How fast does the wind blow on Jupiter? 

While east-west winds on Jupiter blow at hundreds of meters per second because of the high-speed rotation of the gas giant planet, the north-south winds creep slowly, at one meter per second, and are difficult to measure. Imagine trying to track the path of a leaf drifting lazily upward inside hurricane-force winds. That is the challenge for astronomers measuring Jupiter's atmosphere. 

New Mexico State University astronomers, collaborating with an international team of scientists, have produced the first map of the atmospheric circulation of Jupiter using Doppler spectroscopy, with help from a device set up at the Dunn Solar Telescope in Sunspot, New Mexico.

The Doppler device is called JOVIAL (Jupiter: Oscillations from Velocity Imaging At several Longitudes). 

"So far, our knowledge about wind speed on the other solar system planets is obtained by taking pictures of them at different times, and measuring how much clouds move," said Jason Jackiewicz, NMSU astronomy professor and department head. "The method is called cloud-tracking," performed from images taken by space probes such as the NASA Voyager or Cassini missions, the Hubble Space Telescope, or ground-based facilities. "The alternative technique considered by JOVIAL consists of directly measuring the atmospheric motion through the Doppler effect. This effect refers to the change of wavelength that happens when an object that emits or reflects waves (light or sound) moves fast enough with respect to the observer."

Jackiewicz, Stephen Markham, NMSU post-doctoral fellow and Clyde Tombaugh Scholar, and Cristo Sanchez, NMSU astronomy graduate student, are part of a team, led by Observatoire de la Côte d'Azur (OCA, France) with collaborators from Japan as well as other researchers in the United States and Europe. They are among 28 authors of a paper titled "Three-dimensional Atmospheric Dynamics of Jupiter from Ground-based Doppler Imaging Spectroscopy in the Visible" published in April's "Planetary Science Journal."Link here.

"This exciting technology called Doppler imaging is now being applied to giant planets from multiple telescopes around the world through this initiative,"Markham said. "A Doppler image can measure those extremely minute shifts in the frequency of light to allow us to determine these atmospheric velocities. The JOVIAL instrument is not on board the Hubble Space Telescope or any other mission that has gone to these planets. We're hoping that by using these observations, we can motivate the use of this instrument on future spacecraft missions."

The next significant improvement using the JOVIAL instruments will be when they are placed out of the Earth's atmosphere. "A game-changing setup would consist of placing a similar instrument in space because 99% of our problems can be connected to atmospheric turbulence, which alters the measurements," said François-Xavier Schmider, director of research at OCA and JOVIAL principal investigator. 

Jackiewicz has been collaborating on the project for 10 years. Markham was working with the team in France before joining NMSU. The group reached a major milestone by producing a two-dimensional zonal velocity map of Jupiter five years ago. Their recent publication provides a three-dimensional atmospheric map.

The zonal wind map agrees with results from cloud tracking, validating the Doppler spectroscopy technique. In addition to the zonal wind map, the team published maps of the meridional and vertical atmospheric motions.

The data from the JOVIAL Doppler spectroscopy provided added insight to measurements from the Hubble Space Telescope. 

"The wind measurements from the Hubble are clean and crisp and give us probably the most accurate wind measurements that we can compare to," said Sanchez. "But Hubble is limited to only two different wind components. So, this leaves a third component of winds called the vertical velocities or the radial winds that kind of circulate inwards and outwards. This is where adding our own measurements to the limited two-dimensional measurements of the Hubble Space Telescope can help us interpret this third dimension, what these vertical velocities might be." 

A key resource for this project is the historic Dunn Solar Telescope, managed by NMSU and built in Sunspot, New Mexico, in the 1960s by the U.S. Air Force. NMSU astronomers discovered it has an excellent optical quality and an optimal location to observe conditions of Jupiter at night, so they set up the device there. 

"The Dunn happens to have the characteristics that make observing Jupiter easy because Jupiter and the sun are in the same part of the sky," said Jackiewicz. "During the day, the telescope follows the sun and that's almost the same path that we can use to observe Jupiter when the sun goes down. We're fortunate to have that facility and plan to schedule a month of observations each year to do this."

The full article can be seen at https://newsroom.nmsu.edu/news/nmsu-researchers-join-france--japan-to-develop-new-jupiter-wind-map/s/daa57416-a6d4-447b-bf72-9405395969bc