Handheld spectral analyzer turns smartphone into diagnostic tool


Scienceadaily.com - Researchers at the University of Illinois at Urbana-Champaign have developed technology that enables a smartphone to perform lab-grade medical diagnostic tests that typically require large, expensive instruments. Costing only $550, the spectral transmission-reflectance-intensity (TRI)-Analyzer from Bioengineering and Electrical & Computer Engineering Professor Brian Cunningham's lab attaches to a smartphone and analyzes patient blood, urine, or saliva samples as reliably as clinic-based instruments that cost thousands of dollars.

"Our TRI Analyzer is like the Swiss Army knife of biosensing," said Cunningham, the Donald Biggar Willett Professor of Engineering and director of the Micro + Nanotechnology Lab at Illinois. "It's capable of performing the three most common types of tests in medical diagnostics, so in practice, thousands of already-developed tests could be adapted to it."

In a recently published paper, Cunningham's team used the TRI Analyzer to perform two commercially available assays -- a test to detect a biomarker associated with pre-term birth in pregnant women and the PKU test for newborns to indirectly detect an enzyme essential for normal growth and development. Their tests results were comparable to those acquired with clinic-grade spectrometer instrumentation.

"The TRI Analyzer is more of a portable laboratory than a specialized device," said Kenny Long, an MD/PhD student and lead author of the research study.

Among the many diagnostic tests that can be adapted to their point-of-care smartphone format, Long said, is an enzyme-linked immunosorbent assay (ELISA), which detects and measures a wide variety of proteins and antibodies in blood and is commonly used for a wide range of health diagnostics tests. The system is capable of detecting the output of any test that uses a liquid that changes color, or a liquid that generates light output (such as from fluorescent dyes).

The TRI Analyzer operates by converting the smartphone camera into a high-performance spectrometer. Specifically, the analyzer illuminates a sample fluid with the phone's internal white LED flash or with an inexpensive external green laser diode. The light from the sample is collected in an optical fiber and guided through a diffraction grating into the phone's rear-facing internal camera. These optical components are all arranged within a 3D-printed plastic cradle.

The TRI Analyzer can simultaneously measure multiple samples by using a microfluidic cartridge that slides through an opening in the back of the cradle. This ability to analyze multiple samples quickly and reliably makes the Analyzer suitable for patients who lack convenient access to a clinic or hospital with diagnostic test facilities or for patients with urgent health situations requiring rapid results.

"Our Analyzer can scan many tests in a sequence by swiping the cartridge past the readout head, in a similar manner to the way magnetic strip credit cards are swiped," said Long.

In addition to its applications in health diagnostics, Cunningham said the TRI Analyzer can also be applied to point-of use applications that include animal health, environmental monitoring, drug testing, manufacturing quality control, and food safety. The patented technology is available for license.

Source : University of Illinois College of Engineering

Lunar dynamo’s lifetime extended by at least 1 billion years


Scienceadaily.com - New evidence from ancient lunar rocks suggests that an active dynamo once churned within the molten metallic core of the moon, generating a magnetic field that lasted at least 1 billion years longer than previously thought. Dynamos are natural generators of magnetic fields around terrestrial bodies, and are powered by the churning of conducting fluids within many stars and planets. In a paper published today in Science Advances, researchers from MIT and Rutgers University report that a lunar rock collected by NASA's Apollo 15 mission exhibits signs that it formed 1 to 2.5 billion years ago in the presence of a relatively weak magnetic field of about 5 microtesla. That's around 10 times weaker than Earth's current magnetic field but still 1,000 times larger than fields in interplanetary space today.

Several years ago, the same researchers identified 4-billion-year-old lunar rocks that formed under a much stronger field of about 100 microtesla, and they determined that the strength of this field dropped off precipitously around 3 billion years ago. At the time, the researchers were unsure whether the moon's dynamo -- the related magnetic field -- died out shortly thereafter or lingered in a weakened state before dissipating completely.

