Science news in brief: Rome's metro digs up archaeological marvels and scientists name new northern lights 'Steve'

A roundup of news from around the world

A second-century 'commander's house' is the latest structure to be uncovered as Italy renovates the underground railway in the capital (Rex)

Rome’s subway project keeps digging up archaeological marvels

For archaeologists, the excavation of Rome’s newest subway line has been the gift that keeps on giving.

Two years after a second-century military barracks was found during the excavation of the Amba Aradam station, archaeologists presented the remains of a richly decorated domus, or house, that they believe belonged to the commander of the military post.

Even after the discovery of the military complex, “we didn’t imagine that we’d find a house with a central courtyard”, a fountain and at least 14 rooms, says Simona Morretta, the state archaeologist responsible for the site. One of the rooms appears to have been heated.

The foundation of another structure was also excavated at the same level, some 40 feet below the surface. Archaeologists believe it was probably used as a warehouse.

Morretta says the domus was remarkably well-preserved. “The decorations were mainly intact, both the patterned mosaic floors and the frescoed walls,” she says.

The walls of the domus had been levelled at a height of 5 feet and the rooms filled in with dirt, suggesting that it had been intentionally buried during the third century, just before the Roman Emperor Aurelian began building the protective walls that would encircle the city, in 271 AD.

The excavation also unearthed rare wooden artefacts, such as wood forms used to build foundations. “You normally don’t find wood remains in Rome,” Morretta notes, but with the subway lines travelling at nearly 100 feet below ground, archaeologists have been able to excavate deeper than usual.

As of now, 21 of 24 stations of the new route, Line C, which links the city centre to an area east of Rome, are operational. The San Giovanni station, which will showcase some of the artefacts found during its construction, is expected to open soon.

The domus and the warehouse will be removed from the site and temporarily preserved in special containers while construction on the Amba Aradam station continues. The ruins will eventually be returned to the site to form the centrepiece – visible to passengers – of the modern station, which is scheduled to open in 2022.

A newly discovered difference between alligators and crocodiles

How do you tell an alligator from a crocodile?

The most obvious way to discern the two reptiles is to stare down their sinister snouts. Alligators have U-shaped faces that are wide and short, while crocodiles have slender, almost V-shaped muzzles. And if you’re daring enough, take a gander at their chompers. When an alligator closes its mouth, you tend to see only its upper teeth. Crocodiles on the other hand flash a toothy grin with their top and bottom teeth interlacing.

Many of the differences between the two centre on their heads and mouths. Now, researchers from Japan have identified what they believe to be another feature that sets the reptiles apart: alligators tend to have shorter humerus bones in their forelimbs and shorter femurs in their hind limbs than crocodiles.

“This information could help explain differences in their ecology and locomotion, including the strange fact that, while small crocodiles have been observed to bound and gallop, alligators have not,” says Julia Molnar, an evolutionary biologist from the New York Institute of Technology College of Osteopathic Medicine who was not involved in the study.

The differences are small, but the finding may provide insights into the ways in which the two reptiles move.

Masaya Iijima, a vertebrate paleontologist from Hokkaido University in Japan and lead author on the study, measured more than 120 alligator and crocodile skeletons from nearly a dozen museums across the world. Then he analysed the results using a statistical model. The specimens mostly belonged to extinct crocodilians, which is the supergroup that encompasses both alligators and crocodiles, as well as caimans and gharials.

Alligators and crocodiles diverged evolutionarily during the Late Cretaceous period some 80 million years ago. To put that into context, humans and chimpanzees split ways about 7 million years ago. Both reptiles also survived the mass extinction event that wiped out the dinosaurs, and since then have remained relatively unchanged. That includes the differences seen in their limb proportions, according to Iijima.

After a volcano’s ancient super-eruption, humanity may have thrived

Supervolcanoes have the power to cough up enough ash to coat entire continents. They emit waves of hot gas, rocks and ash that flow down their slopes at speeds so great they strip away vegetation and kill anyone in their path. And they carve vast depressions in the planet, leaving permanent scars.

And yet, they might not be as apocalyptic as previously thought. About 74,000 years ago, a supervolcano at the site of present-day Lake Toba on the Indonesian island of Sumatra rocked our world. But while it was the largest volcanic eruption of the past two million years, a new study published in Nature suggests that humans not only survived the event – they thrived.

The study counters previous hypotheses, which suggest that the behemoth was so disastrous it caused the human species to teeter on the brink of extinction.

The Toba super-eruption expelled roughly 10,000 times more rock and ash than the 1980 Mount St Helens eruption. So much ejecta would have darkened skies worldwide, causing scientists to speculate that it might have plunged the Earth into a volcanic winter. In such a cold world, plants may have ceased growing, glaciers may have advanced, sea levels may have dropped and rainfall may have slowed.

