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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.
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Last Updated Nov 11, 2024 Related Terms
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By NASA
3 min read
Buckle Up: NASA-Funded Study Explores Turbulence in Molecular Clouds
This image shows the distribution of density in a simulation of a turbulent molecular cloud. NASA/E. Scannapieco et al (2024) On an airplane, motions of the air on both small and large scales contribute to turbulence, which may result in a bumpy flight. Turbulence on a much larger scale is important to how stars form in giant molecular clouds that permeate the Milky Way.
In a new NASA-funded study in the journal Science Advances, scientists created simulations to explore how turbulence interacts with the density of the cloud. Lumps, or pockets of density, are the places where new stars will be born. Our Sun, for example, formed 4.6 billion years ago in a lumpy portion of a cloud that collapsed.
“We know that the main process that determines when and how quickly stars are made is turbulence, because it gives rise to the structures that create stars,” said Evan Scannapieco, professor of astrophysics at Arizona State University and lead author of the study. “Our study uncovers how those structures are formed.”
Giant molecular clouds are full of random, turbulent motions, which are caused by gravity, stirring by the galactic arms and winds, jets, and explosions from young stars. This turbulence is so strong that it creates shocks that drive the density changes in the cloud.
The simulations used dots called tracer particles to traverse a molecular cloud and travel along with the material. As the particles travel, they record the density of the part of the cloud they encounter, building up a history of how pockets of density change over time. The researchers, who also included Liubin Pan from Sun Yat Sen University in China, Marcus Brüggen from the University of Hamburg in Germany, and Ed Buie II from Vassar College in Poughkeepsie, New York, simulated eight scenarios, each with a different set of realistic cloud properties.
This animation shows the distribution of density in a simulation of a turbulent molecular cloud. The colors represent density, with dark blue indicating the least dense regions and red indicating the densest regions. Credit: NASA/E. Scannapieco et al (2024) The team found that the speeding up and slowing down of shocks plays an essential role in the path of the particles. Shocks slow down as they go into high-density gas and speed up as they go into low-density gas. This is akin to how an ocean wave strengthens when it hits shallow water by the shore.
When a particle hits a shock, the area around it becomes more dense. But because shocks slow down in dense regions, once lumps become dense enough, the turbulent motions can’t make them any denser. These lumpiest high-density regions are where stars are most likely to form.
While other studies have explored molecular cloud density structures, this simulation allows scientists to see how those structures form over time. This informs scientists’ understanding of how and where stars are likely to be born.
“Now we can understand better why those structures look the way they do because we’re able to track their histories,” said Scannapieco.
This image shows part of a simulation of a molecular cloud. The colors represent density, with dark blue indicating the least dense regions and red indicating the densest regions. Tracer particles, represented by black dots, traverse the simulated cloud. By examining how they interact with shocks and pockets of density, scientists can better understand the structures in molecular clouds that lead to star formation. NASA/E. Scannapieco et al (2024) NASA’s James Webb Space Telescope is exploring the structure of molecular clouds. It is also exploring the chemistry of molecular clouds, which depends on the history of the gas modeled in the simulations. New measurements like these will inform our understanding of star formation.
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By European Space Agency
With the initial images from each of the instruments aboard ESA’s EarthCARE satellite now in hand, it's time to reveal how these four advanced sensors work in synergy to measure exactly how clouds and aerosols influence the heating and cooling of our atmosphere.
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By NASA
Earth (ESD)Earth Home Explore Climate Change Science in Action Multimedia Data For Researchers 4 min read
Via NASA Plane, Scientists Find New Gamma-ray Emission in Storm Clouds
Tropical thunderstorm with lightning, near the airport of Santa Marta, Colombia. Credit: Oscar van der Velde There’s more to thunderclouds than rain and lightning. Along with visible light emissions, thunderclouds can produce intense bursts of gamma rays, the most energetic form of light, that last for millionths of a second. The clouds can also glow steadily with gamma rays for seconds to minutes at a time.
Researchers using NASA airborne platforms have now found a new kind of gamma-ray emission that’s shorter in duration than the steady glows and longer than the microsecond bursts. They’re calling it a flickering gamma-ray flash. The discovery fills in a missing link in scientists’ understanding of thundercloud radiation and provides new insights into the mechanisms that produce lightning. The insights, in turn, could lead to more accurate lightning risk estimates for people, aircraft, and spacecraft.
Researchers from the University of Bergen in Norway led the study in collaboration with scientists from NASA’s Marshall Space Flight Center in Huntsville, Alabama, and NASA’s Goddard Space Flight Center in Greenbelt, Maryland, the U.S. Naval Research Laboratory, and multiple universities in the U.S., Mexico, Colombia, and Europe. The findings were described in a pair of papers in Nature, published Oct. 2.
