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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
Hubble Space Telescope Home NASA’s Hubble Finds… Hubble Space Telescope Hubble Home Overview About Hubble The History of Hubble Hubble Timeline Why Have a Telescope in Space? Hubble by the Numbers At the Museum FAQs Impact & Benefits Hubble’s Impact & Benefits Science Impacts Cultural Impact Technology Benefits Impact on Human Spaceflight Astro Community Impacts Science Hubble Science Science Themes Science Highlights Science Behind Discoveries Hubble’s Partners in Science Universe Uncovered Explore the Night Sky Observatory Hubble Observatory Hubble Design Mission Operations Missions to Hubble Hubble vs Webb Team Hubble Team Career Aspirations Hubble Astronauts News Hubble News Hubble News Archive Social Media Media Resources Multimedia Multimedia Images Videos Sonifications Podcasts E-books Lithographs Fact Sheets Glossary Posters Hubble on the NASA App More Online Activities 5 Min Read NASA’s Hubble Finds Sizzling Details About Young Star FU Orionis
An artist’s concept of the early stages of the young star FU Orionis (FU Ori) outburst, surrounded by a disk of material. Credits:
NASA-JPL, Caltech In 1936, astronomers saw a puzzling event in the constellation Orion: the young star FU Orionis (FU Ori) became a hundred times brighter in a matter of months. At its peak, FU Ori was intrinsically 100 times brighter than our Sun. Unlike an exploding star though, it has declined in luminosity only languidly since then.
Now, a team of astronomers has wielded NASA’s Hubble Space Telescope‘s ultraviolet capabilities to learn more about the interaction between FU Ori’s stellar surface and the accretion disk that has been dumping gas onto the growing star for nearly 90 years. They find that the inner disk touching the star is extraordinarily hot — which challenges conventional wisdom.
The observations were made with the telescope’s COS (Cosmic Origins Spectrograph) and STIS (Space Telescope Imaging Spectrograph) instruments. The data includes the first far-ultraviolet and new near-ultraviolet spectra of FU Ori.
“We were hoping to validate the hottest part of the accretion disk model, to determine its maximum temperature, by measuring closer to the inner edge of the accretion disk than ever before,” said Lynne Hillenbrand of Caltech in Pasadena, California, and a co-author of the paper. “I think there was some hope that we would see something extra, like the interface between the star and its disk, but we were certainly not expecting it. The fact we saw so much extra — it was much brighter in the ultraviolet than we predicted — that was the big surprise.”
A Better Understanding of Stellar Accretion
Originally deemed to be a unique case among stars, FU Ori exemplifies a class of young, eruptive stars that undergo dramatic changes in brightness. These objects are a subset of classical T Tauri stars, which are newly forming stars that are building up by accreting material from their disk and the surrounding nebula. In classical T Tauri stars, the disk does not touch the star directly because it is restricted by the outward pressure of the star’s magnetic field.
The accretion disks around FU Ori objects, however, are susceptible to instabilities due to their enormous mass relative to the central star, interactions with a binary companion, or infalling material. Such instability means the mass accretion rate can change dramatically. The increased pace disrupts the delicate balance between the stellar magnetic field and the inner edge of the disk, leading to material moving closer in and eventually touching the star’s surface.
This is an artist’s concept of the early stages of the young star FU Orionis (FU Ori) outburst, surrounded by a disk of material. A team of astronomers has used the Hubble Space Telescope’s ultraviolet capabilities to learn more about the interaction between FU Ori’s stellar surface and the accretion disk that has been dumping gas onto the growing star for nearly 90 years. They found that the inner disk, touching the star, is much hotter than expected—16,000 kelvins—nearly three times our Sun’s surface temperature. That sizzling temperature is nearly twice as hot as previously believed. NASA-JPL, Caltech
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The enhanced infall rate and proximity of the accretion disk to the star make FU Ori objects much brighter than a typical T Tauri star. In fact, during an outburst, the star itself is outshined by the disk. Furthermore, the disk material is orbiting rapidly as it approaches the star, much faster than the rotation rate of the stellar surface. This means that there should be a region where the disk impacts the star and the material slows down and heats up significantly.
“The Hubble data indicates a much hotter impact region than models have previously predicted,” said Adolfo Carvalho of Caltech and lead author of the study. “In FU Ori, the temperature is 16,000 kelvins [nearly three times our Sun’s surface temperature]. That sizzling temperature is almost twice the amount prior models have calculated. It challenges and encourages us to think of how such a jump in temperature can be explained.”
To address the significant difference in temperature between past models and the recent Hubble observations, the team offers a revised interpretation of the geometry within FU Ori’s inner region: The accretion disk’s material approaches the star and once it reaches the stellar surface, a hot shock is produced, which emits a lot of ultraviolet light.
