In the strange, dark world of the ocean floor, underwater fissures, called hydrothermal vents, host complex communities of life. These vents belch scorching hot fluids into extremely cold seawater, creating the chemical forces necessary for the small organisms that inhabit this extreme environment to live.

In a newly published study, biogeoscientists Jeffrey Dick and Everett Shock have determined that specific hydrothermal seafloor environments provide a unique habitat where certain organisms can thrive. In so doing, they have opened up new possibilities for life in the dark at the bottom of oceans on Earth, as well as throughout the solar system. Their results have been published in the Journal of Geophysical Research: Biogeosciences.

On land, when organisms get energy out of the food they eat, they do so through a process called cellular respiration, where there is an intake of oxygen and the release of carbon dioxide. Biologically speaking, the molecules in our food are unstable in the presence of oxygen, and it is that instability that is harnessed by our cells to grow and reproduce, a process called biosynthesis.

But for organisms living on the seafloor, the conditions for life are dramatically different.

“On land, in the oxygen-rich atmosphere of Earth, it is familiar to many people that making the molecules of life requires energy,” said co-author Shock of Arizona State University’s School of Earth and Space Exploration and the School of Molecular Sciences. “In stunning contrast, around hydrothermal vents on the seafloor, hot fluids mix with extremely cold seawater to produce conditions where making the molecules of life releases energy.”

In deep-sea microbial ecosystems, organisms thrive near vents where hydrothermal fluid mixes with ambient seawater. Previous research led by Shock found that the biosynthesis of basic cellular building blocks, like amino acids and sugars, is particularly favorable in areas where the vents are composed of ultramafic rock (igneous and meta-igneous rocks with very low silica content), because these rocks produce the most hydrogen.

Besides basic building blocks like amino acids and sugars, cells need to form larger molecules, or polymers, also known as biomacromolecules. Proteins are the most abundant of these molecules in cells, and the polymerization reaction (where small molecules combine to produce a larger biomolecule) itself requires energy in almost all conceivable environments.

“In other words, where there is life, there is water, but water needs to be driven out of the system for polymerization to become favorable,” said lead author Dick, who was a postdoctoral scholar at ASU when this research began and who is currently a geochemistry researcher in the School of Geosciences and Info-Physics at Central South University in Changsha, China. “So, there are two opposing energy flows: release of energy by biosynthesis of basic building blocks, and the energy required for polymerization.”

What Dick and Shock wanted to know is what happens when you add them up: Do you get proteins whose overall synthesis is actually favorable in the mixing zone?

They approached this problem by using a unique combination of theory and data.

From the theoretical side, they used a thermodynamic model for the proteins, called “group additivity,” which accounts for the specific amino acids in protein sequences as well as the polymerization energies. For the data, they used all the protein sequences in an entire genome of a well-studied vent organism called Methanocaldococcus jannaschii.

By running the calculations, they were able to show that the overall synthesis of almost all the proteins in the genome releases energy in the mixing zone of an ultramafic-hosted vent at the temperature where this organism grows the fastest, at around 185 degrees Fahrenheit (85 Celsius). By contrast, in a different vent system that produces less hydrogen (a basalt-hosted system), the synthesis of proteins is not favorable.

“This finding provides a new perspective on not only biochemistry but also ecology because it suggests that certain groups of organisms are inherently more favored in specific hydrothermal environments,” Dick said. “Microbial ecology studies have found that methanogens, of which Methanocaldococcus jannaschii is one representative, are more abundant in ultramafic-hosted vent systems than in basalt-hosted systems. The favorable energetics of protein synthesis in ultramafic-hosted systems are consistent with that distribution.”

For next steps, Dick and Shock are looking at ways to use these energetic calculations across the tree of life, which they hope will provide a firmer link between geochemistry and genome evolution.

“As we explore, we’re reminded time and again that we should never equate where we live as what is habitable to life,” Shock said.

