In the coming years, NASA and the European Space Agency (ESA) will send two robotic missions to explore Jupiter’s icy moon Europa. These are none other than NASA’s Europa Clipper and the ESA’s Jupiter Icy Moons Explorer (JUICE), which will launch in 2024, and 2023 (respectively). Once they arrive by the 2030s, they will study Europa’s surface with a series of flybys to determine if its interior ocean could support life. These will be the first astrobiology missions to an icy moon in the outer Solar System, collectively known as “Ocean Worlds.”
One of the many challenges for these missions is how to mine through the thick icy crusts and obtain samples from the interior ocean for analysis. According to a proposal by Dr. Theresa Benyo (a physicist and the principal investigator of the lattice confinement fusion project at NASA’s Glenn Research Center), a possible solution is to use a special reactor that relies on fission and fusion reactions. This proposal was selected for Phase I development by the NASA Innovative Advanced Concepts (NIAC) program, which includes a $12,500 grant.
The list of Ocean Worlds is long and varied, ranging from Ceres in the Main Asteroid Belt, the moons of Jupiter (Callisto, Ganymede, and Europa), Saturn (Titan, Enceladus, and Dione), Neptune’s largest moon (Triton), and Pluto and other bodies in the Kuiper Belt. These worlds are all believed to have interior oceans heated by tidal flexing due to gravitational interaction with their parent body or (in the case of Ceres and Pluto) the decay of radioactive elements. Further evidence of these oceans and activity includes surface plumes and striated features indicating exchanges between the surface and interior.
The main challenge for exploring the interiors of these worlds is the thickness of their ice sheets, which can be up to 40 km (25 mi) deep. In Europa’s case, different models have yielded estimates of between 15 and 25 km (10 and 15 mi). In addition, the proposed probe will need to contend with hydrostatic ice with varying compositions (such as ammonia and silicate rock) at different depths, pressures, temperatures, and densities. It will also have to contend with water pressure, maintain communications with the surface, and return samples to the surface.
NASA has explored the possibility of using a heating or boring probe to pass through the icy sheet to access the interior ocean. In particular, researchers have proposed using a nuclear-powered probe that would rely on radioactive decay to generate heat and melt through the surface ice. However, a team of NASA researchers led by Dr. Benyo has proposed a new method that would rely on something other than conventional radioactive isotopes – plutonium-238 or enriched uranium-235. Instead, their method would involve triggering nuclear fusion reactions between the atoms of a solid metal.
Their method, known as Lattice Confinement Fusion, was described in two papers published in the April 2020 issue of Physical Review C, titled “Nuclear fusion reactions in deuterated metals” and “Novel nuclear reactions observed in bremsstrahlung-irradiated deuterated metals.” As Dr. Benyo explained in a recent NASA Glenn Research Center press statement:
“Scientists are interested in fusion, because it could generate enormous amounts of energy without creating long-lasting radioactive byproducts. However, conventional fusion reactions are difficult to achieve and sustain because they rely on temperatures so extreme to overcome the strong electrostatic repulsion between positively charged nuclei that the process has been impractical.”
Convention fusion methods generally come down to inertial or magnetic confinement. With inertial confinement, fuels such as deuterium or tritium (hydrogen-2 or -3) are compressed to extreme pressures (for nanoseconds) where fusion can occur. In magnetic confinement (tokamak reactors), the fuel is heated until it reaches temperatures in excess of what occurs at the center of the Sun – 15 million °C (27 million °F) – to achieve nuclear fusion. This new method creates fusion reactions within the confines of a metal lattice loaded with deuterium fuel at ambient temperatures.
This new method creates an energetic environment inside the lattice where individual atoms achieve equivalent fusion-level kinetic energies. This is accomplished by packing the lattices with deuterium at densities one billion times greater than in tokamak reactors, where a neutron source accelerates deuterium atoms (deuterons) to the point that they collide with neighboring deuterons, causing fusion reactions. For their experiments, Dr. Benyo and her colleagues exposed deuterons to a 2.9+MeV energetic X-ray beam, creating energetic neutrons and protons.
