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By NASA
4 min read
Preparations for Next Moonwalk Simulations Underway (and Underwater)
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
6 min read
Preparations for Next Moonwalk Simulations Underway (and Underwater)
NASA’s SPHEREx observatory undergoes integration and testing at BAE Systems in Boulder, Colorado, in April 2024. The space telescope will use a technique called spectroscopy across the entire sky, capturing the universe in more than 100 colors. BAE Systems The space telescope will detect over 100 colors from hundreds of millions of stars and galaxies. Here’s what astronomers will do with all that color.
NASA’s SPHEREx mission won’t be the first space telescope to observe hundreds of millions of stars and galaxies when it launches no later than April 2025, but it will be the first to observe them in 102 colors. Although these colors aren’t visible to the human eye because they’re in the infrared range, scientists will use them to learn about topics that range from the physics that governed the universe less than a second after its birth to the origins of water on planets like Earth.
“We are the first mission to look at the whole sky in so many colors,” said SPHEREx Principal Investigator Jamie Bock, who is based jointly at NASA’s Jet Propulsion Laboratory and Caltech, both in Southern California. “Whenever astronomers look at the sky in a new way, we can expect discoveries.”
Short for Spectro-Photometer for the History of the Universe, Epoch of Reionization and Ices Explorer, SPHEREx will collect infrared light, which has wavelengths slightly longer than what the human eye can detect. The telescope will use a technique called spectroscopy to take the light from hundreds of millions of stars and galaxies and separate it into individual colors, the way a prism transforms sunlight into a rainbow. This color breakdown can reveal various properties of an object, including its composition and its distance from Earth.
NASA’s SPHEREx mission will use spectroscopy — the splitting of light into its component wavelengths — to study the universe. Watch this video to learn more about spectroscopy. NASA’s Goddard Space Flight Center Here are the three key science investigations SPHEREx will conduct with its colorful all-sky map.
Cosmic Origins
What human eyes perceive as colors are distinct wavelengths of light. The only difference between colors is the distance between the crests of the light wave. If a star or galaxy is moving, its light waves get stretched or compressed, changing the colors they appear to emit. (It’s the same with sound waves, which is why the pitch of an ambulance siren seems to go up as its approaches and lowers after it passes.) Astronomers can measure the degree to which light is stretched or compressed and use that to infer the distance to the object.
SPHEREx will apply this principle to map the position of hundreds of millions of galaxies in 3D. By doing so, scientists can study the physics of inflation, the event that caused the universe to expand by a trillion-trillion fold in less than a second after the big bang. This rapid expansion amplified small differences in the distribution of matter. Because these differences remain imprinted on the distribution of galaxies today, measuring how galaxies are distributed can tell scientists more about how inflation worked.
Galactic Origins
SPHEREx will also measure the collective glow created by all galaxies near and far — in other words, the total amount of light emitted by galaxies over cosmic history. Scientists have tried to estimate this total light output by observing individual galaxies and extrapolating to the trillions of galaxies in the universe. But these counts may leave out some faint or hidden light sources, such as galaxies too small or too distant for telescopes to easily detect.
With spectroscopy, SPHEREx can also show astronomers how the total light output has changed over time. For example, it may reveal that the universe’s earliest generations of galaxies produced more light than previously thought, either because they were more plentiful or bigger and brighter than current estimates suggest. Because light takes time to travel through space, we see distant objects as they were in the past. And, as light travels, the universe’s expansion stretches it, changing its wavelength and its color. Scientists can therefore use SPHEREx data to determine how far light has traveled and where in the universe’s history it was released.
Water’s Origins
SPHEREx will measure the abundance of frozen water, carbon dioxide, and other essential ingredients for life as we know it along more than 9 million unique directions across the Milky Way galaxy. This information will help scientists better understand how available these key molecules are to forming planets. Research indicates that most of the water in our galaxy is in the form of ice rather than gas, frozen to the surface of small dust grains. In dense clouds where stars form, these icy dust grains can become part of newly forming planets, with the potential to create oceans like the ones on Earth.
The mission’s colorful view will enable scientists to identify these materials, because chemical elements and molecules leave a unique signature in the colors they absorb and emit.
Big Picture
Many space telescopes, including NASA’s Hubble and James Webb, can provide high-resolution, in-depth spectroscopy of individual objects or small sections of space. Other space telescopes, like NASA’s retired Wide-field Infrared Survey Explorer (WISE), were designed to take images of the whole sky. SPHEREx combines these abilities to apply spectroscopy to the entire sky.
By combining observations from telescopes that target specific parts of the sky with SPHEREx’s big-picture view, scientists will get a more complete — and more colorful — perspective of the universe.
More About SPHEREx
SPHEREx is managed by JPL for NASA’s Astrophysics Division within the Science Mission Directorate in Washington. BAE Systems (formerly Ball Aerospace) built the telescope and the spacecraft bus. The science analysis of the SPHEREx data will be conducted by a team of scientists located at 10 institutions across the U.S. and in South Korea. Data will be processed and archived at IPAC at Caltech, which manages JPL for NASA. The mission principal investigator is based at Caltech with a joint JPL appointment. The SPHEREx dataset will be publicly available.
For more information about the SPHEREx mission visit:
https://www.jpl.nasa.gov/missions/spherex/
News Media Contact
Calla Cofield
Jet Propulsion Laboratory, Pasadena, Calif.
626-808-2469
calla.e.cofield@jpl.nasa.gov
2024-152
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Last Updated Oct 31, 2024 Related Terms
SPHEREx (Spectro-Photometer for the History of the Universe and Ices Explorer) Astrophysics Galaxies Jet Propulsion Laboratory The Search for Life The Universe Explore More
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