JunoCam Captures Dynamics of Jupiter’s Great Red Spot


A camera on the Juno spacecraft has returned stunning high-resolution images of Jupiter’s Great Red Spot. What can we learn about the properties of this long-lived storm?

A Dramatic Storm

Great Red Spot Hubble

The Great Red Spot, as imaged by Hubble in 2017. [NASA/ESA/A. Simon (GSFC)]

Jupiter’s Great Red Spot, an exceptionally long-lived storm churning south of Jupiter’s equator, has been observed continuously for nearly two centuries. Though this atmospheric vortex is the largest and longest-lived of any planet in our solar system, our observations suggest that the Great Red Spot is gradually shrinking: the major axis of the ellipse was ~21° in longitude 40 years ago, and only ~14° in the last few years. Some studies suggest the Great Red Spot may even vanish within the next 20 years.

Our current understanding of the morphology of this storm comes primarily from detailed observations by spacecraft since 1979 — first by the two Voyager spacecraft as they flew by, then by the Galileo orbiter, and then by the Hubble Space Telescope. These past observations have ranged in resolution from about 15 to 150 km per pixel. Now, since the 2016 arrival of the Juno spacecraft in orbit around Jupiter, there’s a new player in town: JunoCam.

cloud-top morphologies

Identification of different Great-Red-Spot features and winds. See article text for label descriptions. [Adapted from Sánchez-Lavega et al. 2018]

JunoCam: Public Outreach and Science

JunoCam is a visible-light camera with a 58° field of view. The camera scans as the spacecraft rotates, producing images with resolution down to 7 km per pixel in some areas! JunoCam’s remarkable photos of Jupiter’s atmospheric patterns — taken as Juno skims just thousands of kilometers above Jupiter’s cloud tops — have certainly drawn the public eye. But though JunoCam’s primary intent is as a tool for public engagement, its images can serve a scientific purpose as well.

In a new study, a team of scientists led by Agustín Sánchez-Lavega (University of the Basque Country, Spain) have used the unprecedented detail of JunoCam’s observations to examine the various cloud morphologies inside the Great Red Spot.

Rich Dynamics

Great Red Spot features

Close views of the five features the authors identify within the Great Red Spot cloud tops. Click to enlarge. [Adapted from Sánchez-Lavega et al. 2018]

Sánchez-Lavega and collaborators identify five particular morphologies within the cloud tops of the Great Red Spot:

  1. Compact cloud clusters
    Several groups of compact clouds resemble altocumulus clouds observed on Earth. These may suggest condensation of ammonia.
  2. Mesoscale waves
    Interfering trains of wave packets indicate stable conditions in this region.
  3. Spiraling vortices
    A large eddy of ~500 km in radius suggest a region of intense horizontal wind shear.
  4. Central turbulent nucleus
    The red nucleus of the Great Red Spot spans ~5,200 km in length (that’s about 40% of Earth’s diameter) and ~3,150 km in width.
  5. Large dark thin filaments
    Undulating dark gray filaments 2,000–7,000 km in length circulate at high speeds around the outer park of the vortex. These may be darker aerosols or represent areas with different altitudes.

The team’s measurements of the overall wind field in the Great Red Spot demonstrate that though the Spot may be dramatically shrinking, its wind field has shown little change over 40 years of observation. The rich variety of morphologies we’re seeing therefore likely represents just the top of a dynamical system with a much deeper circulation.

We can’t wait to see what else JunoCam reveals during the Juno mission!


“The Rich Dynamics of Jupiter’s Great Red Spot from JunoCam: Juno Images,” A. Sánchez-Lavega et al 2018 AJ 156 162. doi:10.3847/1538-3881/aada81

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