This process could allow for fast-fission reactions using lattices built from metals like depleted uranium, thorium, or erbium (Er68) in a molten lithium matrix. The team also observed the production of more energetic neutrons, indicating that boosted fusion reactions – aka. screened Oppenheimer-Phillips (O-P) nuclear stripping reactions – also occur in the process. According to Dr. Benyo, either fusion process is scalable and could be a pathway to a new type of nuclear-powered spacecraft:
“The resulting hybrid fusion fast fission nuclear reactor will be smaller than a traditional fission reactor where a lower mass power source is needed and provide efficient operation with thermal waste heat from reactor heats probe to melt through ice shelf to sub-ice oceans.”
A bonus of this new process is the critical role that metal lattice electrons whose negative charges help “screen” positively charged deuterons. According to the theory developed by project theoretical physicist Dr. Vladimir Pines, this screening allows adjacent deuterons to approach one another more closely. This reduces the chance that they will scatter while increasing the likelihood that they will tunnel through the electrostatic barrier and promote fusion reactions. According to NASA project principal investigator Dr. Bruce Steinetz, there are hurdles to overcome, but the project is off to a good start:
“The current findings open a new path for initiating fusion reactions for further study within the scientific community. However, the reaction rates need to be increased substantially to achieve appreciable power levels, which may be possible utilizing various reaction multiplication methods under consideration.”
This type of nuclear process could be part of a Europa Lander, a proposed NASA mission that would build on the research conducted by the Europa Clipper and JUICE. With more study and development, this technology could also be used to create power systems for long-duration exploration missions, similar to NASA’s Kilopower Reactor Using Stirling Technology (KRUSTY) project. The same technology could enable new engine concepts like the Nuclear-Thermal and Nuclear-Electric Propulsion (NTP/NEP) NASA and other space agencies are investigating.
Finally, this proposed method could have applications for life here on Earth, providing a new kind of nuclear energy and medical isotopes for nuclear medicine. As Leonard Dudzinski, the Chief Technologist for Planetary Science at NASA’s Science Mission Directorate (SMD), said:
“The key to this discovery has been the talented, multi-disciplinary team that NASA Glenn assembled to investigate temperature anomalies and material transmutations that had been observed with highly deuterated metals, We will need that approach to solve significant engineering challenges before a practical application can be designed.”
Rare ‘big fuzzy green ball’ comet visible in B.C. skies, a 50000-year sight
In the night sky, a comet is flying by Earth for the first time in 50,000 years.
Steve Coleopy, of the South Cariboo Astronomy Club, is offering some tips on how to see it before it disappears.
The green-coloured comet, named C/2022 E3 (ZTF), is not readily visible to the naked eye, although someone with good eyesight in really dark skies might be able to see it, he said. The only problem is it’s getting less visible by the day.
“Right now the comet is the closest to earth and is travelling rapidly away,” Coleopy said, noting it is easily seen through binoculars and small telescopes. “I have not been very successful in taking a picture of it yet, because it’s so faint, but will keep trying, weather permitting.”
At the moment, the comet is located between the bowl of the Big Dipper and the North Star but will be moving toward the Planet Mars – a steady orange-coloured point of light- in the night sky over the next couple of weeks, according to Coleopy.
“I have found it best to view the comet after 3:30 in the morning, after the moon sets,” he said. “It is still visible in binoculars even with the moon still up, but the view is more washed out because of the moonlight.”
He noted the comet looks like a “big fuzzy green ball,” as opposed to the bright pinpoint light of the stars.
“There’s not much of a tail, but if you can look through the binoculars for a short period of time, enough for your eyes to acclimatize to the image, it’s quite spectacular.”
To know its more precise location on a particular evening, an internet search will produce drawings and pictures of the comet with dates of where and when the comet will be in each daily location.
