Earth was barren, flat and almost entirely under water 4.4 billion years ago

Zircon crystals as old as 4.4 billion years were found in sandstone at Jack Hills of Western Australia.

Scientists at The Australian National University (ANU) say the early Earth was likely to be barren, flat and almost entirely under water with a few small islands, following their analysis of tiny mineral grains as old as 4.4 billion years.

Lead researcher Dr Antony Burnham said the team studied zircon mineral grains that were preserved in sandstone rocks in the Jack Hills of Western Australia and which were the oldest fragments of the Earth ever found.

"The history of the Earth is like a book with its first chapter ripped out with no surviving rocks from the very early period, but we've used these trace elements of zircon to build a profile of the world at that time," said Dr Burnham from the ANU Research School of Earth Sciences.

"Our research indicates there were no mountains and continental collisions during Earth's first 700 million years or more of existence -- it was a much more quiet and dull place.

"Our findings also showed that there are strong similarities with zircon from the types of rocks that predominated for the following 1.5 billion years, suggesting that it took the Earth a long time to evolve into the planet that we know today."

Dr Burnham said the zircon grains that eroded out of the oldest rocks were like skin cells found at a crime scene.

"We used the granites of southeast Australia to decipher the link between zircon composition and magma type, and built a picture of what those missing rocks were," he said.

The first known form of life emerged some time later, around 3.8 billion years ago.

Dr Burnham said the zircon formed by melting older igneous rocks rather than sediments.

"Sediment melting is characteristic of major continental collisions, such as the Himalayas, so it appears that such events did not occur during these early stages of Earth's history," he said.

Dr Burnham said scientists in the field were able to build on each other's work to gain a better understanding of early Earth.

"The samples of zircon from Jack Hills have been collected over the course of several decades by many people, while chemical analyses carried out by an ANU research group 20 years ago have proved invaluable," he said.

From Science Daily

Archaeogeneticist pinpoints Indian population origins using today's populace

Indian women in saris.

In addition to its vast patchwork of languages, cultures and religions, the Indian Subcontinent also harbours huge genetic diversity. Where did its peoples originate? This is an area of huge controversy among scholars and scientists. A University of Huddersfield PhD student is lead author of an article that tries to answer the question using genetic evidence.

A problem confronting archaeogenetic research into the origins of Indian populations is that there is a dearth of sources, such as preserved skeletal remains that can provide ancient DNA samples. Marina Silva and her co-authors have instead focused on people alive in the Subcontinent today.

They show that some genetic lineages in South Asia are very ancient. The earliest populations were hunter-gatherers who arrived from Africa, where modern humans arose, more than 50,000 years ago. But further waves of settlement came from the direction of Iran, after the last Ice Age ended 10-20,000 years ago, and with the spread of early farming.

These ancient signatures are most clearly seen in the mitochondrial DNA, which tracks the female line of descent. But Y-chromosome variation, which tracks the male line, is very different. Here the major signatures are much more recent. Most controversially, there is a strong signal of immigration from Central Asia, less than 5,000 years ago.

This looks like a sign of the arrival of the first Indo-European speakers, who arose amongst the Bronze Age peoples of the grasslands north of the Caucasus, between the Black and Caspian Seas. They were male-dominated, mobile pastoralists who had domesticated the horse -- and spoke what ultimately became Sanskrit, the language of classical Hinduism -- which more than 200 years ago linguists showed is ultimately related to classical Greek and Latin.

Migrations from the same source also shaped the settlement of Europe and its languages, and this has been the subject of most recent research, said Marina Silva. She has tried to tip the balance back towards India, and her findings are discussed in the article titled A genetic chronology for the Indian Subcontinent points to heavily sex-biased dispersals. It appears in the journal BMC Evolutionary Biology.

Authors of the new article include Professor Martin Richards, who heads the University of Huddersfield's Archaeogenetics Research Group. Member of the group are also co-authors of another recent paper, which focuses in depth on just one of the lineages found in India, Origin and spread of mitochondrial haplogroup U7, which has just appeared in the journal Scientific Reports.