The results reported today support the latter scenario: After the moon's magnetic field dwindled, it nonetheless persisted for at least another billion years, existing for a total of at least 2 billion years.

Study co-author Benjamin Weiss, professor of planetary sciences in MIT's Department of Earth, Atmospheric and Planetary Sciences (EAPS), says this new extended lifetime helps to pinpoint the phenomena that powered the moon's dynamo. Specifically, the results raise the possibility of two different mechanisms -- one that may have driven an earlier, much stronger dynamo, and a second that kept the moon's core simmering at a much slower boil toward the end of its lifetime.

"The concept of a planetary magnetic field produced by moving liquid metal is an idea that is really only a few decades old," Weiss says. "What powers this motion on Earth and other bodies, particularly on the moon, is not well-understood. We can figure this out by knowing the lifetime of the lunar dynamo."

Weiss' co-authors are lead author Sonia Tikoo, a former MIT graduate student who is now an assistant professor at Rutgers; David Shuster of the University of California at Berkeley; Clément Suavet and Huapei Wang of EAPS; and Timothy Grove, the R.R. Schrock Professor of Geology and associate head of EAPS.

Apollo's glassy recorders

Since NASA's Apollo astronauts brought back samples from the lunar surface, scientists have found some of these rocks to be accurate "recorders" of the moon's ancient magnetic field. Such rocks contain thousands of tiny grains that, like compass needles, aligned in the direction of ancient fields when the rocks crystallized eons ago. Such grains can give scientists a measure of the moon's ancient field strength.

Until recently, Weiss and others had been unable to find samples much younger than 3.2 billion years old that could accurately record magnetic fields. As a result, they had only been able to gauge the strength of the moon's magnetic field between 3.2 and 4.2 billion years ago.

"The problem is, there are very few lunar rocks that are younger than about 3 billion years old, because right around then, the moon cooled off, volcanism largely ceased and, along with it, formation of new igneous rocks on the lunar surface," Weiss explains. "So there were no young samples we could measure to see if there was a field after 3 billion years."

There is, however, a small class of rocks brought back from the Apollo missions that formed not from ancient lunar eruptions but from asteroid impacts later in the moon's history. These rocks melted from the heat of such impacts and recrystallized in orientations determined by the moon's magnetic field.

Weiss and his colleagues analyzed one such rock, known as Apollo 15 sample 15498, which was originally collected on Aug. 1, 1971, from the southern rim of the moon's Dune Crater. The sample is a mix of minerals and rock fragments, welded together by a glassy matrix, the grains of which preserve records of the moon's magnetic field at the time the rock was assembled.

"We found that this glassy material that welds things together has excellent magnetic recording properties," Weiss says.

Baking rocks

The team determined that the rock sample was about 1 to 2.5 billion years old -- much younger than the samples they previously analyzed. They developed a technique to decipher the ancient magnetic field recorded in the rock's glassy matrix by first measuring the rock's natural magnetic properties using a very sensitive magnetometer.

They then exposed the rock to a known magnetic field in the lab, and heated the rock to close to the extreme temperatures in which it originally formed. They measured how the rock's magnetization changed as they increased the surrounding temperature.

"You see how magnetized it gets from getting heated in that known magnetic field, then you compare that field to the natural magnetic field you measured beforehand, and from that you can figure out what the ancient field strength was," Weiss explains.

The researchers did have to make one significant adjustment to the experiment to better simulate the original lunar environment, and in particular, its atmosphere. While the Earth's atmosphere contains around 20 percent oxygen, the moon has only imperceptible traces of the gas. In collaboration with Grove, Suavet built a customized, oxygen-deprived oven in which to heat the rocks, preventing them from rusting while at the same time simulating the oxygen-free environment in which the rocks were originally magnetized.

"In this way, we finally have gotten an accurate measurement of the lunar field," Weiss says.

