FYFD

Tag: planetary science

  • Slushy Snow Affects Antarctic Ice Melt

    Slushy Snow Affects Antarctic Ice Melt

    More than a tenth of Antarctica’s ice projects out over the sea; this ice shelf preserves glacial ice that would otherwise fall into the Southern Ocean and raise global sea levels. But austral summers eat away at the ice, leaving meltwater collected in ponds (visible above in bright blue) and in harder-to-spot slush. Researchers taught a machine-learning algorithm to identify slush and ponds in satellite images, then used the algorithm to analyze nine years’ worth of imagery.

    The group found that slush makes up about 57% of the overall meltwater. It is also darker than pure snow, absorbing more sunlight and leading to more melting. Many climate models currently neglect slush, and the authors warn that, without it, models will underestimate how much the ice is melting and predict that the ice is more stable than it truly is. (Image credit: Copernicus Sentinel/R. Dell; research credit: R. Dell et al.; via Physics Today)

  • Underground Convection Thaws Permafrost Faster

    Underground Convection Thaws Permafrost Faster

    In recent years, Arctic permafrost has thawed at a surprisingly fast pace. Much of that is, of course, due to the rapid warming caused by climate change. But some of that phenomenon lives underground, where water’s unusual properties cause convection in gaps between rocks, sediment, and soil.

    Water is densest not as ice but as water. This is why ice cubes float in your glass. Water’s densest form is actually a liquid at 4 degrees Celsius. For water-logged Arctic soils, this means that the densest layer is not at the frozen depth but at a higher, shallower depth. This places a dense liquid-infused layer over a lighter one, a recipe for unstable convection.

    Illustration of underground convection and permafrost thaw. On the left: temperature and density of the water in Arctic soil varies with depth. The temperature decreases with depth, but because water is densest at 4 degrees Celsius, the density is greatest at a shallower depth than the freezing interface. As a result of this unstable configuration (dense water over less dense water), convection can occur (right side).
    Illustration of underground convection and permafrost thaw. On the left: temperature and density of the water in Arctic soil varies with depth. The temperature gets colder the deeper you go, but because water is densest at 4 degrees Celsius, the density is greatest at a shallower depth than the freezing interface. As a result of this unstable configuration (dense water over less dense water), convection can occur (right).

    In a recent numerical simulation, researchers found that this underground convection caused permafrost to thaw much more quickly than it would due to heat conduction alone. In fact, the effects appeared in as little as one month, so in a single summer, this convection could have a big effect on the thaw depth. (Image credit: top – Florence D., figure – M. Magnani et al.; research credit: M. Magnani et al.)

  • Water Suspected Beneath Mars

    Water Suspected Beneath Mars

    The surface features of Mars — crossed by river deltas and sedimentary deposits — indicate a watery past. Where that water went after the planet lost its atmosphere 3 – 4 billion years ago is an open question. But a new study suggests that quite a bit of that water moved underground rather than escaping to space.

    The research team analyzed seismic data from the Mars InSight Lander. Marsquakes and meteor strikes on the Red Planet send seismic waves through the planet’s interior. The waves’ speed and other characteristics change as they pass through different materials, and by comparing different waves picked up from the same originating source, scientists can back out what the waves passed through on the way to the detector. In this case, the team concluded that the data best fit a layer of water-filled fractured igneous rock 11.5 – 20 kilometers below the surface. They estimate that the water trapped in this subsurface layer is enough to cover the surface of the planet in a 1 – 2 kilometer deep ocean. (Image credit: NASA/JPL-Caltech; research credit: V. Wright et al.; via Physics World)

  • An Exoplanet With Earth-Like Temperatures

    An Exoplanet With Earth-Like Temperatures

    Although researchers have identified thousands of exoplanets in the last 25 years, most of them are far larger and far hotter than Earth. But a team recently announced the discovery of a temperate neighbor, Gliese 12 b, some 40 light years away. Gliese 12 b is a rocky Venus-sized planet orbiting the cool red dwarf star Gliese 12. Based on the star’s energy output and the planet’s characteristics, the team estimate its equilibrium temperature — about how hot it would be without an atmosphere — as 42 degrees Celsius. (For comparison, Earth’s average surface temperature is 15 degrees Celsius and rising.) The next goal will be to determine whether Gliese 12 b has an atmosphere and, if so, what it’s made up of. (Image credit: NASA/JPL-Caltech/R. Hurt; research credit: S. Dholakia et al.; via Gizmodo)

  • Junggar Basin Aglow

    Junggar Basin Aglow

    The low sun angle in this astronaut photo of Junggar Basin shows off the wind- and water-carved landscape. Located in northwestern China, this region is covered in dune fields, appearing along the top and bottom of the image. The uplifted area in the top half of the image is separated by sedimentary layers that lie above the reddish stripe in the center of the photo. Look closely in this middle area, and you’ll find the meandering banks of an ephemeral stream. Then the landscape transitions back into sandy wind-shaped dunes. (Image credit: NASA; via NASA Earth Observatory)

  • Venusian Lava Flows

    Venusian Lava Flows

    Venus is often known as Earth’s twin, given its similar size and proximity. But, thanks to its runaway greenhouse effect, Venus is a hellish landscape buried beneath a hot atmosphere of carbon dioxide and sulfuric acid. Unlike Earth, Venus is not tectonically active, though it does have active volcanoes. A recent study re-examined synthetic aperture radar data from the Magellan spacecraft mission in the early 1990s and found that the data contained evidence of fresh lava flows.

