The dramatic discovery of active volcanoes on Io was made by Linda Morabito and her colleagues from this navigation picture, taken March 8 at a range from Io of 4.5 million kilometers. On the bright edge, the immense plume of volcanic ash from Pele (P₁) rises nearly 300 kilometers above the surface. At the terminator, the border between day and night on Io, a second smaller cloud from the volcano Loki (P₂) catches the sunlight. These two eruptions—captured on this single discovery photograph—are much larger than the largest terrestrial volcanic eruption known. [P-21306 B/W]
Once the existence of giant volcanic eruptions on Io was recognized, a reexamination of the Voyager 1 encounter pictures revealed many more plumes. These two views of Prometheus (P₃) were found by Joseph Veverka and Robert Strom on March 12 when they reproduced earlier pictures.
The plume is silhouetted against the black space, although it is also possible to see dark “feet” where the falling material reaches the surface. [P-21295]
The complex jets of material are clearly seen as dark streaks against the light background of the surface of Io. The plume itself rose more than 100 kilometers above Io’s surface. [P-21294]
Meanwhile, new information about Jupiter was released to the public. A long-exposure (three minutes and twelve seconds) image of the dark side of the planet, taken with the wide-angle camera while in the shadow of the planet, caught Jupiter showing off some Jovian “fireworks.” A long, broad, white streak across the picture was a visible aurora, the largest aurora ever seen—almost 29 000 kilometers long. In addition, nineteen smaller bright splotches, looking insignificant by comparison, were in reality “superbolts” of lightning. Since huge electrical discharges such as lightning can, under the right circumstances, power chemical reactions that form complex organic molecules, the discovery of lightning on Jupiter could have profound implications. Was “lightning-inspired” organic synthesis going on in Jupiter’s atmosphere? No one knew.
Returning to JPL on Sunday night, Brad Smith got his first look at the Morabito picture of the volcanic cloud. Early Monday morning, other Imaging Team scientists saw it. As soon as the JPL computers were operating, Joseph Veverka and Robert Strom began working with the two interactive TV terminals to look for evidence in other pictures of ongoing eruptions. Faint clouds or plumes would not show up in normally processed pictures, but could be brought out easily with the computer-controlled displays. By midmorning, several additional volcanic plumes had been found.
Linda Morabito shows the discovery photo of the volcanic eruptions on Io. [P-21718]