From ice cream makers to lava lamps

From their experiments, the researchers determined that, around 1 to 2.5 billion years ago, the moon harbored a relatively weak magnetic field, with a strength of about 5 microtesla -- two orders of magnitude weaker than the moon's field around 3 to 4 billion years ago. Such a dramatic dip suggests to Weiss and his colleagues that the moon's dynamo may have been driven by two distinct mechanisms.

Scientists have proposed that the moon's dynamo may have been powered by the Earth's gravitational pull. Early in its history, the moon orbited much closer to the Earth, and the Earth's gravity, in such close proximity, may have been strong enough to pull on and rotate the rocky exterior of the moon. The moon's liquid center may have been dragged along with the moon's outer shell, generating a very strong magnetic field in the process.

It's thought that the moon may have moved sufficiently far away from the Earth by about 3 billion years ago, such that the power available for the dynamo by this mechanism became insufficient. This happens to be right around the time the moon's magnetic field strength dropped. A different mechanism may have then kicked in to sustain this weakened field. As the moon moved away from the Earth, its core likely sustained a low boil via a slow process of cooling over at least 1 billion years.

"As the moon cools, its core acts like a lava lamp -- low-density stuff rises because it's hot or because its composition is different from that of the surrounding fluid," Weiss says. "That's how we think the Earth's dynamo works, and that's what we suggest the late lunar dynamo was doing as well."

The researchers are planning to analyze even younger lunar rocks to determine when the dynamo died off completely.

"Today the moon's field is essentially zero," Weiss says. "And we now know it turned off somewhere between the formation of this rock and today."

This research was supported, in part, by NASA.

Source : Massachusetts Institute of Technology

Brain Cells Found to Control Aging


Scienceadaily.com - Scientists at Albert Einstein College of Medicine have found that stem cells in the brain's hypothalamus govern how fast aging occurs in the body. The finding, made in mice, could lead to new strategies for warding off age-related diseases and extending lifespan. The paper was published online today in Nature.

The hypothalamus was known to regulate important processes including growth, development, reproduction and metabolism. In a 2013 Nature paper, Einstein researchers made the surprising finding that the hypothalamus also regulates aging throughout the body. Now, the scientists have pinpointed the cells in the hypothalamus that control aging: a tiny population of adult neural stem cells, which were known to be responsible for forming new brain neurons.

"Our research shows that the number of hypothalamic neural stem cells naturally declines over the life of the animal, and this decline accelerates aging," says senior author Dongsheng Cai, M.D., Ph.D., (professor of molecular pharmacology at Einstein. "But we also found that the effects of this loss are not irreversible. By replenishing these stem cells or the molecules they produce, it's possible to slow and even reverse various aspects of aging throughout the body."

In studying whether stem cells in the hypothalamus held the key to aging, the researchers first looked at the fate of those cells as healthy mice got older. The number of hypothalamic stem cells began to diminish when the animals reached about 10 months, which is several months before the usual signs of aging start appearing. "By old age -- about two years of age in mice -- most of those cells were gone," says Dr. Cai.

The researchers next wanted to learn whether this progressive loss of stem cells was actually causing aging and was not just associated with it. So they observed what happened when they selectively disrupted the hypothalamic stem cells in middle-aged mice. "This disruption greatly accelerated aging compared with control mice, and those animals with disrupted stem cells died earlier than normal," says Dr. Cai.

Could adding stem cells to the hypothalamus counteract aging? To answer that question, the researchers injected hypothalamic stem cells into the brains of middle-aged mice whose stem cells had been destroyed as well as into the brains of normal old mice. In both groups of animals, the treatment slowed or reversed various measures of aging.

Dr. Cai and his colleagues found that the hypothalamic stem cells appear to exert their anti-aging effects by releasing molecules called microRNAs (miRNAs). They are not involved in protein synthesis but instead play key roles in regulating gene expression. miRNAs are packaged inside tiny particles called exosomes, which hypothalamic stem cells release into the cerebrospinal fluid of mice.

