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By NASA
4 min read
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The mystery of why life uses molecules with specific orientations has deepened with a NASA-funded discovery that RNA — a key molecule thought to have potentially held the instructions for life before DNA emerged — can favor making the building blocks of proteins in either the left-hand or the right-hand orientation. Resolving this mystery could provide clues to the origin of life. The findings appear in research recently published in Nature Communications.
Proteins are the workhorse molecules of life, used in everything from structures like hair to enzymes (catalysts that speed up or regulate chemical reactions). Just as the 26 letters of the alphabet are arranged in limitless combinations to make words, life uses 20 different amino acid building blocks in a huge variety of arrangements to make millions of different proteins. Some amino acid molecules can be built in two ways, such that mirror-image versions exist, like your hands, and life uses the left-handed variety of these amino acids. Although life based on right-handed amino acids would presumably work fine, the two mirror images are rarely mixed in biology, a characteristic of life called homochirality. It is a mystery to scientists why life chose the left-handed variety over the right-handed one.
A diagram of left-handed and right-handed versions of the amino acid isovaline, found in the Murchison meteorite.NASA DNA (deoxyribonucleic acid) is the molecule that holds the instructions for building and running a living organism. However, DNA is complex and specialized; it “subcontracts” the work of reading the instructions to RNA (ribonucleic acid) molecules and building proteins to ribosome molecules. DNA’s specialization and complexity lead scientists to think that something simpler should have preceded it billions of years ago during the early evolution of life. A leading candidate for this is RNA, which can both store genetic information and build proteins. The hypothesis that RNA may have preceded DNA is called the “RNA world” hypothesis.
If the RNA world proposition is correct, then perhaps something about RNA caused it to favor building left-handed proteins over right-handed ones. However, the new work did not support this idea, deepening the mystery of why life went with left-handed proteins.
The experiment tested RNA molecules that act like enzymes to build proteins, called ribozymes. “The experiment demonstrated that ribozymes can favor either left- or right-handed amino acids, indicating that RNA worlds, in general, would not necessarily have a strong bias for the form of amino acids we observe in biology now,” said Irene Chen, of the University of California, Los Angeles (UCLA) Samueli School of Engineering, corresponding author of the Nature Communications paper.
In the experiment, the researchers simulated what could have been early-Earth conditions of the RNA world. They incubated a solution containing ribozymes and amino acid precursors to see the relative percentages of the right-handed and left-handed amino acid, phenylalanine, that it would help produce. They tested 15 different ribozyme combinations and found that ribozymes can favor either left-handed or right-handed amino acids. This suggested that RNA did not initially have a predisposed chemical bias for one form of amino acids. This lack of preference challenges the notion that early life was predisposed to select left-handed-amino acids, which dominate in modern proteins.
“The findings suggest that life’s eventual homochirality might not be a result of chemical determinism but could have emerged through later evolutionary pressures,” said co-author Alberto Vázquez-Salazar, a UCLA postdoctoral scholar and member of Chen’s research group.
Earth’s prebiotic history lies beyond the oldest part of the fossil record, which has been erased by plate tectonics, the slow churning of Earth’s crust. During that time, the planet was likely bombarded by asteroids, which may have delivered some of life’s building blocks, such as amino acids. In parallel to chemical experiments, other origin-of-life researchers have been looking at molecular evidence from meteorites and asteroids.
“Understanding the chemical properties of life helps us know what to look for in our search for life across the solar system,” said co-author Jason Dworkin, senior scientist for astrobiology at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and director of Goddard’s Astrobiology Analytical Laboratory.
Dworkin is the project scientist on NASA’s OSIRIS-REx mission, which extracted samples from the asteroid Bennu and delivered them to Earth last year for further study.
“We are analyzing OSIRIS-REx samples for the chirality (handedness) of individual amino acids, and in the future, samples from Mars will also be tested in laboratories for evidence of life including ribozymes and proteins,” said Dworkin.
The research was supported by grants from NASA, the Simons Foundation Collaboration on the Origin of Life, and the National Science Foundation. Vázquez-Salazar acknowledges support through the NASA Postdoctoral Program, which is administered by Oak Ridge Associated Universities under contract with NASA.
