четверг, 13 февраля 2020 г.

Understanding the Impact of Satellite Constellations on Astronomy

Credit: NSF’s National Optical-Infrared Astronomy Research Laboratory/CTIO/AURA/DELVE

In June 2019, the International Astronomical Union expressed concern about the negative impact that the planned mega-constellations of communication satellites may have on astronomical observations and on the pristine appearance of the night sky when observed from a dark region. We here present a summary of the current understanding of the impact of these satellite constellations.

Following the statement of June 2019, IAU’s Commission B7 Protection of Existing and Potential Observatory Sites and the Executive Committee Working Group Dark and Quiet Sky Protection were asked by the IAU Executive Committee to assess the situation and to start discussions with the companies that are responsible for launching and operating the mega-constellations in order to study measures to mitigate their interference.

Commission B7 has requested the input of astronomers from different organisations (Vera C. Rubin Observatory, U. Michigan, CAHA, ESO and ESA) skilled in modeling the frequency, location and brightness of satellite mega-constellations. Some of those results are presented below. The results of the simulations, given the large number of parameters involved and the associated assumptions and uncertainties, are to be considered preliminary. 

  • While there is large uncertainty about the future number of satellites, some simulations were conducted on the basis of a large sample of over 25 000 satellites from representative satellite constellations from different companies. With this sample, the number of satellites above the horizon at any given time would be between ~1500 and a few thousand, depending on the latitude. Most of these will appear very close to the horizon, only a few of them passing directly overhead; for instance, about 250 to 300 would have an elevation of more than 30 degrees over the horizon (i.e. where the sky is clear from obstructions, and where most of the astronomical observations are performed). The vast majority of these will be too faint to be visible to the naked eye [1] [2] [3].

  • When the Sun is 18 degrees below the horizon (i.e. when the night becomes dark), the number of illuminated satellites above the horizon would be around 1000 (with around 160 at elevations higher than 30 degrees). The numbers decrease further towards the middle of the night, when more satellites are in the Earth's shadow (e.g., no reflected sunlight) [1] [2] [3] .

  • At the moment it is difficult to predict how many of the illuminated satellites will be visible to the naked eye, because of uncertainties in their actual reflectivity (also since experiments are being carried out by SpaceX to reduce the reflectivity of a Starlink satellite by adopting different coatings). The appearance of the pristine night sky, particularly when observed from dark sites, will nevertheless be altered, because the new satellites could be significantly brighter than existing orbiting man-made objects. The interference with the uncontaminated view of the night sky will be particularly important in the regions of the sky close to the horizon and less evident at high elevation [1] [2].

  • The prominent trains of satellites (“strings of pearls”), often seen in images and videos, are significant immediately after launch and during the orbit-raising phase when they are considerably brighter than they are at their operational altitude and orientation. The global effect depends on how long the satellites are in this phase and on the frequency of launches [2].

  • Apart from their naked-eye visibility, it is estimated that the trails of the constellation satellites will be bright enough to saturate modern detectors on large telescopes. Wide-field scientific astronomical observations will therefore be severely affected. For instance, in the case of modern fast wide-field surveys, like the ones to be carried out by the Rubin Observatory (formerly known as LSST), it is estimated that up to 30% of the 30-second images during twilight hours will be affected. Instruments with a smaller field of view would be less affected. In theory, the effects of the new satellites could be mitigated by accurately predicting their orbits and interrupting observations, when necessary, during their passage. Data processing could then be used to further “clean” the resulting images. However, the large number of trails could create significant and complicated overheads to the scheduling and operation of astronomical observations [1] [3].
A summary of the findings and of the actions that have so far been undertaken is presented in a specific IAU Theme.

The focus of this Statement has been on the optical wavelengths. This is not to underplay the effect on the radio and submillimetre wavelength ranges, which is still under investigation. The IAU considers the consequences of satellite constellations worrisome. They will have a negative impact on the progress of ground-based astronomy, radio, optical and infrared, and will require diverting human and financial resources from basic research to studying and implementing mitigating measures.

A great deal of attention is also being given to the protection of the uncontaminated view of the night sky from dark places, which should be considered a non-renounceable world human heritage. This is one of the main messages communicated on the dedicated IAU–UNESCO web site on astronomical heritage.

