News Feeds

Researchers have observed electric charges traveling across the interface of two different semiconductor materials. Using scanning ultrafast electron (SUEM) techniques, the research team has directly visualized the fleeting phenomenon for the first time.

Researchers have observed electric charges traveling across the interface of two different semiconductor materials. Using scanning ultrafast electron (SUEM) techniques, the research team has directly visualized the fleeting phenomenon for the first time.

Per- and polyfluoroalkyl chemicals, known commonly as PFAS, could take over 40 years to flush out of contaminated groundwater.

Chemists have developed a new chemical reaction that will allow researchers to synthesize selectively the left-handed or right-handed versions of 'mirror molecules' found in nature and assess them for potential use against cancer, infection, depression, inflammation and a host of other conditions.

The small island nations of the South Pacific are facing the harsh reality of sea level rise. Within 50 years they will be swamped by rising seas linked to climate change. That’s part of a stark forecast from a sea level change science team at NASA and leading universities.

The group used satellites to predict rising ocean levels. According to their data, Pacific nations such as Tuvalu, Kiribati, and Fiji will experience an increased rise in sea levels. That threatens the homes and livelihoods of millions of people.

The Team’s Work

The team that examined the rise of sea levels threatening South Pacific nations is part of an interdisciplinary research group at NASA. Its job is to improve our understanding of sea-level change over time. The members analyzed the South Pacific threat at the request of the affected nations and coordinated with the U.S. State Department. They created high-resolution maps showing which areas of different Pacific Island nations would be vulnerable to high-tide flooding. The maps outline the potential for flooding. In addition, they take into account different greenhouse gas emissions scenarios, ranging from best-case to business-as-usual to worst-case.

One of the islands of Tuvalu. Sea level rise threatens to swamp the islands of this nation within 50 years. Courtesy NASA.

A combination of space-based and ground-based measurements can yield more precise sea level rise projections. That should give an improved understanding of the impacts on countries in the Pacific. Still, it’s one thing to create predictive models and share that data with affected nations. It’s quite another to actually experience the gradual rise of sea levels as the people of the South Pacific islands and other low-lying areas along the world’s coastlines.

“I am living the reality of climate change,” said Grace Malie, a youth leader from Tuvalu who is involved with the Rising Nations Initiative, a United Nations-supported program led by Pacific Island nations to help preserve their statehood and protect the rights and heritage of populations affected by climate change. “Everyone (in Tuvalu) lives by the coast or along the coastline, so everyone gets heavily affected by this.”

How NASA Tracks Sea-level Rise

Researchers from the University of Hawaii, the University of Colorado, and Virginia Tech all took part in the study, which used a new Pacific Islands Flooding Tool for the project. The data they use comes from measurements by satellites, shipboard and airborne instruments, and supercomputer analysis. The result is a more precise assessment of sea levels and their rise and fall over time. Using this data, the science teams found some worrying trends.

The portal to NASA’s Pacific Islands flooding analysis tool to help scientists assess sea level rise in low-lying areas. Courtesy NASA.

“Sea level will continue to rise for centuries, causing more frequent flooding,” said Dr. Nadya Vinogradova Shiffer, who directs ocean physics programs for NASA’s Earth Science Division. “NASA’s new flood tool tells you what the potential increase in flooding frequency and severity look like in the next decades for the coastal communities of the Pacific Island nations.”

What Affects Sea Level?

Sea level rise is based on a number of factors, including melting of glaciers and other ice packs and ocean warming related to pumping greenhouse gases into the atmosphere. Based on the data from NASA satellites, the Pacific Islands most at risk will see at least a 15-cm sea level rise by 2050. That’s nearly an order of magnitude higher than all Pacific Island nations experience now. To give you an idea of how that will affect specific places, Tuvalu currently sees less than five high tide flood days per year. By 2050, residents will experience at least 25 flood days each year. Kiribati will see 65 flood events. The maps produced by the NASA-led team for these and other islands should help these nations plan for future flood mitigation efforts.

“Science and data can help the community of Tuvalu in relaying accurate sea level rise projections,” said Malie. “This will also help with early warning systems, which is something that our country is focusing on at the moment.”

