to make cells’ basic unit of chemical energy, the molecule ATP. As crucial as mitochondria are to cells, their origins remain somewhat mysterious, although there are clear hints of descent from a more independent organism, widely assumed to have been a bacterium.

Mitochondria have a double-membrane structure like that of some bacteria, and-again, like bacteria-contain their own DNA. Analyses of the mitochondrial genome suggest that it shares an ancient ancestor with modern Rickettsia bacteria, which can live within the cells of their hosts and cause disease. Stronger support for the bacterial origin of mitochondria theory would come from experiments showing that independent bacteria could indeed be transformed, in an evolution-like progression, into mitochondria-like symbionts. To that end, the Scripps Research scientists engineered E. coli bacteria that could live in, depend upon, and provide key assistance to, cells of Saccharomyces cerevisiae, also known as baker’s yeast.

The researchers started by modifying E. coli to lack the gene encoding thiamin, making the bacteria dependent on the yeast cells for this essential vitamin. At the same time, they added to the bacteria a gene for ADP/ATP translocase, a transporter protein, so that ATP produced within the bacterial cells would be supplied to their yeast-cell hosts-mimicking the central function of real mitochondria. The team also modified the yeast so that their own mitochondria were deficient at supplying ATP. Thus the yeast would be dependent on the bacteria for normal, mitochondria-based ATP production.

The team found that some of the engineered bacteria, after being modified with surface proteins to protect them from being destroyed in the yeast, lived and proliferated in harmony with their hosts for more than 40 generations and appeared to be viable indefinitely. “The modified bacteria seem to accumulate new mutations within the yeast to better adapt to their new surroundings,” says Lubica Supekova, PhD, co-first author of the PNAS paper and a staff scientist at Scripps Research.

With this system established, the team will try to evolve the E. coli to become mitochondria-like organelles. For the new E. coli endosymbiont, adapting to life inside yeast could allow it an opportunity to radically slim its genome. A typical E. coli bacterium, for example, has several thousand genes, whereas mitochondria have evolved a stripped-down set of just 37.

The Scripps Research team rounded out the study with further gene-subtraction experiments, and the results were promising: they found they could eliminate not just the E. coli thiamin gene but also the genes underlying the production of the metabolic molecule NAD and the amino acid serine, and still get a viable symbiosis.

“We are now well on our way to showing that we can delete the genes for making all 20 amino acids, which comprise a significant part of the E. coli genome,” says Schultz. “Once we’ve achieved that, we’ll move on to deleting genes for the syntheses of cofactors and nucleotides, and within a few years we hope to be able to get a truly minimal endosymbiotic genome.”

The researchers also hope to use similar endosymbiont-host systems to investigate other important episodes in evolution, such as the origin of chloroplasts, light-absorbing organelles that have a mitochondria-like role in supplying energy to plants.

Source: The Scripps Research Institute [October 29, 2018]