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ATMOSPHERIC SCIENCES
Cassini
Cassini's high-resolution images and movies helped scientists learn even more about Jupiter's atmosphere. For example, Cassini's pictures showed that the up-and-down circulation of gases in Jupiter's clouds went in the opposite direction of what scientists had thought. And like Galileo, Cassini observed lightning.
The spacecraft also helped pave the way for Juno. Its views of Jupiter's poles helped scientists plan Juno's polar observations. Cassini's RADAR instrument demonstrated a technique called microwave radiometry that Juno will also use to map and probe Jupiter's atmosphere.
Atmospheric gases release thermal energy in the form of microwave radiation. By measuring this microwave emission, the RADAR instrument on Cassini--whose main mission is to explore Saturn--created some of the best maps ever made of Saturn's atmosphere.
Over six years exploring Saturn, it made five, high-resolution maps--specifically of the microwave emission that radiates at a wavelength of 2.2 centimeters. This particular wavelength of radiation comes from ammonia, so studying this emission allows scientists to learn how ammonia is distributed across Saturn, how ammonia clouds form, and how the atmosphere circulates around the planet.
The spacecraft also helped pave the way for Juno. Its views of Jupiter's poles helped scientists plan Juno's polar observations. Cassini's RADAR instrument demonstrated a technique called microwave radiometry that Juno will also use to map and probe Jupiter's atmosphere.
Atmospheric gases release thermal energy in the form of microwave radiation. By measuring this microwave emission, the RADAR instrument on Cassini--whose main mission is to explore Saturn--created some of the best maps ever made of Saturn's atmosphere.
Over six years exploring Saturn, it made five, high-resolution maps--specifically of the microwave emission that radiates at a wavelength of 2.2 centimeters. This particular wavelength of radiation comes from ammonia, so studying this emission allows scientists to learn how ammonia is distributed across Saturn, how ammonia clouds form, and how the atmosphere circulates around the planet.
Cassini’s microwave radiometer global maps of Saturn from five observation campaigns are shown. The black stripe in the middle is equatorial region where the rings blocked the spacecraft’s view of the atmosphere. Latitudinal bands of atmospheric turbulence appear above and below the calmer regions near the equator. In the lower map, the region dominated by the Great Northern Storm of 2011 to 12 is the prominent white area above the equator.
Cassini's maps revealed numerous discoveries about Saturn's atmosphere. For example, the RADAR instrument found stormy regions with less ammonia than its surroundings, suggesting that there were deep and broad downdrafts in the atmosphere. It found a dearth of ammonia in what's called the Great Northern Storm--an enormous swirling storm that lasted from 2010 to 2011, stretching for 190,000 miles (300,000 kilometers) around the planet. The maps also showed that the calm and quiet regions that make up most of the atmosphere were remarkably stable.