The researchers extracted miRNA-containing exosomes from hypothalamic stem cells and injected them into the cerebrospinal fluid of two groups of mice: middle-aged mice whose hypothalamic stem cells had been destroyed and normal middle-aged mice. This treatment significantly slowed aging in both groups of animals as measured by tissue analysis and behavioral testing that involved assessing changes in the animals' muscle endurance, coordination, social behavior and cognitive ability.

The researchers are now trying to identify the particular populations of microRNAs and perhaps other factors secreted by these stem cells that are responsible for these anti-aging effects -- a first step toward possibly slowing the aging process and treating age-related diseases.

The article is titled, "Hypothalamic stem cells control ageing speed partly through exosomal miRNAs." The other authors are Yalin Zhang. Ph.D., Min Soo Kim, Ph.D., Baosen Jia, Ph.D., Jingqi Yan, Ph.D., Juan Pablo Zuniga-Hertz, Ph.D., and Cheng Han, Ph.D., all at Einstein.

The study was supported by grants from the National Institutes of Health (DK078750, AG031774 , HL113180, and DK099136).

Scientists Restore Youthful Plasticity to the Brains of Adult Mice


Scienceadaily.com - Like much of the rest of the body, the brain loses flexibility with age, impacting the ability to learn, remember, and adapt. Now, scientists at University of Utah Health report they can rejuvenate the plasticity of the mouse brain, specifically in the visual cortex, increasing its ability to change in response to experience. Manipulating a single gene triggers the shift, revealing it as a potential target for new treatments that could recover the brain's youthful potential. The research was published online in the Proceedings of the National Academy of Sciences (PNAS) on August 8.

"It's exciting because it suggests that by just manipulating one gene in adult brains, we can boost brain plasticity," says lead investigator Jason Shepherd, Ph.D., Associate Professor of Neurobiology and Anatomy at University of Utah Health.

"This has implications for potentially reducing normal cognitive decline with aging, or boosting recovery from brain injury after stroke or traumatic brain injury," he says. Additional research will need to be done to determine whether plasticity in humans and mice is regulated in the same way.

The dramatic way in which the brain changes over time has long captured the imagination of scientists. A "critical window" of brain plasticity explains why certain eye conditions such as lazy eye can be corrected during early childhood but not later in life. The phenomenon has raised the questions: What ordinarily keeps the window open? And, once it's shut, can plasticity be restored?

Earlier work that Shepherd carried out in collaboration with Mark Bear, Ph.D., a professor at the Massachusetts Institute of Technology and co-author of the current study, showed that the critical window never opens in mice lacking a gene called Arc. Temporarily closing a single eye of a young mouse for a few days deprives the visual cortex of normal input, and the neurons' electrophysiological response to visual experience changes. By contrast, young mice without Arc cannot adapt to the new experience in the same way.

"Given our previous studies, we wondered whether Arc is essential for controlling the critical period of plasticity during normal brain development," says Shepherd.

If there is no visual plasticity without Arc, the thinking goes, then perhaps the gene plays a role in keeping the "critical window" open.

In support of the idea, the new investigation finds that in the mouse visual cortex, Arc rises and falls in parallel with visual plasticity. The two peak in teen mice and fall sharply by middle-age, suggesting they are linked.

The researchers probed the connection further in two more ways. First, in collaboration with co-author Harohiko Bito, Ph.D., a professor at the University of Tokyo, they tested mice that have a strong supply of Arc throughout life. At middle-age, these mice responded to visual deprivation as robustly as their juvenile counterparts. By prolonging Arc's availability, the window of plasticity remained open for longer.

Manipulating Arc is not the first treatment to prolong plasticity. Chronically treating mice with an antidepressant, fluoxetine, and raising rodents in a stimulating environment with toys and plenty of social interaction, are among other paradigms that do the same.

But the second set of experiments raised the bar higher. Viruses were used to deliver Arc to middle age mice, after the critical window had closed. Following the intervention, these older mice responded to visual deprivation as a youngster woulds. In this case even though the window had already shut, Arc enabled it to open once again.

