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China’s first space station, Tiangong-1, is expected to fall to Earth sometime between March 31 and April 1. No fooling.

Most of the 10.4-meter-long station will burn up as it zooms through Earth’s atmosphere. But some parts will survive and reach the ground, according to the European Space Agency’s Space Debris Office. No one can be sure where or when those pieces will hit. Even within hours of the station reaching the atmosphere, the final hit zone predictions will cover thousands of kilometers. ESA predicts that any latitude between 42.8° N (so as far north as Chicago) and 42.8° S (down to Tasmania) is fair game. The geometry of the station’s orbit means that the edges of that zone are more likely to be hit than the equator.
Much of that area is oceans or uninhabited. “The personal probability of being hit by a piece of debris from Tiangong-1 is actually 10 million times smaller than the yearly chance of being hit by lightning,” according to ESA. (If you’re wondering, the annual chance of getting zapped in the United States is 1 in 1,083,000.)
Launched in 2011, Tiangong-1 — which means Heavenly Palace — was visited twice by Chinese astronauts, in 2012 and in 2013. The craft was supposed to last only two years, and China put it into sleep mode after the second visit to prepare to steer it back to Earth for a controlled reentry. But in March 2016, the Chinese space agency announced that they had lost contact with the craft and expected it to reenter the atmosphere sometime in 2017
Reentry is unlikely to be dangerous, but it will look cool. The disintegrating space station will blaze through the sky like a fireball. ESA and the Chinese space agency are running daily updates on the station’s location, so check back to see if it will be visible where you are.

PHOENIX — A new, breathable material that can also block biological or chemical threats could offer comfortable protection for people working in contaminated environments or dangerous military zones.

The bottom layer of the material, described April 3 at the Materials Research Society spring meeting, features carbon nanotube pores embedded within a flexible synthetic polymer film. These pores are just a few nanometers across — too small for bacterial or viral cells to squeeze through, but wide enough for sweat to escape.
The top layer offers further protection. It is made of another, spongy polymer that normally allows water and other molecules to pass through. But when the polymer comes into contact with G-series nerve agents — the family of toxic chemicals that includes sarin gas — it flattens into a dense sheet that seals over the carbon nanopores underneath. The polymer can be restored to its original state by soaking it in a high-pH chemical broth.

Both layers together are still less than half the thickness of a sheet of paper, and could be laid over fabrics without putting the wearer at risk of overheating. That’s an improvement over the typical protective gear that’s permanently sealed against contaminants, said study coauthor Francesco Fornasiero, a chemical engineer at Lawrence Livermore National Laboratory in California.

In early testing, the material completely blocked out dengue virus cells, as well as 90 percent of the chemical diethyl chlorophosphate, used as a stand-in for toxic nerve agents. The researchers are working to make the material even more impervious to dangerous chemicals, Fornasiero said.

About 50 million years ago, a monitor lizard in what is now Wyoming perceived the world through four eyes. Saniwa ensidens is the only known jawed vertebrate to have had two eyelike photosensory structures at the top of the head, in addition to the organs we commonly think of as eyes, researchers report April 2 in Current Biology.

The structures are called the pineal and parapineal organs. Among animals alive today, only the jawless fish called a lamprey has both structures. But many modern reptiles have a so-called third eye, the pineal organ.
The researchers examined fossils collected 150 years ago by Yale University students. Scans of the fossils using a technique called X-ray computed tomography revealed spaces in the skull for both the third and fourth eye.

What the ancient lizard did with these organs isn’t known, but some modern vertebrates use the amplified photosensitivity they glean from the pineal glands to navigate. S. ensidens may have been able to perceive polarized light and use the angle of the sun like a compass, as some modern lizards do. Or it may have navigated using Earth’s magnetic field, much like some amphibians and migratory birds.

There’s a great future in plastics.

A new kind of plastic can, when exposed to the right chemicals, break down into the same basic building blocks that it came from and be rebuilt again and again. The recyclable material is more durable than previous attempts to create reusable plastics, researchers report inthe April 27 Science.

Designing plastics that can be easily reused is one line of attack against the global plastic waste problem. Only about 10 percent of plastic ever made gets recycled, according to a 2017 study in Science Advances. But the material is so cheap and useful that hundreds of millions of tons of it keeps getting churned out each year.
A major impediment to plastic recycling is that most plastics degrade into molecules that aren’t immediately useful. Transforming those molecules back into plastic or into some other product requires many chemical reactions, which makes the recycling process less efficient. And while biodegradable plastics have become popular in recent years, they break down only if the right microbes are present. More often than not, these plastics end up lingering in landfills or floating in the ocean. Creating plastics that could be broken down into their building blocks and reused without additional processing and purifying could help reduce the pollution buildup.

