Much of What We Thought About Jupiter Is Wrong

This enhanced-color composite photo shows Jupiter’s south pole from NASA’s Juno spacecraft 32,000 miles above the gas giant. The oval features are cyclones up to 600 miles wide.
This enhanced-color composite photo shows Jupiter’s south pole from NASA’s Juno spacecraft 32,000 miles above the gas giant. The oval features are cyclones up to 600 miles wide.
NASA/JPL-Caltech/SwRI/MSSS/Betsy Asher Hall/Gervasio Robles

Scientists have had time to study the data returned from the NASA spacecraft Juno and are discovering that pretty much everything they thought they knew about Jupiter’s interior is wrong. “I think we’re all sort of feeling the humility and humbleness,” said Scott Bolton, the principal investigator of Juno, during a press teleconference today, May 25. “It is making us rethink how giant planets work not only in our system but throughout the galaxy.”

The findings from Juno’s initial Jupiter orbits were published today in the journals Science and Geophysical Research Letters. The latter is a special issue devoted to Juno data and includes more than two dozen reports.

TEXAS-SIZED AMMONIA CYCLONES ARE ONLY THE BEGINNING

Juno, which launched in 2011 and entered Jupiter's orbit on July 4, 2016, is the first spacecraft to give scientists a real view of Jupiter’s poles, and what they’ve found is unlike anything expected.

“Jupiter from the poles doesn’t look anything like it does from the equator,” Bolton said.

Images reveal that Jupiter’s famous bands do not continue to the north and south poles. Rather, the poles are characterized by a bluish hue, chaotic swirls, and ovular features, which are Texas-sized ammonia cyclones. The precise mechanism behind them is unknown. Their stability is equally a mystery. As the Juno mission progresses, repeat visits to the poles and new data on the evolution of the cyclones will answer some of these questions.

The poles aren't identical, either. “The fact that the north and south pole don’t really look like each other is also a puzzle to us,” Bolton said.

One interesting observation was a happy accident. Because of Juno’s unique orbit, the spacecraft always crosses a terminator—that is, the line dividing where the planet is in full illumination of the Sun, and the far side, in total darkness. This is useful because topological relief can be seen at this line. (To see this in action, look through a telescope at a half-full moon. The shadows where light meets dark give a vivid sense of the heights of mountains and the depths of craters.) During an orbit, there happened to be a 4300-mile-wide storm at Jupiter’s terminator near the north pole, and scientists noticed shadows. The storm was towering over its cloud surroundings like a tornado on a Kansas prairie.

INTENSE PRESSURE SQUEEZES HYDROGEN INTO A METALLIC FLUID

Jupiter's core with metallic hydrogen fluid envelope
What may lie within the heart of Jupiter: a possible inner “rock” core surrounded by metallic hydrogen and an outer envelope of molecular hydrogen, all hidden beneath the visible cloud deck.
NASA/JPL-Caltech/SwRI

Bolton explained that the goal of Juno is "looking inside Jupiter pretty much every way we know how.” Juno carries an instrument called a microwave radiometer, designed to see through Jupiter’s clouds and to collect data on the dynamics and composition of its deep atmosphere. (The instrument is sensitive to water and ammonia but is presently looking only at ammonia.) So far, the data are mystifying and wholly unexpected. Most scientists previously believed that just below the clouds, Jupiter’s atmosphere is well mixed. Juno has found just the opposite: that levels of ammonia vary greatly, and that the structure of the atmosphere does not match the visible zones and belts. Ammonia is emanating from great depths of the planet and driving weather systems.

Scientists still don’t know whether Jupiter has a core, or what it’s composed of if it exists. For insight, they’re studying the planet’s magnetosphere. Deep inside the gas giant, the pressure is so great that the element hydrogen has been squeezed into a metallic fluid. (Atmospheric pressure is measured in bars. Pressure at the surface of the Earth is one bar. On Jupiter, it’s 2 million. And at the core it would be around 40 million bars.) The movement of this liquid metallic hydrogen is thought by scientists to create the planet’s magnetic field. By studying the field, Juno can unlock the mysteries of the core’s depth, size, density, and even whether it exists, as predicted, as a solid rocky core. “We were originally looking for a compact core or no core,” Bolton said, “but we’re finding that it’s fuzzy—perhaps partially dissolved.”