    The team found two areas near volcanoes where the surface backscatter changed significantly between orbital observations. After examining many possible explanations for the changes, the team concluded that the differences were most likely due to new lava. They even performed the same analysis for a volcanic field here on Earth between known lava flows and observed the same behavior. Combined with another recent study that found evidence of volcanic activity in Magellan data, signs are pointing toward Venus being about as volcanically active as our own planet, even if the mechanisms driving the volcanism differ. (Image credit: NASA/JPL-Caltech; research credit: D. Sulcanese et al.; via Gizmodo)

  • Rocky Exoplanet With an Atmosphere

    Rocky Exoplanet With an Atmosphere

    In the past few decades, the number of exoplanets we’ve found has ballooned to over 5,000, but most of these worlds are gas giants closer to Jupiter than our rocky Earth. But a recent study has turned up evidence of a rocky exoplanet that, like Earth, has an atmosphere made up of more than hydrogen.

    By combining observations from the JWST with those from other telescopes, the team found that 55 Cancri e — an exoplanet nearly 9 times more massive than Earth in a system about 41 light years from us — probably has an atmosphere made up of carbon dioxide or carbon monoxide. 55 Cancri e is still a planet extremely unlike our own, though; it’s tidally locked to its star so that one side always faces the star, and its equilibrium temperature is an estimated 2000 Kelvin. That’s actually a lower temperature than expected, indicating that an atmosphere is helping distribute heat around the planet. Based on the JWST measurements, the researchers suggest that the planet’s volatile atmosphere could be supported by outgassing from a magma ocean. (Image credit: NASA/ESA/CSA/R. Crawford; research credit: R. Hu et al.; via Gizmodo)

  • How Venus Is Losing Its Water

    How Venus Is Losing Its Water

    Since Venus formed at the same time as Earth and is similar in size, scientists believe it once had the same amount of water our planet does. Today, hellish Venus has hardly any water, a fact scientists have struggled to explain completely. Most of its water was lost long ago, as incoming particles from the solar wind stripped water from the upper atmosphere; unlike Earth, Venus doesn’t enjoy the protection of a magnetic field.

    But that mechanism doesn’t explain just how arid Venus is now. A new study instead suggests that Venus’s water loss is ongoing, driven by simple chemical reactions. The team found that molecules of HCO+ (an ion made from one hydrogen, one carbon, and one oxygen atom) could mix with any remaining water to form a positively-charged molecule. Due to that charge, the chemical easily attracts loose electrons. Once combined, however, the resulting molecule is too energetic and breaks apart; when it does so, it releases highly-energetic hydrogen, which escapes the atmosphere into space. Without that hydrogen, water molecules can’t reform. This process of dissociative recombination could explain why the rest of Venus’s water has disappeared.

    Science missions that have flown to Venus so far haven’t been equipped to measure HCO+, and the authors recommend this as a priority for future missions to our neighbor. With that data, we could confirm or disprove this mechanism for Venusian water loss. (Image credit: NASA; research credit: M. Chaffin et al.; via Gizmodo)

  • The Unusual Auroras of Mars

    The Unusual Auroras of Mars

    Earth, Saturn, and Jupiter have auroras at their poles, generated by the interaction of their global magnetic fields with the solar wind. Mars has no global magnetic field, only remnants of one frozen into areas of its crust; yet it, too, has auroras. Mars’s auroras are rarer and discrete. They occur most often over the southern hemisphere, and researchers now think they know why.

    Four billion years ago, we think Mars had a global magnetic field, much like Earth does. But somehow the planet lost that field. The traces that remain are caught in the minerals of its crust, much like the ancient magnetic fields recorded in areas of the Earth’s sea floor. These magnetized regions of Mars’s crust, shown above as contours in pink and blue, are where the discrete auroras occur.

    Using data from NASA’s MAVEN spacecraft, which orbits Mars, the team discovered a pattern. They found that auroras occur most often when the magnetic lines of the incoming solar wind run antiparallel to the magnetic field lines of the crust. This suggests that the auroras happen as a result of magnetic reconnection, a process where antiparallel magnetic field lines rearrange themselves, releasing energy as a result. Reconnection events provide an opportunity for electrons from the solar wind to accelerate into Mars’s atmosphere, exciting molecules there and generating the auroras. So far we’ve only caught the auroras in UV light, but hopefully one day we’ll see them in visible light as well. (Image credit: R. Lillis et al.; research credit: C. Bowers et al. and B. Johnston et al.; via APS Physics)

  • Reimagining Mars’ Interior

    Reimagining Mars’ Interior

    Older models of Mars assumed a liquid metal core beneath a solid mantle of silicates, but recent studies indicate that structure is missing at least one layer. Using data from the InSight lander’s seismometer, two teams independently calculated that a liquid silicate layer must surround the planet’s core. In September 2021, three meteorite pieces impacted Mars far from the InSight lander’s position. Since the Mars Reconnaissance Orbiter could exactly pinpoint the impact location, researchers were able to calculate just how long it took seismic waves from the impact to reach the lander.

    Like on Earth, Mars has two varieties of seismic wave: transverse S-waves that only travel through solids and longitudinal P-waves that travel through both liquid and solid layers. S-waves reflect off any liquid-solid boundary, following a different path to a seismometer than P-waves that refract across the boundary and travel through liquid. For more of the story behind this discovery, check out this article at Physics Today. (Image credit: Mars – NASA/JPL-Caltech/University of Arizona, illustration – J. Sieben/J. Keisling; research credit: H. Samuel et al. and A. Khan et al.; via Physics Today)

    An illustration of Mars' interior and the paths followed by seismic waves before InSight picked them up.
    An illustration of Mars’ interior and the paths followed by seismic waves before InSight picked them up.