Assessing Sea Level Rise

Not every area in the world experiences the same amount of flooding. Local conditions and coastlines contribute to area-specific floods. The impact that 15 centimeters of sea level rise will have varies from country to country. Some regions will see nuisance flooding several times a year in flat or low-lying areas. Others face inundation for longer periods with higher amounts of water.

“We’re always focused on the differences in sea level rise from one region to another, but in the Pacific, the numbers are surprisingly consistent,” said Ben Hamlington, a sea level researcher at NASA’s Jet Propulsion Laboratory in Southern California and the agency’s sea level change science team lead.

The impacts of sea level rise will vary from place to place and depend on topography, shapes of coastlines, and other factors. Better predictive tools will help scientists understand where sea levels will rise the most and share that information with affected populations. Researchers would like to combine satellite data on ocean levels with ground-based measurements of sea levels at specific points, as well as with better land elevation information. “But there’s a real lack of on-the-ground data in these countries,” said Hamlington.

Real-world Experience

The combination of space-based and ground-based measurements can yield more precise sea level rise projections and an improved understanding of the impacts on countries in the Pacific. Still, it’s one thing to create predictive models and share that data with affected nations. It’s quite another to actually experience the gradual rise of sea levels as the people of the South Pacific islands and other low-lying areas along the world’s coastlines.

People in these regions experience different types of threats from the oceans. Flooding can occur when the ocean inundates the land during tropical storms, typhoons, and hurricanes. It can also happen during exceptionally high tides, called king tides.

An example of sunny day king tide flooding submerging street infrastructure outside the City of Miami Fire Station 13. Sea level rise contributes to increased incidences of such flooding. Credit: Mike Sukop/NOAA.

Another avenue for flooding is saltwater intrusion into underground areas. That pushes the water table to the surface. “There are points on the island where we will see seawater bubbling from beneath the surface and heavily flooding the area,” Malie added.

Places like Tuvalu will benefit from better tools to predict sea level rise. It’s not just a matter of preventing flooding, but one of a nation’s survival now and over the next few decades. “The future of the young people of Tuvalu is already at stake,” said Malie. “Climate change is more than an environmental crisis. It is about justice, survival for nations like Tuvalu, and global responsibility.”

For More Information

NASA Analysis Shows Irreversible Sea Level Rise for Pacific Islands
Sea Level Change
Pacific Islands Flooding Tool

The post Satellites are Tracking the Ongoing Sea Level Rise Swamping Pacific Island Nations appeared first on Universe Today.

In recent years, the number of known extrasolar planets (aka. exoplanets) has grown exponentially. To date, 5,799 exoplanets have been confirmed in 4,310 star systems, with thousands more candidates awaiting confirmation. What has been particularly interesting to astronomers is how M-type (red dwarf) stars appear to be very good at forming rocky planets. In particular, astronomers have detected many gas giants and planets that are several times the mass of Earth (Super-Earths) orbiting these low-mass, cooler stars.

Consider TOI-6383A, a cool dwarf star less than half the mass of the Sun that orbits with an even smaller, cooler companion – the red dwarf star TOI-6383B. In a recent study, an international team of astronomers with the Searching for Giant Exoplanets around M-dwarf Stars (GEMS) survey detected a giant planet transiting in front of the primary star, designated TOI-6383Ab. This planet is similar in size and mass to the system’s companion star, which raises questions about the formation of giant planets in red dwarf star systems.

The team was led by Lia Marta Bernabò, a PhD astronomy student at the University of Texas at Austin (UTA) and the German Aerospace Center (DLR). She was joined by colleagues with the GEMS collaboration, which includes astronomers from the Center for Planetary Systems Habitability, the Carnegie Science Earth and Planets Laboratory, the Center for Exoplanets and Habitable Worlds, the ETH Zurich Institute for Particle Physics & Astrophysics, the Anton Pannekoek Institute for Astronomy, NOIRLab, the NASA Goddard Space Flight Center, and multiple universities and institutes. The paper that details their findings was recently accepted for publication by the Astronomical Journal.

