Available data showing ice thickness variation already allows a prediction for the upper ocean of Enceladus, a moon of Saturn, and a NASA mission’s planned orbital survey of Europa’s ice shell should do the same for the much larger Jovian moon, enhancing the mission’s findings about whether it could support life.

The researchers propose that a process called “ice pumping,” which they’ve observed below Antarctic ice shelves, likely shapes the undersides of Europa’s and Enceladus’ ice shells, but should also operate at Ganymede and Titan, large moons of Jupiter and Saturn, respectively. They show that temperature ranges where the ice and ocean interact — important regions where ingredients for life may be exchanged — can be calculated based on an ice shell’s slope and changes in water’s freezing point at different pressures and salinities.

“If we can measure the thickness variation across these ice shells, then we’re able to get temperature constraints on the oceans, which there’s really no other way yet to do without drilling into them,” said Britney Schmidt, associate professor of astronomy and of earth and atmospheric sciences. “This gives us another tool for trying to figure out how these oceans work. And the big question is, are things living there, or could they?”

Along with current and former members of Planetary Habitability and Technology Lab, Schmidt is a co-author of “Ice-Ocean Interactions on Ocean Worlds Influence Ice Shell Topography,” published in the Journal of Geophysical Research: Planets.

In 2019, using the remotely operated Icefin robot, Schmidt’s team observed ice pumping inside a crevasse beneath Antarctica’s Ross Ice Shelf.

The researchers mapped ranges of potential shell thickness, pressure and salinity for ocean worlds with varying gravity and concluded that ice pumping would occur in the most probable scenarios, though not in all. They found that ice-ocean interactions on Europa may be similar to those observed beneath the Ross Ice Shelf — evidence that such regions may be some of the most Earth-like on alien worlds, said Justin Lawrence, a visiting scholar at the Cornell Center for Astrophysics and Planetary Science and a program manager at Honeybee Robotics.

NASA’s Cassini probe generated data sufficient to predict a temperature range for Enceladus’ ocean, based on the slope of its ice shell from poles to equator: minus 1.095 degrees to minus 1.272 degrees Celsius. Knowing temperatures informs understanding of how heat flows through oceans and how they circulate, affecting habitability.

The researchers expect ice pumping to be weak at Enceladus, a small moon (the width of Arizona) with dramatic topography, while at larger Europa — nearly the size of Earth’s moon — they predict it acts quickly to smooth and flatten the ice shell’s base.

Schmidt said the work demonstrates how research investigating climate change on Earth can also benefit planetary science, a reason NASA has supported Icefin’s development.

“There’s a connection between the shape of the ice shell and the temperature in the ocean,” Schmidt said. “This is a new way to get more insight from ice shell measurements that we hope to be able to get for Europa and other worlds.”

The research was supported by NASA’s Future Investigators in NASA Earth and Space Science and Technology (FINESST) program and the National Science Foundation.

But what if humans could have jellyfish explore the oceans on our behalf, reporting back what they find? New research conducted at Caltech aims to make that a reality through the creation of what researchers call biohybrid robotic jellyfish. These creatures, which can be thought of as ocean-going cyborgs, augment jellyfish with electronics that enhance their swimming and a prosthetic “hat” that can carry a small payload while also making the jellyfish swim in a more streamlined manner.

The work, published in the journal Bioinspiration & Biomimetics, was conducted in the lab of John Dabiri (MS ’03, PhD ’05), the Centennial Professor of Aeronautics and Mechanical Engineering, and builds on his previous work augmenting jellyfish. Dabiri’s goal with this research is to use jellyfish as robotic data-gatherers, sending them into the oceans to collect information about temperature, salinity, and oxygen levels, all of which are affected by Earth’s changing climate.

“It’s well known that the ocean is critical for determining our present and future climate on land, and yet, we still know surprisingly little about the ocean, especially away from the surface,” Dabiri says. “Our goal is to finally move that needle by taking an unconventional approach inspired by one of the few animals that already successfully explores the entire ocean.”

Throughout his career, Dabiri has looked to the natural world, jellyfish included, for inspiration in solving engineering challenges. This work began with early attempts by Dabiri’s lab to develop a mechanical robot that swam like jellyfish, which have the most efficient method for traveling through water of any living creature. Though his research team succeeded in creating such a robot, that robot was never able to swim as efficiently as a real jellyfish. At that point, Dabiri asked himself, why not just work with jellyfish themselves?