But designing such a plastic polymer is a balancing act, says Michael Shaver, a polymer chemist at the University of Edinburgh who wasn’t part of the study. Polymers are long chains of small molecules, called monomers, that link together like beads on a string. Monomers that need extreme temperatures or too much chemical coaxing to join up into polymers might not be practical building blocks. And resulting polymers need to be stable up to a high enough temperature that, say, pouring hot coffee into a cup made of them won’t destabilize the chains and make the plastic melt into a sticky puddle.
Polymer chemist Jianbo Zhu and his colleagues at Colorado State University in Fort Collins set out to solve this challenge. The team had had some luck in the past creating a polymer that could be broken down into its starting molecules. But the resulting plastics created by their lab and others on the same track were too soft and temperature-sensitive to have much practical use.
This time, Zhu and his colleagues modified one of their previous creations, a small ringed molecule, by adding another ring in a way that braced the molecule into a particular conformation. That rigidity helped the monomers quickly link together at room temperature into polymer chains that are heat-stable.
Then, when exposed to certain mild chemicals or high enough heat, the polymers degraded back into monomers. The researchers were able to repeat this cycle several times, showing that, in theory, the polymer could be infinitely recyclable.

While each monomer is locked into a particular conformation, not all of them have the same shape even though they’re made from the same chemical recipe. Mixing two different conformations of monomers created an even stronger plastic, says Zhu.

“This is probably the best system out there,” Shaver says.

Still, it’s not perfect yet: Zhu and his colleagues plan to tinker with the monomer design more in the future to make the resulting plastic a bit less brittle. Eventually, they hope to commercialize the product.

As opioid-related deaths rise in the United States, so has the role of synthetic opioids — primarily illicit fentanyl, mixed into heroin or made into counterfeit pills (SN Online: 3/29/18). In 2016, synthetics surged past prescription opioids and were involved in 19,413 deaths, compared with 17,087 deaths involving prescription opioids, researchers report May 1 in JAMA. The study is based on data from the National Vital Statistic System’s record of all U.S. deaths.

“Synthetic opioids are much deadlier than prescription opioids,” says emergency physician Leana Wen, Health Commissioner of Baltimore, who was not involved in the study. Fentanyl, for example, is about 50 to 100 times more potent than morphine. The illicit origins of many synthetic opioids make the public health response more difficult, she says. “We can track prescriptions; it’s much harder to track illegally trafficked drugs.”

Clearwing moths may not look all that dangerous, despite having largely see-through wings like bees and wasps. But some fly like fierce insects best left well alone.

Four clearwing species from Southeast Asian rainforests aren’t perfect mimics of local bees and wasps. Yet the resemblance looked much stronger when entomologist Marta Skowron Volponi of the University of Gdansk in Poland and her husband, nature filmmaker Paolo Volponi, spent days at a time poised with a video camera on riverbanks to capture the flight patterns. Four clearwing species occasionally showed up, including a shaggy Aschistophleps that turned out to be a species new to science.

That newly named A. argentifasciata and two other species flew in slow, zigzaggy paths that resembled the meanderings of local stingless bees. (This kind of bee is not great for snacking birds because it bites fiercely.) Another clearwing moth flew distinctly faster with broader turning sweeps instead of zigzags, much like a wasp.

Behaving like something that stings or bites may be an advantage for moths that forgo the cover of night and fly in daylight with its abundance of hungry birds and other predators that hunt by sight. Even imperfect body mimics get convincing in the air, Skowron Volponi and her colleagues report May 2 in Biology Letters.

Jupiter’s icy moon Europa may have been spitting into space for at least 20 years. Analyzing old Galileo mission data suggests that the NASA spacecraft flew through a plume of water vapor from the moon during a 1997 flyby, researchers report May 14 in Nature Astronomy.

“We now have very compelling support for the idea that Europa does possess plumes,” says study coau
Whether the moon, Jupiter’s fourth largest, has such geysers has been a lingering mystery. One of the most tantalizing results from Galileo, which orbited Jupiter from 1995 to 2003, was evidence that Europa harbors a deep ocean of liquid water beneath an icy shell. Then in 2012, data from the Hubble Space Telescope revealed high concentrations of charged hydrogen and oxygen atoms, or ions, over Europa’s southern hemisphere, a potential sign of water vapor escaping into space (SN: 1/25/14, p. 6).

The putative plumes have played peekaboo ever since (SN Online: 1/11/18), continuing to intrigue astronomers hoping to search the moon’s water for signs of life.