A giant star orbits one of the stars in the binary star system TOI-6383. As both stars are dwarf stars, a problem due to the mass budget comes up. Credit: DLR

The TOI6383 system consists of two red dwarf stars located about 560 light-years from Earth. The primary (A) is about 46% as massive as the Sun and about as large and has an estimated surface temperature of 3444 K (3,170 °C; 5,740 °F) – about 60% of the Sun’s surface temperature. Its companion (B) is 20.5% as massive as our Sun, 22% its size, and has an estimated surface temperature of 3121 K (2848 °C; 5,158 °F). Meanwhile, TOI6383Ab has a mass and size comparable to Jupiter and an orbital period of about 1.79 days.

Based on the all-sky coverage of NASA’s Transiting Exoplanet Survey Satellite (TESS), the GEMS survey team is dedicated to searching for giant exoplanets around M-dwarf stars (GEMS) using the Transit Method (Transit Photometry). This consists of monitoring stars for periodic dips in brightness, which could indicate planets passing (aka transiting) in front of their parent stars relative to the observer. The exoplanet was detected by TESS and confirmed by a combination of follow-photometry and radial velocity measurements using ground-based telescopes.

This survey aims to test theories of how planets form, which can be divided into two main categories. The first scenario is the core-accretion model, where planetesimals coagulate around a massive core. However, this model has come to be questioned in recent decades, largely because it is inconsistent with the mass budget and time scales for the formation of M dwarfs. Dwarf stars typically have less massive protoplanetary disks around them, meaning there is insufficient material to form giant planets.

The second scenario is the rapid formation model, where a massive protostellar disk disintegrates into clumps under its own gravity, which then accrete material and form planets. The discovery of this latest massive planet around a low-mass star will help astronomers to test these competing models. To date, only 20 massive exoplanets have been detected around M-type red dwarfs. The GEMS survey seeks to increase this inventory to at least 40, whereupon more precise tests of these models can be made.

Further Reading: DLR Institute of Planetary Research, Astronomical Journal

The post Exoplanet Discovered in a Binary System Could Explain Why Red Dwarfs Form Massive Planets appeared first on Universe Today.

A new technique uses glowing molecules, laser light and microscopes to measure distances as minuscule as 0.1 nanometres – the width of a typical atom

When three massive objects meet in space, they influence each other through gravity in ways that evolve unpredictably. In a word: Chaos. That is the conventional understanding. Now, a researcher has discovered that such encounters often avoid chaos and instead follow regular patterns, where one of the objects is quickly expelled from the system. This new insight may prove vital for our understanding of gravitational waves and many other aspects of the universe.

A new solution deposition process for semiconductors yields high-performing transistors by introducing more defects, counterintuitively. Researchers used these devices to construct high- speed logic circuits and an operational high-resolution inorganic LED display.

When lightning cracks on Earth, especially high-energy electrons may fall out of Earth's inner radiation belt, according to a new study -- an electron 'rain' that could threaten satellites, and even humans, in orbit.

An organic catalyst offers chemists precise control over a vital step in activating hydrocarbons.

Reader Nick sent me this 4-minute video about a young Indian girl—only ten years old—has become an accomplished wildlife photographer. I’ve started the video at the point at which her “PBS News Weekend” piece begins. It’s a short video but a heartwarming one, and this young woman is going to go far.  It doesn’t hurt that she has access to some of the most charismatic wildlife in the world!

Her prize-winning “Nature Photographer of the Year” photo is stunning.

Materials researchers have created a new composite material that combines two incompatible properties: stiff yet with a high damping capacity.

A new computer simulation of how our brains develop and grow neurons has been built. Along with improving our understanding of how the brain works, researchers hope that the models will contribute to neurodegenerative disease research and, someday, stem cell research that helps regenerate brain tissue.

Nearly 6000 species and subspecies of earthworms have been identified by scientists – but the true number could top 30,000

Over at sapiens.org, an anthropology magazine, author Elaine Guevara (a lecturer in evolutionary anthropology at Duke) takes modern genetics education to task.  Making a number of assertions about what students from high school to college learn in their genetics courses, Guevara claims that this type of education imparts “zombie ideas”: outdated but perpetually revived notions that prop up biological racism.  Her main topic is race, and she does offer some insights that modern genetics has given us about differences between geographic populations (I prefer to use “populations” rather than “races”), but these insights have been known for a long time. By failing to tell us that the errors earlier biologists have made about race have been refined and, to a large degree, dispelled, Guevara is herself deficient in describing the state of modern genetics.