"It was incredible to see that in adult mice, who have gone through normal development and aging, simply overexpressing Arc with a virus restored plasticity," says co-first author Kyle Jenks, a graduate student in Shepherd's lab.

The prevailing notion of how plasticity declines is that as the brain develops, inhibitory neurons mature and become stronger. Shepherd explains that he believes their findings add a new dimension for how critical periods of learning are regulated.

"Increased inhibition in the brain makes it harder to express activity-dependent genes, like Arc, in response to experience or learning," he says. "And that leads to decreased brain plasticity."

Normally, Arc is rapidly activated in response to stimuli and is involved in shuttling neurotransmitter receptors out of synapses that neurons use to communicate with one another. Additional research will need to be done to understand precisely how manipulating Arc boosts plasticity.

Whether Arc is involved in regulating the plasticity of other neurological functions mediated by other brain structures, like learning, memory, or repair, remains to be tested but will be examined in the future, says Shepherd.

Source : University of Utah Health

DNA from Viking cod bones suggests 1,000 years of European fish trade


Scienceadaily.com - Norway is famed for its cod. Catches from the Arctic stock that spawns each year off its northern coast are exported across Europe for staple dishes from British fish and chips to Spanish bacalao stew.

Now, a new study published today in the journal PNAS suggests that some form of this pan-European trade in Norwegian cod may have been taking place for 1,000 years.

Latest research from the universities of Cambridge and Oslo, and the Centre for Baltic and Scandinavian Archaeology in Schleswig, used ancient DNA extracted from the remnants of Viking-age fish suppers.

The study analysed five cod bones dating from between 800 and 1066 AD found in the mud of the former wharves of Haithabu, an early medieval trading port on the Baltic. Haithabu is now a heritage site in modern Germany, but at the time was ruled by the King of the Danes.

The DNA from these cod bones contained genetic signatures seen in the Arctic stock that swims off the coast of Lofoten: the northern archipelago still a centre for Norway's fishing industry.

Researchers say the findings show that supplies of 'stockfish' -- an ancient dried cod dish popular to this day -- were transported over a thousand miles from northern Norway to the Baltic Sea during the Viking era.

Prior to the latest study, there was no archaeological or historical proof of a European stockfish trade before the 12th century.

While future work will look at further fish remains, the small size of the current study prevents researchers from determining whether the cod was transported for trade or simply used as sustenance for the voyage from Norway.

However, they say that the Haithabu bones provide the earliest evidence of fish caught in northern Norway being consumed on mainland Europe -- suggesting a European fish trade involving significant distances has been in operation for a millennium.

"Traded fish was one of the first commodities to begin to knit the European continent together economically," says Dr James Barrett, senior author of the study from the University of Cambridge's McDonald Institute for Archaeological Research.

"Haithabu was an important trading centre during the early medieval period. A place where north met south, pagan met Christian, and those who used coin met those who used silver by weight."

"By extracting and sequencing DNA from the leftover fish bones of ancient cargoes at Haithabu, we have been able to trace the source of their food right the way back to the cod populations that inhabit the Barents Sea, but come to spawn off Norway's Lofoten coast every winter.

"This Arctic stock of cod is still highly prized -- caught and exported across Europe today. Our findings suggest that distant requirements for this Arctic protein had already begun to influence the economy and ecology of Europe in the Viking age."

Stockfish is white fish preserved by the unique climate of north Norway, where winter temperature hovers around freezing. Cod is traditionally hung out on wooden frames to allow the chill air to dry the fish. Some medieval accounts suggest stockfish was still edible as much as ten years after preservation.

The research team argue that the new findings offer some corroboration to the unique 9th century account of the voyages of Ohthere of Hålogaland: a Viking chieftain whose visit to the court of King Alfred in England resulted in some of his exploits being recorded.

"In the accounts inserted by Alfred's scribes into the translation of an earlier 5th century text, Ohthere describes sailing from Hålogaland to Haithabu," says Barrett. Hålogaland was the northernmost province of Norway.

