Cosmic Mystery Deepens After New Measurement of the Rate of Expansion of the Universe

New measurement of Hubble constant adds to cosmic mystery.

New measurements of the rate of expansion of the universe, led by astronomers at the University of California, Davis, add to a growing mystery: Estimates of a fundamental constant made with different methods keep giving different results.

“There’s a lot of excitement, a lot of mystification and from my point of view it’s a lot of fun,” said Chris Fassnacht, professor of physics at UC Davis and a member of the international SHARP/H0LICOW collaboration, which made the measurement using the W.M. Keck telescopes in Hawaii.

A paper about the work is published by the Monthly Notices of the Royal Astronomical Society.

The Hubble constant describes the expansion of the universe, expressed in kilometers per second per megaparsec. It allows astronomers to figure out the size and age of the universe and the distances between objects.

Graduate student Geoff Chen, Fassnacht, and colleagues looked at light from extremely distant galaxies that is distorted and split into multiple images by the lensing effect of galaxies (and their associated dark matter) between the source and Earth. By measuring the time delay for light to make its way by different routes through the foreground lens, the team could estimate the Hubble constant.

Using adaptive optics technology on the W.M. Keck telescopes in Hawaii, they arrived at an estimate of 76.8 kilometers per second per megaparsec. As a parsec is a bit over 30 trillion kilometers and a megaparsec is a million parsecs, that is an excruciatingly precise measurement. In 2017, the H0LICOW team published an estimate of 71.9, using the same method and data from the Hubble Space Telescope. 

Hints of new physics

The new SHARP/H0LICOW estimates are comparable to that by a team led by Adam Reiss of Johns Hopkins University, 74.03, using measurements of a set of variable stars called the Cepheids. But it’s quite a lot different from estimates of the Hubble constant from an entirely different technique based on the cosmic microwave background. That method, based on the afterglow of the Big Bang, gives a Hubble constant of 67.4, assuming the standard cosmological model of the universe is correct.

An estimate by Wendy Freedman and colleagues at the University of Chicago comes close to bridging the gap, with a Hubble constant of 69.8 based on the luminosity of distant red giant stars and supernovae. 

A difference of 5 or 6 kilometers per second over a distance of over 30 million trillion kilometers might not seem like a lot, but it’s posing a challenge to astronomers. It might provide a hint to a possible new physics beyond the current understanding of our universe. 

On the other hand, the discrepancy could be due to some unknown bias in the methods. Some scientists had expected that the differences would disappear as estimates got better, but the difference between the Hubble constant measured from distant objects and that derived from the cosmic microwave background seems to be getting more and more robust. 

“More and more scientists believe there’s a real tension here,” Chen said. “If we try to come up with a theory, it has to explain everything at once.”

New NASA Research Identifies Pathway for Greenland Meltwater to Reach Ocean

New NASA research found that large crevasses provide aquifer water upstream of Greenland’s Helheim Glacier with a clear escape to the ocean. This discovery helps confirm that the water, which is held in a layer of crunchy, granular snow called firn, contributes to sea level rise.

Cracks in the Greenland Ice Sheet let one of its aquifers drain to the ocean, new NASA research finds. The aquifers, discovered only recently, are unusual in that they trap large amounts of liquid water within the ice sheet. Until now, scientists did not know what happened to the water stored away in this reservoir — the discovery will help fine tune computer models of Greenland’s contribution to sea level rise.

“This paper illuminates the fate of the aquifer’s water,” said Kristin Poinar, lead author of the study and a postdoctoral fellow at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “Before, we didn’t know if the water froze inside the ice sheet or reemerged onto the ice surface. In either of those scenarios, the meltwater would not contribute to sea level rise.”

Now, using a new computer model that tests whether certain meltwater-filled cracks can fracture to the base of the ice sheet, Poinar and her colleagues have shown that the meltwater does reach the ocean.

Greenland contributes water to the sea mainly through surface melt and ice flow. Studies have shown that surface melt has increased in recent decades. In western Greenland, so much surface melts forms that it creates a network of rivers and lakes, which drain through the ice to the underlying bedrock, from where water flows to the ocean.

But southeast Greenland is very different – lakes and rivers do not form, although the ice does melt. Instead, vast reservoirs of water become trapped within the firn layer (a band of compacted snow). In 2011, scientists discovered these aquifers around 40 feet (12 meters) beneath the surface of the ice. Researchers calculated that these firn aquifers cover around 8,455 square miles (21,900 square kilometers) of Greenland and hold a Lake Tahoe-sized volume of water. The aquifer remains liquid year-round because the region’s heavy snow fall creates a thick blanket­ that insulates the aquifer from the freezing air temperatures above.

