Ocean study

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Ocean ghost currents undo gravity

Flinders University researcher Jochen Kaempf has discovered how ghost currents and sediment can ‘reverse’ the force of gravity.

The study, published in the Journal of Marine Science, shows how suspended sediment particles in the ocean appear to move upwards, despite being heavier than seawater, due to these ‘ghost currents’.

“To put it simply, the vehicle of this transport are currents that, while carrying sediments around and keeping them in suspension, leave the ambient seawater and its dissolved properties almost unchanged,” says Kaempf.

“Such current, that I call ghost currents, adhere to the laws of physics and can move sediment particles over vast distances relative to the ambient seawater, also in directions opposite to the buoyancy force.”

Eggy colours

Salamander eggs masses. Egg masses are either completely clear or opaque white. Credit: Mark Urban, University of Connecticut

New research shows that the egg masses of salamanders have different colours due to two evolutionary forces.

Scientists studied spotted salamanders (Ambystoma maculatum) in ponds in Pennsylvania, USA, where they return to the water to produce eggs – but some egg clumps are opaque while others are transparent.

According to the study, published in Biology Letters, the salamanders experienced genetic drift, which generally leads to a reduction of traits. At the same time, the populations experienced balancing selection, a type of selection that preserves different traits. Together, this led to only two egg colour traits.

“Ultimately we found a tension between these two evolutionary processes, with genetic drift potentially leading to a reduction of diversity in this system, and balancing selection working to maintain it,” says Sean Giery from Penn State, who led the team.

Poop Core

In some hardcore science, researchers have uncovered clues about Jamaica’s past from a 4,300-year-old poop core.

Thin slices of the bat guano core from Home Away from Home Cave, Jamaica. Credit: Chris Grooms

The two-metre poop core, made from layers of guano from fruit-eating bats (Artibeus jamaicensis­­) over the centuries, showed what bats ate over a long period. Plants and insects that were abundant at certain times were eaten and excreted, so the guano core showed distinct layers that reflected the changing landscape and climate.

For example, some layers had more plants than insects, suggesting that it was a drier period.

“Drier conditions tend to be bad for insects,” says researcher Jules Blais, from the University of Ottawa in Canada. “We surmised that fruit diets were favoured during dry periods.”

“It’s remarkable they can find biochemical markers that still contain information 4,000 years later,” says Michael Bird from James Cook University, Queensland. “In the tropics, everything breaks down fast.”

The study is published in the Journal of Geophysical Research: Biogeosciences.

Snakes aren’t slimy – they’re nanoslimy

Some snakes might do better on different terrain because of their skin chemistry.

Previously, researchers found snakes are covered with an incredibly thin layer of lipids – an oily layer only one or two nanometres thick.

“Some people are afraid of snakes because they think they’re slimy, but biologists tell them snakes aren’t slimy; they’re dry to the touch,” explains lead author and chemist Tobias Weidner from the Aarhus University, Denmark. “That’s true, but it’s also not true because at the nanoscale we found they actually are greasy and slimy, though you can’t feel it. They’re ‘nanoslimy.’”

In new research, presented at a meeting of the American Chemical Society, Weidner and team also found that the nanoslimy surface chemistry is specific to snakes in different habitats.

“From a snake’s point of view, it makes sense,” says Mette Rasmussen, also from Aarhus University. “You would like to have this friction reduction and wear resistance on both sides if you’re surrounded by your environment instead of only moving across it.”

Super hot meteorites hint at planetary atmospheres

Researchers at the University of California, Santa Cruz, in the US, heated meteorites to see what gases were released and thus estimate what the original atmospheres of other planets might be like.

Samples from three carbonaceous chondrite meteorites (Murchison, Jbilet Winselwan, and Aguas Zarcas) were analysed in the outgassing experiments. Credit: M. Thompson

“When the building blocks of a planet are coming together, the material is heated and gases are produced, and if the planet is large enough the gases will be retained as an atmosphere,” explains study co-author Myriam Telus from UC Santa Cruz. “We’re trying to simulate in the laboratory this very early process when a planet’s atmosphere is forming so we can put some experimental constraints on that story.”

The results, published in Nature Astronomy, suggest that the initial atmospheres of terrestrial planets may be different to what was previously thought. Instead of hydrogen and helium, similar to the Sun, the dominant gas released from the heated meteorites was water vapour, followed by carbon monoxide, carbon dioxide, and some hydrogen and hydrogen sulphide.

“We want to do this for a wide variety of meteorites to provide better constraints for the theoretical models of exoplanetary atmospheres,” Telus concludes.