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Last Updated Nov 21, 2024 EditorWilliam SteigerwaldContactNancy N. Jonesnancy.n.jones@nasa.govLocationGoddard Space Flight Center Related Terms
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By NASA
This illustration shows a red, early-universe dwarf galaxy that hosts a rapidly feeding black hole at its center. Using data from NASA’s James Webb Space Telescope and Chandra X-ray Observatory, a team of astronomers have discovered this low-mass supermassive black hole at the center of a galaxy just 1.5 billion years after the Big Bang. It is pulling in matter at a phenomenal rate — over 40 times the theoretical limit. While short lived, this black hole’s “feast” could help astronomers explain how supermassive black holes grew so quickly in the early universe.NOIRLab/NSF/AURA/J. da Silva/M. Zamani A rapidly feeding black hole at the center of a dwarf galaxy in the early universe, shown in this artist’s concept, may hold important clues to the evolution of supermassive black holes in general.
Using data from NASA’s James Webb Space Telescope and Chandra X-ray Observatory, a team of astronomers discovered this low-mass supermassive black hole just 1.5 billion years after the big bang. The black hole is pulling in matter at a phenomenal rate — over 40 times the theoretical limit. While short lived, this black hole’s “feast” could help astronomers explain how supermassive black holes grew so quickly in the early universe.
Supermassive black holes exist at the center of most galaxies, and modern telescopes continue to observe them at surprisingly early times in the universe’s evolution. It’s difficult to understand how these black holes were able to grow so big so rapidly. But with the discovery of a low-mass supermassive black hole feasting on material at an extreme rate so soon after the birth of the universe, astronomers now have valuable new insights into the mechanisms of rapidly growing black holes in the early universe.
The black hole, called LID-568, was hidden among thousands of objects in the Chandra X-ray Observatory’s COSMOS legacy survey, a catalog resulting from some 4.6 million Chandra observations. This population of galaxies is very bright in the X-ray light, but invisible in optical and previous near-infrared observations. By following up with Webb, astronomers could use the observatory’s unique infrared sensitivity to detect these faint counterpart emissions, which led to the discovery of the black hole.
The speed and size of these outflows led the team to infer that a substantial fraction of the mass growth of LID-568 may have occurred in a single episode of rapid accretion.
LID-568 appears to be feeding on matter at a rate 40 times its Eddington limit. This limit relates to the maximum amount of light that material surrounding a black hole can emit, as well as how fast it can absorb matter, such that its inward gravitational force and outward pressure generated from the heat of the compressed, infalling matter remain in balance.
These results provide new insights into the formation of supermassive black holes from smaller black hole “seeds,” which current theories suggest arise either from the death of the universe’s first stars (light seeds) or the direct collapse of gas clouds (heavy seeds). Until now, these theories lacked observational confirmation.
The new discovery suggests that “a significant portion of mass growth can occur during a single episode of rapid feeding, regardless of whether the black hole originated from a light or heavy seed,” said International Gemini Observatory/NSF NOIRLab astronomer Hyewon Suh, who led the research team.
A paper describing these results (“A super-Eddington-accreting black hole ~1.5 Gyr after the Big Bang observed with JWST”) appears in the journal Nature Astronomy.
About the Missions
NASA’s Marshall Space Flight Center manages the Chandra program. The Smithsonian Astrophysical Observatory’s Chandra X-ray Center controls science operations from Cambridge, Massachusetts, and flight operations from Burlington, Massachusetts.
The James Webb Space Telescope is the world’s premier space science observatory. Webb is solving mysteries in our solar system, looking beyond to distant worlds around other stars, and probing the mysterious structures and origins of our universe and our place in it. Webb is an international program led by NASA with its partners, ESA (European Space Agency) and CSA (Canadian Space Agency).
Read more from NASA’s Chandra X-ray Observatory.
Learn more about the Chandra X-ray Observatory and its mission here:
https://www.nasa.gov/chandra
https://chandra.si.edu
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Elizabeth Laundau
NASA Headquarters
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202-923-0167
elizabeth.r.landau@nasa.gov
Lane Figueroa
Marshall Space Flight Center, Huntsville, Alabama
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By NASA
4 min read
Preparations for Next Moonwalk Simulations Underway (and Underwater)
NASA’s Voyager 2 captured this image of Uranus while flying by the ice giant in 1986. New research using data from the mission shows a solar wind event took place during the flyby, leading to a mystery about the planet’s magnetosphere that now may be solved.NASA/JPL-Caltech NASA’s Voyager 2 flyby of Uranus decades ago shaped scientists’ understanding of the planet but also introduced unexplained oddities. A recent data dive has offered answers.