Click the screenshot to read:

Guevara makes several accusations that, I think, are misleading. I’ll group her misleading conclusions under bold headings (the wording of those is mine). Quotes from her paper, or my paper with Luana Maroja, are indented and identified

1.) Human populations are not as different as we think, and the concept of “race” is incorrect: classical “races” are not genetically distinguishable. Guevara first cites a famous 1972 paper by my Ph.D. advisor, Richard Lewontin, “The Apportionment of Human Diversity“. The paper looked at genetic variation of 17 proteins detected by gel electrophoresis, apportioning the worldwide variation of proteins among individuals within a population, among populations within a classical “race”, and then between seven “races”. He found that of the total genetic variation seen worldwide, 85% occurred among individuals within one geographic population, 8% among populations within a race, and only 6% was found among races.

Thus races were not as genetically different as some people assumed. Lewontin concluded this (bolding is mine):

It is clear that our perception of relatively large differences between human races and subgroups [JAC: note that Lewontin’s “subgroups” correspond to what I would call “populations’], as compared to the variation within these groups, is indeed a biased perception and that, based on randonly chosen genetic differences, human races and populations are remarkably similar to each other, with the largest part by far of human variation being accounted for by the differences between individuals.

Human racial classification is of no social value and is positively destructive of social and human relations. Since such racial classification is now seen to be of virtually no genetic or taxonomic significance either, no justification can be offered for its continuance.

The first paragraph is correct. Later studies using better methods (DNA) have shown that yes, the apportionment of human diversity shows most of it within populations and only a fraction among populations or among “races”.  The classical view that races like “Caucasion”, “Asian” or “Black” showed large and diagnostic genetic differences at single genes was wrong

But the second paragraph is wrong, too, because Lewontin did not raise the possibility (as I’m sure he realized) that small differences among populations (or the groups of populations that constitute classical “races”) can, taken across many, many genes, add up to significant statistical and biological differences. The failure to recognize the power of using genetic data from many genes (we have three billion DNA nucleotides in our genome) is called “Lewontin’s fallacy.” This fallacy was pointed out in 2003 by A.W.F. Edwards and has its own Wikipedia page.

The power of using many genes instead of just an unweighted average of data from individual genes is shown by several things, as Luana Maroja and I pointed out in our paper published in Skeptical Inquirer last year. For one thing, if there were no meaningful genetic differences between populations, you couldn’t use genetic differences to diagnose someone’s ancestry. Yet you can, and with remarkable accuracy, as anyone knows who is aware of their family history and has taken a genetic test like those offered by 23andMe.  My test showed that I have complete Eastern European ancestry, with 98% of it from Ashkenazi Jews, which comports with what I know of my family history. (I also have a small percentage of genes from Neanderthals.)

Now this tells you the area of the world—the population—from which your ancestors probably came.  It doesn’t deal with “races” as classically defined. Yet a multiple-gene analysis using four races that Americans themselves use in self-identification (African-American, white, east Asian, or Hispanic) can indeed be diagnosed with remarkable accuracy. As Luana and I said in our paper (I’ve bolded the money quote):

Even the old and outmoded view of race is not devoid of biological meaning. A group of researchers compared a broad sample of genes in over 3,600 individuals who self-identified as either African American, white, East Asian, or Hispanic. DNA analysis showed that these groups fell into genetic clusters, and there was a 99.84 percent match between which cluster someone fell into and their self-designated racial classification. This surely shows that even the old concept of race is not “without biological meaning.” But that’s not surprising because, given restricted movement in the past, human populations evolved largely in geographic isolation from one another—apart from “Hispanic,” a recently admixed population never considered a race. As any evolutionary biologist knows, geographically isolated populations become genetically differentiated over time, and this is why we can use genes to make good guesses about where populations come from.

