It’s a regrettable reality that there is never enough time to cover all the interesting scientific stories we come across. So every month, we highlight a handful of the best stories that nearly slipped through the cracks. July’s list includes outfitting cyborg cockroaches with a tiny diving suit for navigating flooded terrain; confirmation that a Medici duke died of malaria, not poisoning; the best evidence to date that Betelgeuse is orbited by a companion star; and evidence that some ancient Egyptian princesses were skilled archers.

Sacrificial Incan boy died of blunt force trauma

Credit: Administrative Archive, Regional Museum of Iquique–CORMUDESI

It's known that the Incas practiced a human sacrifice ritual known as Capachoca, in which children were offered to the mountains and believed to become divine themselves, serving as intermediaries with the gods. This often involved pilgrimages to the remote sacrificial sites, with colonial accounts describing strangulation, asphyxiation, and blunt force trauma as the most common methods of sacrifice. Archaeologists have reanalyzed the remains of one such victim and concluded the boy died from blunt force trauma, rather than freezing to death as previously believed. They described their findings in a paper published in the journal Science Advances.

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One week ago, more than 200 miles above the Earth, a refrigerator-size satellite making its way toward an attempted rescue of NASA's $500 million Swift gamma-ray observatory suddenly spun out of control.

It didn't look good. The spacecraft, named Link, was rotating on multiple axes, rendering it unable to maintain a reliable communications link with the ground and complicating efforts to arrest the spin. Two of the satellite's three reaction wheels, used for pointing, also stopped working. Through sporadic radio contact, engineers discovered a problem with some of the spacecraft's cold gas thrusters used for finer attitude control.

The Link satellite is built, owned, and operated by Katalyst Space Technologies, a satellite servicing startup that won a $30 million contract from NASA to fly up to the Swift observatory, grab onto it, and boost its orbit before succumbing to aerodynamic drag and burning up in the atmosphere.

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A fruit fly hunting a piece of rotting fruit or a mate navigates by smell, following plumes of odor. Out in the wild, turbulent air swirls these plumes into a chaotic, broken landscape—dense chemical filaments laced through long stretches of clean air. A fly trying to find the source gets the smell in stutters, from constantly shifting directions, with no guarantee that a next whiff is coming at all.

Scientist had little idea of how fruit flies manage this chaotic signal with a brain the size of a pinhead. For a long time, biologists stood by the “surge and cast” model, which posited that insects solved this with hardwired reflexes. The idea was that, when a fly registers the plume with olfactory neurons in its antennae, it simply flies upwind until it’s gone and then flies side to side attempting to catch it again. But now a team led by Vanessa Ruta, a neuroscientist at the Rockefeller University, has shown that fruit flies do something far more advanced.

A treadmill for flies

The trouble with the traditional surge and cast model is that it struggles to explain how an insect tracks a meandering plume across long distances. Chemical cues floating in the air in the natural environment are often sparse and unreliable. But those same features make the mechanism behind olfactory navigation notoriously difficult to test. "Odors are invisible," Ruta says, "and often they're carried along by turbulent airflow." We’ve got no way of knowing what the animal is smelling from one moment to the next.

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When the history of our ancestry is written, the fact that we've interbred with some of our closest relatives, the Neanderthals and Denisovans, will have a central role. And it will be tempting to write it as a very tidy story: Once we got genomes from these other groups, it was possible to identify the sequences in our genomes that we shared with them.

But in reality, as scientists started poking large enough collections of data, there were regular hints of some strange ancestry in our genomes. It was hard to pin down, though, at least in part because the 2 percent on average of Neanderthal DNA found in many populations does not guarantee that any two individuals will have the same 2 percent. So having the genomes of those two groups made sense of some things researchers had already been seeing.

But knowing what we do about Neanderthal and Denisovan DNA is now allowing researchers to answer a somewhat different question: Is there anything else? Using recently developed analytical techniques, they find evidence of a third lineage that we apparently interbred with before any modern humans left Africa. Again, there were hints of this earlier, but so far, there has been no genome from a modern human relative to help us understand the details—the source of this DNA remains a "ghost lineage."

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Human eyes don’t register the infrared portion of the light spectrum because infrared photons don't carry enough energy to trigger the signaling pathway inside our light-sensing cells. But we’ve been able to make devices that give us a visual representation of what’s happening in the infrared.

A team at the Beijing Institute of Technology, led by Xin Tang and Ge Mu, has now built a device that lets people see infrared in a new way. Instead of just translating it to visible shades of green as it’s done in standard night-vision goggles, it translates different infrared wavelengths into distinct parts of the visual spectrum, giving the eye something closer to natural vision.

Researchers achieved that by combining mercury telluride colloidal quantum dots, which absorb infrared light, and a dual-layer OLED, which converts that absorbed energy into visible color. Stacked together with the right internal wiring, they make incoming infrared radiation come out the other side as an ordinary-looking, full-color image.

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While recycling is a mathematically obvious response to the finite, non-renewable nature of many resources, the economic math is often challenging. For many materials, it can be hard to compete with virgin materials on a cost basis. Fast-moving technologies like electric vehicles throw in an added complication: By the time a car is scrapped, the industry may have moved on to a different battery chemistry. That reduces the value of recycling the car’s battery back into the production chain.

Still, a study led by Xin Xiong at Nanjing University finds that in China, recycling could become the dominant source of many key materials needed to manufacture EV components over the coming decades.

Modeling manufacturing needs

The researchers set out to model how the supply of recycled materials compares to manufacturing demand in China between 2010 and 2050. It covers materials relevant to batteries across hybrid, battery-electric, and even fuel-cell vehicles (lithium, cobalt, nickel, manganese, phosphorus, sodium, sulfur, and graphite), as well as several critical elements used in electric motors (copper, neodymium, dysprosium, samarium, and cerium).

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