When NASA’s Voyager 2 spacecraft flew by Uranus in 1986, it provided scientists’ first — and, so far, only — close glimpse of this strange, sideways-rotating outer planet. Alongside the discovery of new moons and rings, baffling new mysteries confronted scientists. The energized particles around the planet defied their understanding of how magnetic fields work to trap particle radiation, and Uranus earned a reputation as an outlier in our solar system.
Now, new research analyzing the data collected during that flyby 38 years ago has found that the source of that particular mystery is a cosmic coincidence: It turns out that in the days just before Voyager 2’s flyby, the planet had been affected by an unusual kind of space weather that squashed the planet’s magnetic field, dramatically compressing Uranus’ magnetosphere.
“If Voyager 2 had arrived just a few days earlier, it would have observed a completely different magnetosphere at Uranus,” said Jamie Jasinski of NASA’s Jet Propulsion Laboratory in Southern California and lead author of the new work published in Nature Astronomy. “The spacecraft saw Uranus in conditions that only occur about 4% of the time.”
The first panel of this artist’s concept depicts how Uranus’s magnetosphere — its protective bubble — was behaving before the flyby of NASA’s Voyager 2. The second panel shows an unusual kind of solar weather was happening during the 1986 flyby, giving scientists a skewed view of the magnetosphere.NASA/JPL-Caltech Magnetospheres serve as protective bubbles around planets (including Earth) with magnetic cores and magnetic fields, shielding them from jets of ionized gas — or plasma — that stream out from the Sun in the solar wind. Learning more about how magnetospheres work is important for understanding our own planet, as well as those in seldom-visited corners of our solar system and beyond.
That’s why scientists were eager to study Uranus’ magnetosphere, and what they saw in the Voyager 2 data in 1986 flummoxed them. Inside the planet’s magnetosphere were electron radiation belts with an intensity second only to Jupiter’s notoriously brutal radiation belts. But there was apparently no source of energized particles to feed those active belts; in fact, the rest of Uranus’ magnetosphere was almost devoid of plasma.
The missing plasma also puzzled scientists because they knew that the five major Uranian moons in the magnetic bubble should have produced water ions, as icy moons around other outer planets do. They concluded that the moons must be inert with no ongoing activity.
Solving the Mystery
So why was no plasma observed, and what was happening to beef up the radiation belts? The new data analysis points to the solar wind. When plasma from the Sun pounded and compressed the magnetosphere, it likely drove plasma out of the system. The solar wind event also would have briefly intensified the dynamics of the magnetosphere, which would have fed the belts by injecting electrons into them.
The findings could be good news for those five major moons of Uranus: Some of them might be geologically active after all. With an explanation for the temporarily missing plasma, researchers say it’s plausible that the moons actually may have been spewing ions into the surrounding bubble all along.
Planetary scientists are focusing on bolstering their knowledge about the mysterious Uranus system, which the National Academies’ 2023 Planetary Science and Astrobiology Decadal Survey prioritized as a target for a future NASA mission.
JPL’s Linda Spilker was among the Voyager 2 mission scientists glued to the images and other data that flowed in during the Uranus flyby in 1986. She remembers the anticipation and excitement of the event, which changed how scientists thought about the Uranian system.
“The flyby was packed with surprises, and we were searching for an explanation of its unusual behavior. The magnetosphere Voyager 2 measured was only a snapshot in time,” said Spilker, who has returned to the iconic mission to lead its science team as project scientist. “This new work explains some of the apparent contradictions, and it will change our view of Uranus once again.”
Voyager 2, now in interstellar space, is almost 13 billion miles (21 billion kilometers) from Earth.
News Media Contacts
Karen Fox / Molly Wasser
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Last Updated Nov 11, 2024 Related Terms
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By NASA
In October 1604, a new star appeared in the sky, puzzling astronomers of the day. First observed on Oct. 9, German astronomer Johannes Kepler (1571-1630) began his observations on Oct. 17 and tracked the new star for over a year. During that time, it brightened to magnitude -2.5, outshining Jupiter, and for several weeks remained visible in the daytime. Publication of his detailed observations in 1606 led astronomers to call the star Kepler’s Supernova, today formally designated as supernova SN 1604. Astronomers of the day did not know what caused the star’s sudden appearance and eventual disappearance, but the phenomenon helped shape European cosmology toward the heliocentric model proposed by Polish astronomer Nicolaus Copernicus half a century earlier. Today, astronomers designate SN 1604 as a Type Ia supernova, resulting from the explosion of a white dwarf star, and use ground-based and space-based telescopes to study its remnants.