Then in 1998, Stanley Ambrose, an anthropologist, linked the proposed disaster to genetic evidence that suggested a population bottleneck had occurred around the same time. He was certain that the Toba super-eruption had caused the human population to decline to some 10,000 people.

The latest study, however, suggests that those theories are incorrect, says Michael Petraglia, an archaeologist at the Max Planck Institute for the Science of Human History who was not involved in the study. “We’re not seeing all the drama.”

More than 5,500 miles from the site of the Toba super-eruption in South-east Asia, Curtis Marean, an anthropologist at Arizona State University, and his colleagues discovered signs of its debris at two archaeological sites on South Africa’s southern coast.

Should Ambrose’s theory be correct, there would be fewer signs of human occupation in the layer of soil above the one with the signs of the Toba super-eruption. Marean’s team saw the opposite: after the catastrophic event, there were more signs of human occupation.

That doesn’t mean Toba’s volcanic winter never occurred. Marean speculates that an ensuing global chill may have driven these prehistoric humans to the coast where they were able to survive.

To reach Steve’s place, turn south at the northern lights

For years, sky gazers in Canada have been training their camera lenses on a wispy strand of purple light running across the country from east to west, sometimes flanked by neon green fingers that appear to wave.

It looks like a piece of the aurora borealis, or the northern lights: blushes of pink or green that illuminate the night sky at high latitudes, caused by solar particles interacting with the Earth’s magnetic field. But this strip of light is different. It has always appeared farther south, beyond the bounds of normal aurora sightings.

Amateur aurora watchers have taken hundreds of photographs of this adjacent phenomenon, often drawing out its fluorescent colours with long exposures or photo editing. They called it Steve, as a sort of placeholder until a more formal name can be found.

Now a research paper has shed light on what Steve actually is, and scientists have proposed a moniker: Strong Thermal Emission Velocity Enhancement. So, it’s still Steve. But as a “bacronym” – a retroactive acronym.

The paper, published in Science Advances, a peer-reviewed journal from the American Association for the Advancement of Science, suggests that Steve has a lot in common with a phenomenon called a “sub-auroral ion drift”, or SAID, in which ions flow very quickly from east to west, closer to the equator than the aurora borealis.

Like the northern lights, SAID results from interactions between charged solar particles and the Earth’s magnetosphere.

“It’s something that we know that’s actually been studied for 40 years,” says Elizabeth A MacDonald, a space physicist at Nasa’s Goddard Space Flight centre who led the paper’s research team. “But they have never been seen to have this optical component.”

In other words, SAID usually looks nothing like Steve, with its long purplish streak and green fingers. That leaves many questions unanswered, and scientists are still working on those.

MacDonald and others worked with data from Swarm, a constellation of satellites run by the European Space Agency, and learned that Steve is a strip of ionised gas as hot as the Earth’s core and moving through the air at around 4 miles per second.

Further research revealed that Steve was similar to a sub-auroral ion drift.

High-flying physics for a wild petunia

When it’s time for the hairyflower wild petunia to pass its genes to the next generation, it does it with a bang.

To reproduce, the plants flings tiny seeds from a small torpedo-shaped fruit more than 20 feet through the air. That’s not an easy task.

The seeds are discs about a 10th of an inch in diameter – smaller than the circles that fall out of a hole punch – and 1/50th of an inch thick, the equivalent of three sheets of paper.

“It’s like throwing confetti,” says Dwight Whitaker, a professor of physics at Pomona College in Claremont, California.

But somehow these seeds slice smoothly through the air.

In an article published recently in the Journal of the Royal Society Interface, Whitaker and a trio of undergraduate physics majors worked out what happens in that moment of explosion that launches the seeds so far.

The seeds sit within a small fruit that is a bit over 1 inch long. A spine along each half of the fruit is made of three layers, which shrink at different rates as they dry. That creates a strain that bends them outwards. The two halves remain held together by glue.

Drip some water onto it, the glue dissolves and the fruit violently splits in half.

With ultrahigh speed video – up to 20,000 frames a second – Whitaker and his students slowed down the action, watching as hooks in the fruit accelerated the seeds to speeds of more than 30mph, similar to how the curved scoops used in the sport of jai alai can accelerate a ball to more than 100 mph.

“It just looks like this gentle, beautiful motion,” Whitaker says.

When they did the calculations, they were stunned to find that some of the seeds were spinning at a rate of more than 1,600 revolutions a second. Those at the top of the fruit tended to fly the farthest, while those at the bottom of the fruit tended to wobble and land closer to where they started.

© New York Times