Jupiter’s magnetosphere is the second-largest structure in the solar system, behind only the heliosphere itself. (The heliosphere is the total area influenced by the Sun. Beyond it is interstellar space.) So far, scientists are dumbfounded by the strength of the magnetic field close to the cloud tops—and by its deviations. “What we’ve found is that the magnetic field is both stronger than where we expected it to be strong, and weaker where we expected it to be weak,” said Jack Connerney, the deputy principal investigator of Juno.

Another paper today in Science revealed new findings about Jupiter’s auroras. The Earth’s auroras are Sun-driven, the result of the interaction of the solar winds and Earth’s magnetosphere. Jupiter’s auroras have been known for a while to be different, and related to the planet’s rotation. Juno has taken measurements of the magnetic field and charged particles causing the auroras, and has also taken the first images of the southern aurora. The processes at work are still unknown, but the takeaway is that the mechanics behind Jupiter’s auroras are unlike those of Earth, and call into question how Jupiter interacts with its environment in space.

JUNO ALREADY HAS US REWRITING THE TEXTBOOKS


An enhanced-color closeup of swirling waves of clouds, some just 4 miles across. Some of the small, bright high clouds seem to form squall lines, or a narrow band of high winds and storms associated with a cold front. They're likely composed of water and/or ammonia ice.
NASA/SWRI/MSSS/Gerald Eichstädt/Seán Doran

Understanding Jupiter is essential to understanding not only how our solar system formed, but how the new systems being discovered around stars form and operate as well. The next close approach of Jupiter will take place on July 11, when Juno flies directly over the famed Great Red Spot. Scientists hope to learn more about its depth, action, and drivers.

Juno already has us rewriting the textbooks, and it's only at the beginning of its orbital mission. It's slated to perform 33 polar orbits of Jupiter, each lasting 53.5 days. So far, it's completed only five. The spacecraft’s prime mission will end next year, at which time NASA will have to decide whether it can afford to extend the mission or to send Juno into the heart of Jupiter, where it will be obliterated. This self-destruct plunge would protect that region of space from debris and local, potentially habitable moons from contamination.

Bolton tells Mental Floss that the surprising findings really bring home the fact that to unlock Jupiter, this mission will need to be seen through to completion. “That’s what exciting about exploration: We’re going to a place we’ve never been before and making new discoveries … we’re just scratching the surface.” he says. “Juno is the right tool to do this. We have the right instruments. We have the right orbit. We’re going to win over this beast and learn how it works.”

10 Facts About the Winter Solstice, the Shortest Day of the Year

Matt Cardy/Getty Images
Matt Cardy/Getty Images

Amid the whirl of the holiday season, many are vaguely aware of the approach of the winter solstice, but how much do you really know about it? Whether you're a fan of winter or just wish it would go away, here are 10 things to note—or even celebrate—about the shortest day of the year.

1. The winter solstice HAPPENS ON DECEMBER 21/22 in 2019.

Sun setting behind a tree in the winter
buxtree/iStock via Getty Images

The date of the winter solstice varies from year to year, and can fall anywhere between December 20 and December 23, with the 21st or 22nd being the most common dates. The reason for this is because the tropical year—the time it takes for the sun to return to the same spot relative to Earth—is different from the calendar year. The next solstice occurring on December 20 will not happen until 2080, and the next December 23 solstice will not occur until 2303.

2. The winter solstice hAPPENS AT A SPECIFIC, BRIEF MOMENT.

sun setting through the trees
yanikap/iStock via Getty Images

Not only does the solstice occur on a specific day, but it also occurs at a specific time of day, corresponding to the instant the North Pole is aimed furthest away from the sun on the 23.5 degree tilt of the Earth's axis. This is also the time when the sun shines directly over the Tropic of Capricorn. In 2019, this moment occurs at 4:19 a.m. UTC (Coordinated Universal Time) on December 22. For those on Eastern Standard Time, the solstice will occur at 11:19 p.m. on December 21. And regardless of where you live, the solstice happens at the same moment for everyone on the planet.