In order to mitigate the impacts of satellite constellations that may interfere with professional and amateur astronomical observations, the IAU, in close collaboration with the American Astronomical Society (AAS), will continue to initiate discussions with space agencies and private companies that are planning to launch and operate currently planned and future satellite constellations.

The IAU notes that currently there are no internationally agreed rules or guidelines on the brightness of orbiting manmade objects. While until now this was not considered a priority topic, it is now becoming increasingly relevant. Therefore the IAU will regularly present its findings at the meetings of the UN Committee for Peaceful Uses of Outer Space (COPUOS), bringing the attention of the world Government representatives to the threats posed by any new space initiative on astronomy and science in general. In addition, the specific theme of the mega-satellites will be included in the Programme of the IAU/UNOOSA/IAC Conference Dark and Quiet Skies for Science and Society, which will be held in Santa Cruz de La Palma, Canary Islands, Spain, on 5–8 October 2020.

The IAU stresses that technological progress is only made possible by parallel advances in scientific knowledge. Satellites would neither operate nor properly communicate without essential contributions from astronomy and physics. It is in everybody’s interest to preserve and support the progress of fundamental science such as astronomy, celestial mechanics, orbital dynamics and relativity.




Notes

[1] Hainaut, Olivier (ESO), 2020, On the impact of satellite mega-constellations on astronomical observations, submitted for publication in Astronomy & Astrophysics.

[3] Galadí-Enríquez, David (Calar Alto Observatory), 2020, Geometric simulation of the visibility of Starlink satellite constellation from ground-based optical observatories: LSST as a case study, progress report, private communication.



More information

The IAU is the international astronomical organisation that brings together more than 13 500 professional astronomers from more than 100 countries worldwide. Its mission is to promote and safeguard astronomy in all its aspects, including research, communication, education and development, through international cooperation. The IAU also serves as the internationally recognised authority for assigning designations to celestial bodies and the surface features on them. Founded in 1919, the IAU is the world's largest professional body for astronomers.



Contacts

Piero Benvenuti
Advisor, IAU Executive Committee
Email: piero.benvenuti@unipd.it
Connie Walker
President Commission B7
Email: cwalker@noao.edu

Lars Lindberg Christensen
IAU Press Officer
Tucson, USA
Tel: +1 520 318 8590
Cell: +1 520 461 0433
Email: lchristensen@aura-astronomy.org




* This article was originally published here

Pluto's icy heart makes winds blow


A "beating heart" of frozen nitrogen controls Pluto's winds and may give rise to features on its surface, according to a new study.

Pluto's icy heart makes winds blow
Four images from NASA’s New Horizons’ Long Range Reconnaissance Imager (LORRI) were combined with colour
data from the Ralph instrument to create this global view of Pluto [Credit: NASA/Johns Hopkins University
Applied Physics Laboratory/Southwest Research Institute]
Pluto's famous heart-shaped structure, named Tombaugh Regio, quickly became famous after NASA's New Horizons mission captured footage of the dwarf planet in 2015 and revealed it isn't the barren world scientists thought it was.

Now, new research shows Pluto's renowned nitrogen heart rules its atmospheric circulation. Uncovering how Pluto's atmosphere behaves provides scientists with another place to compare to our own planet. Such findings can pinpoint both similar and distinctive features between Earth and a dwarf planet billions of miles away.

Nitrogen gas -- an element also found in air on Earth -- comprises most of Pluto's thin atmosphere, along with small amounts of carbon monoxide and the greenhouse gas methane. Frozen nitrogen also covers part of Pluto's surface in the shape of a heart. During the day, a thin layer of this nitrogen ice warms and turns into vapor. At night, the vapor condenses and once again forms ice. Each sequence is like a heartbeat, pumping nitrogen winds around the dwarf planet.


New research in AGU's Journal of Geophysical Research: Planets suggests this cycle pushes Pluto's atmosphere to circulate in the opposite direction of its spin -- a unique phenomenon called retro-rotation. As air whips close to the surface, it transports heat, grains of ice and haze particles to create dark wind streaks and plains across the north and northwestern regions.

"This highlights the fact that Pluto's atmosphere and winds -- even if the density of the atmosphere is very low -- can impact the surface," said Tanguy Bertrand, an astrophysicist and planetary scientist at NASA's Ames Research Center in California and the study's lead author.

