A team of astronomers has obtained what they say the most detailed radio map yet of the atmosphere of Jupiter, the largest planet in the solar system.
By using the upgraded Karl G. Jansky Very Large Array (VLA) radio astronomy observatory in New Mexico to measure radio emissions from Jupiter’s atmosphere in wavelength bands where clouds are transparent, the astronomers have revealed the massive movement of ammonia gas that underlies the colorful bands, spots and whirling clouds visible to the naked eye.
Reporting in the latest issue of the journal Science, published on June 3, the researchers say they were able to see as deep as 100 kilometers below the cloud tops, as they measured the amount of absorption of thermal radio emissions by ammonia gas.
“We in essence created a three-dimensional picture of ammonia gas in Jupiter’s atmosphere, which reveals upward and downward motions within the turbulent atmosphere,” said principal author Imke de Pater, a professor of astronomy at University of California, Berkeley, adding that the map bears a striking resemblance to visible-light images taken by amateur astronomers and the Hubble Space Telescope.
The observations were made over the entire frequency range between 4 and 18 gigahertz, or wavelength between 1.7 and 7 centimeters. And the spatial resolution of the map, 1,300 kilometers, is the best ever achieved.
The map shows ammonia-rich gases rising into and forming the planet’s upper cloud layers: an ammonium hydrosulfide cloud at a temperature near 200 degrees Kelvin, or about minus 73 degrees Celsius; and an ammonia-ice cloud in the cold air of about 160 degrees Kelvin, or minus 113 degrees Celsius. It also shows ammonia-poor air sinking into the planet, and ammonia-poor hotspots that encircle the planet like a belt just north of the equator.
“With radio, we can peer through the clouds and see that those hotspots are interleaved with plumes of ammonia rising from deep in the planet, tracing the vertical undulations of an equatorial wave system,” said Michael Wong, a UC Berkeley research astronomer and a co-author of the study.
The U.S. National Aeronautics and Space Administration (NASA)’s Juno spacecraft is scheduled to arrive at Jupiter on July 4 and measure the amount of water in the deep atmosphere where the VLA observatory looked for ammonia. Noting that her team will observe Jupiter with the VLA at the same time as Juno’s microwave instruments are probing for water, de Pater said “maps like ours can help put their data into the bigger picture of what’s happening in Jupiter’s atmosphere.”
Built in 1973 through 1980 with 27 radio telescopes, each with a 25-meter antenna, in a Y-shaped array, the VLA observatory received an upgrade that lasted a decade and improved its sensitivity by a factor of 10. (Xinhua)