And this:

More recent work, taking advantage of our ability to easily sequence whole genomes, confirms a high concordance between self-identified race and genetic groupings. One study of twenty-three ethnic groups found that they fell into seven broad “race/ethnicity” clusters, each associated with a different area of the world. On a finer scale, genetic analysis of Europeans show that, remarkably, a map of their genetic constitutions coincides almost perfectly with the map of Europe itself. In fact, the DNA of most Europeans can narrow down their birthplace to within roughly 500 miles. [See below for the European data.]

You can also identify the “classical” races used in self-identification using some morphological traits. As we wrote:

But you don’t even need DNA sequences to predict ethnicities quite accurately. Physical traits can sometimes do the job: AI programs can, for instance, predict self-reported race quite accurately from just X-ray scans of the chest.

Population differences summed across genes can tell us more, too:

On a broader scale, genetic analysis of worldwide populations has allowed us to not only trace the history of human expansions out of Africa (there were several), but to assign dates to when H. sapiens colonized different areas of the world. This has been made easier with recent techniques for sequencing human “fossil DNA.” On top of that, we have fossil DNA from groups such as Denisovans and Neanderthals, which, in conjunction with modern data, tells us these now-extinct groups bred in the past with the ancestors of “modern” Homo sapiens, producing at least some fertile offspring (most of us have some Neanderthal DNA in our genomes). Although archaeology and carbon dating have helped reconstruct the history of our species, these have largely been supplanted by sequencing the DNA of living and ancient humans.

Finally, there are nearly diagnostic differences between populations in genes that evolved in an adaptive way, like known genes for resistance to low oxygen, short stature or skin pigmentation. Here’s a figure from a 2015 Science paper by Sarah Tishkoff:

None of this would be possible if there were not significant genetic and biological differences between populations.  We did not maintain that there are always diagnostic differences between populations at single genes that can group them into races, but that there are statistical differences in frequencies of variable genes among populations that are biologically meaningful.  Nor did we claim that the classically-defined races are absolutely geographically distinct with little intermixing, or have nearly fixed differences in frequencies of variable genes. That’s not true, and all geneticists realize this now. (But note that even the classically defined “races” generally differ in gene frequencies and in some biological traits to an extent that they can be diagnosed.)

The reality is that we should be dealing with populations, and populations—roughly defined as geographically different groups of people that largely breed among themselves—show diagnostic genetic and morphological differences.

Yet Guevara misleads the reader by relying solely on Lewontin’s paper and neglecting all the work done since that showing that yes, there is diagnostic geographic variation among populations (note that Lewontin implied that the concept of “population” is about as meaningless as “race”). Here are cxcerpts from Guevara’s paper:

Lewontin published his calculations in a short paper in 1972 that ended with this definitive conclusion: “Since … racial classification is now seen to be of virtually no genetic or taxonomic significance either, no justification can be offered for its continuance.” His results have been replicated time and again over the last 50 years, as datasets have ballooned from a handful of proteins to hundreds of thousands of human genomes.

But despite huge strides in genetics research—leaving no doubt about the validity of Lewontin’s conclusions—genetics curricula taught in U.S. secondary and post-secondary schools still largely reflect a pre-1970s view.

This lag in curricula is more than a worry for those in the ivory tower. Increasingly, genomics plays a leading role in health care, criminal justice, and our sense of identity and connection to others. At the same time, scientific racism is on the rise, reaching more people than ever thanks to social media. Outdated education fails to dispel this disinformation.

Leaving “no doubt about the validity of Lewontin’s conclusions”?  Nope.  The apportionment of variation is without doubt, but not his conclusion that populations or races are without biological meaning.

None of the critiques of Lewontin’s paper, including Edwards’s famous clarification, are even mentioned by Guevara. And, in fact, I don’t know of any biologists in post-secondary genetics education who still teach the view that “Race and ethnicity are social constructs, without scientific or biological meaning.” (This is a quote from JAMA reproduced in the Coyne and Maroja paper. And perhaps some people teach this erroneous view, but no biologist that I know of.) That JAMA statement is completely misleading, as I hope I’ve shown above. The delineation and definition of classical races was itself misleading and often tied to racism in the past, but, as we see, even self-identified classical races can be diagnosed through genes or morphology, and generally do fall into clusters using analysis of multiple genes.

