FYFD

Tag: planetary science

  • Uranus Emits More Than Thought

    Uranus Emits More Than Thought

    Since Voyager 2 visited Uranus in 1986, scientists have debated the odd ice giant’s heat balance. The other giant planets of our solar system — Jupiter, Saturn, and Neptune — all emit much more heat than they absorb from the sun, indicating that they have strong internal heat sources. Voyager 2’s measurements from Uranus indicated only weak heat emissions.

    But a new study indicates that Uranus does, in fact, have an internal heat source contributing to its heat flux. The study combined observations with a global model of Uranus across the planet’s full 84-year orbit and concluded that Uranus emits 12.5% more internal heat than it absorbs from the sun. That suggests that Uranus may not be so different from its fellow giants, but the planet’s large seasonal variations and differences across hemispheres raise plenty of questions about the planet’s interior structure. (Image credit: NASA; research credit: X. Wang et al.; via Gizmodo)

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  • What Makes a Dune?

    What Makes a Dune?

    Wind and water can form sandy ripples in a matter of minutes. Most will be erased, but some can grow to meter-scale and beyond. What distinguishes these two fates? Researchers used a laser scanner to measure early dune growth in the Namib Desert to see. They found that the underlying surface played a big role in whether sand gathered or disappeared from a given spot. Surfaces like gravel, rock, or moistened sand were better for starting a dune than loose sand was. Each of these surface types affected how much sand the wind could carry off, as well as whether grains bounced or stuck where they landed. Every trapped sand grain made the surface a little rougher, increasing the chances of trapping the next sand grain. Over time, the gathering sand forms a bump that affects the wind flow nearby, further shaping the proto-dune. As long as the wind isn’t strong enough to scour the surface clean, it will keep gathering sand as the process continues. (Image credit: M. Gheidarlou; research credit: C. Rambert et al.; via Eos)

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  • Cutting Out Canyons

    Cutting Out Canyons

    Over the millennia, the Colorado River has carved some of the deepest and most dramatic canyons on our planet. This astronaut photo shows the river near its dam at Lake Powell. The strip of white edging the lake is the “bathtub ring” that shows how the water level has varied over the years. The deep canyons — over 400 meters from the Horn in the center of the photo to the river beside it — throw shadows across the landscape. To reach these depths, the Colorado River incised its path into bedrock that was tectonically uplifted. (Image credit: NASA; via NASA Earth Observatory)

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  • Cloud Convection on Titan

    Cloud Convection on Titan

    Saturn’s moon Titan is a fascinating mirror to our own planet. It’s the only other planetary body with surface-level liquid lakes and seas, but instead of water, Titan’s are made of frigid ethane and methane. Like Earth, Titan has a weather cycle that includes evaporation, condensation, and rain. And now scientists have made their first observations of clouds convecting in Titan’s northern hemisphere.

    Using data from both the Keck Observatory and JWST, the team tracked clouds on Titan rising to higher altitudes, a critical step in the planet’s methane cycle. This translation took place over a period of days, giving scientists modeling the Saturnian moon new insight into the seasonal behaviors of Titan’s atmosphere. (Image credit: NASA/ESA/CSA/STScI; research credit: C. Nixon et al.; via Gizmodo)

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  • Searching for the Seiche

    Searching for the Seiche

    A rock and ice face in Dickson Fjord after its collapse.

    On 16 September 2023, seismometers around the world began ringing, registering a signal that — for 9 days — wobbled back and forth every 92 seconds. A second, similar signal appeared a month later, lasting about a week. Researchers tracked the signal’s origin to a remote fjord in East Greenland, where it appeared a glacier front had collapsed. The falling rocks and ice triggered a long-lasting wave — a seiche — that rang back and forth through the fjord for days.

    Simulations showed that a seiche was plausible from a rockfall like the two that caused the seismic signal, but, without first-hand observations, no one could be certain. Now a new study has looked at satellite data to confirm the seiche. Researchers found that the then-new Surface Water and Ocean Topography (SWOT) satellite and its high-resolution altimeters had passed over the fjord multiple during the two landslide events. And, sure enough, the satellite captured data showing the water surface in the fjord rising and falling as the seiche ricocheted back and forth.

    It’s a great reminder that having multiple instrument types monitoring the Earth gives us far better data than any singular one. Without both seismometers and the satellite, it’s unlikely that scientists could have truly confirmed a seiche that no one saw firsthand. (Image credit: S. Rysgaard; research credit: T. Monahan et al.; via Eos)

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  • Venusian Gravity Currents

    Venusian Gravity Currents

    Radar measurements of Venus‘s surface reveal the remains of many volcanic eruptions. One type of feature, known as a pancake dome, has a very flat top and steep sides; one dome, Narina Tholus, is over 140 kilometers wide. Since their discovery, scientists have been puzzling out how such domes could form. A recent study suggests that the Venusian surface’s elasticity plays a role.