“Jellyfish are the original ocean explorers, reaching its deepest corners and thriving just as well in tropical or polar waters,” Dabiri says. “Since they don’t have a brain or the ability to sense pain, we’ve been able to collaborate with bioethicists to develop this biohybrid robotic application in a way that’s ethically principled.”

Previously, Dabiri’s lab implanted jellyfish with a kind of electronic pacemaker that controls the speed at which they swim. In doing so, they found that if they made jellyfish swim faster than the leisurely pace they normally keep, the animals became even more efficient. A jellyfish swimming three times faster than it normally would uses only twice as much energy.

This time, the research team went a step further, adding what they call a forebody to the jellies. These forebodies are like hats that sit atop the jellyfish’s bell (the mushroom-shaped part of the animal). The devices were designed by graduate student and lead author Simon Anuszczyk (MS ’22), who aimed to make the jellyfish more streamlined while also providing a place where sensors and other electronics can be carried.

“Much like the pointed end of an arrow, we designed 3D-printed forebodies to streamline the bell of the jellyfish robot, reduce drag, and increase swimming performance,” Anuszczyk says. “At the same time, we experimented with 3D printing until we were able to carefully balance the buoyancy and keep the jellyfish swimming vertically.”

To test the augmented jellies’ swimming abilities, Dabiri’s lab undertook the construction of a massive vertical aquarium inside Caltech’s Guggenheim Laboratory. Dabiri explains that the three-story tank is tall, rather than wide, because researchers want to gather data on oceanic conditions far below the surface.

“In the ocean, the round trip from the surface down to several thousand meters will take a few days for the jellyfish, so we wanted to develop a facility to study that process in the lab,” Dabiri says. “Our vertical tank lets the animals swim against a flowing vertical current, like a treadmill for swimmers. We expect the unique scale of the facility — probably the first vertical water treadmill of its kind — to be useful for a variety of other basic and applied research questions.”

Swim tests conducted in the tank show that a jellyfish equipped with a combination of the swimming pacemaker and forebody can swim up to 4.5 times faster than an all-natural jelly while carrying a payload. The total cost is about $20 per jellyfish, Dabiri says, which makes biohybrid jellies an attractive alternative to renting a research vessel that can cost more than $50,000 a day to run.

“By using the jellyfish’s natural capacity to withstand extreme pressures in the deep ocean and their ability to power themselves by feeding, our engineering challenge is a lot more manageable,” Dabiri adds. “We still need to design the sensor package to withstand the same crushing pressures, but that device is smaller than a softball, making it much easier to design than a full submarine vehicle operating at those depths.

“I’m really excited to see what we can learn by simply observing these parts of the ocean for the very first time,” he adds.

Dabiri says future work may focus on further enhancing the bionic jellies’ abilities. Right now, they can only be made to swim faster in a straight line, such as the vertical paths being designed for deep ocean measurement. But further research may also make them steerable, so they can be directed horizontally as well as vertically.

Funding for the research was provided by the National Science Foundation and the Charles Lee Powell Foundation.

The research, published in Alzheimer’s & Dementia: The Journal of the Alzheimer’s Association, used virtual reality to test the spatial navigation of 100 asymptomatic midlife adults, aged 43-66, from the PREVENT-Dementia prospective cohort study.

Participants had a hereditary or physiological risk of Alzheimer’s disease, due to either a gene (the APOE-ε4 allele) that puts them at risk of the condition, a family history of Alzheimer’s disease, or lifestyle risk factors such as low levels of physical activity. Crucially, these participants were around 25 years younger than their estimated age of dementia onset.

Led by Professor Dennis Chan, the study used a test designed by Dr Andrea Castegnaro and Professor Neil Burgess (all UCL Institute of Cognitive Neuroscience), in which participants were asked to navigate within a virtual environment while wearing VR headsets.

The researchers found that people at greater risk of developing Alzheimer’s disease, regardless of risk factor, were selectively impaired on the VR navigation task, without a corresponding impairment on other cognitive tests. The authors say their findings suggest that impairments in spatial navigation may begin to develop years, or even decades, before the onset of any other symptoms.