Most of Pluto's nitrogen ice is confined to Tombaugh Regio. Its left "lobe" is a 1,000-kilometer (620-mile) ice sheet located in a 3-kilometer (1.9-mile) deep basin named Sputnik Planitia -- an area that holds most of the dwarf planet's nitrogen ice because of its low elevation. The heart's right "lobe" is comprised of highlands and nitrogen-rich glaciers that extend into the basin.

"Before New Horizons, everyone thought Pluto was going to be a netball -- completely flat, almost no diversity," Bertrand said. "But it's completely different. It has a lot of different landscapes and we are trying to understand what's going on there."

Western winds

Bertrand and his colleagues set out to determine how circulating air -- which is 100,000 times thinner than that of Earth's -- might shape features on the surface. The team pulled data from New Horizons' 2015 flyby to depict Pluto's topography and its blankets of nitrogen ice. They then simulated the nitrogen cycle with a weather forecast model and assessed how winds blew across the surface.

The group discovered Pluto's winds above 4 kilometers (2.5 miles) blow to the west -- the opposite direction from the dwarf planet's eastern spin -- in a retro-rotation during most of its year. As nitrogen within Tombaugh Regio vaporizes in the north and becomes ice in the south, its movement triggers westward winds, according to the new study. No other place in the solar system has such an atmosphere, except perhaps Neptune's moon Triton.

The researchers also found a strong current of fast-moving, near-surface air along the western boundary of the Sputnik Planitia basin. The airflow is like wind patterns on Earth, such as the Kuroshio along the eastern edge of Asia. Atmospheric nitrogen condensing into ice drives this wind pattern, according to the new findings. Sputnik Planitia's high cliffs trap the cold air inside the basin, where it circulates and becomes stronger as it passes through the western region.

The intense western boundary current's existence excited Candice Hansen-Koharcheck, a planetary scientist with the Planetary Science Institute in Tucson, Arizona who wasn't involved with the new study.


"It's very much the kind of thing that's due to the topography or specifics of the setting," she said. "I'm impressed that Pluto's models have advanced to the point that you can talk about regional weather."

On the broader scale, Hansen-Koharcheck thought the new study was intriguing. "This whole concept of Pluto's beating heart is a wonderful way of thinking about it," she added.

These wind patterns stemming from Pluto's nitrogen heart may explain why it hosts dark plains and wind streaks to the west of Sputnik Planitia. Winds could transport heat -- which would warm the surface -- or could erode and darken the ice by transporting and depositing haze particles. If winds on the dwarf planet swirled in a different direction, its landscapes might look completely different.

"Sputnik Planitia may be as important for Pluto's climate as the ocean is for Earth's climate," Bertrand said. "If you remove Sputnik Planitia -- if you remove the heart of Pluto -- you won't have the same circulation," he added.

The new findings allow researchers to explore an exotic world's atmosphere and compare what they discover with what they know about Earth. The new study also shines light on an object 6 billion kilometers (3.7 billion miles) away from the sun, with a heart that captivated audiences around the globe.

"Pluto has some mystery for everybody," Bertrand said.

Source: American Geophysical Union [February 04, 2020]



* This article was originally published here

'Flammable ice' discovery offers up clue to life on other planets


Scientists studying so-called 'flammable ice' in the Sea of Japan have made a startling discovery—the existence of life within microscopic bubbles.

'Flammable ice' discovery offers up clue to life on other planets
Scientists have dubbed this image of a microhabitat that grew in methane hydrate the 'Death Star' - it grew from microbial
activity at near freezing temperatures, deep underwater, in one of the countless isolated pockets of saltwater
and oil found within methane hydrate [Credit: University of Aberdeen]
The microhabitats are grown by microbes within tiny bubbles of oil and water found in sheets of frozen gas and ice, and offer a tantalising clue as to the potential for life on other planets.

The tiny bubbles are scattered within large underwater rafts of hydrate, known as 'flammable ice' or methane hydrate, which forms when ice traps methane within its molecular structure.

The discovery of the microhabitats is revealed in a paper published in the journal Scientific Reports, a Nature publication. It stemmed from a larger project led by Professor Ryo Matsumoto from Meiji University in Japan, which was investigating methane hydrate as an energy source that emits less waste-carbon than traditional fossil fuels.


