March 15, 2013
Hot Spots In Jupiter’s Atmosphere Ride A Merry-Go-Round
Watch the video “Jupiter´s Hot Spots”
Brett Smith for redOrbit.com - Your Universe Online
Planetary scientists at NASA have found that a weather phenomenon also found in Earth´s atmosphere is responsible for the activity of so-called ℠hot spots´ slightly bigger than North America drifting across Jupiter´s atmosphere.
Using images taken by NASA's Cassini spacecraft as it passed Jupiter en route to Saturn, scientists have determined that hot pockets of gas in Jupiter's atmosphere are created by a Rossby wave, an upper atmospheric phenomenon that also drives weather patterns on Earth. According to the NASA team´s report in the journal Icarus, the waves are not only responsible for creating the hot spots but also for moving them around the planet as well as up and down through layers of the atmosphere, similar to the motion of a horse on a carousel.
"This is the first time anybody has closely tracked the shape of multiple hot spots over a period of time, which is the best way to appreciate the dynamic nature of these features," said the study's lead author David Choi, from NASA's Goddard Space Flight Center in Greenbelt, Maryland.
To gain a better understanding of how the hot spots behave, the team created time-lapse movies from Cassini images taken during its pass of Jupiter in 2000. Covering about two Earth months, the movies focus on a particular line of hot spots located bout 7 degrees north of the giant planet´s equator. The team examined the daily and weekly shifts in the hot spots´ sizes and shapes.
The team´s findings expand on the data collected from NASA´s Galileo mission, which dropped a probe directly into a hot spot in Jupiter´s atmosphere in 1995. The Galileo mission provided the only direct evidence NASA scientists have gathered from the solar system´s largest planet.
"Galileo's probe data and a handful of orbiter images hinted at the complex winds swirling around and through these hot spots, and raised questions about whether they fundamentally were waves, cyclones or something in between," said co-author Ashwin Vasavada, a researcher at NASA's Jet Propulsion Laboratory in Pasadena, Calif.
"Cassini's fantastic movies now show the entire life cycle and evolution of hot spots in great detail,” added Vasavada, who was on the Cassini flight team when the ship passed Jupiter in 2000.
From the Cassini movies, the researchers were able to visualize and track the winds in and around each hot spot. They noticed how spiraling vortices within Jupiter´s atmosphere merge with the hot spots and tracked the movements of smaller, cirrus-type clouds that interact with the spots.
Through these observations, the team was able to measure the true wind speed of the jet stream that carried the hot spots around the planet: about 300 to 450 mph. Within the fast paced jet stream, the hotspots were dragged along at a slower pace of about 225 mph.
The observations of the Cassini images and the calculations of the atmospheric speeds led the team to determine that a Rossby wave was responsible for the hotspots´ activity. The researchers said these findings will help them to understand how the rest of Jupiter´s atmosphere is constructed.