The last paragraph of Guevara’s quote above shows the ideological motivation behind her paper: we must dismiss the existence of biological races and genetic differences between populations because it emphasizes differences between humans, and thus could lead to ranking of human populations, and thence to racism.  But, as Ernst Mayr recognized, accepting differences does not mean you have to view groups as being morally or legally unequal. We give a quote by evolutionist Ernst May quote in our Skeptical Inquirer paper:

Equality in spite of evident non-identity is a somewhat sophisticated concept and requires a moral stature of which many individuals seem to be incapable. They rather deny human variability and equate equality with identity. Or they claim that the human species is exceptional in the organic world in that only morphological characters are controlled by genes and all other traits of the mind or character are due to “conditioning” or other non-genetic factors. … An ideology based on such obviously wrong premises can only lead to disaster. Its championship of human equality is based on a claim of identity. As soon as it is proved that the latter does not exist, the support of equality is likewise lost. (Mayr 1963)

Thus, the second conclusion of Guevara is wrong:

2.) “High genetic variation exists within geographic regions, and little variation distinguishes geographic regions.”

Well, that’s sort-of true, but, as we said, that “little variation among geographic regions” can, when added up, diagnose populations sufficiently to not only tell you your geographic ancestry, but also to reconstruct the evolutionary and migratory history of human populations. Guevara dismisses these ancestry tests, though she doesn’t tell us why they are wrong:

Helping the zombie persist, direct-to-consumer genetic tests, like those offered by 23andMe and AncestryDNA, can reinforce misconceptions about human variation. These services have become many people’s primary reference point for human genetics information. To be marketable, the companies must communicate their results in simple, familiar ways that also appear meaningful and reliable. This usually entails simplifying genetic ancestry to bright, high-contrast colors, pinned definitively to geographic regions.

And yet, at the same time, Guevara admires the same kind of data—genetic differences between living populations (as well as “ancient fossil DNA”)—as being of value:

In addition to genomes from living humans, DNA extracted from ancient humans over the past two decades has revealed incredible insights. Across time, past humans frequently migrated, mated with, or displaced people they encountered in other regions—resulting in a tangled tree of human ancestry. The ancient DNA results refute any notion of deep, separate roots for humans in different geographic regions.

Well, there are deep roots for some groups (the Neanderthal lineage, for example, separated form the lineage leading to modern humans about 400,000 years ago), and this comes from both fossil and DNA evidence.  The “tangled tree” may be correct in some ways (we did hybridize with Neanderthals, and other populations exchanged genes to different degrees), but it’s not tangled enough to completely efface the evolutionary history of human populations.

All this leads to a third misleading conclusion:

3) Races are social constructs. Any differences between races are largely caused by racism rather than genes. As Guevara says:

As laid out by a major professional association for biological anthropologists, race is a social reality that affects our biology. For the last several hundred years in the U.S. and other colonized lands, racism has influenced people’s access to nutritious food, education, economic opportunities, health care, safety, and more. As a consequence, and precisely because of the environmental influence on most traits, the social construction of race is a risk factor for many health conditions and outcomes, including maternal and infant mortality, asthma, and COVID-19 severity.

This again shows both an ideological motivation and a misleading conclusion. Even the classical biological races (and even more so worldwide populations) are NOT social constructs, but are associated with genetic, morphological, and adaptive differences.  If races are purely socially constructed, how could you tell them apart in the first place? You need some kind of genetic marker. In the case of racism in America, the differences between African-Americans and whites were “constructed” based on skin pigmentation, hair texture, and other traits—traits based on genetic differences. Those differences served to mark out which people were considered different, and then “inferior”, though, as I said, genetic differences among people say nothing about moral or legal equality. THAT is the lesson that needs to be imparted, not the falsity that there are no genetic differences among groups.

