The scientific community has largely assumed that planets covered in a deep ocean would not support the cycling of minerals and gases that keeps the climate stable on Earth, and thus wouldn’t be friendly to life. But the study, published Aug. 30 in The Astrophysical Journal, found that ocean planets could stay in the “sweet spot” for habitability much longer than previously assumed. The authors based their findings on more than a thousand simulations.

“This really pushes back against the idea you need an Earth clone — that is, a planet with some land and a shallow ocean,” said Edwin Kite, assistant professor of geophysical sciences at UChicago and lead author of the study.

As telescopes get better, scientists are finding more and more planets orbiting stars in other solar systems. Such discoveries are resulting in new research into how life could potentially survive on other planets, some of which are very different from Earth — some may be covered entirely in water hundreds of miles deep.

Because life needs an extended period to evolve, and because the light and heat on planets can change as their stars age, scientists usually look for planets that have both some water and some way to keep their climates stable over time. The primary method we know of is how Earth does it. Over long timescales, our planet cools itself by drawing down greenhouse gases into minerals and warms itself up by releasing them via volcanoes.

But this model doesn’t work on a water world, with deep water covering the rock and suppressing volcanoes.

Kite, and Penn State coauthor Eric Ford, wanted to know if there was another way. They set up a simulation with thousands of randomly generated planets, and tracked the evolution of their climates over billions of years.

“The surprise was that many of them stay stable for more than a billion years, just by luck of the draw,” Kite said. “Our best guess is that it’s on the order of 10 percent of them.”

These lucky planets sit in the right location around their stars. They happened to have the right amount of carbon present, and they don’t have too many minerals and elements from the crust dissolved in the oceans that would pull carbon out of the atmosphere. They have enough water from the start, and they cycle carbon between the atmosphere and ocean only, which in the right concentrations is sufficient to keep things stable.

“How much time a planet has is basically dependent on carbon dioxide and how it’s partitioned between the ocean, atmosphere and rocks in its early years,” said Kite. “It does seem there is a way to keep a planet habitable long-term without the geochemical cycling we see on Earth.”

The simulations assumed stars that are like our own, but the results are optimistic for red dwarf stars, too, Kite said. Planets in red dwarf systems are thought to be promising candidates for fostering life because these stars get brighter much more slowly than our sun — giving life a much longer time period to get started. The same conditions modeled in this paper could be applied to planets around red dwarfs, they said: Theoretically, all you would need is the steady light of a star.

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Last week, the scientists described results that they didn’t expect to find. In the paper, published online on Aug. 24 in PLOS ONE, they reported that the jaw joint bone, the center around which chewing activity revolves (literally), appears to have evolved based more on an animal’s size than what it eats.

While focused on carnivorans, the research may also provide some clues to how jaw joints function in general, including in humans and could improve the understanding of temporomandibular disorders (TMJ), which cause pain in the jaw joint and in the muscles that control the jaw.

“Even though it is clear that the carnivoran jaw joint is important for feeding, no one knew if jaw joint bone structure across species was related to the mechanical demands of feeding,” explained M. Aleksander Wysocki, first author and a doctoral student in the new computational cell biology, anatomy and pathology graduate program in the Department of Pathology and Anatomical Sciences in the Jacobs School.

Wysocki and co-author Jack Tseng, PhD, assistant professor in the Department of Pathology and Anatomical Sciences in the Jacobs School, took a multifaceted approach. They examined 40 different carnivoran species from bobcats to wolves, looking at the jaw joint bone called the mandibular condyle.

The jaw’s pivot point

“The mandibular condyle is the pivot point of the jaw, it functions similarly to the way the bolt of a door hinge does,” Wysocki said. “Studies have shown that this joint is loaded with force during chewing.”

He noted that the team was especially interested in the intricate, spongey bone structures inside the jaw joint, also known as trabecular bone. “We thought that this part of the skull would be the best candidate for determining relationships between food type and anatomy.”

For example, because hyenas crush bone while consuming their prey, it could be assumed that their jaw joints would need to be capable of exerting significant force. “On the other hand, an animal that eats plants wouldn’t be expected to require that kind of jaw joint structure,” he said. “But we found that diet has a weaker relationship with skull anatomy than we thought. Mostly it’s the animals’ size that determines jaw joint structure and mechanical properties.”

The researchers took computed tomography (CT) scan data of skulls from 40 species at the American Museum of Natural History, then built 3D models of them, from which they extracted the internal bone structure. Using a 3D printer, the scientists then printed 3D cores, based on virtual “core samples” taken from the mandibular condyle of each jaw joint, which they then scaled and tested for strength.

“Using a compression gauge, we measured how rigid these jaw joint structures were and how much force they could withstand,” Wysocki said. 

No significant correlation

The testing revealed no significant correlations between the shape or mechanical performance of the jaw joint bone and the diets of particular carnivorans.

“The mandibular condyle absorbs compressive force during chewing so we hypothesized that this was a part of the skull that was likely to be influenced by what the animal eats,” Wysocki said. “It turns out that body size is the key factor determining the complexity of jaw joint bone structure and strength.”

He noted that some previous research has revealed that despite the wide variety of diets consumed by different carnivorans, the overall skull shape is considerably influenced by non-feeding variables.

“Still, given how critical the temporomandibular joint is in capturing prey and eating it, these results are very striking,” he said. “For over a century, it has been assumed that skull shape is closely related to what an animal eats. And now we have found that jaw joint bone structure is related to carnivoran body size, not what the animal is eating.”