Left: Portrait of Johannes Kepler by August Köhler. Middle: Kepler’s book about his observations of the 1604 supernova open to the page depicting the location of the new star. Right: Closeup of Kepler’s illustration of the location of the new star, designated N, in the constellation Ophiuchus near the right foot of the serpent-bearer.
Italian astronomer Lodovico delle Colombo first observed the supernova in the constellation Ophiuchus on Oct. 9. Kepler, then working in Prague, heard rumors of the new star but did not observe it until Oct. 17. He continued to monitor the star for over a year, inspired by the earlier work of Danish astronomer Tycho Brahe’s observations of a similar phenomenon, the 1572 supernova. The new star quickly brightened to magnitude -2.5, outshining Jupiter, and for three weeks could be seen in the daytime before finally fading into obscurity in March 1606. Kepler could only make naked eye observations, since Italian astronomer Galileo Galilei didn’t turn his newly invented telescope to the skies for another four years after SN 1604 faded from view.
Later in 1606, Kepler summarized his observations in his book De Stella nova in pede Serpentarii (On the New Star in Ophiuchus’ Foot), published in Prague. SN 1604 is believed to be about 20,000 light years away, near the edge of a dark nebula complex. Kepler and his contemporaries observed not only the last known supernova to occur in the Milky Way Galaxy but also the last supernova visible to the naked eye until 1987. That one, Supernova 1987A, appeared in the Large Magellanic Cloud, a small satellite galaxy of the Milky Way.
A Type Ia supernova results from a white dwarf drawing in material from a nearby red giant star, the additional mass leading to a runaway thermonuclear explosion.
Astronomers today understand that what Kepler and others believed as the birth of a new star actually represented the violent death of a star. Astronomers today classify supernovas according to their characteristics, and SN 1604 belongs to the group known as Type Ia supernovas, typically found in binary star systems composed of a white dwarf and a red giant. The gravitation force of the white dwarf draws in material from its larger less dense companion until it reaches a critical mass, around 1.4 times the mass of our Sun. At that point, a runaway thermonuclear chain reaction begins, causing a release of tremendous amounts of energy, including light, that we see as a sudden brightening of an otherwise dim star.
Images of Kepler’s supernova remnants in different portions of the electromagnetic spectrum. Left: X-ray image from the Chandra X-ray Observatory. Middle: Visible image from the Hubble Space Telescope. Right: Infrared image from the Spitzer Space Telescope.
Supernova explosions leave remnants behind and those of SN 1604 remain visible today. Ground-based and space-based instruments using different parts of the electromagnetic spectrum study these remnants to gain a better understanding of their origins. The remnants of SN 1604 emit energy most strongly in the radio and X-ray parts of the electromagnetic spectrum. In recent years, astronomers have used Type Ia supernovas to determine the rate of expansion of the universe. Because Type Ia supernovas all occur in stars of about 1.4 solar masses, they give out about the same amount of light. This makes them useful as distance indicators – if one Type Ia supernova is dimmer than another one, it is further away by an amount that astronomers can calculate. Based on this information, astronomers believe that the expansion of the universe is accelerating, possibly caused by the presence of a mysterious substance called dark energy.
Events in world history in 1604:
January 1 – First performance of William Shakespeare’s play A Midsummer’s Night’s Dream.
March 22 – Karl IX begins his rule as King of Sweden.
August 5 – Sokolluzade Mehmed Pasha becomes the new Ottoman Grand Vizier in Constantinople.
August 18 – England and Spain sign the Treaty of London, ending their 20-year war.
September 1 – Sri Guru Granth Sahib, Sikhism’s religious text, is installed at Hamandir Sahib in Amritsar, India.
October 4 – Emperor of Ethiopia Za Dengel is killed in battle with the forces of Za Sellase, who restores his cousin Yaqob to the throne.
November 1 – First performance of William Shakespeare’s tragedy Othello.
December 29 – A magnitude 8.1 earthquake shakes the Taiwan Strait causing significant damage.
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