From Science Daily

Researchers identify 6,500 genes that are expressed differently in men and women

6,500 genes are expressed differently in men and women.

Men and women differ in obvious and less obvious ways -- for example, in the prevalence of certain diseases or reactions to drugs. How are these connected to one's sex? Weizmann Institute of Science researchers recently uncovered thousands of human genes that are expressed -- copied out to make proteins -- differently in the two sexes. Their findings showed that harmful mutations in these particular genes tend to accumulate in the population in relatively high frequencies, and the study explains why. The detailed map of these genes, reported in BMC Biology, provides evidence that males and females undergo a sort of separate, but interconnected evolution.

Several years ago, Prof. Shmuel Pietrokovski and Dr. Moran Gershoni of the Weizmann Institute's Molecular Genetics Department asked why the prevalence of certain human diseases is common. Specifically, about 15% of couples trying to conceive are defined as infertile, which suggested that mutations that impair fertility are relatively widespread. This seems paradoxical: Common sense says that these mutations, which directly affect the survival of the species by reducing the number of offspring, should have been quickly weeded out by natural selection. Pietrokovski and Gershoni showed that mutations in genes specific to sperm formation persist precisely because the genes are expressed only in men. A mutation that is problematic for only half the population, no matter how detrimental, is freely passed on to the next generation by the other half.

In the present study, the researchers expanded their analyses to include genes that, though not necessary for fertility, are still expressed differently in the two sexes. To identify these genes, the scientists turned to the GTEx project -- a very large study of human gene expression recorded for numerous organs and tissues in the bodies of close to 550 adult donors. That project enabled, for the first time, the comprehensive mapping of the human sex-differential genetic architecture.

Pietrokovski and Gershoni looked closely at around 20,000 protein-coding genes, sorting them by sex and searching for differences in expression in each tissue. They eventually identified around 6,500 genes with activity that was biased toward one sex or the other in at least one tissue. For example, they found genes that were highly expressed in the skin of men relative to that in women's skin, and they realized that these were related to the growth of body hair. Gene expression for muscle building was higher in men; that for fat storage was higher in women.

Yet another difference

The two then looked at tendencies to accumulate mutations, to see if natural selection puts more or less pressure on genes that are specific to men or women. That is, to what extent are harmful mutations weeded out or tolerated in the population? Indeed, the researchers found that the efficiency of selection is weaker in many such genes. "The more a gene was specific to one sex, the less selection we saw on the gene. And one more difference: This selection was even weaker with men," says Gershoni. Although they do not have a complete explanation for this additional difference, the researchers point to a theory of sexual evolution first proposed in the 1930s: "In many species, females can produce only a limited number of offspring while males can, theoretically, father many more; so the species' survival will depend on more viable females in the population than males," explains Pietrokovski. "Thus natural selection can be more 'lax' with the genes that are only harmful to males."

Aside from the sexual organs, the researchers discovered quite a few sex-linked genes in the mammary glands -- not so surprising, except that about half of these genes were expressed in men. Because men have fully fitted but basically nonfunctional mammary equipment, the scientists made an educated guess that some of these genes might suppress lactation.

Less obvious locations included genes that were found to be expressed only in the left ventricle of the heart in women. One of these genes, which is also related to calcium uptake, showed very high expression levels in younger women that sharply decreased with age; the scientists think that they are active in women up to menopause, protecting their hearts, but leading to heart disease and osteoporosis in later years when the gene expression is shut down. Yet another gene that was mainly expressed in women was active in the brain, and though its exact function is unknown, the scientists think it may protect the neurons from Parkinson's -- a disease that has a higher prevalence and earlier onset in men. The researchers also identified gene expression in the liver in women that regulates drug metabolism, providing molecular evidence for the known difference in drug processing between women and men.

"The basic genome is nearly the same in all of us, but it is utilized differently across the body and among individuals," says Gershoni. "Thus, when it comes to the differences between the sexes, we see that evolution often works on the level of gene expression." Pietrokovski adds: "Paradoxically, sex-linked genes are those in which harmful mutations are more likely to be passed down, including those that impair fertility. From this vantage point, men and women undergo different selection pressures and, at least to some extent, human evolution should be viewed as co-evolution. But the study also emphasizes the need for a better understanding of the differences between men and women in the genes that cause disease or respond to treatments."