First author, Dr Coco Newton (UCL Institute of Cognitive Neuroscience), who carried out the work while at University of Cambridge said: “Our results indicated that this type of navigation behaviour change might represent the very earliest diagnostic signal in the Alzheimer’s disease continuum — when people move from being unimpaired to showing manifestation of the disease.”

The researchers also found that there was a strong gender difference in how participants performed, with the impairment being observed in men and not women.

Dr Newton added: “We are now taking these findings forward to develop a diagnostic clinical decision support tool for the NHS in the coming years, which is a completely new way of approaching diagnostics and will hopefully help people to get a more timely and accurate diagnosis.

“This is particularly important with the emergence of anti-amyloid treatments for Alzheimer’s, which are considered to be most effective in the earliest stages of the disease.

“It also highlights the need for further study of the differing vulnerability of men and women to Alzheimer’s disease and the importance of taking gender into account for both diagnosis and future treatment.”

Professor Chan said: “We are excited by these findings for two main reasons. First, they improve detection of the clinical onset of Alzheimer’s disease, critical for prompt application of treatments.

“Second, the VR navigation test is based on our knowledge of the spatial properties of cells in the brain’s temporal lobe, and the application of cellular neuroscience to clinical populations helps bridge the gap in understanding how disease at the neuronal level can result in the clinical manifestation of disease. This knowledge gap currently represents one of the biggest barriers to progress in Alzheimer’s research.”

The research was carried out in collaboration with the University of Cambridge, jointly funded by the Alzheimer’s Society and an MSD research grant.

Dr Richard Oakley, Associate Director of Research and Innovation at Alzheimer’s Society, said: “One in three people born today will go on to develop dementia, and early and accurate diagnosis of the diseases that cause the condition are vital for people to access the right support, plan for the future, and receive appropriate treatment.

“Very early symptoms of dementia can be subtle and difficult to detect, but problems with navigation are thought to be some of the first changes in Alzheimer’s disease.

“This study was part funded by Alzheimer’s Society and used virtual reality technology showing that a healthy person’s navigation abilities are linked to their dementia risk, based on genetic and environmental factors.

“This innovative technology is a long way from becoming a diagnostic test, but it does provide more evidence about the role of navigational abilities as an early sign of Alzheimer’s disease. More work is needed to develop this technology, but it will be exciting to see how this research may offer a way to spot disease-specific changes early and help people living with dementia in future.”

A fossil skeleton of Perucetus was discovered in Peru and described in a paper in Nature last year. The animal lived about 39 million years ago and belonged to an extinct group of early whales called the basilosaurids.

Perucetus’ bones are unusually dense. Mammal bones usually have a solid exterior and are spongy or hollow in the center. Some animals have more of the center filled in with solid bone, making them dense and heavy. In aquatic animals, heavy bones can offset buoyancy from body fat and blubber, allowing the animal to maintain neutral buoyancy in water or — in the case of the hippopotamus — to walk on river beds.

The fossil whale bones have both extensive in-filling and extra growth of bone on the outside as well, a condition called pachyostosis also seen in some modern aquatic mammals, such as manatees.

Based on a series of assumptions, the original authors (Giovanni Bianucci at the University of Pisa, Italy and colleagues) estimated a body mass for Perucetus of 180 metric tons (ranging from 85 to 340 metric tons). This would make Perucetus as heavy as, or heavier than the biggest blue whales known, even though it is considerably shorter at 17 meters long compared to a blue whale at about 30 meters.

How to weigh a whale?

Professor Ryosuke Motani, a paleobiologist at the UC Davis Department of Earth and Planetary Sciences, said that these estimates would make Perucetus impossibly dense.

“It would have been a job for the whale to stay at the surface, or even to leave the sea bottom — it would have required continuous swimming against the gravity to do anything in the water,” Motani said.

Motani and Nick Pyenson at the Smithsonian Institute National Museum of Natural History reexamined the assumptions used to make those estimates.

The first problem is that Bianucci et al used the fossil bones to estimate the weight of the skeleton, then extrapolated to the weight of the entire animal, assuming that the skeletal and non-skeletal mass would scale at the same rate with increasing body size. But measurements of other animals show this is not the case, Motani and Pyenson argue.

The original estimates also overestimated how much overall body mass increases as a result of pachyostosis. But evidence from manatees shows that their bodies are relatively light relative to their skeletal mass.

