It hit Jupiter in 1994, but Comet Shoemaker-Levy 9 still seems to have things to teach us about the largest planet in the Solar System.
A new study of the comet’s impact findings – still moving around Jupiter’s atmosphere – has made the first direct measurement of the gas giant’s powerful stratospheric winds, in a cloudless atmosphere.
There, narrow bands of wind called jets – like Earth’s jet streams – blow at up to 400 meters per second at high latitudes. That’s around 1,440 km / h (895 mph) – well over the maximum wind speeds of around 620 km / h seen in the Great Red Spot’s cyclonal storm.
The team ‘s discovery and study suggests that these jets could be a colossal vortex, about 50,000 kilometers in diameter and 900 kilometers high.
“A vortex of this magnitude,” said astronaut Thibault Cavalié of the Laboratoire d’Astrophysique de Bordeaux in France, “would be a unique epistemological beast in our Solar System.”
The death of Comet Shoemaker-Levy 9 was one of the most dramatic events we have ever seen in the Solar System. First, as the frozen rock moved near Jupiter, it was torn apart by the massive drag of the planet.
The fragments spent two years on Earth in closer and closer orbit, until finally, in July 1994, they hit Jupiter’s atmosphere in a lively display of fireworks.
To scientists, it was a wonderful gift. The effect was churning out Jupiter’s atmosphere, revealing new molecules and shaking Jupiter’s surface for months. This allowed me to measure wind speed and new studies of Jupiter’s atmospheric fusion, as well as its magnetic field.
The comet’s influence also added new molecules that were not already present to Jupiter. These included ammonia – which disappeared within a few months – and hydrogen cyanide, which can still be seen in the Jovian stratosphere to this day.
This hydrogen cyanide was discovered by a team of scientists using 42 of the 66 antennas of the Atacama Large Millimeter / Submillimeter Array in Chile. Using this powerful instrument, astronomers observed the Doppler movement of hydrogen cyanide – the way in which the electromagnetic wavelength of the molecule propagates or shortens as it moves away from or to the viewer.
“By measuring this movement, we were able to reduce the wind speed as one passing train speed could be reduced by the change in the frequency of the train whistle,” the person said. Vincent Hue planetary scientist from the Southwestern Research Institute in the USA.
Studying the length of these movements will allow scientists to work out how fast the hydrogen cyanide is moving.
Around the planet’s equator, strong stratospheric wind jets blow at average speeds of about 600 kilometers per hour. All the time. Here on Earth, the highest wind speed ever recorded was 407 km / h (253 mph), and that was at the time of a wild tropical bike ride.
One of the most interesting jets, however, was found just below Jupiter’s permanent auroral oval, hundreds of kilometers below the auroral winds. It was clockwise in the north and counterclockwise in the south, at speeds of up to 300 to 400 meters per second. The team believes this jet is the lowest tail of the auroral wind.
Previous studies had predicted that the auroral winds would decrease in strength as the altitude subsided, spreading before reaching the stratosphere, so this was a surprise – a beautiful display of the multi- unprecedented atmospheric complexity in an already known planet that was atmospherically complex.
And it sets the stage for future ideas from upcoming missions, such as the European Space Agency’s JUpiter ICy moons Explorer (JUICE) probe, and the massive Telescope under construction right now.
“These ALMA results open a new window for the study of Jupiter’s auroral regions,” Cavalié said.
The research was published in Astronomy & Astronomy.