Temporal evolution of the color of Jupiter’s storm Oval BA

From 1998 to 2000, three white anticyclonic storms in Jupiter’s South Temperate Belt merged to form the single storm Oval BA. This new storm maintained the white color of the storms from which it formed until late 2005 when it began to redden. The new red color was confirmed by amateur astronomers and Hubble Space Telescope observations in late 2005 and 2006. Starting in 2008, Oval BA began gradually lightening back to white, appearing first as a white core surrounded by a red collar and then completely lightening back to white within the past year. Images taken by the Hubble Space Telescope in 2019 for the Outer Planet Atmospheres Legacy (OPAL) program show that Oval BA now appears to be nearly as white as when it first formed. In this work, we report on the analysis of hyperspectral image cubes of Jupiter obtained with the NMSU Acousto-Optic Imaging Camera (NAIC) on the Astrophysical Research Consortium’s 3.5 meter telescope at Apache Point Observatory. These hyperspectral image cubes were acquired in support of the Juno mission, providing observations that are complementary to those acquired by Juno. During Juno’s perijove passes of Jupiter, Juno passes over a narrow range of longitudes and is unable to capture the whole planet. The NAIC image cubes are taken at the same time as Juno’s perijove passes and capture the full disk of Jupiter, providing contextual data for Juno’s high spatial resolution imagery. The NAIC image cubes span the wavelengths 470 nm to 950 nm, covering the optical and very near infrared, with images taken every 2 nm, yielding 241 unique images of Jupiter in each image cube. The image cubes used in this work were acquired on the night of May 27, 2019 which corresponds to the 20th perijove pass made by Juno. Using these image cubes, we will characterize the optical spectrum of Oval BA in its re-whitened state. This will allow us to compare Oval BA’s current spectrum to that during its reddened state, thereby establishing the temporal evolution of the color of this storm feature. This will provide important inputs for radiative transfer modeling, allowing us to simulate the cloud structure within Oval BA and its temporal evolution.