“These firn aquifers are the analogs to the surface water that we can see in western Greenland,” Poinar said. “Southeast Greenland is perpetually covered in snow and has hardly any bare ice, so in the summer water doesn’t pool up like it does on bare ice in western Greenland, forming lakes and rivers; instead, it percolates downward and disappears into places where we can’t see it.”

Poinar studied a segment of the aquifer located in the Helheim Glacier area in southeast Greenland, where ground-penetrating radar measurements collected by Operation IceBridge, NASA’s aerial survey of changes in polar ice, showed that a 2-mile long section of the aquifer had drained a large volume of water between the spring of 2012 and the spring of 2013.

Directly downstream of this section of the aquifer, the researchers identified a field of crevasses (cracks in the ice); due to gravity, they thought, the aquifer water should flow into these openings. To find out whether the water refroze within the crevasses or fractured all the way to the bedrock, Poinar built a computer model of how water from the firn aquifer widens, deepens, and refreezes within the cracks. The model demonstrated that the water makes the crevasses crack faster than the water can refreeze, thus allowing the meltwater to reach the bedrock in a matter of weeks to months.

“There’s a limit to how much water the crevasses can hold; once they reach that limit, they fracture to the base of the ice sheet and deliver that water to the bed, from where it can travel relatively quickly to the ocean,” Poinar said. “We found that the volume of meltwater drained through this particular aquifer-crevasse field system is comparable to what comes out of a western Greenland supraglacial lake or river system.”

Poinar said that although her study is focused on a specific section of the aquifer, there are other areas in southeast Greenland that are likely to host similar combinations of firn aquifers and nearby crevasse fields. She said that her future work will focus on how this newly discovered drainage system integrates over the entire Greenland ice sheet, and also on measuring how the water drained from the aquifer lubricates the bedrock and impacts the flow of the ice sheet.

“Kristin’s finding is a key component in understanding the importance of the firn aquifer system,” said Rick Forster, a glaciologist at the University of Utah who was part of the field team that discovered the aquifer in 2011. “Her model shows that water is getting to the bed, and that adds a whole different level of significance to how that storage of water might affect changes in sea level rise in the future.”

Recovering From the Brink of Extinction, Humpback Whale Population Rises Faster Than Expected

A population of humpback whales in the South Atlantic has rebounded after near miss with extinction.

Intense pressure from the whaling industry in the 20^th century saw the western South Atlantic population of humpbacks diminish to only 450 whales. It is estimated that 25,000 whales were caught over approximately 12 years in the early 1900s.

Protections were put in place in the 1960s as scientists noticed worldwide that populations were declining. In the mid-1980s, the International Whaling Commission issued a moratorium on all commercial whaling, offering further safeguards for the struggling population.

A new study co-authored by Grant Adams, John Best and André Punt from the University of Washington’s School of Aquatic and Fishery Sciences shows the western South Atlantic humpback (Megaptera novaeangliae) population has grown to 25,000. Researchers believe this new estimate is now close to pre-whaling numbers.

The findings were published on October 16, 2019, in the journal Royal Society Open Science.

“We were surprised to learn that the population was recovering more quickly than past studies had suggested,” said Best, a UW doctoral student.

The study follows a previous assessment conducted by the International Whaling Commission between 2006 and 2015. Those findings indicated the population had only recovered to about 30% of its pre-exploitation numbers. Since that assessment was completed, new data has come to light, providing more accurate information on catches — including struck-and-lost rates — and genetics and life-history.

“Accounting for pre-modern whaling and struck-and-lost rates where whales were shot or harpooned but escaped and later died, made us realize the population was more productive than we previously believed,” said Adams, a UW doctoral student who helped construct the new model.

By incorporating detailed records from the whaling industry at the outset of commercial exploitation, researchers have a good idea of the size of the original population. Current population estimates are made from a combination of air- and ship-based surveys, along with advanced modeling techniques.

The model built for this study provides scientists with a more comprehensive look at the recovery and current status of the humpback population. The authors anticipate it can be used to determine population recovery in other species in more detail as well.

“We believe that transparency in science is important,” said Adams. “The software we wrote for this project is available to the public and anyone can reproduce our findings.”

Lead author Alex Zerbini of the NOAA Alaska Fisheries Science Center’s Marine Mammal Laboratory stressed the importance of incorporating complete and accurate information when conducting these assessments, and providing population assessments without biases. These findings come as good news, he said, providing an example of how an endangered species can come back from near extinction.

“Wildlife populations can recover from exploitation if proper management is applied,” Zerbini said.