Prof. Shmuel Pietrokovski's research is supported by the Leo and Julia Forchheimer Center for Molecular Genetics; and the estate of Georges Lustgarten. Prof. Shmuel Pietrovski is the incumbent of the Herman and Lilly Schilling Foundation Professorial Chair.

Read more at Science Daily

Anemonefish dads do almost anything to support their offspring

Male anemonefish are the primary caregivers in the nest. A new study examines how hormones influence their commitment to fathering.

Like the father in "Finding Nemo," anemonefish dads will do almost anything to support their offspring. Their parenting instincts are so strong that if you give a bachelor anemonefish a scoop of anemonefish eggs from an unrelated nest, he will care for them -- constantly nipping at them to remove debris and fanning them with oxygen-rich waters -- as if they were his own. (Any other fish would eat them, researchers say.)

A new study of this species, Amphiprion ocellaris, reveals some of the potent hormonal signals that regulate this gallant paternal instinct. Researchers report that anemonefish rely on a signaling molecule that is almost identical to oxytocin -- known as the love hormone in humans and also associated with mothering -- to maintain their fatherly fidelity. When researchers blocked this hormone, known as isotocin, in the male fish, the dads stopped tending to their young.

This is not the first study to show that isotocin regulates paternal care in fish, but it is the first to focus on the anemonefish, which the researchers describe as a paragon of fatherly love.

"Because the fish are so committed to their role as fathers, we're able in the lab to dissociate their parental behavior -- the fanning and the nipping -- from behaviors associated with courtship, territory defense and nest defense," said University of Illinois graduate student Ross DeAngelis, who led the study with psychology professor Justin Rhodes. "This allows us to look at how the brain regulates male parental care in isolation from other behaviors that occur simultaneously."

The researchers also analyzed how another hormone, arginine vasotocin, influences paternal care in anemonefish. Other studies suggest the hormone plays a role in regulating dominance, aggression and courtship. It also has a homolog in humans, known as arginine vasopressin.

"All these peptides -- isotocin and oxytocin, arginine vasopressin and vasotocin -- have very similar genetics and very similar molecular structures across species," Rhodes said. "They all evolved from the same gene."

When the researchers blocked vasotocin in one of a pair of male anemonefish, the treated males displayed significantly less aggression than their untreated counterparts. Blocking vasotocin in anemonefish fathers, however, yielded an unexpected result: The dutiful dads became even more attentive to their offspring.

"We were surprised by this because these fish display such a high level of parental effort in the laboratory that it's hard to imagine there being an increase," DeAngelis said. "Our hypothesis is that by blocking vasotocin signaling, you're reducing vigilance and nest defense, allowing a greater allotted effort to be directed toward parental care."

Whether the patterns in anemonefish also hold true for humans remains to be seen, the researchers said. Paternal care is rare in vertebrates, and mammalian fathers tend to be indifferent to the survival of their offspring, they said.

The anemonefish is particularly faithful to his mate and offspring because he's trapped with them on a single anemone that offers the family shelter and defense, the researchers said.

But the similarities between anemonefish and other species likely outweigh the differences, they said. There is evidence, for example, that oxytocin also plays a role in human fathering.

"There has been a lot of recent research showing that these behaviors -- like aggression or reproduction or parental care -- are sort of ubiquitously distributed across vertebrates, and the mechanisms that promote and maintain those behaviors are similar in all species," DeAngelis said.