The international research team made their discovery while flying a battery of detectors aboard a NASA ER-2 research aircraft. In July 2023, the ER-2 set out on a series of 10 flights from MacDill Air Force Base in Tampa, Florida. The plane flew figure-eight flight patterns a few miles above tropical thunderclouds in the Caribbean and Central America, providing unprecedented views of cloud activity.
The scientific payload was developed for the Airborne Lightning Observatory for Fly’s Eye Geostationary Lightning Mapper Simulator and Terrestrial Gamma-ray Flashes (ALOFT) campaign. Instrumentation in the payload included weather radars along with multiple sensors for measuring gamma rays, lightning flashes, and microwave emissions from clouds.
NASA’s high-flying ER-2 airplane carries instrumentation in this artist’s impression of the ALOFT mission to record gamma rays (colored purple for illustration) from thunderclouds.Credit: NASA/ALOFT team The researchers had hoped ALOFT instruments would observe fast radiation bursts known as terrestrial gamma-ray flashes (TGFs). The flashes, first discovered in 1992 by NASA’s Compton Gamma Ray Observatory spacecraft, accompany some lightning strikes and last only millionths of a second. Despite their high intensity and their association with visible lightning, few TGFs have been spotted during previous aircraft-based studies.
“I went to a meeting just before the ALOFT campaign,” said principal investigator Nikolai Østgaard, a space physicist with the University of Bergen. “And they asked me: ‘How many TGFs are you going to see?’ I said: ‘Either we’ll see zero, or we’ll see a lot.’ And then we happened to see 130.”
However, the flickering gamma-ray flashes were a complete surprise.
“They’re almost impossible to detect from space,” said co-principal investigator Martino Marisaldi, who is also a University of Bergen space physicist. “But when you are flying at 20 kilometers [12.5 miles] high, you’re so close that you will see them.” The research team found more than 25 of these new flashes, each lasting between 50 to 200 milliseconds.
The abundance of fast bursts and the discovery of intermediate-duration flashes could be among the most important thundercloud discoveries in a decade or more, said University of New Hampshire physicist Joseph Dwyer, who was not involved in the research. “They’re telling us something about how thunderstorms work, which is really important because thunderstorms produce lightning that hurts and kills a lot of people.”
More broadly, Dwyer said he is excited about the prospects of advancing the field of meteorology. “I think everyone assumes that we figured out lightning a long time ago, but it’s an overlooked area … we don’t understand what’s going on inside those clouds right over our heads.” The discovery of flickering gamma-ray flashes may provide crucial clues scientists need to understand thundercloud dynamics, he said.
Turning to aircraft-based instrumentation rather than satellites ensured a lot of bang for research bucks, said the study’s project scientist, Timothy Lang of NASA’s Marshall Space Flight Center in Huntsville, Alabama.
“If we had gotten one flash, we would have been ecstatic — and we got well over 100,” he said. This research could lead to a significant advance in our understanding of thunderstorms and radiation from thunderstorms. “It shows that if you have the right problem and you’re willing to take a little bit of risk, you can have a huge payoff.”
By James Riordon
NASA’s Earth Science News Team
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Last Updated Oct 02, 2024 EditorJenny MarderContactJames RiordonLocationMarshall Space Flight Center Related Terms
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By European Space Agency
Video: 00:03:12 There’s a mystery out there in deep space – and solving it will make Earth safer. That’s why the European Space Agency’s Hera mission is taking shape – to go where one particular spacecraft has gone before.
On 26 September 2022, moving at 6.1 km/s, NASA’s DART spacecraft crashed into the Dimorphos asteroid. Part of our Solar System changed. The impact shrunk the orbit of the Great Pyramid-sized Dimorphos around its parent asteroid, the mountain-sized Didymos.
This grand experiment was performed to prove we could defend Earth against an incoming asteroid, by striking it with a spacecraft to deflect it. DART succeeded. But that still leaves many things scientists don’t know: What is the precise mass and makeup of Dimorphos? What did the impact do to the asteroid? How big is the crater left by DART’s collision? Or has Dimorphos completely cracked apart, to be held together only by its own weak gravity?
That’s why we’re going back – with ESA’s Hera mission. The spacecraft will revisit Dimorphos to gather vital close-up data about the deflected body, to turn DART’s grand-scale experiment into a well-understood and potentially repeatable planetary defence technique.
The mission will also perform the most detailed exploration yet of a binary asteroid system – although binaries make up 15% of all known asteroids, one has never been surveyed in detail.
Hera will also perform technology demonstration experiments, including the deployment ESA’s first deep space ‘CubeSats’ – shoebox-sized spacecraft to venture closer than the main mission then eventually land – and an ambitious test of 'self-driving' for the main spacecraft, based on vision-based navigation.
By the end of Hera’s observations, Dimorphos will become the best studied asteroid in history – which is vital, because if a body of this size ever struck Earth it could destroy a whole city. The dinosaurs had no defence against asteroids, because they never had a space agency. But – through Hera – we are teaching ourselves what we can do to reduce this hazard and make space safer.
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