Dr. Glen T. Snyder, lead author of the study, was melting hydrate to study methane gas when he noticed an unusual powder consisting of microscopic spheroids with mysterious dark cores. He then set about collecting a group of like-minded scientists to investigate further.

Using analytical techniques pioneered at the University of Aberdeen and suited to small sample quantities, Dr. Stephen Bowden from the University's School of Geosciences was able to show that oil was being degraded in the microenvironments within the methane hydrate.

"In combination with the other evidence collected by my colleagues, my results showed that even under near-freezing temperatures, at extremely high pressures, with only heavy oil and saltwater for food-sources, life was flourishing and leaving its mark," Dr. Bowden said.


Dr. Snyder continued: "The methane in 'methane hydrate' is known to form as microbes degrade organic matter on the seafloor.

"But what we never expected to find was microbes continuing to grow and produce these spheroids, all of the time while isolated in tiny cold dark pockets of saltwater and oil.

"It certainly gives a positive spin to cold dark places, and opens up a tantalizing clue as to the existence of life on other planets.

Dr. Bowden added: "It certainly changes how I think about things. Providing they have ice and a little heat, all those frigid cold planets at the edge of every planetary system could host tiny microhabitats with microbes building their own 'death stars' and making their own tiny little atmospheres and ecosystems, just as we discovered here."

Source: University of Aberdeen [February 05, 2020]



* This article was originally published here

Astronomers discover unusual monster galaxy in the very early universe


An international team of astronomers led by scientists at the University of California, Riverside, has found an unusual monster galaxy that existed about 12 billion years ago, when the universe was only 1.8 billion years old.

Astronomers discover unusual monster galaxy in the very early universe
The three panels show, from left to right, what XMM-2599's evolutionary trajectory might be, beginning as a dusty
star-forming galaxy, then becoming a dead galaxy, and perhaps ending up as a "brightest cluster galaxy,"
or BCG [Credit: NRAO/AUI/NSF/B. Saxton; NASA/ESA/R. Foley; NASA/StScI]
Dubbed XMM-2599, the galaxy formed stars at a high rate and then died. Why it suddenly stopped forming stars is unclear.

"Even before the universe was 2 billion years old, XMM-2599 had already formed a mass of more than 300 billion suns, making it an ultramassive galaxy," said Benjamin Forrest, a postdoctoral researcher in the UC Riverside Department of Physics and Astronomy and the study's lead author. "More remarkably, we show that XMM-2599 formed most of its stars in a huge frenzy when the universe was less than 1 billion years old, and then became inactive by the time the universe was only 1.8 billion years old."

The team used spectroscopic observations from the W. M. Keck Observatory's powerful Multi-Object Spectrograph for Infrared Exploration, or MOSFIRE, to make detailed measurements of XMM-2599 and precisely quantify its distance.


"In this epoch, very few galaxies have stopped forming stars, and none are as massive as XMM-2599," said Gillian Wilson, a professor of physics and astronomy at UCR in whose lab Forrest works.  "The mere existence of ultramassive galaxies like XMM-2599 proves quite a challenge to numerical models. Even though such massive galaxies are incredibly rare at this epoch, the models do predict them. The predicted galaxies, however, are expected to be actively forming stars. What makes XMM-2599 so interesting, unusual, and surprising is that it is no longer forming stars, perhaps because it stopped getting fuel or its black hole began to turn on. Our results call for changes in how models turn off star formation in early galaxies."

The research team found XMM-2599 formed more than 1,000 solar masses a year in stars at its peak of activity -- an extremely high rate of star formation. In contrast, the Milky Way forms about one new star a year.

"XMM-2599 may be a descendant of a population of highly star-forming dusty galaxies in the very early universe that new infrared telescopes have recently discovered," said Danilo Marchesini, an associate professor of astronomy at Tufts University and a co-author on the study.

The evolutionary pathway of XMM-2599 is unclear.

"We have caught XMM-2599 in its inactive phase," Wilson said. "We do not know what it will turn into by the present day. We know it cannot lose mass. An interesting question is what happens around it. As time goes by, could it gravitationally attract nearby star-forming galaxies and become a bright city of galaxies?"