Read more at Science Daily

A lot of galaxies need guarding

Like the quirky characters in the upcoming film Guardians of the Galaxy Vol. 2, NASA's Hubble Space Telescope has some amazing superpowers, specifically when it comes to observing galaxies across time and space. One stunning example is galaxy cluster Abell 370, which contains a vast assortment of several hundred galaxies tied together by the mutual pull of gravity. That's a lot of galaxies to be guarding, and just in this one cluster! Photographed in a combination of visible and near-infrared light with the Hubble's Advanced Camera for Surveys and Wide Field Camera 3 in Sept. 2009 to Feb. 2015, the immense cluster is a rich mix of galaxy shapes. Entangled among the galaxies are mysterious-looking arcs of blue light. These are actually distorted images of remote galaxies behind the cluster. These far-flung galaxies are too faint for Hubble to see directly. Instead, the gravity of the cluster acts as a huge lens in space, magnifying and stretching images of background galaxies like a funhouse mirror. Abell 370 is located approximately 4 billion light-years away in the constellation Cetus, the Sea Monster. It is the last of six galaxy clusters imaged in the recently concluded Frontier Fields project -- an ambitious, community-developed collaboration among NASA's Great Observatories and other telescopes that harnessed the power of massive galaxy clusters and probed the earliest stages of galaxy development.

Much like the eclectic group of space rebels in the upcoming film Guardians of the Galaxy Vol. 2, NASA's Hubble Space Telescope has some amazing superpowers, specifically when it comes to observing innumerable galaxies flung across time and space.

A stunning example is a galaxy cluster called Abell 370 that contains an astounding assortment of several hundred galaxies tied together by the mutual pull of gravity. That's a lot of galaxies to be guarding, and just in this one cluster!

Photographed in a combination of visible and near-infrared light, the immense cluster is a rich mix of galaxy shapes. The brightest and largest galaxies in the cluster are the yellow-white, massive, elliptical galaxies containing many hundreds of billions of stars each. Spiral galaxies -- like our Milky Way -- have younger populations of stars and are bluish.

Entangled among the galaxies are mysterious-looking arcs of blue light. These are actually distorted images of remote galaxies behind the cluster. These far-flung galaxies are too faint for Hubble to see directly. Instead, the cluster acts as a huge lens in space that magnifies and stretches images of background galaxies like a funhouse mirror. The massive gravitational field of the foreground cluster produces this phenomenon. The collective gravity of all the stars and other matter trapped inside the cluster warps space and affects light traveling through the cluster, toward Earth.

Nearly a hundred distant galaxies have multiple images caused by the lensing effect. The most stunning example is "the Dragon," an extended feature that is probably several duplicated images of a single background spiral galaxy stretched along an arc.

Astronomers chose Abell 370 as a target for Hubble because its gravitational lensing effects can be used for probing remote galaxies that inhabited the early universe.

Abell 370 is located approximately 4 billion light-years away in the constellation Cetus, the Sea Monster. It is the last of six galaxy clusters imaged in the recently concluded Frontier Fields project. This ambitious, community-developed collaboration among NASA's Great Observatories and other telescopes harnessed the power of massive galaxy clusters and probed the earliest stages of galaxy development. The program reveals galaxies that are 10 to 100 times fainter than any previously observed.

From Science Daily

Battered Earth revived by mineral weathering after mass extinction

Bedrock of Earth got severely beaten up by hothouse climate conditions during one of planet’s mass extinctions some 200 million years ago. But the process also allowed life to bounce back.

One of the Big Five mass extinction events occurred some 200 million years ago. Giant volcanic eruptions and an asteroid impact have been blamed for causing the disastrous change of climate, killing off nearly half of the species on Earth. 

The time epoch is called late Triassic. Amounts of carbon dioxide released through the volcanic activity during this time were staggering. Concentrations of CO2 in the atmosphere were up to 1000 ppm or so due to the volcanic activities of the period. For comparison, we have just recently reached 410 ppm of CO2 in the atmosphere today, a concentration that worries many scientists.

“In addition to the warming effects of the CO2 release, dissociation of massive amounts of methane hydrates had intensified the warming effect during the mass extinction. “ says Jochen Knies of CAGE and Geological Survey of Norway. He is a coauthor on recent Nature Communication study that has found evidence of impact of hothouse climate conditions of the late Triassic in Scandinavia.

Precisely dating deeply impacted bedrock

Published in Nature Communications by Ola Fredin (Geological Survey of Norway) and colleagues, these new findings shed light on how high greenhouse gas concentrations caused the bedrock to disintegrate through chemical weathering. Chemical weathering is caused by water reacting with the mineral grains in rocks to form new minerals, such as clay mineral illite. These reactions occur particularly when the water is acidic, as is the case when the CO2 levels are high.