Planet Survival Around FU Ori
Understanding the mechanisms of FU Ori’s rapid accretion process relates more broadly to ideas of planet formation and survival.
“Our revised model based on the Hubble data is not strictly bad news for planet evolution, it’s sort of a mixed bag,” explained Carvalho. “If the planet is far out in the disk as it’s forming, outbursts from an FU Ori object should influence what kind of chemicals the planet will ultimately inherit. But if a forming planet is very close to the star, then it’s a slightly different story. Within a couple outbursts, any planets that are forming very close to the star can rapidly move inward and eventually merge with it. You could lose, or at least completely fry, rocky planets forming close to such a star.”
Additional work with the Hubble UV observations is in progress. The team is carefully analyzing the various spectral emission lines from multiple elements present in the COS spectrum. This should provide further clues on FU Ori’s environment, such as the kinematics of inflowing and outflowing gas within the inner region.
“A lot of these young stars are spectroscopically very rich at far ultraviolet wavelengths,” reflected Hillenbrand. “A combination of Hubble, its size and wavelength coverage, as well as FU Ori’s fortunate circumstances, let us see further down into the engine of this fascinating star-type than ever before.”
These findings have been published in The Astrophysical Journal Letters.
The observations were taken as part of General Observer program 17176.
The Hubble Space Telescope has been operating for over three decades and continues to make ground-breaking discoveries that shape our fundamental understanding of the universe. Hubble is a project of international cooperation between NASA and ESA (European Space Agency). NASA’s Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope and mission operations. Lockheed Martin Space, based in Denver, also supports mission operations at Goddard. The Space Telescope Science Institute in Baltimore, which is operated by the Association of Universities for Research in Astronomy, conducts Hubble science operations for NASA.
Facebook logo @NASAHubble @NASAHubble Instagram logo @NASAHubble Media Contacts:
Claire Andreoli (claire.andreoli@nasa.gov)
NASA’s Goddard Space Flight Center, Greenbelt, MD
Abigail Major, Ray Villard
Space Telescope Science Institute, Baltimore, MD
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Last Updated Nov 21, 2024 Editor Andrea Gianopoulos Location NASA Goddard Space Flight Center Related Terms
Astrophysics Astrophysics Division Goddard Space Flight Center Hubble Space Telescope Stars Keep Exploring Discover More Topics From Hubble
Hubble Space Telescope
Since its 1990 launch, the Hubble Space Telescope has changed our fundamental understanding of the universe.
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By NASA
1 min read
Preparations for Next Moonwalk Simulations Underway (and Underwater)
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By NASA
5 min read
5 Surprising NASA Heliophysics Discoveries Not Related to the Sun
With NASA’s fleet of heliophysics spacecraft, scientists monitor our Sun and investigate its influences throughout the solar system. However, the fleet’s constant watch and often-unique perspectives sometimes create opportunities to make discoveries that no one expected, helping us to solve mysteries about of the solar system and beyond.
Here are five examples of breakthroughs made by NASA heliophysics missions in other fields of science.
This graphic shows missions in NASA’s Heliophysics Division fleet as of July 2024. NASA Thousands and Thousands of Comets
The SOHO mission — short for Solar and Heliospheric Observatory, which is a joint mission between ESA (European Space Agency) and NASA — has a coronagraph that blocks out the Sun in order to see the Sun’s faint outer atmosphere, or corona.
It turns out SOHO’s coronagraph also makes it easy to spot sungrazing comets, those that pass so close to the Sun that other observatories can’t see them against the brightness of our star.
Before SOHO was launched in December 1995, fewer than 20 sungrazing comets were known. Since then, SOHO has discovered more than 5,000.
The vast number of comets discovered using SOHO has allowed scientists to learn more about sungrazing comets and identify comet families, descended from ancestor comets that broke up long ago.
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Two sungrazing comets fly close to the Sun in these images captured by ESA/NASA’s SOHO (Solar and Heliospheric Observatory). They were the 3,999th and 4,000th comets discovered in SOHO images. ESA/NASA/SOHO/Karl Battams Dimming of a Supergiant
In late 2019, the supergiant star Betelgeuse began dimming unexpectedly. Telescopes all over the world — and around it — tracked these changes until a few months later when Betelgeuse appeared too close to the Sun to observe. That’s when NASA’s STEREO (Sun-watching Solar Terrestrial Relations Observatory (STEREO) came to the rescue.
For several weeks in the middle of 2020, STEREO was the only observatory able to see Betelgeuse. At the time, the STEREO-A spacecraft was trailing behind Earth, at a vantage point where Betelgeuse was still far enough away from the Sun to be seen. This allowed astronomers to keep tabs on the star while it was out of view from Earth.
STEREO’s observations revealed another unexpected dimming between June and August of 2020, when ground-based telescopes couldn’t view the star.
