Webb Telescope Targets Jupiter's moons Callisto and IO

Jupiter's and its four largest moons Io, Europa, Ganymede and Callisto, shown from top to bottom. Credit: NASA

November 18, 2022

This week James Webb Space Telescope has spent several hours observing Jupiter and its moons Callisto and IO. The Mikulski Archive for Space Telescopes at the Space Telescope Science Institute (STScI), the science operations hub for Webb, houses all of these data. However, it takes time for these fascinating new discoveries to progress from unpublished, peer-reviewed science to published publications.

The third largest moon in our solar system, Callisto is the second largest moon orbiting Jupiter. It is comparable in size to Mercury. Callisto was once viewed by some scientists as an uninteresting "ugly duckling moon" and a "hunk of rock and ice." That's because there didn't seem to be anything going on in the crater-covered world—nothing like active volcanoes or moving tectonic plates. Data from NASA's Galileo satellite, however, showed that Callisto might be hiding a salty ocean beneath its surface. That discovery added the once-seemingly-dead moon to the list of planets that might contain life. James Webb Telescope is scheduled to observe Callisto on November 15, 2022.

Io is a vibrant object. Io, the nearest giant moon to Jupiter, experiences entire surface lava inundations every few thousand years and experiences the highest level of volcanic activity of any moon in the solar system. The black and red material is likely less than a few years old and correlates to the most recent volcanic eruptions. The side of Io that is constantly facing away from Jupiter is shown in this photograph taken by the robotic spacecraft Galileo. Although the colors in this image have been changed to increase contrast, they are actually composite images of infrared, green, and violet light. James Webb Telescope is scheduled to observe IO on November 15, 2022.

New scientific discoveries are examined by professionals as part of a well-established quality-control process before being published in a journal. When a scientist or group of scientists completes a research of a certain celestial object and submits their written findings for publication to an established journal, the peer review process gets started. The manuscript will subsequently be distributed by the journal's editors to other researchers in the same field in order to get their reviews and input. Only papers that goes through this process and are accepted for publication in the journal; these papers must also adhere to sound scientific standards and acknowledge and build upon prior studies. Before releasing scientific findings with the general public, NASA relies on this peer-review procedure to guarantee their quality and correctness. It will be exciting to see what additional details James Webb Telescope will provide on Jupiter and its moons Callisto and IO.