Now Guevara may be correct that the “social construct” view is the one taught, erroneously, in high school and college.  But she’s wrong in thinking that Lewontin’s paper supports that “social construct” view.  In fact, the social construct view is largely wrong, with some exceptions centered on the outmoded view of “classical races”, but it appears to dominate anthropology and the social sciences. Anybody holding that view for either populations or groups of geographically contiguous populations needs to read the Coyne and Maroja paper.

4). Humans aren’t peas.  According to Guevara, Mendel’s work on peas, as taught in school, buttresses scientific racism, too:

I, along with others, am concerned that this focus instills and reinforces a false pre-Lewontin view that humans, like Mendel’s peas, come in discrete types. In reality, early studies of peas and other inbred, domesticated species have little relevance for human genetics.

Indeed, it is of little relevance to human genetics, but I’m not aware of any teacher who describes Mendel’s work—which served to show how genes sort themselves out during reproduction—and uses it to conclude, “See, human races are as distinct as round and wrinkled peas.”

In the end, both races and populations of humans show genetic and evolved morphological differences—less than we thought, say, a hundred years ago—but differences that are still significant in useful ways. To say that races or populations are purely social constructs is simply wrong, and to use Lewontin’s paper to reinforce that conclusion is doubly wrong.

Now reader Lou Jost has argued that Lewontin couldn’t really mathematically partition genetic variation the way he did because Lewontin used the wrong method. Regardless, it’s clear that there is more genetic variation at a given locus within a population than between populations or the groups of populations once deemed “races”.  But in the end there is a tremendous amount of information of biological and evolutionary significance to be gained by adding up the small genetic differences we see between human populations.

To end, here’s a map of genetic variation among populations in Europe, showing how the genetic variation (grouped by principal components analysis) lines up nicely with the geographic variation in populations. That’s because genetic differences evolved between semi-isolated groups of people, and that is why we can tell with considerable accuracy where our ancestors came from

Paper: Gilbert et al. 2022

Geography (populations sampled are in black)

Genetics (grouping of individuals using two axes of a principal components analysis. Look how well the geography (identified by color above) matches the genetics!

 

It could be quite a night!

A powerful solar flare (an explosion on the Sun) about 36 hours ago created a large and fast coronal mass ejection (a cloud of subatomic particles heading away from the Sun) that is due to arrive at Earth in the next few hours (it will show up less than an hour before it arrives as chaos in this data.) UPDATE: IT HAS ARRIVED; IF IT’S DARK WHERE YOU ARE, GO LOOK. That could mean problems for the electrical grid. It could also mean strong auroras (northern and southern lights) far from the poles. The timing, if correctly predicted, is such that Asia and Europe may have the best chances, but the auroras could potentially last until it is dark in the Americas too.

Also, just after sunset tonight, we may with difficulty be able to see Comet A3 (short for Comet C/2023 A3 Tsuchinshan-ATLAS ). The comet is bright — some reports give it a brightness comparable to the planet Venus, although more diffuse — but so is twilight. UPDATE: I HAVE BEEN WARNED THAT THE RAPID BRIGHTNING PERIOD, DUE TO A LIGHT SCATTERING EFFECT, MAY ALREADY BE OVER. IF SO, THE STATEMENTS HERE MAY BE TOO OPTIMISTIC. The comet is roughly ten Sun-widths above and slightly to the right of the Sun, and should be visible 15-30 minutes after sunset if you have a low and mostly cloudless horizon. Best bet is to bring binoculars and scan the sky; you’ll notice it much more easily, even if it is visible to the naked eye.

Each day following, the comet will be higher in the sky at sunset, making it more visible in late twilight, but it will also become intrinsically dimmer. Experts seem to disagree about when it will be at its best, but this weekend should be good, if not before.

Thanks to a couple of readers who are helping fill my lacuna of wildlife photos. I now have more than a week’s worth, but please keep sending them in.

Today’s photos come from reader Mary Rasmussen, whose captions and IDs are indented. Click on the photos to enlarge them.

Birds Along the Northern Lake Michigan Shore

In Michigan’s Upper Peninsula, this shoreline serves as a crucial part of a migratory flyway for birds journeying from the southern U.S. and beyond, through Wisconsin, across an archipelago, and northward into Canada. Despite being 350 miles north of Chicago, this region falls within the same climatic zone.

