How did valleys form on early Mars? Some say in ice…

Featured image: The Nirgal Vallis river valley on Mars as seen by the HRSC Camera onboard the European Space Agency’s Mars Express mission. Image credit: ESA/DLR/FU Berlin.

Paper: Valley formation on early Mars by subglacial and fluvial erosion.

Authors: Anna Grau Galofre, A. Mark Jellinek & Gordon R. Osinski.

“Some say the world will end in fire/ Some say in ice” begins the famous poem by Robert Frost. But what about how worlds begin? For years the theory of a “warm and wet” early Mars has been the conventional explanation for the vast valley networks formed billions of years ago that we can see on the surface today. Now, a new study suggests that at least some of these valleys could have formed under colossal ice sheets, in a distinctly more icy world.

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Building mountains

Featured image: Yushan (Jade Mountain) in Taiwan. From Wikimedia Commons by Kailing3 under a CC-BY-SA 3.0 license.

Paper: Coseismic Uplift of the 1999 Mw7.6 Chi‐Chi Earthquake and Implication to Topographic Change in Frontal Mountain Belts

Authors: R.Y. Chuang, C.H. Lu, C.J. Yang, Y.S. Lin, and T.Y. Lee

Journal: Geophysical Research Letters

The height of a mountain range results from a hard-fought battle between tectonic plates and the forces of erosion. Earthquakes generated by clashes between plates cause the upward motion of rock even as they shake the landscape, causing large and numerous landslides. When a large earthquake occurs, which process wins? Does more rock go up than come down, leading to a higher mountain range? Or does shaking-induced erosion remove more material than is uplifted by the earthquake? New research suggests that earthquakes might be able to build mountains up faster than landslides can bring them down.

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When space is time: evolving soil hydrology on glacial moraines

Featured image: The Stein Glacier in the central Swiss Alps, where the study was conducted. Left panel © Google, right panels CC BY Florian Lustenberger in Hartmann et al. 2020.

Paper: Field observations of soil hydrological flow path evolution over 10 millennia

Authors: Hartmann , A., Semenova, E., Weiler, M., & Blume, T.

The way water flows through soil and sediments can be incredibly diverse. In the simplest case, water flows uniformly through all of the pore space between grains. Most soils act very differently though. Water moves quickly through certain pathways and not at all through other areas. This preferential flow of water has important consequences for the ability of the soil to hold water, and for the movement of nutrients and contaminants. Understanding what factors affect the evolution of preferential flow pathways can help scientists better understand how soils work now, and how they will respond to human induced changes into the future.

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Rivers underground

Featured Image: The River Styx emerging from Mammoth Cave by Daniel Schwen. From Wikipedia under a CC-BY-SA license.

Paper: Modeling cave cross‐section evolution including sediment transport and paragenesis
Authors: M.P. Cooper and M.D. Covington

It’s not easy to watch caves form. It happens slowly and out of view, so we know relatively little about cave passage erosion compared to our knowledge of how rivers at Earth’s surface work. New research suggests that the same physical erosion processes that cut river channels at the surface might also be at work underground, adding new depth to our understanding of cave genesis.

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Looking for life on Mars: what can the valleys that once flowed into Jezero crater tell us about the best rocks to sample?

Featured image: Artist depiction of the Mars 2020 Perseverance Rover on Mars. Public domain (NASA/JPL-Caltech).

Paper: Fluvial Regimes, Morphometry, and Age of Jezero Crater Paleolake Inlet Valleys and Their Exobiological Significance for the 2020 Rover Mission Landing Site.

Authors: Nicolas Mangold, Gilles Dromart, Veronique Ansan, Francesco Salese, Maarten G. Kleinhans, Marion Masse, Cathy Quantin-Nataf, and Kathryn M. Stack.

On Mars, we see a very different landscape to that on Earth. Although now an arid planet, great scars visible from space – such as the colossal Valles Marineris, which dwarfs Earth’s Grand Canyon – hint at a once watery world. But scientists still aren’t sure whether water on Mars might once have hosted life. On the 30th of July, NASA will launch the Mars 2020 mission, which will gather clues about the planet’s past and seek signs of ancient life on Mars. An essential part of such a space mission is extensive planning, so that scientists can target the most important rocks for study and sampling when the rover gets to Mars. A recent study by Nicolas Mangold and colleagues did just that by looking closely at the landing site for this next Mars mission, known as Jezero crater.

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Rivers of Memory: India

Paper: Evolution of modern river systems: an assessment of ‘landscape memory’ in Indian river systems

Authors: Vikrant Jain, Sonam, Ajit Singh, Rajiv Sinha, S. K. Tandon

“A river cuts through rock not because of its power, but because of its persistence.”

James N Watkins

In geomorphology, the persistence of rivers is etched into the very landscape – a memory of the forces that once shaped it, and continue to do so, slowly, and inexorably. Landscape memory, as Gary John Brierley once wrote, is the imprint of the past upon contemporary landscapes, which include geologic, climatic, and anthropogenic factors.

The rivers of the Indian subcontinent bear witness to forces that shaped them over millennia – and a recent publication in the Journal of International Geosciences traces the evolution of India’s river systems at different time scales.

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Sediment riding on ice to the rescue of vulnerable salt marshes

Featured image by Jennifer Crowder from Pixabay.

Paper: Enhanced, climate-driven sedimentation on salt marshes
Authors: D.M. FitzGerald, Z.J. Hughes, I.Y. Georgiou, S. Black, A. Novak
Journal: Geophysical Research Letters

Accelerated sea level rise threatens to drown many of the world’s salt marshes, but sediment riding on ice rafts might be coming to the rescue. Continue reading “Sediment riding on ice to the rescue of vulnerable salt marshes”

Do melting glaciers release extra sediment?

Featured image: Pitztal Glacier, Austria by annca on Pixabay

Paper: Increased Subglacial Sediment Discharge in a Warming Climate: Consideration of Ice Dynamics, Glacial Erosion, and Fluvial Sediment Transport
Authors: Ian Delaney and Surendra Adhikari

The world’s glaciers are shrinking, sending great quantities of water downstream in a geologic instant. But new research shows a lesser-known effect of climate warming: a large increase in sediment released from melting glaciers that might rearrange the shape of Earth’s surface. Continue reading “Do melting glaciers release extra sediment?”