JWST solves decades-long mystery about why Saturn appears to change its spin

Saturn has puzzled scientists for many years. Measurements taken by NASA's Cassini spacecraft in 2004 suggested the planet's rotation rate was slowly changing over time—yet this should not have been possible, as a planet cannot simply speed up or slow down its spin.
Researchers now have used the most powerful space telescope ever built to answer one of the longest-standing puzzles in planetary science—why does Saturn appear to spin at a different speed depending on how you measure it? The findings, published in the Journal of Geophysical Research: Space Physics, reveal for the first time the complex patterns of heat and electrically charged particles in Saturn's aurora, and show that the entire system is driven by a self-sustaining feedback loop powered by the planet's own northern lights.
Using the James Webb Space Telescope (JWST), the team observed Saturn's northern auroral region—the equivalent of Earth's northern lights—continuously for a full Saturnian day, capturing detailed measurements that were simply not possible with any previous instrument.

By analyzing the infrared glow from a molecule called trihydrogen cation, which forms in Saturn's upper atmosphere and acts as a natural thermometer, the researchers were able to produce the first high-resolution maps of both temperature and particle density across Saturn's auroral region.
The level of detail was extraordinary. Previous measurements had errors of around 50 degrees Celsius, roughly on a par with the differences the scientists were trying to detect, and were produced by combining broad regions of the hot polar aurora. The new JWST data was ten times more accurate than previous measurements, allowing the team to map fine details of heating and cooling across Saturn's auroral region for the very first time.
What the team found was that these temperature and density patterns match remarkably well with predictions made by computer models more than a decade ago, but only if the source of heat is placed exactly where the main auroral emissions enter the atmosphere.

This means Saturn's aurora is not just a visual display—it is actively heating the atmosphere in a specific location. That localized heating drives winds, which in turn generate the electrical currents responsible for the aurora. The aurora then heats the atmosphere again, sustaining the whole cycle.
Part 1

What we are seeing is essentially a planetary heat pump. Saturn's aurora heats its atmosphere, the atmosphere drives winds, the winds produce currents that power the aurora, and so it goes on. The system feeds itself.

"For decades, we knew something strange was happening with Saturn's apparent rotation rate, but we could not explain it. We then showed it was being driven by atmospheric winds, but we still did not know why those winds existed. These new observations, made possible by JWST, finally give us the evidence we needed to close that loop."

The findings also have broader implications. The research suggests that what happens in Saturn's atmosphere directly influences conditions in its surrounding magnetosphere—the vast region of space shaped by the planet's magnetic field—which in turn feeds energy back into the system. This two-way relationship between the atmosphere and magnetosphere may help explain why the effect is so stable and long-lasting.

Tom S. Stallard et al, JWST/NIRSpec Reveals the Atmospheric Driver of Saturn's Variable Magnetospheric Rotation Rate, Journal of Geophysical Research: Space Physics (2026). DOI: 10.1029/2025ja034578

Part 2

New study uncovers mechanism explaining how obesity increases cancer risk

Obesity increases cancer risk by causing organs such as the liver, kidneys, and pancreas to enlarge primarily through an increase in cell number (hyperplasia), not just cell size. This expansion raises the number of cells susceptible to mutations, thereby elevating cancer risk. Organ size may predict cancer risk more accurately than BMI, highlighting the importance of maintaining a healthy weight early in life.

The study, published in Cancer Research,reveals a major driving force behind how obesity increases cancer risk across multiple organs.

The findings emphasize the importance of maintaining a healthy weight from early childhood and propose a potentially more accurate way than body mass index (BMI) to predict the increase in cancer risk associated with obesity.
The study reveals that excess weight doesn't just affect metabolism or hormones—it can physically enlarge organs, creating more opportunities for cancer to take hold. Understanding that process matters because it helps explain how everyday health choices can shape cancer risk years or even decades down the line."

In other words, as a person gains weight, their organs also grow in size by accumulating more cells to meet the higher energy needs of a bigger body. Having more cells boosts the odds of more DNA errors as cells divide, increasing the likelihood of cancer.
To test this hypothesis, researchers conducted a two-pronged study.
First, the team evaluated 747 adults whose weight in relationship to their height spanned the complete BMI spectrum, from underweight (18.5 BMI) all the way to severely obese (40-plus BMI). Using CT scans, the researchers measured the size of each adult's liver, kidneys, and pancreas.

This study is the first to analyze the size of multiple organs in a large cohort of individuals across the full BMI spectrum.

The scientists discovered that the organs grew larger as body weight increased. For every 5-point increase in BMI, the liver grew by 12%, kidneys by 9%, and the pancreas by 7%.

Next, the research team counted the cells in samples of kidney tissue taken from autopsies and reanalyzed biopsy data from living patients. The lab showed that more than 60% of the kidneys' growth resulted from an increase in the number of cells in the organ, a process called hyperplasia. The rest was due to individual cells growing bigger, or hypertrophy.
The new finding corrects earlier theories that larger organ size in obese individuals resulted primarily from fatter cells. Rather, obesity mainly increases the number of cells at risk for copying errors, uncontrollable growth, and potential malignancy.

This increase in organ size has harmful consequences.
The more cells in an organ, the more mutations and the greater the risk of one cell going awry during division and becoming cancerous.
Overall, the study showed a strong link between organ size enlargement and cancer risk across all three organs, confirming the mathematical predictions. The finding provides evidence for this as a major mechanism of tumorigenesis induced by obesity, in addition to factors like inflammation and hormonal imbalances.

This newly discovered effect of obesity can be large—with organs even doubling in size.

"When an organ doubles in size, it is expected to roughly double its risk of developing cancer", say the researchers.
Noting the relationship between diet and cancer, the authors emphasized the importance of maintaining a healthy weight from a young age.

Sophie Pénisson et al, Hyperplasia Functions as a Link Between Obesity and Cancer, Cancer Research (2026). DOI: 10.1158/0008-5472.can-25-2487