The study also looks at how the revival of South Atlantic humpbacks may have ecosystem-wide impacts. Whales compete with other predators, like penguins and seals, for krill as their primary food source. Krill populations may further be impacted by warming waters due to climate change, compressing their range closer to the poles.

“Long-term monitoring of populations is needed to understand how environmental changes affect animal populations,” said Zerbini.

Other co-authors are Phillip Clapham of Alaska Fisheries Science Center and Jennifer Jackson of the British Antarctic Survey.

This research was funded by the Pew Bertarelli Ocean Legacy Project, the U.S. National Marine Fisheries Service-National Oceanic and Atmospheric Administration, the British Antarctic Survey and the University of Washington.

230 Million Year Old Arthropods Found Preserved in Amber

Arthropods from the Triassic period have been discovered preserved in amber. They are 100 million years older than previous amber inclusions. The two mites and one fly were found in millimeter-scale droplets of amber from northeastern Italy.

Researchers published their findings in the journal Proceedings of the National Academy of Sciences. 

Arthropods are invertebrate animals including insects, arachnids and crustaceans. The specimens were preserved with microscopic fidelity, allowing the estimation of the amount of evolutionary change over millions of years. Arthropods are more than 400 million years old, but before now the oldest record of these animals in amber dates to about 130 million years, in the Cretaceous period.

The amber droplets range between 2 to 6 mm in length, were buried in the Dolomite Alps of northeastern Italy and excavated by Eugenio Ragazzi and Guido Roghi of the University of Padova. Over 70,000 droplets were screened for inclusions by a team of German scientists led by Alexander Schmidt, of the Georg-August University in Göttingen.

Two of the specimens are a new species of mites, Triasacarus fedelei and Ampezzoa triassica. They are the oldest fossils of a group called Eriophyoidea, which has about 3,500 living species, all of which feed on plants and sometimes form abnormal growth called galls on their bodies.

T. fedelei and A. triassica fed on a now extinct conifer, but 97% of today’s gall mites feed on flowering plants. These mites existed before the appearance of flowering plants. The mites seemed to have evolved and endured even when flowering plants entered the environment. The fly couldn’t be identified because some of its body parts weren’t well preserved.

There was a huge change in flora and fauna in the Triassic, because it was right after one of the most acute extinction pulses in the geological time record, the Permian-Triassic extinction event, which occurred 252.28 Ma. This could help elucidate how life continued to evolve.

Meet the ‘Mold Pigs,’ a Newly Discovered Invertebrate From 30 Million Years Ago

Fossils preserved in Dominican amber reveal a new family, genus and species of microinvertebrate from the mid-Tertiary period, a discovery that shows unique lineages of the tiny creatures were living 30 million years ago.

 The findings by George Poinar Jr. of the Oregon State University College of Science give a rare look at a heretofore unknown clade of invertebrates, along with their fungal food source and other animals that lived in their habitat.

 Poinar, an international expert in using plant and animal life forms preserved in amber to learn more about the biology and ecology of the distant past, informally calls the new animals “mold pigs” for their resemblance to swine, and their diet.

Scientifically, they are Sialomorpha dominicana, from the Greek words for fat hog (sialos) and shape (morphe). Invertebrate means not having a backbone, and invertebrates account for roughly 95 percent of animal species.

 “Every now and then we’ll find small, fragile, previously unknown fossil invertebrates in specialized habitats,” Poinar said. “And occasionally, as in the present case, a fragment of the original habitat from millions of years ago is preserved too.

The mold pigs can’t be placed in any group of currently existing invertebrates – they share characteristics with both tardigrades, sometimes referred to as water bears or moss pigs, and mites but clearly belong to neither group.”

 The several hundred individual fossils preserved in the amber shared warm, moist surroundings with pseudoscorpions, nematodes, fungi, and protozoa, Poinar said. “The large number of fossils provided additional evidence of their biology, including reproductive behavior, developmental stages and food,” he said.

“There is no extant group that these fossils fit into, and we have no knowledge of any of their descendants living today. This discovery shows that unique lineages were surviving in the mid-Tertiary.”

The Tertiary period began 65 million years ago and lasted for more than 63 million years. About 100 micrometers long, the mold pigs had flexible heads and four pairs of legs. They grew by molting their exoskeleton and fed mainly on fungi, supplementing that food source with small invertebrates.

 “No claws are present at the end of their legs as they are with tardigrades and mites,” Poinar said.

“Based on what we know about extant and extinct microinvertebrates, S. dominicana appears to represent a new phylum. The structure and developmental patterns of these fossils illustrate a time period when certain traits appeared among these types of animals. But we don’t know when the Sialomorpha lineage originated, how long it lasted, or whether there are descendants living today.”