“We have managed to precisely date deeply weathered crystalline bedrock from the North Sea and across Scandinavia, which then was part of the supercontinent Pangea. We did this by detailed geomorphological and mineralogical analyses of weathered rocks combined with the dating of clay mineral illite”, says Knies.

All the dated samples show that intensive and widespread chemical weathering occurred under hothouse conditions during the late Triassic. The bedrock was slowly transformed, and the transformation co-occurred with emerging volcanic activity.

Bedrock eventually removes CO2

The hothouse conditions of this mass extinction caused oceans to eventually become depleted of oxygen, and thus become unbearable to live in. But weathering of silicate in the bedrock of Pangea, and subsequent formation of carbonate, tied up the CO2 into the minerals, slowly removing the greenhouse gas from the atmosphere.

Read more at Science Daily

Noise created by humans is pervasive in US protected areas

This is an acoustic recording station at the iconic tourist attraction Alcatraz Island in San Francisco Bay, Golden Gate National Park, California.

Protected areas in the United States, representing 14 percent of the land mass, provide places for respite, recreation, and natural resource conservation. However, noise pollution poses novel threats to these protected areas, according to a first-of-its-kind study from scientists at Colorado State University and the U.S. National Park Service.

Researchers found that noise pollution was twice as high as background sound levels in a majority of U.S. protected areas, and caused a ten-fold or greater increase in noise pollution in 21 percent of protected areas.

The often-overlooked impacts of noise, driven by expansion of human activities and transportation networks, are encroaching into the furthest reaches of remote areas, according to the study. The research findings highlight the pervasiveness and identify the primary drivers of noise in protected areas.

Rachel Buxton, lead author and post-doctoral researcher in the Department of Fish, Wildlife, and Conservation Biology in the Warner College of Natural Resources, said the team was surprised by how prevalent noise pollution was in protected areas.

"The noise levels we found can be harmful to visitor experiences in these areas, and can be harmful to human health, and to wildlife," she said. "However, we were also encouraged to see that many large wilderness areas have sound levels that are close to natural levels. Protecting these important natural acoustic resources as development and land conversion progresses is critical if we want to preserve the character of protected areas."

Anthropogenic, or human-caused, noise is an unwanted or inappropriate sound created by humans, such as sounds emanating from aircraft, highways, industrial, or residential sources. Noise pollution is noise that interferes with normal activities, such as sleeping and conversation. It can also diminish a person's quality of life.

Measuring noise pollution is a challenging task, given its diffusive nature and since sound is not easily monitored remotely over large spatial scales; it can't be measured by satellite or other visual observations. Instead, for this study, the team analyzed millions of hours of sound measurements from 492 sites around the continental U.S. The results summarized predictions of existing sound levels, estimates of natural sound levels, and the amount that anthropogenic noise raises levels above natural levels, which is considered noise pollution.

How prevalent is noise pollution in protected areas? The research team found anthropogenic noise doubled background sound levels in 63 percent of U.S. protected areas, and caused a ten-fold or greater increase in background levels in 21 percent of protected areas.

In other words, noise reduced the area that natural sounds can be heard by 50 to 90 percent. This also means that what could be heard at 100 feet away could only be heard from 10 to 50 feet.

This reduced capacity to hear natural sound reduces the restorative properties of spending time in nature, such as mood enhancement and stress reduction, interfering with the enjoyment typically experienced by park visitors. Noise pollution also negatively impacts wildlife by distracting or scaring animals, and can result in changes in species composition.

High levels of noise pollution were also found in critical habitat for endangered species, namely in endangered plant and insect habitats. "Although plants can't hear, many animals that disperse seeds or pollinate flowers can hear, and are known to be affected by noise, resulting in indirect impacts on plants," said Buxton.

The study also revealed that high noise pollution levels within protected areas were in specific locations, where noise reduction techniques may best be targeted. The biggest noise-causing culprits were roads, aircraft, human development, and resource extraction.

