When Cassini arrived at the Saturnian system in 2004, the southern hemisphere was enjoying summertime, while the northern was in the midst of winter. The spacecraft spied a broad, warm, high-altitude vortex at Saturn’s southern pole, but none at the planet’s northern pole.

A new long-term study has now spotted the first glimpses of a northern polar vortex forming high in the atmosphere as Saturn’s northern hemisphere approached summertime. This warm vortex sits hundreds of kilometres above the clouds, in a layer of atmosphere known as the stratosphere, and reveals an unexpected surprise.

“The edges of this newly-found vortex appear to be hexagonal, precisely matching a famous and bizarre hexagonal cloud pattern we see deeper down in Saturn’s atmosphere,” says Leigh Fletcher of the University of Leicester, UK, lead author of the new study.

“While we did expect to see a vortex of some kind at Saturn’s north pole as it grew warmer, its shape is really surprising. Either a hexagon has spawned spontaneously and identically at two different altitudes, one lower in the clouds and one high in the stratosphere, or the hexagon is in fact a towering structure spanning a vertical range of several hundred kilometres.”

Saturn’s cloud levels host the majority of the planet’s weather, including the pre-existing north polar hexagon. This feature was discovered by NASA’s Voyager spacecraft in the 1980s and has been studied for decades; it is a long-lasting wave potentially tied to Saturn’s rotation, a type of phenomenon also seen on Earth in structures such as the Polar Jet Stream.

Its properties were revealed in detail by Cassini, which observed it in multiple wavelengths — from the ultraviolet to the infrared — using instruments including its Composite Infrared Spectrometer (CIRS). However, at the start of the mission this instrument could not peer further up in the northern stratosphere, which had temperatures around -158 degrees Celsius — some 20 degrees too cold for reliable CIRS infrared observations — leaving these higher-altitude regions relatively unexplored for many years.

“One Saturnian year spans roughly 30 Earth years, so the winters are long,” adds co-author Sandrine Guerlet from Laboratoire de Météorologie Dynamique, France.

“Saturn only began to emerge from the depths of northern winter in 2009, and gradually warmed up as the northern hemisphere approached summertime.”

A strange process at play within Saturn’s atmosphere sped up this warming: as air sank at the north pole, the upper hexagon warmed increasingly quickly, and the transport of air downwards made the abundance of several minor species more concentrated. The increased temperature allowed Fletcher and colleagues to study the polar vortex in infrared light.

“We were able to use the CIRS instrument to explore the northern stratosphere for the first time, from 2014 onwards,” adds Guerlet. “As the polar vortex became more and more visible, we noticed it had hexagonal edges, and realised that we were seeing the pre-existing hexagon at much higher altitudes than previously thought.”

This indicates that Saturn’s two poles behave very differently — there was no hexagon at the south pole, either at the cloud tops or above, when it was observed early in Cassini’s mission during southern summer. The northern vortex is also nowhere near as mature as the southern vortex, as it is cooler, and displays different dynamics from its southern counterpart.

“This could mean that there’s a fundamental asymmetry between Saturn’s poles that we’re yet to understand, or it could mean that the north polar vortex was still developing in our last observations and kept doing so after Cassini’s demise,” adds Fletcher. The Cassini mission came to an end in September 2017.

The presence of a hexagon way up in Saturn’s northern stratosphere, hundreds of kilometres above the clouds, suggests that there is much more to learn about the dynamics at play in the gas giant’s atmosphere.

A single, towering hexagonal structure that stretches up through the atmosphere would be unlikely given that wind conditions change considerably with altitude. However, by investigating the atmospheric properties in the northern region, Fletcher and colleagues also determined that waves like the hexagon should be unable to propagate upwards — they should remain trapped in the cloud-tops, as previously thought.

“One way that wave ‘information’ can leak upwards is via a process called evanescence, where the strength of a wave decays with height but is just about strong enough to still persist up into the stratosphere,” explains Fletcher. “We simply need to know more. It’s quite frustrating that we only discovered this stratospheric hexagon right at the end of Cassini’s lifespan.”

