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NEW ORLEANS — Saturn’s mighty rings cast a long shadow on the gas giant — and not just in visible light.

Final observations from the Cassini spacecraft show that the rings block the sunlight that charges particles in Saturn’s atmosphere. The rings may even be raining charged water particles onto the planet, researchers report online December 11 in Science and at the fall meeting of the American Geophysical Union.

In the months before plunging into Saturn’s atmosphere in September (SN Online: 9/15/17), the Cassini spacecraft made a series of dives between the gas giant and its iconic rings (SN Online: 4/21/17). Some of those orbits took the spacecraft directly into Saturn’s ionosphere, a layer of charged particles in the upper atmosphere. The charged particles are mostly the result of ultraviolet radiation from the sun separating electrons from atoms.
Jan-Erik Wahlund of the Swedish Institute of Space Physics in Uppsala and Ann Persoon of the University of Iowa in Iowa City and their colleagues examined data from 11 of Cassini’s dives through the rings. The researchers found a lower density of charged particles in the regions associated with the ring shadows than elsewhere in the ionosphere. That finding suggests the rings block ultraviolet light, the team concludes.

Blocked sunlight can’t explain everything surprising about the ionosphere, though. The ionosphere was more variable than the researchers expected, with its electron density sometimes changing by more than an order of magnitude from one Cassini orbit to the next.

Charged water particles chipped off of the rings could periodically splash into the ionosphere and sop up the free electrons, the researchers suggest. This idea, known as “ring rain,” was proposed in the 1980s (SN: 8/9/86, p. 84) but has still never been observed directly.

On an expedition to an icy island chain off the Antarctic Peninsula’s northern tip, researchers discovered a massive supercolony of more than 1.5 million Adélie penguins, according to a study published March 2 in Scientific Reports.

Scientists had known of an Adélie penguin colony (Pygoscelis adeliae) in these Danger Islands, but satellite images revealed more guano on the rocky islands than could be explained by the colony’s expected numbers.

Even though the tiny island chain is only about 10 kilometers across, researchers hadn’t realized the extent of the penguin population, says study coauthor Heather Lynch, an ecologist at Stony Brook University in New York. “In the Antarctic, distances are so vast, something major could be just around the corner and you wouldn’t know.”
The researchers did a preliminary head count, took drone images and collected mud cores during a 2015 expedition. The team then spent about a year using a computer algorithm to analyze the images to more fully count 751,527 penguin nests, Lynch says. For every nesting bird, the scientists assumed there was a partner penguin out at sea.
Next, the team hopes to analyze the guano content in the collected layers of mud to discover how long the penguins have been nesting in the Danger Islands.
The discovery is good news for fans of the flightless bird. Elsewhere in Antarctica where the climate is more volatile, penguin colonies are in decline. “I hope this provides impetus for a marine protected area in the Danger Islands with expanded borders from what has been proposed,” Lynch says.

Archaeopteryx was a flapper, not just a glider. The shape of the ancient bird’s wing bones suggests it was capable of short bursts of active, flapping flight, similar to how modern birds like pheasants and quails fly to escape predators, a new study finds.

One of the earliest birds, Archaeopteryx lived about 150 million years ago during the Jurassic Period, spanning the evolutionary gap between modern birds and feathered dinosaurs. Fossils of the primitive fowl have been instrumental in the recognition that birds are dinosaurs (SN Online: 7/31/14). But researchers have long wrangled over how well these ancient dino-birds could fly.
Archaeopteryx doesn’t have several features considered essential to flight in modern birds, such as a keeled breastbone to which several important flight muscles attach; a ball-and-socket arrangement that allows the wing to flap fully up over the back and down again; and a muscle pulley system that links chest and shoulder muscles, allowing the birds to swiftly alternate between powerful downstrokes and upstrokes. Previous researchers also have suggested that Archaeopteryx’s plumage was too delicate and might have snapped with vigorous flapping (SN: 6/5/10, p. 12). Based on these observations, the primitive bird was thought to merely glide from branch to branch, rather than flapping its wings to fly.

Paleontologist Dennis Voeten and colleagues decided to look for other features that might indicate the dino-birds flapped their wings while flying. The researchers used X-ray microtomography to examine two different wing bones — the humerus, or upper arm bone, and a lower arm bone called the ulna — in three Archaeopteryx fossils.

The team compared the thickness of the bones’ walls and their resistance to torsion — a twisting force that birds’ wings withstand during flapping flight — with similar bones from several dinosaurs, flying reptiles called pterosaurs and modern birds. Archaeopteryx had wing bone structures most similar to pheasants and quails, birds that are capable of small bursts of active flapping flight, the researchers report March 13 in Nature Communications.

In examining the shape of the wing bones, the study takes a novel approach to the question of whether Archaeopteryx could fly, says ornithologist Gerald Mayr of the Senckenberg Research Institute Frankfurt, who was not involved in the research.
But the study doesn’t answer whether Archaeopteryx could launch itself from the ground into the air. “Their results convincingly show that it could do active flight” once it was already airborne, Mayr says. “What they do not explain is how it would have been possible to produce strong flapping flight to take off from the ground.” Other early birds might have used a combination of wing and leg strength to launch into the air, but this hasn’t been shown for Archaeopteryx (SN: 11/26/16, p. 9).

To understand whether and how Achaeopteryx actually flew, researchers would need to reconstruct the animal’s full range of motion — a challenging prospect given that muscles don’t fossilize, says Voeten, of Palacký University Olomouc in the Czech Republic.

The primitive birds, without flight adaptations such as the muscle pulley system, wouldn’t have been capable of the full range of flapping motion birds today use. Instead, other parts of its anatomy indicate Archaeopteryx may have thrown its wings upward and forward, similar to a swimmer’s butterfly stroke, Voeten says. “Dedicated studies would need to show if it would work that way.”