Our cabin is perched on an ancient sand dune along this rugged coast:

Just a mile offshore, several small, uninhabited islands dot the landscape. These islands become nocturnal roosts for hundreds of Sandhill Cranes (Antigone canadensis) which then traverse the skies daily to and from nearby farm fields:

Occasionally, a pair of cranes chooses our shore for nesting, successfully raising a chick this season:

The Sandhill Cranes are known for their distinctive, almost prehistoric bugle call, which resonates loudly across the landscape (JAC: You can hear a variety of their calls here.)

A Great Blue Heron (Ardea herodias) wades along the shore, scanning the clear pools for small fish and tadpoles:

Killdeer (Charadrius vociferus), with their nearly perfect camouflage, blend into the rocky shore so well that I usually don’t see them until they move:

The Turkey Vulture (Cathartes aura) is a carrion feeder that is often here in groups soaring over the shore in search of dead fish, birds and other animals. It uses thermals to glide through the air and a keen sense of smell to find its food:

A nest of Bald Eagles (Haliaeetus leucocephalus) is situated nearby along the shoreline. Occasionally, a gathering of four or five juvenile and adult Bald Eagles can be observed on the shore.

The eagles were landing at the end of our kayak ramp. I was able to get these shots because of the distraction of a large fish that had washed ashore:

Flocks of American White Pelicans (Pelecanus erythrorhynchos) frequent the islands and follow the fishing boats when the boats are heading in with their catch:

Pelicans are very large birds, having the second-largest wingspan of any North American bird. We found this skeleton on the shore. Here is the Pelican partial skeleton next to my dog Sylvie for scale. (55 lb. Golden Retriever) Sylvie looks unhappy because we would not let her keep the skeleton:

Equipment: I use a Nikon D500 camera with a NIKKOR 200-500mm lens.

The ion tail of C/2023 A3 (Tsuchinshan-ATLAS) could appear as a blue streak across the northern hemisphere sky during October, in a rare event thought to happen only every few decades

Meteorites strike Earth every day. It’s estimated that about 100 – 300 metric tonnes of material strike our planet every year. Most of it consists of sand-grain sized dust that burns up in the atmosphere, but each year a few thousand will reach Earth’s surface.

The vast majority of meteorites trace their origins to comets or the asteroid belt, but some of them come from the Moon or Mars. We know this by analyzing their chemical composition. While the Lunar meteorites have much to tell us, it is the Martian meteorites that are the greatest treasure for they are the only fragments of the Red Planet we currently have. By studying their chemistry and composition we have learned that Mars was once a warm and wet world similar to Earth.

There are about 200 meteorites we have confirmed as Martian in origin. There composition shows that they likely originated from about 10 large impacts on Mars. To be powerful enough to throw fragments of Mars into space, the impacts must have been large enough to make sizable craters, perhaps dozens of kilometers across. Which raises an interesting question. Which particular craters are connected to the meteorites we have? A new study in Science Advances explores this question.

A fragment of a Martian meteorite. Credit: Brian Koberlein

The team started by looking at the chemical similarities in each group of associated meteorites. From this they could get an idea of the age and geology of a particular impact site. They then compared this to the known age and composition of various regions of Mars, looking for craters that were a reasonable match. They were able to find an originating crater for about five of the groups.

This is important because knowing the precise origin gives us a more accurate picture of the evolution of Mars. We already have a good general understanding of the early history of Mars, but with specific impact sites we can compare regions. Perhaps early seas existed on Mars while other regions became deserts. Which regions were the last to dry, and therefore might be good sites for finding evidence of life. The study also found impact craters that are similar to the ones that produces meteorites but have no associated meteorites. As we find more Martian rocks, they might be part of new groups originating from these impacts.

Until we can recover rocks from Mars directly, the couple hundred Martian meteorites are our only physical link to our red neighbor. And thanks to this study we have a better idea of that link.

Reference: Herd, Christopher DK, et al. “The source craters of the martian meteorites: Implications for the igneous evolution of Mars.” Science Advances 10.33 (2024): eadn2378.

The post Most Mars Meteorites Came From Five Craters appeared first on Universe Today.