Some protected areas have introduced effective techniques to reduce noise, launching shuttle services to cut back on traffic, implementing quiet zones where visitors are encouraged to quietly enjoy protected area surroundings, and creating noise corridors, aligning flight patterns over roads.

"Numerous noise mitigation strategies have been successfully developed and implemented, so we already have the knowledge needed to address noise issues," said George Wittemyer, an associate professor at Colorado State University and the senior author of the study. "Our work provides information to facilitate such efforts in respect to protected areas where natural sounds are integral."

Read more at Science Daily

New theory on how Earth's crust was created

Conventional theory holds that all of the early Earth's crustal ingredients were formed by volcanic activity. Now, however, earth scientists have put forth a theory with a novel twist: some of the chemical components of this material settled onto Earth's early surface from the steamy atmosphere that prevailed at the time.

More than 90% of Earth's continental crust is made up of silica-rich minerals, such as feldspar and quartz. But where did this silica-enriched material come from? And could it provide a clue in the search for life on other planets?

Conventional theory holds that all of the early Earth's crustal ingredients were formed by volcanic activity. Now, however, McGill University earth scientists Don Baker and Kassandra Sofonio have published a theory with a novel twist: some of the chemical components of this material settled onto Earth's early surface from the steamy atmosphere that prevailed at the time.

First, a bit of ancient geochemical history: Scientists believe that a Mars-sized planetoid plowed into the proto-Earth around 4.5 billion years ago, melting the Earth and turning it into an ocean of magma. In the wake of that impact -- which also created enough debris to form the moon -- the Earth's surface gradually cooled until it was more or less solid. Baker's new theory, like the conventional one, is based on that premise.

The atmosphere following that collision, however, consisted of high-temperature steam that dissolved rocks on the Earth's immediate surface -- "much like how sugar is dissolved in coffee," Baker explains. This is where the new wrinkle comes in. "These dissolved minerals rose to the upper atmosphere and cooled off, and then these silicate materials that were dissolved at the surface would start to separate out and fall back to Earth in what we call a silicate rain."

To test this theory, Baker and co-author Kassandra Sofonio, a McGill undergraduate research assistant, spent months developing a series of laboratory experiments designed to mimic the steamy conditions on early Earth. A mixture of bulk silicate earth materials and water was melted in air at 1,550 degrees Celsius, then ground to a powder. Small amounts of the powder, along with water, were then enclosed in gold palladium capsules, placed in a pressure vessel and heated to about 727 degrees Celsius and 100 times Earth's surface pressure to simulate conditions in the Earth's atmosphere about 1 million years after the moon-forming impact. After each experiment, samples were rapidly quenched and the material that had been dissolved in the high temperature steam analyzed.

The experiments were guided by other scientists' previous experiments on rock-water interactions at high pressures, and by the McGill team's own preliminary calculations, Baker notes. Even so, "we were surprised by the similarity of the dissolved silicate material produced by the experiments" to that found in the Earth's crust.

Their resulting paper, published in the journal Earth and Planetary Science Letters, posits a new theory of "aerial metasomatism" -- a term coined by Sofonio to describe the process by which silica minerals condensed and fell back to earth over about a million years, producing some of the earliest rock specimens known today.

"Our experiment shows the chemistry of this process," and could provide scientists with important clues as to which exoplanets might have the capacity to harbor life Baker says.

Read more at Science Daily

Climate Change-Driven Extinction of Alpine Plant Species May Go Undetected

Researchers working in the Austrian Alps warn that current models may be missing the impending extinction of alpine plants that are unable to migrate from or adapt to a warming climate.

While current models tend to look for the mere presence or absence of a plant species as the primary indicator of how well they are adapting to changing climate conditions, a team of scientists at the University of Zurich say that they’re missing important data — namely, the density and age structure of these populations.

“For now, presence or absence at a given location has been the model, but even if you have the presence of the species, it may be doing quite badly,” said evolutionary biologist Frédéric Guillaume, who led the study published today in Nature Communications. 