Coleopy notes the comet will only be visible for a few more weeks, and then it won’t return for about 50,000 years.
Extreme species deficit of nitrogen-converting microbes in European lakes
Sampling of Lake Constance water from 85 m depth, in which ammonia-oxidizing archaea make up as much as 40% of all microorganisms
An international team of researchers led by microbiologists from the Leibniz Institute DSMZ-German Collection of Microorganisms and Cell Cultures GmbH in Braunschweig, Germany, shows that in the depths of European lakes, the detoxification of ammonium is ensured by an extremely low biodiversity of archaea. The researchers recently published their findings in the prestigious international journal Science Advances. The team led by environmental microbiologists from the Leibniz Institute DSMZ has now shown that the species diversity of these archaea in lakes around the world ranges from 1 to 15 species. This is of particularly concern in the context of global biodiversity loss and the UN Biodiversity Conference held in Montreal, Canada, in December 2022. Lakes play an important role in providing freshwater for drinking, inland fisheries, and recreation. These ecosystem services would be at danger from ammonium enrichment. Ammonium is an essential component of agricultural fertilizers and contributes to its remarkable increase in environmental concentrations and the overall im-balance of the global nitrogen cycle. Nutrient-poor lakes with large water masses (such as Lake Constance and many other pre-alpine lakes) harbor enormously large populations of archaea, a unique class of microorganisms. In sediments and other low-oxygen environments, these archaea convert ammonium to nitrate, which is then converted to inert dinitrogen gas, an essential component of the air. In this way, they contribute to the detoxification of ammonium in the aquatic environment. In fact, the species predominant in European lakes is even clonal and shows low genetic microdiversity between different lakes. This low species diversity contrasts with marine ecosystems where this group of microorganisms predominates with much greater species richness, making the stability of ecosystem function provided by these nitrogen-converting archaea potentially vulnerable to environmental change.
Maintenance of drinking water quality
Although there is a lot of water on our planet, only 2.5% of it is fresh water. Since much of this fresh water is stored in glaciers and polar ice caps, only about 80% of it is even accessible to us humans. About 36% of drinking water in the European Union is obtained from surface waters. It is therefore crucial to understand how environmental processes such as microbial nitrification maintain this ecosystem service. The rate-determining phase of nitrification is the oxidation of ammonia, which prevents the accumulation of ammonium and converts it to nitrate via nitrite. In this way, ammonium is prevented from contaminating water sources and is necessary for its final conversion to the harmless dinitrogen gas. In this study, deep lakes on five different continents were investigated to assess the richness and evolutionary history of ammonia-oxidizing archaea. Organisms from marine habitats have traditionally colonized freshwater ecosystems. However, these archaea have had to make significant changes in their cell composition, possible only a few times during evolution, when they moved from marine habitats to freshwaters with much lower salt concentrations. The researchers identified this selection pressure as the major barrier to greater diversity of ammonia-oxidizing archaea colonizing freshwaters. The researchers were also able to determine when the few freshwater archaea first appeared. Ac-cording to the study, the dominant archaeal species in European lakes emerged only about 13 million years ago, which is quite consistent with the evolutionary history of the European lakes studied.
Slowed evolution of freshwater archaea
The major freshwater species in Europe changed relatively little over the 13 million years and spread almost clonally across Europe and Asia, which puzzled the researchers. Currently, there are not many examples of such an evolutionary break over such long time periods and over large intercontinental ranges. The authors suggest that the main factor slowing the rapid growth rates and associated evolutionary changes is the low temperatures (4 °C) at the bottom of the lakes studied. As a result, these archaea are restricted to a state of low genetic diversity. It is unclear how the extremely species-poor and evolutionarily static freshwater archaea will respond to changes induced by global climate warming and eutrophication of nearby agricultur-al lands, as the effects of climate change are more pronounced in freshwater than in marine habitats, which is associated with a loss of biodiversity.
