Methane on Enceladus might hint at alien life
In the vast ocean beneath the icy crust of Saturn’s moon Enceladus, a mysterious process is churning out methane – and it could be a sign that life teems in the subsurface world, according to a new study in Nature Astronomy.
In 2005, the Cassini spacecraft discovered water-rich plumes blasting up from the surface this frozen world – evidence for an ocean of water beneath the ice. More than 100 geysers have since been found, emitting other materials mixed in with the water including dihydrogen, carbon dioxide and methane.
“We wanted to know: Could Earthlike microbes that ‘eat’ the dihydrogen and produce methane explain the surprisingly large amount of methane detected by Cassini?” says Regis Ferriere from the University of Arizona.
But actually searching for microbes on the ocean’s floor would be extremely challenging, involving missions not expected to launch for decades.
Instead, Ferriere and colleagues constructed mathematical models incorporating geochemistry and microbial ecology, which suggested that Cassini’s data can be explained by microbial activity in hydrothermal events, similar to methane-production in these environments on Earth.
“Obviously, we are not concluding that life exists in Enceladus’ ocean,” Ferriere says. “Rather, we wanted to understand how likely it would be that Enceladus’ hydrothermal vents could be habitable to Earthlike microorganisms.”
The answer? Very likely. But the alternative is exciting too – there may be an abiotic process on Enceladus that we see have here on Earth.
Leonardo da Vinci’s DNA
A new study in the journal Human Evolution has traced the family tree of the great Renaissance artist Leonardo da Vinci over 21 generations – or 690 years.
The results, which come from a decade-long investigation, document the continuous male line of the family from 1331 through to today. It also identifies all 14 living male descendants of the famous artist. While da Vinci had no children himself, he had 22 half-brothers.
The researchers believe that this family tree – including the DNA of da Vinci’s ancestors – may help determine whether bones interred in a French chapel belong to the man himself, and perhaps one day probe a potential genetic basis for his artistic talent.
Fossil shark scales reveal human impact
By looking at 7000-year-old fossilised shark scales from a coral reef in Panama, researchers have shown that shark populations have since declined three-fold in the region, with swift-swimming species hit the hardest.
“These results give us new insight into what a ‘healthy’ shark community might look like on a coral reef before human exploitation,” says Erin Dillon, a doctoral student at the University of California Santa Barbara and lead author on the paper, published in PNAS.
With skeletons made of cartilage, sharks don’t readily fossilise – except for their teeth and scales. Dillon and team compared the abundance and variety of microscopic fossilised scales found in sediment a fossil reef in Bocas del Toro, on Panama’s Caribbean coast. This allowed them to reconstruct prehistoric population numbers.
“We showed that tiny shark scales can be well-preserved and found in high enough abundances to reconstruct shark baselines over long ecological timescales,” Dillon says. “We found about a 71% decrease in total shark abundance between the mid-Holocene – before major human impact in our study region – and now.”
Trout on meth?
A new study in the Journal of Experimental Biology has found that freshwater methamphetamine pollution may be turning brown trout into junkies. This comes mere weeks after we learned that crayfish act weirdly when their water is contaminated with antidepressants, and highlights the fact that current water treatments aren’t equipped to deal with the traces of drugs we consume.
Researchers led by the Czech University of Life Sciences Prague studied the behaviour of brown trout (Salmo trutta), which they first isolated in a tank for two months in water with low levels of methamphetamine; then, they transferred the fish to a fresh tank but offered them the opportunity to return to the meth-laced water.
Initially, the drug-exposed fish were more likely to return than a control group who had been in freshwater the whole time, and evidence of the drug was found in their brains for up to 10 days after.
Co-author of the study, Pavel Horký, expresses concern that addiction could cause fish to congregate near unhealthy discharge sites. “The elicitation of drug addiction in wild fish could represent another example of unexpected pressure on species living in urban environments,” he concludes.
Earliest evidence of wing-based communication
Scientists have discovered a fossilised insect wing from the Late Carboniferous period, and it’s the earliest evidence we have that insects use wings to communicate.
The study, published in Communications Biology, describes the fossilized wing belonging to a giant grasshopper-like insect of the order Titanoptera. The new species, called Theiatitan Azari, displays a particular wing shape and structure that suggests it used its wings to reflect light or generate sound for communication.
“Acoustic communication is well-known in insects since the Mesozoic, but earlier evidence of this behavior is rare,” the authors write in their paper.
This discovery pushes the emergence of this behaviour back to the late Carboniferous, 310 million years ago – 50 million years older than the previous evidence.
“Whether these communication systems were used to attract sexual partners and/or escape predators remain to be demonstrated,” the authors conclude.
Lauren Fuge is a science journalist at Cosmos. She holds a BSc in physics from the University of Adelaide and a BA in English and creative writing from Flinders University.
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