Featured image: A chimney structure from the Sea Cliff hydrothermal vent field located more than 8,800 feet (2,700 meters) below the sea’s surface at the submarine boundary of the Pacific and Gorda tectonic plates. Photo by Ocean Exploration Trust

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Provided by Arizona State University

A team of researchers at the Instituto de Astrofísica de Canarias (IAC) and the Instituto Nacional de Astrofísica, Óptica y Electrónica (INAOE), Mexico, has discovered lithium in the oldest and coldest brown dwarf where the presence of this valuable element has been confirmed so far. This substellar object, called Reid 1B, preserves intact the earliest known lithium deposit in our cosmic neighbourhood, dating back to a time before the formation of the binary system to which it belongs. The discovery was made using the OSIRIS spectrograph on the Gran Telescopio Canarias (GTC), at the Roque de los Muchachos Observatory (Garafía, La Palma), in the Canary Islands. The study has just been published in the journal Monthly Notices of the Royal Astronomical Society.

Brown dwarfs, also known as “coffee coloured dwarfs” or “failed stars” are the natural link between stars and planets. They are more massive than Jupiter but now sufficiently to burn hydrogen, which is the fuel the stars use to shine. For that reason these substellar objects were not observed until observers detected them in the mid 1990’s. They are particularly interesting because it was predicted that some of them could preserve intact their content of lithium, sometimes known as “white petroleum” because of its rarity and its relevance.

In the past twenty years astronomers have detected, and followed the orbital motions of binaries formed by brown dwarfs in the solar neighbourhood. They have determined their masses dynamically using Kepler’s laws, the mathematical formulae produced in the XVII century by Johannes Kepler to describe the motions of astronomical bodies moving under the effects of their mutual gravitation, such as the system formed by the Earth and the Sun. In some of these systems the primary component has a mass sufficient to burn lithium while the secondary may not have this mass. However until now the theoretical models had not been put to the test.

Using the OSIRIS spectrograph on the Gran Telescopio Canarias (GTC, or Grantecan) currently the largest optical and infrared telescope in the world, at the Roque de los Muchachos Observatory (ORM), a team of researchers at the Instituto de Astrofísica de Canarias (IAC) and the Instituto Nacional de Astrofísica, Óptica y Electrónica (INAOE) made high sensitivity spectroscopic observations, between February and August this year, of two binaries whose components are brown dwarfs.

They did not detect lithium in three of them, but they did find it in Reid 1B, the faintest and coolest of the four. Doing this they made a remarkable discovery, a deposit of cosmic lithium which is not destroyed, whose origin dates back before the formation of the system to which Reid 1B belongs. It is, in fact, the coolest, faintest extrasolar object where lithium has been found, in a quantity 13 thousand times greater than the amount there is on Earth. This object, which has an age of 1.100 million years, and a dynamical mass 41 times bigger than that of Jupiter (the largest planet in the Solar System), is 16.9 light years away from us.

A chest of hidden treasure

Observations of lithium in brown dwarfs allow us to estimate their masses with a degree of accuracy, based on nuclear reactions. The thermonuclear masses found this way must be consistent with the dynamical masses found, with less uncertainty, from orbital analysis. However the researchers have found that the lithium is preserved up to a dynamical mass which is 10% lower than that predicted by the most recent theoretical models. This discrepancy seems to be significant, and suggests that there is something in the behaviour of brown dwarfs that we still don’t understand.

“We have been following the trail of lithium in brown dwarfs for three decades” says Eduardo Lorenzo Martín Guerrero de Escalante, Research Professor of the Higher Council for Scientific Research (CSIC) at the IAC who is the first author of the article, “and finally we have been able to make a precise determination of the boundary in mass between its preservation and its destruction, and compare this with the theoretical predictions”. The researcher adds that “there are thousands of millions of brown dwarfs in the Milky Way. The lithium contained in brown dwarfs is the largest known deposit of this valuable element in our cosmic neighbourhood”.

Carlos del Burgo Díaz co-author of the article, a researcher at the INAOE, a public research centre of the Mexican CONACYT, explains that “although primordial lithium was created 13.800 million years ago, together with hydrogen and helium, as a result of he nuclear reactions in the primordial fireball of the Big Bang, now there is as much as four times more lithium in the Universe”. According to this researcher “although this element can be destroyed, it is also created in explosive events such as novae and supernovae, so that brown dwarfs such as Reid 1B can wrap it up and protect it as if it was a chest of hidden treasure”.