"While no cargo of dried fish is mentioned, this may be because it was simply too mundane a detail," says Barrett. "The fish-bone DNA evidence is consistent with the Ohthere text, showing that such voyages between northern Norway and mainland Europe were occurring."

"The Viking world was complex and interconnected. This is a world where a chieftain from north Norway may have shared stockfish with Alfred the Great while a late-antique Latin text was being translated in the background. A world where the town dwellers of a cosmopolitan port in a Baltic fjord may have been provisioned from an Arctic sea hundreds of miles away."

The sequencing of the ancient cod genomes was done at the University of Oslo, where researchers are studying the genetic makeup of Atlantic cod in an effort to unpick the anthropogenic impacts on these long-exploited fish populations.

"Fishing, particularly of cod, has been of central importance for the settlement of Norway for thousands of years. By combining fishing in winter with farming in summer, whole areas of northern Norway could be settled in a more reliable manner," says the University of Oslo's Bastiaan Star, first author of the new study.

Star points to the design of Norway's new banknotes that prominently feature an image of cod, along with a Viking ship, as an example of the cultural importance still placed on the fish species in this part of Europe.

"We want to know what impact the intensive exploitation history covering millennia has inflicted on Atlantic cod, and we use ancient DNA methods to investigate this," he says.

The study was funded by the Research Council of Norway and the Leverhulme Trust.

Source : University of Cambridge

Microbe New to Science Found in Self-fermented Beer


Scienceadaily.com - In May 2014, a group of scientists took a field trip to a small brewery in an old warehouse in Seattle, Washington. They were looking for some yeast to sequence—and to taste some beer, if it came down to it. Cody Morris, then brewmaster of Epic Ales, ushered them through the building, warning of a large hole in the floor. Then he brought the group over to one of the old wine casks in which Morris was brewing a “wild beer.”

“We opened it and it was alive,” says Maitreya Dunham, a geneticist at the University of Washington in Seattle who led the sudsy expedition. The liquid in the barrel was bubbling away vigorously. “It was definitely an actively fermenting mixture,” she says.

Whereas standard beers like Heineken or Sierra Nevada are produced by adding one type of yeast—usually a Saccharomyces species—wild brewers like Morris coax a community of bugs from the environment to settle in and ferment beer, an old Belgian tradition. But like many brewers making wild beers, Morris admitted he had no idea what microbes were living in the barrel staves that had inoculated his beer. Could the scientists figure it out?

The team accepted the challenge. Dunham and her colleagues collected a bit of the company's “Old Warehouse” beer into a plastic tube. If it was a mixture of microbes, it would be the perfect sample for a technique she and her colleagues were developing called Hi-C sequencing, which disentangles the genomic sequences of a community of microbe species using formaldehyde to link DNA fragments within the same cell. “The inference is that if two pieces of DNA are crosslinking to each other, they must have come from the same cell,” Dunham explains.

What she found got her excited. Using the Hi-C technique, the team identified a yeast belonging to the genus Pichia, which turned out to be a hybrid of a known species called P. membranifaciens and another Pichia species completely new to science, the team recently reported on the preprint server bioRxiv. (Such yeast hybrids are common in brewing; in fact, lager yeast was recently discovered to be a hybrid of two Saccharomyces species.) The scientists dubbed the new hybrid Pichia apotheca–Greek for “warehouse.”

The brew also contained Saccharomyces and yet another yeast genus, Brettanomyces, which is found in many wild beers and sold commercially. In addition, the mix contained Lactobacillus, Pediococcus, and Acetobacter bacteria, all known to imbue a sour character to a beer.

Dunham's team tried to brew a beer with P. apotheca alone, but that didn't work; the yeast produced little alcohol. That's not unusual; most yeasts found in mixed cultures won't brew a beer well on their own. But the hybrid may contribute to Old Warehouse's taste, the researchers write in their paper. Other Pichia species are known to spoil a beer, but the new hybrid seems to smell better, Dunham says. She's open to providing brewers with microbe isolates, if they want to experiment with them.