3. The winter solstice mARKS THE LONGEST NIGHT AND SHORTEST DAY OF THE YEAR FOR THE NORTHERN HEMISPHERE.

sun setting over Central Park
rmbarricarte/iStock via Getty Images

As most are keenly aware, daylight hours grow shorter and shorter as the winter solstice approaches, and begin to slowly lengthen afterward. It's no wonder that the day of the solstice is referred to in some cultures as the "shortest day of the year" or "extreme of winter." New York City will experience 9 hours and 15 minutes of sunlight, compared to 15 hours and 5 minutes on the summer solstice. Helsinki, Finland, will get 5 hours and 49 minutes of light. Barrow, Alaska, will not have a sunrise at all (and hasn't since mid-November; its next sunrise will be on January 22), while the North Pole has had no sunrise since October. The South Pole, though, will be basking in the glow of the midnight sun, which won't set until March.

4. ANCIENT CULTURES VIEWED THE WINTER SOLSTICE AS A TIME OF DEATH AND REBIRTH.

snow on tree branches
Eerik/iStock via Getty Images

The seeming death of the light and very real threat of starvation over the winter months would have weighed heavily on early societies, who held varied solstice celebrations and rites meant to herald the return of the sun and hope for new life. Scandinavian and Germanic pagans lit fires and may have burned Yule logs as a symbolic means of welcoming back the light. Cattle and other animals were slaughtered around midwinter, followed by feasting on what was the last fresh meat for several months. The modern Druidic celebration Alban Arthan reveres the death of the Old Sun and birth of the New Sun.

5. THE  shortest DAY of the year MARKS THE DISCOVERY OF NEW AND STRANGE WORLDS.

Pilgrims landing at Plymouth Rock
Hulton Archive/Getty Images

The Pilgrims arrived at Plymouth on December 21, 1620, to found a society that would allow them to worship freely. On the same day in 1898, Pierre and Marie Curie discovered radium, ushering in an atomic age. And on December 21, 1968, the Apollo 8 spacecraft launched, becoming the first manned moon mission.

6. THE WORD SOLSTICE TRANSLATES ROUGHLY TO "SUN STANDS STILL."

colorful sunset
a_Taiga/iStock via Getty Images

Solstice derives from the Latin scientific term solstitium, containing sol, which means "sun," and the past participle stem of sistere, meaning "to make stand." This comes from the fact that the sun’s position in the sky relative to the horizon at noon, which increases and decreases throughout the year, appears to pause in the days surrounding the solstice. In modern times, we view the phenomenon of the solstice from the position of space, and of the Earth relative to the sun. Earlier people, however, were thinking about the sun's trajectory, how long it stayed in the sky and what sort of light it cast.

7. STONEHENGE IS ALIGNED TO THE SUNSET ON the WINTER SOLSTICE.

Stonehenge sunset
jessicaphoto/iStock via Getty Images

The primary axis of the megalithic monument is oriented to the setting sun, while Newgrange, another structure built around the same time as Stonehenge, lines up with the winter solstice sunrise. Some have theorized that the position of the sun was of religious significance to the people who built Stonehenge, while other theories hold that the monument is constructed along natural features that happen to align with it. The purpose of Stonehenge is still subject to debate, but its importance on the winter solstice continues into the modern era, as thousands of hippies, pagans, and other types of enthusiasts gather there every year to celebrate the occasion.

8. ANCIENT ROMANS CELEBRATED REVERSALS AT THE MIDWINTER FESTIVAL OF SATURNALIA.

Saturnalia parade
A Saturnalia celebration in England in 2012.
Christopher Furlong/Getty Images

The holiday, which began as a festival to honor the agricultural god Saturn, was held to commemorate the dedication of his temple in 497 BCE. It quickly became a time of widespread revelry and debauchery in which societal roles were overturned, with masters serving their slaves and servants being allowed to insult their masters. Mask-wearing and play-acting were also part of Saturnalia's reversals, with each household electing a King of Misrule. Saturnalia was gradually replaced by Christmas throughout the Roman Empire, but many of its customs survive as Christmas traditions.