Co-author Michael Cooper, a professor of astronomy at UC Irvine, said this outcome is a strong possibility.

"Perhaps during the following 11.7 billion years of cosmic history, XMM-2599 will become the central member of one of the brightest and most massive clusters of galaxies in the local universe," he said. "Alternatively, it could continue to exist in isolation. Or we could have a scenario that lies between these two outcomes."

The team has been awarded more time at the Keck Observatory to follow up on unanswered questions prompted by XMM-2599.

"We identified XMM-2599 as an interesting candidate with imaging alone," said co-author Marianna Annunziatella, a postdoctoral researcher at Tufts University. "We used Keck to better characterize and confirm its nature and help us understand how monster galaxies form and die. MOSFIRE is one of the most efficient and effective instruments in the world for conducting this type of research."

Study results appear in the Astrophysical Journal.

Author: Iqbal Pittalwala | Source: University of California - Riverside [February 05, 2020]



* This article was originally published here

Study shows acceleration of global mean ocean circulation since 1990s


A study published in the journal Science Advances, suggests global ocean circulation has accelerated during the past two decades. The research team found that oceanic kinetic energy shows a statistically significant increase since early 1990s, calculating a 36-percent acceleration of global mean ocean circulation.

Study shows acceleration of global mean ocean circulation since 1990s
Credit: University of California - San Diego
The trend is particularly prominent in the global tropical oceans, reaching depths of thousands of meters. The deep-reaching acceleration of the ocean circulation is mainly induced by a planetary intensification of surface winds, authors said.

The study was led by Shijian Hu, who performed the work as a postdoctoral researcher in the laboratory of Janet Sprintall, an oceanographer at Scripps Institution of Oceanography at the University of California San Diego who is a co-author of the paper. Hu is now a scientist at the CAS Key Laboratory of Ocean Circulation and Waves, at the Institute of Oceanology (IOCAS) in Qingdao, China.


"The magnitude and extent of the acceleration in ocean currents we detected throughout the global ocean and to 2000-meter (6,560 foot) depth was quite surprising," said Sprintall. "While we expected some response to the increased winds over the past two decades, that the acceleration was above and beyond that was an unexpected response that is likely due to global climate change."

Large-scale ocean circulation is the main dynamic process that redistributes ocean water mass and heat and plays an important role in Earth's environment and climate system. It regulates land temperatures, most notably in regions such as western Europe where a flow of relatively warm water makes the climate of cities such as Madrid warmer than cities such as New York, despite being at the same latitude.

Study shows acceleration of global mean ocean circulation since 1990s
Areas of ocean shown in orange have experienced positive trends in kinetic energy
in the past 30 years [Credit: Shijian Hu]
Because of internal dynamic processes and natural variability, ocean circulation in different regions has different responses to global climate warming. And there is still a lack of systematic and continuous direct observations of the earth's ocean circulation. Hence circulation trends have not been well-understood, study authors said.

A growing body of evidence suggests, though, that continuous greenhouse gas emissions due to human activities give rise to Earth's energy imbalance and continuous ocean warming. Thus, it is essential to know what large-scale ocean circulation is going to be under the background of global warming, said study co-authors.


An international team of scientists from IOCAS, Scripps, NOAA and the Commonwealth Scientific and Industrial Research Organization in Australia used ocean circulation and wind speed data from multiple sources, including observations from the global Argo network of robotic floats and numerical simulations, to investigate global mean ocean circulation and global mean sea surface wind speed. They concluded that the recent acceleration is far greater than what would be explained by natural variability. The rest is induced by the influence of continuous greenhouse gas emissions.

The intensified surface winds since the early 1990s, the authors said, spurs ocean circulation. The acceleration may lead to enhanced heat and water mass transport, so additional energy would be redistributed more evenly and the water cycle in the ocean may be intensified as well. Heat in upper ocean layers may be transferred into the deep ocean more efficiently due to the deep reach of this acceleration. Further research is needed to explore the implications of this study, the authors said.

Author: Robert Monroe | Source: University of California - San Diego [February 05, 2020]



* This article was originally published here

New global biodiversity study provides unified map of life on land and in the ocean


New research led by the Monterey Bay Aquarium and partner organizations yielded the first comprehensive global biodiversity map documenting the distribution of life both on land and in the ocean.