This research has been financed by funding from the Spanish Ministry of Economic Affairs and Digital Transformation (MINECO) and by the European Fund for Regional Developomente (FEDER) via project PID2019-109522GB-C53.

The Gran Telescopio Canarias, and the Observatories of the Instituto de Astrofísica de Canarias (IAC) are part of the network of Singular Scientific and Technical Infrastructures (ICTS) of Spain.

Article: “New constraints on the minimum mass for thermonuclear lithium burning in brown dwarfs”, Monthly Notices of the Royal Astronomical Society; Martín, Eduardo L.; Lodieu, Nicolas; del Burgo, Carlos; octubre de 2021.

DOI: 10.1093/mnras/stab2969
arXiv: arXiv:2110.11982
Bibcode: 2021MNRAS.tmp.2787M 

*Figure caption: The Spanish-Mexican team has found that the boundary between those objects which destroy lithium and those which preserve it lies at 51.5 times the mass of Jupiter. The brown dwarf Reid 1B is a major deposti fo lithium which will never be destroyed. Planets such as Jupiter and the Earth are even less massive and do not destroy their lithium. The Sun has destroyed all the lithium that was in its nucleus and preserves some in its upper layers, which are slowly mixing with its interior. Credit: Gabriel Pérez Díaz, SMM (IAC)

Caption to the animation: The dynamical masses of the binary systems are measured by following their orbital motions and applying Kepler’s laws. These masses are very accurate, and should coincide exactly with the masses which are obtained from the nuclear reactions which take place in the components of these systems. However when one compares the dynamical masses with the nuclear masses, the balance is tipped to one side, which means changes have to be made to obtain an equilibrium to deepen our understanding of the properties of these substellar objects. Credit: Gabriel Pérez Díaz, SMM (IAC)

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Provided by IAC

A team of UArizona-led researchers think that the near-Earth asteroid Kamo`oalewa might actually be a miniature moon.

A near-Earth asteroid named Kamo`oalewa could be a fragment of our moon, according to a paper published today in Communications Earth and Environment by a team of astronomers led by the University of Arizona.

Kamo`oalewa is a quasi-satellite – a subcategory of near-Earth asteroids that orbit the sun but remain relatively close to Earth. Little is known about these objects because they are faint and difficult to observe. Kamo`oalewa was discovered by the PanSTARRS telescope in Hawaii in 2016, and the name – found in a Hawaiian creation chant – alludes to an offspring that travels on its own. The asteroid is roughly the size of a Ferris wheel – between 150 and 190 feet in diameter – and gets as close as about 9 million miles from Earth.

Due to its orbit, Kamo`oalewa can only be observed from Earth for a few weeks every April. Its relatively small size means that it can only be seen with one of the largest telescopes on Earth. Using the UArizona-managed Large Binocular Telescope on Mount Graham in southern Arizona, a team of astronomers led by UArizona planetary sciences graduate student Ben Sharkey found that Kamo`oalewa’s pattern of reflected light, called a spectrum, matches lunar rocks from NASA’s Apollo missions, suggesting it originated from the moon.

Researchers aren’t yet be sure how the asteroid may have broken loose from the moon. That’s partly because there are no other known asteroids with lunar origins.

“I looked through every near-Earth asteroid spectrum we had access to, and nothing matched,” said Sharkey, the paper’s lead author.

A debate over Kamo`oalewa’s origins between Sharkey and his adviser, UArizona associate professor of lunar and planetary sciences Vishnu Reddy, led to another three years of hunting for a plausible explanation.

“We doubted ourselves to death,” said Reddy, a co-author who started the project in 2016. After missing the chance to observe the asteroid in April 2020 due to a COVID-19 shutdown of the Large Binocular Telescope, the team found the final piece of the puzzle in 2021.

“This spring, we got much needed follow-up observations and went, ‘Wow it is real,'” Sharkey said. “It’s easier to explain with the moon than other ideas.”