“This paper provides a proof-of-concept for using this method to study other spontaneously fermented beers,” says Ronn Friedlander, a co-founder of Aeronaut Brewing in Somerville, Massachusetts, who has a Ph.D. in bioengineering. What’s also striking, he says, is that the mixture Dunham and her team identified is very close to the “Roeselare” blend that commercial yeast provider Wyeast markets to brewers who want to inoculate a wild beer artificially. That mix contains a Belgian-style ale strain, Saccharomyces, two Brettanomyces strains, Lactobacillus, and Pediococcus, Friedlander says.

Perhaps wild beer fermentation is a more predictable process than once thought, Friedlander says. “This might point to specific niches that must be filled in a microbially stable, aging beer,” he says.

And that means brewers and scientists may be one step closer to unveiling the alchemy of spontaneous fermentation.

Source : Sciencemag

SwRI Part of International Team Identifying Primordial Asteroids

Astronomers have identified the oldest asteroid families and, by process of elimination, the oldest intact asteroids in the main belt. A team including SwRI scientists developed a technique to identify ancient asteroid families that have drifted apart. Asteroid surfaces heat up during the day (as illustrated by this image) and cool down at night, giving off radiation that can act as a sort of mini-thruster. This force can cause asteroids to drift widely over time, making it difficult to identify families of fragments leftover after asteroid collisions eons ago.
Scienceadaily.com - Southwest Research Institute (SwRI) was part of an international team that recently discovered a relatively unpopulated region of the main asteroid belt, where the few asteroids present are likely pristine relics from early in solar system history. The team used a new search technique that also identified the oldest known asteroid family, which extends throughout the inner region of the main asteroid belt.

The main belt contains vast numbers of irregularly shaped asteroids, also known as planetesimals, orbiting the Sun between Mars and Jupiter. As improved telescope technology finds smaller and more distant asteroids, astronomers have identified clusters of similar-looking bodies clumped in analogous orbits. These familial objects are likely fragments of catastrophic collisions between larger asteroids eons ago. Finding and studying asteroid families allows scientists to better understand the history of main belt asteroids.

“By identifying all the families in the main belt, we can figure out which asteroids have been formed by collisions and which might be some of the original members of the asteroid belt,” said SwRI Astronomer Dr. Kevin Walsh, a coauthor of the online Science paper detailing the findings. “We identified all known families and their members and discovered a gigantic void in the main belt, populated by only a handful of asteroids. These relics must be part of the original asteroid belt. That is the real prize, to know what the main belt looked like just after it formed.”

Identifying the very oldest asteroid families, those billions of years old, is challenging, because over time, a family spreads out. As asteroids rotate in orbit around the Sun, their surfaces heat up during the day and cool down at night. This creates radiation that can act as a sort of mini-thruster, causing asteroids to drift widely over time. After billions of years, family members would be almost impossible to identify, until now. The team used a novel technique, searching asteroid data from the inner region of the belt for old, dispersed families. They looked for the “edges” of families, those fragments that have drifted the furthest.

“Each family member drifts away from the center of the family in a way that depends on its size, with small guys drifting faster and further than the larger guys,” said team leader Marco Delbo, an astronomer from the Observatory of Cote d’Azur in Nice, France. “If you look for correlations of size and distance, you can see the shapes of old families.”

“The family we identified has no name, because it is not clear which asteroid is the parent,” Walsh said. “This family is so old that it appears to have formed over 4 billion years ago, before the gas giants in the outer solar system moved into their current orbits. The giant planet migration shook up the asteroid belt, removing many bodies, possibly including the parent of this family.”

The team plans to apply this new technique to the entire asteroid belt to reveal more about the history of the solar system by identifying the primordial asteroids versus fragments of collisions. This research was supported by the French National Program of Planetology and the National Science Foundation. The resulting paper, “Identification of a primordial asteroid family constrains the original planetesimal population,” appears in the August 3, 2017, online edition of Science.

Source : Southwest Research Institute