New global biodiversity study provides unified map of life on land and in the ocean
Global terrestrial and marine biodiversity patterns: (a) Observed species richness derived from the distributions
 of 44,575 marine and 22,830 terrestrial species. Species richness is ln-transformed and rescaled within each
 domain (terrestrial and marine) and plotted on a 50 km equal area grid. (b) Artificial neural network model
predictions (ANNs) of species richness considering a suite of 29 environmental drivers. (c) Model residuals
highlight areas that are particularly species-rich (underpredicted, blue) and species-poor (overpredicted, red)
regions relative to the underlying environmental drivers. These highlight locations of exceptional biodiversity
such as reef ecosystems of the (i) Coral Triangle and (ii) Marianas Archipelago and wet forests of the
 (iii) tropical Andes and (iv) Eastern Arc mountains. It also identifies species-poor settings like
isolated islands (v, Madagascar) and major biogeographic boundaries in the ocean (vi, Andesite line).
Arrows designate species-poor marine regions with high velocity boundary currents. (d) Latitude
does not affect model performance, as there are no systematic meridional differences between
observed and modelled richness. The northern-hemisphere bias of land, and the corresponding
abundance of shallow ocean environments, generates a similar imbalance of marine species
richness. Chart area represents the average species richness, zonally, in 2° latitude bins
[Credit: Tyler O. Gagne et al. 2020]
The study published in PLOS ONE offers the most complete picture available of where life occurs on Earth and what the most critical environmental factors are for determining why it's in specific places. The study's authors envision it providing a way to adapt management practices as climate change disrupts ecosystems across the planet.

"Maps typically show us where we are, but this study also shows us where we are going," said Dr. Kyle Van Houtan, Monterey Bay Aquarium chief scientist and senior author. "Previous biodiversity maps show either land or sea with the other area grayed out. We brought these two realms, and these two scientific domains, together to show that all animals are essential parts of an intricate whole."


Determining where species are most abundant, along with charting the patterns of their movements, represents one of the pillars of ecology. But for a long time, such studies have focused mostly on the terrestrial realm due to the greater accessibility and lower cost of sampling on land.

"We are terrestrial creatures, and so we have a natural bias favoring the land," said Dr. Clinton Jenkins, a professor at the IPE -- Institute for Ecological Research in Sao Paulo, Brazil. "However, much of the world's diversity is aquatic, living in the 70% of the earth's surface that is either ocean, lakes and rivers. Our goal is to better understand life on earth as a whole, not just the parts with which we are most familiar."

Through this study, scientists have developed a better and more accurate understanding of where species on land and in the sea occur now, where they might end up moving, and how we can best protect them in a changing world.

"By gathering information on ocean and terrestrial realms, we reconcile two scientific communities with the same objective: to provide a unified and objective portrait of life on earth that has sustained humanity for centuries," said Dr. Gabriel Reygondeau, research associate at the University of British Columbia and Yale University.


The interdisciplinary research team -- including NGO, university, and government scientists from the United States, Canada, and Brazil -- began by compiling data on more than 67,000 marine and terrestrial species.

Then, the team used artificial neural networks, a branch of artificial intelligence or machine learning, to help explain the observed patterns. This approach allowed the team to document and rank the influence of two dozen environmental factors on the distribution of biodiversity.

The resulting map is the most extensive effort to unify the known distribution of species on land and in the ocean, revealing places that are especially species-rich and species-poor. Coral reefs in the ocean and montane forests on land, for example, are especially diverse, containing more species than the environmental variables alone might predict.


The study also helps identify the environmental drivers that influence whether life will thrive or struggle in the future.

"This helps us document where climate change mechanisms may influence animals most and identify environmental conditions that have more or less biodiversity than we might expect," said co-author Dr. Elliott Hazen, a research ecologist with NOAA's Southwest Fisheries Science Center. "We need to understand the drivers of biodiversity to preserve species within ecosystems that are moving due to changing environmental conditions, and to allow us to take a more dynamic approach towards protecting them."

Now, resource managers working to protect critical habitats and species in a time of accelerating global change can use the study's documenting and ranking of environmental drivers to guide future conservation work.

