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)
Tag: planetary science
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
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
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
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
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
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
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)
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Martian Mud Volcanoes
Mars features mounds that resemble our terrestrial mud volcanoes, suggesting that a similar form of mudflow occurs on Mars. But Mars’ thin atmosphere and frigid temperatures mean that water — a prime ingredient of any mud — is almost always in either solid or gaseous form on the planet. So researchers explored whether salty muds could flow under Martian conditions. They tested a variety of salts, at different concentrations, in a low-pressure chamber calibrated to Mars-like temperatures and pressures. The salts lowered water’s freezing point, allowing the muds to remain fluid. Even a relatively small amount of sodium chloride — 2.5% by weight — allowed muds to flow far. The team also found that the salt content affected the shape the flowing mud took, with flows ranging from narrow, ropey patterns to broad, even sheets. (Image credit: P. Brož/Wikimedia Commons; research credit: O. Krýza et al.; via Eos)
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Climate Change and the Equatorial Cold Tongue
A cold region of Pacific waters stretches westward along the equator from the coast of Ecuador. Known as the equatorial cold tongue, this region exists because trade winds push surface waters away from the equator and allow colder, deeper waters to surface. Previous climate models have predicted warming for this region, but instead we’ve observed cooling — or at least a resistance to warming. Now researchers using decades of data and new simulations report that the observed cooling trend is, in fact, a result of human-caused climate changes. Like the cold tongue itself, this new cooling comes from wind patterns that change ocean mixing.
As pleasant as a cooling streak sounds, this trend has unfortunate consequences elsewhere. Scientists have found that this cooling has a direct effect on drought in East Africa and southwestern North America. (Image credit: J. Shoer; via APS News)
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