Understanding how and why Saturn’s north polar vortex has assumed a hexagonal shape will shed light on how phenomena deeper down in an atmosphere can influence the environment high up above, something that is of particular interest to scientists trying to figure out how energy is transported around in planetary atmospheres.

Saturn’s north polar region is expected to continue developing in coming years; the northern hemisphere passed summer solstice in May 2017, and is on track for its autumn equinox in 2024.

“Saturn’s northern hexagon is an iconic feature on one of the most charismatic members of the Solar System, so to discover that it still holds major mysteries is very exciting,” says Nicolas Altobelli, ESA Project Scientist for the Cassini-Huygens mission.

“The Cassini spacecraft continued to provide new insights and discoveries right up to the very end. Without a capable spacecraft like Cassini, these mysteries would have remained unexplored. It shows just what can be accomplished by an international team sending a sophisticated robotic explorer to a previously unexplored destination — with results that keep flowing even when the mission itself has ended.”

“This pushes back cheese-making by 4,000 years,” said Sarah B. McClure, associate professor of anthropology.

The presence of milk in pottery in this area is seen as early as 7,700 years ago, 500 years earlier than fermented products, said the researchers. DNA analysis of the populations in this area indicate that the adults were lactose-intolerant, but the children remained able to consume milk comfortably up to the age of ten.

“First, we have milking around, and it was probably geared for kids because it is a good source of hydration and is relatively pathogen-free,” said McClure. “It wouldn’t be a surprise for people to give children milk from another mammal.”

However, about 500 years later, the researchers see a shift not only from pure milk to fermented products, but also in the style and form of pottery vessels.

“Cheese production is important enough that people are making new types of kitchenware,” said McClure. “We are seeing that cultural shift.”

When only meat, fish and some milk residue is found in pottery, during the Early Neolithic, the pottery is a style called “Impressed Ware” found throughout the area.

500 years later, in the Middle Neolithic, another pottery style using different technology existed — Danilo pottery — which defines the era in this area and includes plates and bowls. There are three subtypes of Danilo pottery.

Figulina makes up five percent of this type and is highly fired and buff-colored, often slipped and decorated. All this pottery contained milk residue. The other Danilo wares contained animal fats and fresh water fish residue.

Rhyta, which are footed vessels with round bodies and are often animal- or human-shaped, have large openings on the sides and distinctive handles. The researchers found that three of the four rhyta in their sample showed evidence of cheese.

The third category of Danilo ware is sieves, which are often used in cheese-making to strain treated milk when it separates into curds and whey. Three of the four sieves in the sample showed evidence of secondary milk processing into either cheese or other fermented dairy products.

“This is the earliest documented lipid residue evidence for fermented dairy in the Mediterranean region, and among the earliest documented anywhere to date,” the researchers report today (Sept. 5) in PLOS One.

The researchers looked at pottery from two sites in Croatia in Dalmatia — Pokrovnik and Danilo Bitinj. When possible, they selected samples from unwashed pottery, but because some pottery forms are rarer, used washed samples for the sieves. They tested the pottery residue for carbon isotopes, which can indicate the type of fat and can distinguish between meat, fish, milk and fermented milk products. They used radiocarbon dating on bone and seeds to determine the pottery’s age.

According to the researchers, dairying — and especially cheese and fermented milk products — may have opened northern European areas for farming because it reduced infant mortality and allowed for earlier weaning, decreasing the birth interval and potentially increasing population. It also supplied a storable form of nutrition for adults, because the fermentation of cheese and yogurt reduce the lactose content of milk products, making it palatable for adults as well as children.

With a food source that could buffer the risk of farming in colder northern climates, farmers could expand their territories.

The National Science Foundation and the National Geographic Foundation supported this work.