Wysocki said that the reasons for this apparent disconnect may be that larger carnivorans don’t need such powerful jaws because they are proportionately larger than their prey, or possibly because they share the work involved by hunting in groups. He also said that other factors such as developmental constraints of bone structure could play a role in producing the trends observed in the study.

“Our research shows that factors other than diet need to be considered when attempting to understand jaw joint function,” Wysocki concluded. “It turns out that the functional anatomy of the jaw joint is much more complex than we thought.”

For the record, the findings revealed that the species that demonstrated the greatest maximum compressive strength during chewing force simulations, was the wolverine (Gulo gulo), followed by the cheetah (Acinonyx jubatus), the malagasy civet (Fossa fossana), the honey badger (Mellivora capensis) and the kinkajou (Potos flavus).

Tetanus is a vaccine-preventable neglected disease that mostly occurs in regions where vaccination coverage is incomplete. The World Health Organization recommends treating tetanus with patient monitoring, antibody injections, sedation, pain relief, and general supportive care.

In the new work, Jennifer Downs of Weill Cornell Medicine, New York, and colleagues looked at a tetanus patient care protocol implemented in the ICU of Bugando Medical Centre in Tanzania in 2006. The stepwise protocol, which was modified in 2012, emphasized airway control, early administration of medications, and wound care. Patient care and outcomes were analyzed for tetanus patients in three groups — those admitted pre-protocol in 2001 to 2006, those in an Early group, admitted in 2006 to 2011, and a Late group admitted after the protocol was modified, in 2012 to 2016.

The researchers saw a significant increase in utilized care between the Early and Late groups, with more mechanical ventilation, surgical wound care, and tracheostomies used in the Late group. Despite this increase in care, there was no significant change to overall mortality or 7-day mortality between the pre-protocol and post-protocol groups or Early and Late groups, with mortality rates ranging from 40.3% to 60.7% in all groups. There was, however, a decrease in deaths related to airway compromise and increase in deaths due to sepsis in the post-protocol groups.

“Implementation of protocolized care in resource-limited settings is highly complex and requires in-depth monitoring and assessment of patients, staff, and procedures,” the researchers say. “We strongly call from an increase in vaccination coverage for at-risk men in sub-Saharan Africa… with the aim of eliminating this preventable, lethal disease,” they add.

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Researchers at UC Santa Cruz compiled and analyzed data from around the world for earthquakes clearly associated with injection wells. They found that a single injection well can cause earthquakes at distances more than 6 miles (10 kilometers) from the well. They also found that, in general, injecting fluids into sedimentary rock can cause larger, more distant earthquakes than injecting into the underlying basement rock.

“This is problematic, since the current advice is to preferentially inject into the sedimentary sequence as a theoretically safer alternative to the basement rock,” said Emily Brodsky, professor of Earth and planetary sciences at UC Santa Cruz.

Postdoctoral researcher Thomas Goebel said the key issue is the spatial footprint of induced seismicity around the injection well. “It’s not that the basement rock is safe, because there is still the possibility of encountering a fault in the basement rock that can cause a large earthquake, but the probability is reduced because the spatial footprint is smaller,” he said.

In a paper published August 31 in Science, Goebel and Brodsky described two distinct patterns of induced seismicity, which they associated with different physical mechanisms acting in basement rock and sedimentary rock. In the first pattern, associated with injection into basement rock, earthquakes tend to occur in a compact cluster around the well, with a steep decline in earthquakes farther from the well. In the other pattern, associated with sedimentary rock, induced earthquakes decline gradually with distance from the well and occur at much greater distances.

The physical mechanism by which injection wells induce earthquakes was thought to be a direct result of increased fluid pressure in the pores of the rock, causing faults to slip more easily. This mechanism can account for the spatial pattern of seismicity seen with injection into basement rock, Goebel said. But the pattern seen with injection into sedimentary rock suggests a different mechanism resulting from efficient “poroelastic coupling,” which controls the ability of the rock to transmit fluid stresses into the solid rock matrix.

“When you inject water into the ground, it pushes on the surrounding rock and creates elastic stress in the rock, which can put pressure on faults at a distance without putting water into those faults. So if poroelasticity is dominant, you end up with a larger footprint because it’s loading neighboring faults beyond the area of increased pore pressure,” Brodsky said.

According to Goebel, the crystalline basement rock is stiffer and has lower porosity than sedimentary rock. “Therefore, the increase in pore pressure is limited to isolated pockets around the well, and the coupling of that with the overall stress field is low,” he said.

Goebel said their findings help explain the extent of induced seismicity in regions such as Oklahoma where there are many injection sites in oil and gas fields. Oklahoma has seen a dramatic surge in earthquakes since 2010, to the extent that there are now more earthquakes each year in Oklahoma than in California. Goebel and Brodsky did not include sites in Oklahoma in their study, however, because there are so many injection wells they couldn’t isolate the effects of individual wells.

“In Oklahoma, they are injecting into the high-porosity sedimentary unit above the basement, but these elastic stresses can be transmitted over a large distance, so you could activate a large basement fault at a distance of 10 kilometers,” Goebel said. “That may be what we’re seeing in places like Oklahoma.”

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Materials provided by University of California – Santa Cruz. Original written by Tim Stephens. Note: Content may be edited for style and length.