Jia and colleagues examined data from Galileo’s closest Europa flyby, which brought the probe within 206 kilometers of the moon’s surface. Over one spot near the equator, the spacecraft detected sudden changes in its magnetic field and plasma instruments. Using up-to-date computer simulations, the team showed that these changes are best explained by Galileo flying through an active plume. Radiation from Jupiter’s magnetic field would have split water molecules into oxygen and hydrogen ions, and those particles, in turn, would have changed the direction of the magnetic field and the density of plasma within the plume. That spot is also near where Hubble picked up a second sign of escaping water vapor
in 2014 (SN Online: 9/26/16) .
Galileo found no other signs of plumes during its 10 other Europa flybys, which were farther away from the moon. That suggests that any plumes are relatively small, extending not much higher than 200 kilometers above the surface. It’s also unclear if Europa plumes would be spewing constantly or be turning on and off.

Jia is working on magnetic field and plasma instruments for two future missions to Jupiter and its moons: the 2022 European JUICE mission and NASA’s Europa Clipper spacecraft, also planned for the early 2020s. The Clipper spacecraft will make much lower flybys over Europa, skimming as low as 25 kilometers above the surface. The new Galileo results should help in planning those flight paths, he says.

NASA will host a live discussion of these findings at 1:00 p.m. EDT on May 14. You can watch on various platforms, including NASA Television, Facebook Live and YouTube.

Planetary scientist Cynthia Phillips of NASA’s Jet Propulsion Laboratory in Pasadena, Calif., who worked on Galileo as a graduate student but was not involved in the new analysis, says it’s exciting that scientists are using new tools on the old mission data.

“During Galileo, we’d always known there was something weird during this flyby,” she says. But she is still holding out for visual confirmation of the plumes. “Pictures, or it didn’t happen.”

Sluggish memories might be captured via RNA. The molecule, when taken from one sea slug and injected into another, appeared to transfer a rudimentary memory between the two, a new study suggests.

Most neuroscientists believe long-term memories are stored by strengthening connections between nerve cells in the brain (SN: 2/3/18, p. 22). But these results, reported May 14 in eNeuro, buoy a competing argument: that some types of RNA molecules, and not linkages between nerve cells, are key to long-term memory storage.
“It’s a very controversial idea,” admits study coauthor David Glanzman, a neuroscientist at UCLA.

When poked or prodded, some sea slugs (Aplysia californica) will reflexively pull their siphon, a water-filtering appendage, into their bodies. Using electric shocks, Glanzman and his colleagues sensitized sea slugs to have a longer-lasting siphon-withdrawal response — a very basic form of memory. The team extracted RNA from those slugs and injected it into slugs that hadn’t been sensitized. These critters then showed the same long-lasting response to touch as their shocked companions.

RNA molecules come in a variety of flavors that carry out specialized jobs, so it’s not yet clear what kind of RNA may be responsible for the effect, Glanzman says. But he suspects that it’s one of the handful of RNA varieties that don’t carry instructions to make proteins, the typical job of most RNA. (Called noncoding RNAs, these molecules are often involved in manipulating genes’ activity.)

But even the few scientists who question whether the strength of nerve cell connections is the key to long-term memory storage don’t necessarily buy Glanzman’s ideas. The fact that untrained slugs become more sensitive to touch after RNA injection is “amazing,” says biochemist Tomás Ryan of Trinity College Dublin, who wasn’t part of the study. “But it doesn’t go far enough to say that the memory has been transferred.”

After a giant asteroid hit Earth about 66 million years ago, the planet’s climate went on a roller coaster ride.

The space rock’s impact set off tsunamis and wildfires before climate-chilling clouds of sulfur gas engulfed the planet for decades, wiping out most life (SN: 11/25/17, p. 14). As these clouds dissipated, billions of tons of carbon dioxide, which spewed into the atmosphere when the asteroid hit, fueled roughly 100,000 years of global warming, new data suggest. Analyzing fossilized fish bits hints that the influx of the greenhouse gas raised the temperature of the ocean on average by 5 degrees Celsius, scientists report online May 24 in Science.
It’s not surprising that the climate heated up after the collision, which left a 200-kilometer-wide crater centered around what’s now Chicxulub, Mexico, says Johan Vellekoop, a geologist at KU Leuven in Belgium. But finding evidence to back up the warming claim has been challenging.

A common way to estimate past temperatures on Earth is to measure the proportion of heavier to lighter forms of oxygen in the carbonate shells left behind by dead invertebrates. Animals incorporate different oxygen forms into shells, teeth and bones at different rates depending on temperature. But carbonate fossils from around the time of the impact aren’t well enough preserved to be a reliable thermometer.