Guillaume and his team have developed a model that they hope will address this problem, specifically for alpine species that face a unique risk of extinction. Given the inherent limits to their range — constrained to pyramid-shaped mountaintops — and the longevity of alpine plants, they are particularly ill equipped to evolve to warming conditions.

Of particular concern is the age structure of alpine species, which are highly endemic and considered especially vulnerable to climate change. Much like an aging human population, the three alpine flower species and one alpine grass species targeted in the study are failing to produce viable replacements for the aging plants, creating what authors refer to as an “extinction debt.”

“The adults are adapted to a climate of the past, while juveniles must adapt to a new climate,” Guillaume explained. “By producing offspring with genes that were selected in a previous environment, they have a handicap evolving to the current environment.”

If a critical number of juvenile plants don’t take root, the population thins and faces a “demographic deficit” that could eventually lead to its extinction. And because the alpine species included in the study live for a long time, they will appear in current models even if the population is both aging and thinning.

It is a challenge faced by any plant species with a small or geographically fragmented population, attributes that will make its evolution or adaptation to a changing climate more difficult. In the Alps, this scenario is further compounded by the fact that for these plants, the only way to go is up. They quickly run out of space and options.

In the best case scenarios put forth by scientists — that warming will be limited to 1 degree Celsius compared to pre-Industrial Age levels — these populations could recover, so long as the warming slows after 2090, according to authors. But, if climate change continues unabated, alpine plants could face mass extinction.

What’s more, it could be a problem that will go undetected until it's too late, as current models cannot see what authors describe as the “invisible extinction debt.”

Read more at Discovery News

TRAPPIST-1 Planets Have No Large Moons, Study Argues

Artist's impression of a hypothetical exomoon going around an imagined planet. Exomoons have not been discovered yet, but we know of thousands of exoplanet candidates.

While we know of thousands of exoplanets and exoplanet candidates, the search for moons outside of our solar system is just beginning. We don't have a confirmed exomoon discovery yet, but they're bound to be out there.

Finding exomoons will help us better understand habitability on Earth. Some experts say a reason that life arose is our own moon is so close to the size of our planet, which stabilized its axis rotation. However, other studies (such as this 2011 American Astronomical Society paper quoted in a NASA Astrobiology story) argue that the gravitational influence of other planets in our solar system provide enough stability.

A new study looks at the possibilities of large moons in TRAPPIST-1, a notoriously crowded exoplanet system that may have habitable planets within it. Earlier this year, observations from NASA's Spitzer Space Telescope indicated that seven planets here could be rocky and have liquid water on their surfaces, making TRAPPIST-1 the system with the most potentially habitable planets.

But even before NASA's discovery, TRAPPIST-1 was known and pondered by scientists, including the author of the new paper, Stephen Kane, an associate professor of astronomy at San Francisco State University who specializes in exoplanets.

"I have several publications now on exomoons, and for many years I've been thinking about how the ability of a planet to host a moon scales with the presence of nearby planets and proximity to the host star," Kane said in an e-mail. "The discovery of the TRAPPIST-1 system prompted me to finally calculate whether or not planets in compact planetary systems can actually harbor moons."

Artist's impression of the TRAPPIST-1 system, located about 40 light-years from Earth.

Kane cautioned that scientists can't overly attribute Earth's habitability to our moon, because Earth is the only known habitable planet. However, the moon does have an important role: It creates significant tides on Earth, which probably helped create the tidal pools in which early biochemistry could occur.

"The presence of the moon has helped to stabilize changes in the tilt of the Earth's rotational axis, which in turn creates longer periods of climate stability," Kane added. "So although it's difficult to say what the Earth would be like without a moon, we can certainly describe ways in which it has positively influenced our present environment."

For TRAPPIST-1, Kane found that the planets are so tightly packed together that large moons would likely be impossible. While the rotational axes of the planets would quickly change and have more chaotic climates, he said, life could still evolve — it just might take a longer time.

Kane's methodology involved studying the influences of two parameters: the Hill radius, or the area in space in which a planet exerts gravitational influence based on its mass and distance from the host star, and the Roche limit, which identifies where the gravitational effect near a planet is too strong for a moon to survive.

Read more at Discovery News