9. SOME TRADITIONS HOLD THAT DARK SPIRITS WALK THE EARTH ON THE WINTER SOLSTICE.

Snowy woods
Serjio74/iStock via Getty Images

The Iranian festival of Yalda is celebrated on the longest night of the year. In pre-Islamic times, it heralded the birth of Mithra, the ancient sun god, and his triumph over darkness. Zoroastrian lore holds that evil spirits wander the Earth and the forces of the destructive spirit Ahriman are strongest on this long night. People are encouraged to stay up most of the night in the company of one another, eating, talking, and sharing poetry and stories, in order to avoid any brushes with dark entities. Beliefs about the presence of evil on the longest night are also echoed in Celtic and Germanic folklore.

10. SOME THOUGHT THE WORLD WOULD END ON THE 2012 WINTER SOLSTICE.

snowy woods with sun through the trees
Delpixart/iStock via Getty Images

December 21, 2012 corresponds to the date 13.0.0.0.0 in the Mesoamerican Long Count calendar used by the ancient Maya, marking the end of a 5126-year cycle. Some people feared this juncture would bring about the end of the world or some other cataclysmic event. Others took a more New Age-y view (literally) and believed it heralded the birth of a new era of deep transformation for Earth and its inhabitants. In the end, neither of these things appeared to occur, leaving the world to turn through winter solstices indefinitely, or at least as long as the sun lasts.

A version of this story originally ran in 2015.

Cats Make Facial Expressions, But Not Everyone Can Read Them

takoburito/iStock via Getty Images
takoburito/iStock via Getty Images

Science has finally confirmed what humans have suspected for centuries: Cats are inscrutable creatures prone to peculiar behavior. Some of us, however, are still capable of picking up on their subtle emotional cues, including facial expressions, without relying on clues like tails, ears, or whiskers.

This new evidence of a cat’s slightly malleable face comes from a study in the journal Animal Welfare. Researchers at the University of Guelph in Ontario, Canada, recruited 6329 participants to watch a series of 20 video clips featuring cats reacting to either a positive or negative event. A positive interaction was defined as a feline approaching a human for a treat or an owner-identified action the cat traditionally found pleasant, like climbing into a favorite spot. A negative response was when a cat was confronted with something it wanted to avoid, was prevented from going into an area or outside, or was displaying an obvious sign of distress, like growling. (Sounds were edited out.) Most clips were from YouTube, though some were submitted by veterinarians and university colleagues. Breeds with long hair that might obscure facial changes were omitted. Most respondents were cat owners, and 74 percent were women 18 to 44 years old.

Using these brief clips, the researchers asked subjects to classify the cats as exhibiting positive or negative behavior by relying only on closely cropped footage of a cat’s face. They couldn’t rely on the tail or any other body language. The result? The average score was just 59 percent correct, accurately identifying a cat’s mood in an average of 12 out of the 20 clips. These humans, in other words, had little idea what a cat was experiencing based solely on their faces.

So why do researchers think they have any expression at all? Roughly 13 percent of subjects scored well on the test, getting at least 15 of the 20 questions correct. Those that did well were generally people who had extensive experience with cats, like veterinarians. That led researchers to conclude that people can become more attuned to the subtle flickers of emotion that may pass over a cat’s face.

“They could be naturally brilliant, and that’s why they become veterinarians,” Georgia Mason, a behavioral biologist and the study’s senior author, told The Washington Post. “But they also have a lot of opportunity to learn, and they’ve got a motivation to learn, because they’re constantly deciding: Is this cat better? Do we need to change the treatment? Does this cat need to go home? Is this cat about to take a chunk out of my throat?”

The paper appears to offer encouraging evidence that “cat whisperers” really do exist. If you’re curious whether you could be one of them, you can take a shortened version of the video test online.

[h/t Washington Post]

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