Instead, paleogeologist Ken MacLeod of the University of Missouri in Columbia and colleagues analyzed those same types of oxygen ratios in a crushed jumble of fish bones, teeth and scales — a different way to measure past temperatures. The team collected sediment samples from a section of rock in what’s now El Kef, Tunisia, that records the transition between the periods before and after the impact in its layers. (Samples from 2 meters of rock laid down before the impact and 6.6 meters laid down after the strike recorded almost 250,000 years of geologic history.) Back in the lab, the researchers spent hours peering through microscopes to sort out glassy, amber fish teeth and mineralized scales and measure the oxygen content within them.
The ratio of heavier oxygen to lighter decreased by about 1 percent in the fish bits collected after the impact compared with those pieces from before the impact, the team found. That change translates to an increase in seawater temperature of about 5 degrees Celsius — a substantial amount.
The elevated temperatures persisted for about 100,000 years before the planet cooled down again, an analysis of fish debris collected from different levels of rock showed. While the study looked only at ocean temperature, air temperature would probably reflect that increase, too, MacLeod says.

“It’s a pretty robust result,” says Clay Tabor, a climate scientist at the University of Connecticut in Hartford. But getting similar results from sites elsewhere in the world would boost the case that this was a global effect and not a local fluke, he says.

The story is far from over, MacLeod agrees. It’s not clear how long after the impact the warming began, for instance. His team hopes to analyze fish debris from other sites that might reveal finer-scale changes in temperature.

Nothing against trees. But maybe it’s better not to get too dependent on them if you want to survive a big flaming space object crashing into Earth.

The asteroid impact that caused a mass extinction 66 million years probably also triggered the collapse of forests worldwide, a new investigation of the plant fossil record concludes. Needing trees and extensive plant cover for nesting or food could have been a fatal drawback for winged dinosaurs, including some ancient birds. Reconstructing the ecology of ancient birds suggests that modern fowl descended from species that survived because they could live on the ground, an international research team proposes in the June 4 Current Biology.
“You probably would have died anyway regardless of habitat,” says study coauthor Daniel Field, an evolutionary paleobiologist at the University of Bath in England. “But if you could get along on the ground, you at least had a shot at surviving across this devastated landscape.”

The shock wave from the strike probably flattened trees within a radius of 1,500 kilometers, Field says. Wildfires ignited around the planet and then came the acid rain. Clouds of ash and dust may have darkened the sky for several years, and researchers suspect that photosynthesis waned. Yet some lucky birds, but no other dinosaurs, survived the hellscape.

For clues to what made a survivor, researchers turned to fossilized pollen from before and after the fiery impact. Abundant kinds of flower-bearing and cone-bearing plants left pollen just before the asteroid hit and again starting about a thousand years afterward. In between those times of diversity, however, ferns dominated, the team notes. A kind of “disaster flora,” ferns (making spores instead of flowers and seeds) do well at recolonizing land. Seed plants, however, weren’t thriving.

Analyzing evolutionary histories of modern birds supports the idea of tree dependence as a vulnerability for the earliest fowl, the researchers say. Specialists in bird evolution now generally agree on the lowest, oldest branches of the bird family tree, Field says. The bottommost one, for instance, includes such modern species as ground-dwelling ostriches and smaller, flight-capable birds called tinamous, which might be more like the ancient birds that dodged extinction.
Working backward along these low branches, researchers used fossils and known bird traits to reconstruct the most likely lifestyles of the earliest survivors. These probably weren’t tree-dependent birds, the researchers conclude.

The glory days of dinosaurs had had plenty of flying tree-dwellers. So far, paleontologists have identified at least 80 kinds of what are called “opposite birds,” the Enantiornithes (SN: 2/4/17, p. 26). “If you saw one flying around today, you’d say, ‘Well, that’s a bird,’ ” Field explains. Their feet looked like those of birds that perch on tree limbs, so he’s not surprised that a fossil of an opposite bird from this probably arboreal group has never been found in rock formed after the dino doomsday.

What did happen, however, was that when trees and forests came back after the disaster, birds quickly evolved arboreal lifestyles, the team says.

Many people don’t realize that birds almost died off during the mass extinction, too, says paleontologist Stephen Brusatte of the University of Edinburgh who has studied bird evolution but was not involved in the new study. What let the few survivors squeak through, he says, has been a mystery for a long time. The whole scenario of a ground-dweller’s advantage and then a return to the trees “makes a lot of intuitive sense.”