"National parks and marine protected areas were created to protect ecological communities in stable environments, but what do we do if protected species move beyond these boundaries?" asks Dr. Van Houtan. "Our research has pinpointed the environmental factors that allow such a diversity of life to flourish on Earth and enables a flexible, data-driven approach to protect global biodiversity as once-stable conditions become less predictable."

Source: Monterey Bay Aquarium [February 05, 2020]



* This article was originally published here

Study reveals evolutionary clues to honeybees' social complexity


The complex social life of honeybees—with their queens and workers cooperating to produce honey—is deeply entrenched in the public's imagination. But the majority of the world's more than 20,000 bee species are solitary: One female mates, gathers provisions, lays eggs and walls them up with food in a secure spot.

Study reveals evolutionary clues to honeybees' social complexity
Researchers studied the North American small carpenter bee to learn about honeybees' social lives
[Credit: Cullen Franchino]
Recent research at the University of New Hampshire advances our understanding of the evolutionary shift from honeybees' loner ancestors to the social beings they are now. "We know that the honeybees of today evolved from solitary ancestors, but we're still figuring out what biological factors may have contributed to that gradual process," says Wyatt Shell, lead author of the study, published in Proceedings of the Royal Society B.

The subject of the NSF-funded research, the North American small carpenter bee (Ceratina calcarata), has a simple sociality. "For example, instead of departing the nest after laying her eggs, a mother may guard her brood while being supported by just a single working daughter," says Shell.


Comparing relative brain gene expression levels of this honeybee, Shell and co-author Sandra Rehan examined which genes might be associated with traits of foraging (visiting flowers to collect pollen and nectar) and guarding (sitting at the nest entrance to prevent predation or parasitism).

These traits are simultaneously demonstrated by a mother bee and one of her daughters during the early autumn, giving the researchers an opportunity to explore the effects of maturation—from pre-reproductive daughters to post-reproductive mothers—on gene expression.

"This research helps in understanding how the complex social behavior many species show could have developed," says Jodie Jawor, a program director in NSF's Division of Integrative Organismal Systems. "How genes influence behavior is an active area of research to understand how behavior evolves, and how behaviors such as group living and collective activities, as seen in the honeybees, are maintained."

Source: National Science Foundation [February 05, 2020]



* This article was originally published here

Ocean temperatures impact Central American climate more than once thought


Tourists today spend thousands of dollars to explore and enjoy the lush and thriving rainforests of Guatemala.

Ocean temperatures impact Central American climate more than once thought
Matthew Lachniet, professor and chair of the geoscience department at UNLV, completes field work underground
in Rey Marcos Cave, Guatemala, which is a subterranean wonder of stalactites, stalagmites,
and a disappearing river [Credit: Amos Winter, Indiana State University]
It's hard to believe the landscape ever looked any different. But according to new research by UNLV climate scientists, the locations where those jungles exist today likely looked very different less than 9,000 years ago - a blink of an eye by geologic standards.

"We often think of ecosystems as being unchangeable -- that a tropical rainforest is there, and has always been there," said Matthew Lachniet, professor and chair of the geoscience department at UNLV. "But that's not true. Any ecosystem responds to climate changes."


In a study published in the journal Nature Communications, Lachniet and colleagues at Indiana State University, the University of Venice, and other institutions examined the rainfall history of Central America over the last 11,000 years. The results provide context for the development of tropical rainforest ecosystems in the region, and long-sought answers to what has been controlling rainfall in Central America for several millennia.

"Our results suggest that the rainforest as we know it today must have responded to those climate changes, and must be less than 9,000 years old in terms of its functioning and its structure, because the region was too dry before then to sustain it," Lachniet said.

Stalagmite specimens gathered from a tourist cave in Coban, Guatemala, provided this insight and other historical data about the climate history of the region.

Researchers found:

- Solar radiation, or insolation, is widely known to control rainfall amounts in the tropics. Guatemalan cave records, however, tell a different story for the Central American region of the tropics.

- In Central America, rainfall was weak 11,000 years ago, strengthened to modern levels at 9,000 years ago, and showed only a very weak decrease to today, unlike the history of insolation.

- When ice sheets from the last Ice Age melted mostly away -- about 9,000 to 7,000 years ago -- temperature rose and Central American rainfall responded in turn.