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In the marine environment, monitoring the abundance and population trends of a top predator can provide measures of ecosystem health and management success. Fur seals, Arctocephalus pusillus doriferus, are important upper trophic level predators that, in Australia, are a protected marine species facing specific challenges related to fisheries and aquaculture management, ecotourism, potential impacts on seabirds, and response planning for oil spills and other emergencies. For these reasons, it is important to obtain accurate information about their abundance and population changes. An ad-hoc monitoring program coordinated across multiple stakeholders conducted a range-wide census of live pups in the Austral summers of 2002, 2007 and 2013. In the new study, McIntosh and colleagues set out to assess whether the monitoring program for the Australian fur seal is achieving its goals of determining pup abundance and estimating population trends.

The findings reveal that monitoring of the Australian fur seal between the 1970s and 2013 has effectively recorded population changes. The census successfully tracked signs of population recovery up to 2007. In addition, the 2013 census identified the first pup population decline, estimated to be 4.2% per year since 2007, since species-wide protection was implemented. According to the authors, the study highlights the importance of regularly assessing long-term monitoring programs and provides valuable information on how to effectively design and improve these programs.

Roland Pick, of Phillip Island Nature Parks, notes: “As wildlife managers it is important for us to regularly review our monitoring programs to examine the reliability of the information we have collected, and also to identify enhancements which may assist in a greater understanding of any population changes detected. We are currently using drone technology and Citizen Science programs at Phillip Island Nature Parks to enhance our monitoring of Seal Rocks as the largest breeding colony for the species.”

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However, UC Riverside Earth Sciences Professor Robert Allen’s research indicates that what precipitation the state does get will be pretty much limited to the winter months — think deluge-type rainfall rather than snow — and non-winter months will be even dryer than usual, with little or no rain at all.

“It is good news,” Allen said. “But only relative to the alternative of no rain at all.”

Allen’s latest findings build on his 2017 research that concluded global warming will bring increased winter precipitation to California through the end of this century.

The findings are outlined in a paper by Allen and his co-author Ray Anderson, research soil scientist at the USDA-ARS US Salinity Lab, titled “21st century California drought risk linked to model fidelity of the El Niño teleconnection.” It was published September 3 in Climate and Atmospheric Science.

The paper focuses on how “greenhouse-gas-induced climate change” will affect drought conditions in the state. The findings are based on 40 climate models that were compared to actual precipitation, soil moisture, and streamflow in the state between 1950 and 2000.

Historically, about 90 percent of California’s rain and snow have come during the winter months of December, January, and February, Allen said, with sporadic rain scattered over the rest of the year. But now, warming surface temperatures in the tropical Pacific Ocean are expected to amplify the rainy season by sending stormy El Niño conditions over the state in the winter.

Bottom line, Allen said, the flooding and mudslides that accompanied the heavy winter rains of 2017 shouldn’t be considered an aberration, but potentially California’s new weather norm.

The trick will be finding a way to capture excess water for dry periods, he said. “It’s all about smoothing the seasonable differences. If we can take advantage of the enhanced winter rainfall, we can hopefully get through the drying trends the rest of the year.”

Trapping that winter precipitation will be a challenge, however, especially since it’s likely to come more in the form of rain than snow due to the warming climate. Historically, snow in the mountains feeds reservoirs and provides water to agriculture when it is needed in the summer, but rain will just run off unless it is captured.

Allen’s findings also bode ill for California’s fire season. The state’s new norm could mimic — or surpass — the fire season of 2017, the worst in California’s history, as wet winters encourage lush spring growth that will quickly parch during the hot and dry season, becoming wildfire fuel.

In fact, Allen said, these “new norm” projections aren’t for a distant future.

“I think it’s here now, so we need to start acting as quickly as possible,” he said. “Adaptation is incredibly important in response to climate change, and in this case it means enhancing our water storage capabilities, our reservoirs and dam structures, because things are going to become drier in the nonwinter months.”

And for ordinary citizens? This might be a great time to start investing in rain barrels.

“In Southern California, it could mean having native plants in your yard because a grass yard has to be irrigated, and that’s probably not the wisest use of water,” he said. “It’s all about living sustainably.”