It collided with Jupiter in 1994, but comet Shoemaker-Levy 9 still seems to have yet to teach us things about the largest planet in the solar system.
A new analysis of the traces of the comet’s impact, which still increases Jupiter’s atmosphere, has given the first direct measure of the gas giant’s strong stratospheric winds, in the middle layer of the cloudless atmosphere.
There, narrow bands of wind known as air jets, such as Earth’s lightning currents, blow up to 400 meters per second at high latitudes. This is about 1,440 kilometers per hour (895 mph), greatly exceeding the maximum wind speed of about 620 km / h seen in the cyclone storm of the Great Red Spot.
Equipment detection and analysis suggest that these jets could act as a colossal vortex, about 50,000 kilometers in diameter and 900 kilometers high.
“A vortex of this size,” said astronomer Thibault Cavalié of the Laboratoire d’Astrophysique de Bordeaux in France, “would be a unique weather beast in our solar system.”
The death of comet Shoemaker-Levy 9 was one of the most spectacular events we have ever seen in the solar system. First, as the icy rock approached Jupiter, it was broken by the planet’s immense gravitational pull.
The fragments spent two years on Earth in ever closer orbit, until finally, in July 1994, they collided with Jupiter’s atmosphere in a fascinating display of fireworks.
The 1994 Impact of Shoemaker-Levy 9. (ESO)
For scientists, it was an amazing gift. The impact dropped Jupiter’s atmosphere, revealing new molecules and marking Jupiter’s surface for months. This made it possible to measure wind speed and make new studies on the atmospheric composition of Jupiter, as well as its magnetic field.
The impact of the comet also added new molecules that were not yet present on Jupiter. These include ammonia, which disappeared a few months later, and hydrogen cyanide, which can still be detected in the Jovian stratosphere to this day.
It was this hydrogen cyanide that a team of scientists tracked using 42 of the 66 antennas in the Atacama Large Millimeter / Submillimeter Array matrix in Chile. Using this powerful instrument, astronomers observed the Doppler displacement of hydrogen cyanide: the way the wavelength of the molecule’s electromagnetic emission lengthens or shortens depending on whether it moves away from the observer or towards him.
“By measuring this displacement, we were able to deduce the speed of the winds in the same way that we could deduce the speed of a train going through the change in the frequency of the train’s whistle,” said planetary scientist Vincent Hue of Southwest Research Institute in the US.
Analyzing the duration of these displacements allows scientists to calculate the rate at which hydrogen cyanide moves.
Around the planet’s equator, strong stratosphere wind gusts blow at average speeds of about 600 kilometers per hour. All the time. Here on Earth, the maximum wind speed ever recorded was 407 km / h (253 mph), and it was during a wild tropical cyclone.
One of the most intriguing rays, however, was found directly beneath Jupiter’s permanent auroral oval, a few hundred miles 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 ray is the lower tail of the auroral wind.
Previous studies had predicted that auroral winds would decrease in strength as altitude decreased, dissipating before reaching the stratosphere, so it was a surprise: a beautiful demonstration of the invisible atmospheric complexity on a planet. which we already knew was incredibly complex atmospherically.
And it lays the groundwork for future observations of upcoming missions, such as the European Space Agency’s JUpiter ICy moons Explorer (JUICE) spacecraft and the Extremely Large Terrestrial Telescope under construction.
“These ALMA results open a new window for the study of Jupiter’s auroral regions,” Cavalié said.
The research has been published in Astronomy and astrophysics.