Astronomers later concluded that these dimming episodes were caused by an ejection of mass from Betelgeuse — like a coronal mass ejection from our Sun but with about 400 times more mass — which obscured part of the star’s bright surface.
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The background image shows the star Betelgeuse as seen by the Heliospheric Imager aboard NASA’s STEREO (Solar Terrestrial Relations Observatory) spacecraft. The inset figure shows measurements of Betelgeuse’s brightness taken by different observatories from late 2018 to late 2020. STEREO’s observations, marked in red, revealed an unexpected dimming in mid-2020 when Betelgeuse appeared too close to the Sun for other observatories to view it. NASA/STEREO/HI (background); Dupree et al. (inset) The Glowing Surface of Venus
NASA’s Parker Solar Probe studies the Sun’s corona up close — by flying through it. To dive into the Sun’s outer atmosphere, the spacecraft has flown past Venus several times, using the planet’s gravity to fling itself closer and closer to the Sun.
On July 11, 2020, during Parker’s third Venus flyby, scientists used Parker’s wide-field imager, called WISPR, to try to measure the speed of the clouds that obscure Venus’ surface. Surprisingly, WISPR not only observed the clouds, it also saw through them to the surface below.
The images from that flyby and the next (in 2021) revealed a faint glow from Venus’ hot surface in near-infrared light and long wavelengths of red (visible) light that maps distinctive features like mountainous regions, plains, and plateaus.
Scientists aimed WISPR at Venus again on Nov. 6, 2024, during Parker’s seventh flyby, observing a different part of the planet than previous flybys. With these images, they’re hoping to learn more about Venus’ surface geology, mineralogy, and evolution.
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As Parker Solar Probe flew by Venus on its fourth flyby, it captured these images, strung into a video, showing bright and dark features on the nightside surface of the planet. NASA/APL/NRL The Brightest Gamma-Ray Burst
You’ve heard of the GOAT. But have you heard of the BOAT?
It stands for the “brightest of all time”, a gamma-ray burst discovered on Oct. 9, 2022.
A gamma-ray burst is a brief but intense eruption of gamma rays in space, lasting from seconds to hours.
This one, named GRB 221009A, glowed brilliantly for about 10 minutes in the constellation Sagitta before slowly fading.
The burst was detected by dozens of spacecraft, including NASA’s Wind, which studies the perpetual flow of particles from the Sun, called the solar wind, just before it reaches Earth.
Wind and NASA’s Fermi Gamma-Ray Space Telescope measured the brightness of GRB 221009A, showing that it was 70 times brighter than any other gamma-ray burst ever recorded by humans — solidifying its status as the BOAT.
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Astronomers think GRB 221009A represents the birth of a new black hole formed within the heart of a collapsing star. In this artist’s concept, the black hole drives powerful jets of particles traveling near the speed of light. The jets emit X-rays and gamma rays as they stream into space. NASA/Swift/Cruz deWilde A Volcano Blasts Its Way to Space
NASA’s ICON (Ionospheric Connection Explorer) launched in 2019 to study how Earth’s weather interacts with weather from space. When the underwater Hunga Tonga-Hunga Ha‘apai volcano erupted on Jan. 15, 2022, ICON helped show that the volcano produced more than ash and tsunami waves — its effects reached the edge of space.
In the hours after the eruption, ICON detected hurricane-speed winds in the ionosphere — Earth’s electrified upper atmospheric layer at the edge of space. ICON clocked the wind speeds at up to 450 miles per hour, making them the strongest winds the mission had ever measured below 120 miles altitude.
The ESA Swarm mission revealed that these extreme winds altered an electric current in the ionosphere called the equatorial electrojet. After the eruption, the equatorial electrojet surged to five times its normal peak power and dramatically flipped direction.
Scientists were surprised that a volcano could affect the electrojet so severely — something they’d only seen during a strong geomagnetic storm caused by an eruption from the Sun.
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The Hunga Tonga-Hunga Ha’apai eruption on Jan. 15, 2022, caused many effects, some illustrated here, that were felt around the world and even into space. Some of those effects, like extreme winds and unusual electric currents were picked up by NASA’s ICON (Ionospheric Connection Explorer) mission and ESA’s (the European Space Agency) Swarm. Illustration is not to scale. NASA’s Goddard Space Flight Center/Mary Pat Hrybyk-Keith By Vanessa Thomas
NASA’s Goddard Space Flight Center, Greenbelt, Md.
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Last Updated Nov 20, 2024 Related Terms
Comets Fermi Gamma-Ray Space Telescope Gamma-Ray Bursts Goddard Space Flight Center Heliophysics Heliophysics Division ICON (Ionospheric Connection Explorer) Parker Solar Probe (PSP) SOHO (Solar and Heliospheric Observatory) Stars STEREO (Solar TErrestrial RElations Observatory) The Sun The Sun & Solar Physics Uncategorized Venus Volcanoes Wind Mission Explore More
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