Europlanet Science Congress 2022
Palacio de Congresos de Granada, Spain
18 – 23 September 2022
Europlanet Science Congress 2022
Palacio de Congresos de Granada, Spain
18 September – 23 September 2022
EPSC Abstracts
Vol. 16, EPSC2022-802, 2022
Europlanet Science Congress 2022
© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

Jupiter Ammonia Absorption Imaging: Highlights 2020-21

Steven M Hill1 and John Rogers2
Steven M Hill and John Rogers
  • 1United States of America (
  • 2British Astronomical Association, London, UK


As a potential pro-am complement to professional Jovian ammonia observations, continuum-divided 645 nm ammonia absorption observations were made using a small telescope. This paper presents highlights of observations during 2020 and 2021. If this low-cost technique can be promulgated among amateurs, then routine atmospheric monitoring of Jupiter would reach a new level of sophistication.


New microwave and MIR observations, along with models, reveal much about Jupiter's ammonia cycle at depth. For example, the Juno MWR instrument permits the retrieval of the average ammonia abundance to a depth of 100 bar [1]. Additional recent work has used MIR observations to probe to depths of several bars [2-3]. Similarly, there have been efforts at global retrievals using hyperspectral imaging in the optical and NIR [4-5]. Complementing these efforts have been notable improvements in the understanding of the ammonia optical and NIR absorption bands [6]. Slit spectrometry data extend an already long record [7]. Finally, recent work has shown the efficacy of imaging Jovian upper tropospheric features in the 645 nm ammonia absorption band [8], which the current paper expands upon.


Thirty-nine usable observing sessions were carried out during 2020-2021 from the author’s observatory in Denver, Colorado. Fig. 1 shows the observations versus System I longitude. It also depicts Juno perijoves. During July and September 2020 observations overlap with the longitudes observed by Juno on PJ28 and PJ29. The best adjacent observations in 2021 occurred in October (PJ37). Also, near Juno perijove (PJ36), the System 1 longitude range of 140-180 degrees was observed multiple times. This allows for observing the evolution of features in the Equatorial Zone (EZ).

Figure 1: Observing sessions in 2020 (bottom) and 2021 (top). Individual images contributing to ammonia absorption observations are shown (CMOS: blue; CCD: orange). Juno perijove longitudes (Sys. 1) and Earth-facing central meridians (Sys. 1) at perijove are indicated in black and red respectively.


Fig. 2 shows the NEB has reduced ammonia absorption, the EZ is enhanced, and the GRS is reduced. Note the correlation and lack of correlation with obvious visible features. There is a reduction correlated with the GRS, but the reduced absorption region from about 15-25N includes both bright and dark features.