Publication: Ngugi DK, Salcher MM, Andre A-S, Ghai R., Klotz F, Chiriac M-C, Ionescu D, Büsing P, Grossart H-S, Xing P, Priscu JC, Alymkulov S, Pester M. 2022. Postglacial adaptations enabled coloniza-tion and quasi-clonal dispersal of ammonia oxidizing archaea in modern European large lakes. Science Advances: https://www.science.org/doi/10.1126/sciadv.adc9392
PhDr. Sven-David Müller, Head of Public Relations, Leibniz Institute DSMZ-German Collection of Microorganisms and Cell Cultures GmbH
Phone: ++49 (0)531/2616-300
About the Leibniz Institute DSMZ
The Leibniz Institute DSMZ-German Collection of Microorganisms and Cell Cultures is the world’s most diverse collection of biological resources (bacteria, archaea, protists, yeasts, fungi, bacteriophages, plant viruses, genomic bacterial DNA as well as human and animal cell lines). Microorganisms and cell cultures are collected, investigated and archived at the DSMZ. As an institution of the Leibniz Association, the DSMZ with its extensive scientific services and biological resources has been a global partner for research, science and industry since 1969. The DSMZ was the first registered collection in Europe (Regulation (EU) No. 511/2014) and is certified according to the quality standard ISO 9001:2015. As a patent depository, it offers the only possibility in Germany to deposit biological material in accordance with the requirements of the Budapest Treaty. In addition to scientific services, research is the second pillar of the DSMZ. The institute, located on the Science Campus Braunschweig-Süd, accommodates more than 82,000 cultures and biomaterials and has around 200 employees. www.dsmz.de
Scientists are closing in on why the universe exists
Particle astrophysicist Benjamin Tam hopes his work will help us understand a question. A very big one.
“The big question that we are trying to answer with this research is how the universe was formed,” said Tam, who is finishing his PhD at Queen’s University.
“What is the origin of the universe?”
And to answer that question, he and dozens of fellow scientists and engineers are conducting a multi-million dollar experiment two kilometres below the surface of the Canadian Shield in a repurposed mine near Sudbury, Ontario.
The Sudbury Neutrino Observatory (SNOLAB) is already famous for an earlier experiment that revealed how neutrinos ‘oscillate’ between different versions of themselves as they travel here from the sun.
This finding proved a vital point: the mass of a neutrino cannot be zero. The experiment’s lead scientist, Arthur McDonald, shared the Nobel Prize in 2015 for this discovery.
The neutrino is commonly known as the ‘ghost particle.’ Trillions upon trillions of them emanate from the sun every second. To humans, they are imperceptible except through highly specialized detection technology that alerts us to their presence.
Neutrinos were first hypothesized in the early 20th century to explain why certain important physics equations consistently produced what looked like the wrong answers. In 1956, they were proven to exist.
Tam and his fellow researchers are now homing in on the biggest remaining mystery about these tiny particles.
Nobody knows what happens when two neutrinos collide. If it can be shown that they sometimes zap each other out of existence, scientists could conclude that a neutrino acts as its own ‘antiparticle’.
Such a conclusion would explain how an imbalance arose between matter and anti-matter, thus clarifying the current existence of all the matter in the universe.
It would also offer some relief to those hoping to describe the physical world using a model that does not imply none of us should be here.
Guests in this episode (in order of appearance):
Benjamin Tam is a PhD student in Particle Astrophysics at Queen’s University.
Eve Vavagiakis is a National Science Foundation Astronomy and Astrophysics Postdoctoral Fellow in the Physics Department at Cornell University. She’s the author of a children’s book, I’m A Neutrino: Tiny Particles in a Big Universe.
Erica Caden is a research scientist at SNOLAB. Among her duties she is the detector manager for SNO+, responsible for keeping things running day to day.
*This episode was produced by Nicola Luksic and Tom Howell. It is part of an on-going series, IDEAS from the Trenches, some stories are below.
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