Kamo`oalewa’s orbit is another clue to its lunar origins. Its orbit is similar to the Earth’s, but with the slightest tilt. Its orbit is also not typical of near-Earth asteroids, according to study co-author Renu Malhotra, a UArizona planetary sciences professor who led the orbit analysis portion of the study.

“It is very unlikely that a garden-variety near-Earth asteroid would spontaneously move into a quasi-satellite orbit like Kamo`oalewa’s,” said Malhotra, whose lab is working on a paper to further investigate the asteroid’s origins. “It will not remain in this particular orbit for very long, only about 300 years in the future, and we estimate that it arrived in this orbit about 500 years ago.”

Kamo`oalewa is about 4 million times fainter than the faintest star the human eye can see in a dark sky.

“These challenging observations were enabled by the immense light-gathering power of the twin 8.4-meter telescopes of the Large Binocular Telescope,” said study co-author Al Conrad, a staff scientist for the telescope.

The study also included data from the Lowell Discovery Telescope in Flagstaff, Arizona. Other co-authors on the paper include Olga Kuhn, Christian Veillet, Barry Rothberg and David Thompson from the Large Binocular Telescope; Audrey Thirouin from Lowell Observatory; and Juan Sanchez from the Planetary Science Institute in Tucson. The research was funded by NASA’s Near-Earth Object Observations Program.

Featured image: An artist’s impression of Earth quasi-satellite Kamo`oalewa near the Earth-moon system. Using the Large Binocular Telescope, astronomers have shown that it might be a lost fragment of the moon.Addy Graham/University of Arizona

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Provided by University of Arizona

Forming planets are one possible explanation for the rings and gaps observed in disks of gas and dust around young stars. But this theory has trouble explaining why it is rare to find planets associated with rings. New supercomputer simulations show that after creating a ring, a planet can move away and leave the ring behind. Not only does this bolster the planet theory for ring formation, the simulations show that a migrating planet can produce a variety of patterns matching those actually observed in disks.

Young stars are encircled by protoplanetary disks of gas and dust. One of the world’s most powerful radio telescope arrays, ALMA (Atacama Large Millimeter/submillimeter Array), has observed a variety of patterns of denser and less dense rings and gaps in these protoplanetary disks. Gravitational effects from planets forming in the disk are one theory to explain these structures, but follow-up observations looking for planets near the rings have largely been unsuccessful.

In this research a team from Ibaraki University, Kogakuin University, and Tohoku University in Japan used the world’s most powerful supercomputer dedicated to astronomy, ATERUI II at the National Astronomical Observatory of Japan, to simulate the case of a planet moving away from its initial formation site. Their results showed that in a low viscosity disk, a ring formed at the initial location of a planet doesn’t move as the planet migrates inwards. The team identified three distinct phases. In Phase I, the initial ring remains intact as the planet moves inwards. In Phase II, the initial ring begins to deform and a second ring starts forming at the new location of the planet. In Phase III, the initial ring disappears and only the latter ring remains.

These results help explain why planets are rarely observed near the outer rings, and the three phases identified in the simulations match well with the patterns observed in actual rings. Higher resolution observations from next-generation telescopes, which will be better able to search for planets close to the central star, will help determine how well these simulations match reality.

These results appeared as K.D. Kanagawa et al. “Dust rings as a footprint of planet formation in a protoplanetary disk” in The Astrophysical Journal on November 12, 2021.

Featured image: A protoplanetary disk as observed by ALMA (left), and a protoplanetary disk during planetary migration, as obtained from the ATERUI II simulation (right). The dashed line in the simulation represents the orbit of a planet, and the gray area indicates a region not covered by the computational domain of the simulation. Credit: Kazuhiro Kanagawa, ALMA(ESO/NAOJ/NRAO)

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More information: K.D. Kanagawa et al, Dust rings as a footprint of planet formation in a protoplanetary disk, The Astrophysical Journal (2021). arXiv:2109.09579 [astro-ph.EP] arxiv.org/abs/2109.09579

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Provided by National Institutes of Natural Sciences