    According to current models, the pancake domes are gravity currents (like a cold draft under your door, an avalanche, or the Boston Molasses Flood), albeit ones so viscous that they may require hundreds of thousands of Earth-years to settle. Researchers found that their simulated pancake domes best matched measurements from Venus when the lava was about 2.5 times denser than water and flowed over a flexible crust.

    We might have more data to support (or refute) the study’s conclusions soon, but only if NASA’s VERITAS mission to Venus is not cancelled. (Image credit: NASA; research credit: M. Borelli et al.; via Gizmodo)

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  • Martian Streaks Are Dry

    Martian Streaks Are Dry

    Dark lines appearing on Martian slopes have triggered theories of flowing water or brine on the planet’s surface. But a new study suggests that these features are, instead, dry. To explore these streaks, the team assembled a global database of sightings and correlated their map with other known quantities, like temperature, wind speed, and rock slides. By connecting the data across thousands of streaks, they could build statistics about what variables correlated with the streaks’ appearance.

    What they found was that streaks didn’t appear in places connected to liquid water or even frost. Instead, the streaks appeared in spots with high wind speeds and heavy dust accumulation. The team included that, rather than being moist areas, the streaks are dry and form when dust slides down the slope, perhaps triggered by high winds or passing dust devils.

    Although showing that the streaks aren’t associated with water may seem disappointing, it may mean that NASA will be able to explore them sooner. Right now, NASA avoids sending rovers anywhere near water, out of concern that Earth microbes still on the rover could contaminate the Martian environment. (Image credit: NASA; research credit: V. Bickel and A. Valantinas; via Gizmodo)

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  • Io’s Missing Magma Ocean

    Io’s Missing Magma Ocean

    In the late 1970s, scientists conjectured that Io was likely a volcanic world, heated by tidal forces from Jupiter that squeeze it along its elliptical orbit. Only months later, images from Voyager 1’s flyby confirmed the moon’s volcanism. Magnetometer data from Galileo’s later flyby suggested that tidal heating had created a shallow magma ocean that powered the moon’s volcanic activity. But newly analyzed data from Juno’s flyby shows that Io doesn’t have a magma ocean after all.

    The new flyby used radio transmission data to measure any little wobbles that Io caused by tugging Juno off its expected course. The team expected a magma ocean to cause plenty of distortions for the spacecraft, but the effect was much slighter than expected. Their conclusion? Io has no magma ocean lurking under its crust. The results don’t preclude a deeper magma ocean, but at what point do you distinguish a magma ocean from a body’s liquid core?

    Instead, scientists are now exploring the possibility that Io’s magma shoots up from much smaller pockets of magma rather than one enormous, shared source. (Image credit: NASA/JPL/USGS; research credit: R. Park et al.; see also Quanta)

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  • Ponding on the Ice Shelf

    Ponding on the Ice Shelf

    Glaciers flow together and march out to sea along the Amery Ice Shelf in this satellite image of Antarctica. Three glaciers — flowing from the top, left, and bottom of the image — meet just to the right of center and pass from the continental bedrock onto the ice-covered ocean. The ice shelf is recognizable by its plethora of meltwater ponds, which appear as bright blue areas. Each austral summer, meltwater gathers in low-lying regions on the ice, potentially destabilizing the ice shelf through fracture and drainage. This region near the ice shelf’s grounding line is particularly prone to ponding. Regions further afield (right, beyond the image) are colder and drier, often allowing meltwater to refreeze. (Image credit: W. Liang; via NASA Earth Observatory)

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  • Seeking Uranus’s Spin

    Seeking Uranus’s Spin

    Uranus is one of our solar system’s oddest planets. An ice giant, it spins on its side. We originally estimated its rate of rotation using measurements from Voyager 2, the only spacecraft to have visited the planet. But that measurement was so imprecise that within two years, astronomers could no longer use it to predict where the planet’s poles were. Now a new study, drawing on over a decade of Hubble observations of Uranus’s auroras, has pinned down the planet’s rotation rate far more precisely: 17 hours, 14 minutes, and 52 seconds. While that’s within the original measurement’s 36-second margin of error, the new measurement has a margin of error of only 0.036 seconds. In addition to helping plan a theoretical future Uranus mission, this more accurate rotation rate allows researchers to reexamine decades of data, now with certainty about the planet’s orientation at the time of the observation. (Image credit: ESA/Hubble, NASA, L. Lamy, L. Sromovsky; research credit: L. Lamy et al.; via Gizmodo)