Motani and Pyenson estimate that the 17-meter long Perucetus weighed in at 60 to 70 tons, considerably less than the known weights of blue whales. A Perucetus that grew to 20 meters could weigh over 110 tons, still well short of the largest blue whales at 270 tons.

“The new weight allows the whale to come to the surface and stay there while breathing and recovering from a dive, like most whales do,” Motani said.

Paleontologists have not yet uncovered a skull or teeth of Perucetus, so it is hard to tell what it ate. Sustaining a huge body takes a lot of food. Bianucci et al suggested that Perucetus might have browsed on coastal fish and shellfish, or scavenged carcases, as some sharks do. The new slimmed-down size estimate puts Perucetus in a similar range to sperm whales (80 tons, 20 meters long), which hunt large prey such as giant squid.

The massive explosion unleashed a gamma-ray burst, GRB230307A, the second brightest in 50 years of observations and about 1,000 times brighter than a typical gamma-ray burst. GRB230307A was first detected by NASA’s Fermi Gamma-Ray Space Telescope on March 7, 2023.

Using multiple space- and ground-based telescopes, including NASA’s James Webb Space Telescope, the largest and most powerful telescope ever launched into space, scientists were able to pinpoint the source of the gamma-ray burst in the sky and track how its brightness changed.

With the information gathered, the researchers determined the burst was the result of two neutron stars that merged in a galaxy 1 billion light-years from Earth to form a kilonova. The researchers observed evidence of tellurium, one of the rarest elements on Earth.

The breakthrough discovery puts astronomers one step closer to solving the mystery of the origin of elements that are heavier than iron.

“I’m a high energy astrophysicist. I like explosions. I like the gamma rays that come from them. But I’m also an astronomer who really cares about fundamental questions like how did heavy elements form,” Hartmann said.

Gamma-ray bursts (GRBs) are bursts of gamma-ray light — the most energetic form of light — that last anywhere from seconds to minutes. The first GRBs were detected in the 1960s by satellites built to monitor nuclear testing.

GRBs have different causes.

Long duration GRBs are caused by supernovas, the point when a massive star reaches the end of its life and explodes into a burst of light. Short duration GRBs are caused by the merger of two neutron stars, known as a kilonova, or the merger of a neutron star and a black hole.

Although GRB230307A lasted for 200 seconds, scientists saw the afterglow color change from blue to red, a signature of kilonova.

“The burst itself actually indicated a long duration event, and it should have been a normal supernova-type situation. But it had unusual features. It didn’t quite fit the patterns of long bursts,” Hartmann said. “It turns out that this radioactive cloud, that kilonova afterglow, which had all these nuclear synthetic fingerprints in it, is the signature of a binary merger. The excitement comes from using the Webb to identify a chemical fingerprint that we had expected for short bursts and seeing it inside a long burst.”

Hartmann said the Big Bang produced hydrogen and helium. All other elements were made by stars and processes in the interstellar medium.

“Some of them are massive enough to explode and they return that material to their gaseous environments which later make new stars. So, there’s a cycle in the universe that makes us more enriched in carbon, nitrogen, oxygen, all the things we need,” he said. “We call stars the cauldrons of the universe.”

Thermonuclear reactions, or fusion, make stars shine. That leads successively to the production of more heavy elements, Hartmann said. But when it gets to iron, there isn’t much energy left to squeeze out, he said.

So, where do all the heavy elements such as gold and uranium come from?

“The heavy elements have special origins. There are two processes that dominate. One is called rapid; the other is called slow. We believe the r-process happens in those neutron star mergers,” Hartmann said.

Theoretical modeling suggested kilonovas should produce tellurium, but the detection of a spectral line by the James Webb Space Telescope provided experimental evidence. A spectral line is a dark or bright line within a continuous spectrum. It is produced by transitions within atoms or ions.

“We think it’s a pretty secure identification, but it’s not beyond a reasonable doubt like they would say in court,” Hartmann said.

In addition to Hartmann, researchers from several universities in the United States as well as scientists from the Netherlands, the United Kingdom, Italy, Japan, Denmark, Spain, Sweden, Australia, Ireland, France, New Zealand, Canada, Israel, Iceland, Czech Republic and Germany were involved.