- The Central America rainfall record has the same time evolution as ocean and land temperatures over the last 11,000 years; therefore, ocean surface temperatures were more important than the sun's rays in driving rainfall in the region.


"We found that as the oceans warm up, rainfall increases over Central America," Lachniet said.

The team also found that the rainfall variations over the last 3,000 years, during which time the famed Maya civilization reached its maximum urban development and subsequent collapse, were relatively small compared to the total range of rainfall variation captured by the cave deposits.

Lachniet and collaborators spent several days completing field work underground in Rey Marcos Cave, Guatemala for this research, which is a subterranean wonder of stalactites, stalagmites, and a disappearing river.

According to Lachniet, the next phase of the team's research in the region will continue to examine the impacts of climate on the Maya civilization throughout its history. In previous research, Lachniet and an international team of researchers used stalagmite specimens to link the rise and fall of ancient Mesoamerican civilizations to changing rainfall.

Source: University of Nevada, Las Vegas [February 05, 2020]



* This article was originally published here

Scientists grow date palm plants from 2,000-year-old seeds


Methuselah, Adam, Jonah, Uriel, Boaz, Judith and Hannah—all sat dormant in Judea since biblical times. Now scientists have resurrected them in the hopes of better understanding their vanished lineage.

Scientists grow date palm plants from 2,000-year-old seeds
Credit: Abigail Malate
These seven ancient emissaries are date palm plants, now all growing in the southern Israeli community of Ketura. Methuselah came first. He was planted in 2005 from an approximately 2,000-year-old seed found buried under rubble at the ancient fortress of Masada overlooking the Dead Sea.


Since then, he has been joined by the others. As part of a long-term project at the Arava Institute for Environmental Studies in Israel, scientists hope to breed Judean date palms—a variety that was praised in antiquity for its sweetness, large size, long shelf life, and supposed ability to fight disease, but which went extinct hundreds of years ago when repeated conflict wiped out the date plantations.

The ages of the seven successfully sprouted ancient seeds range from around 2,400 to 1,800 years old. The seeds came from three archaeological sites in the Judean desert, including Qumran, where the Dead Sea Scrolls were discovered.

Scientists grow date palm plants from 2,000-year-old seeds
Morphology of six germinated ancient date seeds before planting. (A) Adam, (B) Jonah, (C) Uriel, (D) Boaz,
(E) Judith, (F) Hannah, and (G) HU37A11, an unplanted ancient date seed from Qumran (Cave FQ37)
 used as a control. Scale bars, 0.5 cm (A, no bar size as unmeasured before planting)
[Credit: Guy Eisner/Sarah Sallon et al. 2020]
It's unusual to find seeds that can remain viable for so long. One of the few other examples was in 1995, when researchers reported that they had successfully germinated approximately 1,200-year-old seeds of a Sacred Lotus found in an ancient lake bed in China. Date palm seeds can tolerate dehydration, and the ancient date seeds were found in an extremely dry environment, which may be one reason they survived so long.


The resurrected date palms include both female and male trees, and the researchers are hoping that the trees will eventually produce fruit together. However, the new dates may not be the same as what people ate in ancient times, since ancient date growers would probably have cultivated shoots from select female plants, which perished long ago. The plants grown from their daughter seeds may not have the same qualities. Still, they may display some characteristics that have been lost in modern date varieties.

Scientists grow date palm plants from 2,000-year-old seeds
Germinated ancient date seedlings. Ages in months at time of photograph (A to C) Adam (110 months),
Jonah (63 months), and Uriel (54 months). (D to F) Boaz (54 months), Judith (47 months),
and Hannah (88 months) [Credit: Guy Eisner/Sarah Sallon et al. 2020]
Since the researchers sprouted their first ancient date plant, the tale has captured the public's imagination. "These are something exceptional," Sarah Sallon, one of the leaders of the project, said of the resurrected plants. She said she regularly gets questions about Methuselah from kids. She has even written up his story for a children's book. In a time of seemingly relentless bad news about the environment, the date plant's journey provides some hope for future generations, she said. "It's a story of nature's amazing powers to regenerate itself."

The study is published in Science Advances.

Author: Catherine Meyers | Source: Inside Science, American Institute of Physics [February 05, 2020]



* This article was originally published here

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