Tag: Juno

A global map of Io’s lava lakes. Click for original figure.

Based on data and imagery produced by the Jupiter orbiter Juno as it made a series of fly-bys of the moon Io from 2022 to 2024, scientists have now mapped at least 40 lava lakes amid the numerous volcanoes on the planet. The map above, figure 2 of the paper, shows their location and approximate relative size across Io’s surface. From the paper’s abstract:

Recent observations from the Juno spacecraft have revealed at least 40 lava lakes on Io, one of Jupiter’s moons, using the JIRAM (Jovian InfraRed Auroral Mapper) imager. Most of the large depressions on Io, known as paterae, show signs of heat, indicating that lava lakes are common. The lava lakes vary in size from 10 to 100 km in diameter and have a thin crust, about 5–10 m thick, that appears to be a few years old. The heat observed mainly comes from the larger crust, not the small exposed lava, so it is hard to measure the total heat output from just the thermal data. Additionally, eight of these lava lakes are new discoveries and were not previously known as active hotspots.

One aspect of these lakes found repeatedly in this new data is that their lava appears to rise and fall as a unit, as if the lake’s floor bed acts like a huge piston pushing the whole lake up and down from below, rather than lava entering in or draining out from a central vent. This conclusion appears to settle the debate between these models for explaining why the lava almost never rises high enough to pour out from the lake. Instead, the lakes themselves appear to be stable features, not volcanic calderas from which lava flows to build a mountain.

Click for original image.

The uncertainty of science: Using the JIRAM infrared camera on the Jupiter orbiter Juno, scientists have now created a global map of volcanic activity, showing where it appears the hottest and greatest activity is located.

That data is illustrated by the graphic to the right, taken from figure 1 of the paper. The top row shows the coverage of the planet, with Io’s southern hemisphere getting the fewest observations. The bottom row shows the observed regions with the greatest heat. This quote from the abstract is most revealing:

Using JIRAM, we have mapped where volcanoes are producing the most power and compared that to where we expect higher heat flow from the interior models. Our map doesn’t agree with any of these models very well. JIRAM observed more volcanic activity at the poles than we expected to see based on previous observations. However, since the south pole was only observed twice, it’s possible that these observations don’t represent the average volcanic activity of the south pole. Very bright volcanoes that may have been continuously active for decades were also imaged during these Juno fly-bys, some of which are nearer the poles than the equator.

The conflict between the data and the theories could very well be explained simply by the short term nature of these observations. The models could very well be right, over centuries. For example, the new volcano discovered by Juno is near the equator, suggesting with time those models will turn out to be correct.

Or not. A lot more observations will have to be made of Io before any model of its volcanic activity can be considered trustworthy.

Click for full image.

The Jupiter orbiter Juno successfully completed its 58th close fly-by of the gas giant, during which it also made its closest approach to the volcanic moon Io, zipping past at a distance of 932 miles. The image of Io to the right, cropped and reduced to post here, was taken at that closest Io approach, and shows a mountain on the horizon as well as a large shield volcano in the center (the dark splotch), with a major lava flow to the south. The picture was processed by citizen scientist Brian Swift.

Another image, processed by Björn Jónsson, shows the differences at one volcano dubbed Loki between the December 30, 2023 and the February 3, 2024 flybys. It appears that the brightness of the apron of lava that surrounds the volcano changes significantly depending on the lighting and the angle of view. In December it was almost black. In February it was greyish silver, almost shiny.

Another image, processed by Andrea Luck, captured faint eruption plumes on Io’s edge, caused by an ongoing eruption just beyond the horizon.

Juno still has four more flybys of Io coming up, but none will be as close as the February 3rd approach.

For original global image go here. For original of inset go here.

The first raw Juno images taken of the Jupiter moon Io during its close fly-by on December 30, 2023, the closest in more than twenty years, have been released by the science team and citizen scientists have begun processing them.

The global picture to the right, rotated and reduced to post here, was processed by Kevin Gill. The inset of the volcanic mountains near the terminator was processed by Thomas Thomopoulos. As he notes, to obtain better detail he enhanced the colors and image and then zoomed in.

In the inset, note the northeast flows coming off the two mountains near the center. With the lower mountain, this flow appears to lie on top of a larger flow that extended out almost to the mountain to the right.

Io is a planet of continuous volcanic activity. For example, when the global image above was taken, the plume of a volcano eruption was visible on the right horizon, as shown in this version, its exposure adjusted by Ted Stryk. Catching such eruptions on Io is not unusual, considering its continuous volcanic activity generated by the tidal forces the planet undergoes from its orbit around Jupiter. In fact, the very first plume was imaged in 1979 by Voyager 1 during its short fly-by, and proved a hypothesis of such activity that scientists had only published one week earlier.

On March 1, 2023 the Jupiter orbiter Juno passed within 33,000 miles of the gas giant’s moon Io, getting its first close-up images.

Several citizen scientists have processed those images. The photo to the right, cropped and reduced to post here, was created by Andrew R Brown. This particular picture was one of five taken by Juno during the fly-by. Jason Perry processed all five here, with this caption:

Most of the dark spots seen across Io’s surface are the result of volcanic eruptions. These include East Girru, a dark spot that was not seen the last time Io was seen at this resolution during the New Horizons encounter with Jupiter in February 2007. East Girru was undergoing a major eruption at the time but hadn’t had time to produce a new lava flow before the end of the week-long encounter. This small flow field, measuring 3,200 square kilometers (1,390 square miles) in size, may have also been reactivated during an eruption in October 2021, as seen by Juno JIRAM.

Another apparent surface change is at Chors Patera, which has undergone a significant reddening since Galileo last observed it in October 2001. Reddish materials on Io are indicative of the presence of short-chain sulfur and are often associated with high-temperature, silicate volcanism. Additional dark spots near the terminator, the boundary between Io’s day and night sides, are the shadows of tall mountains. The dark spot at middle right in the upper right image may be due a mountain 5500 meters (18,000 feet) tall.

The smallest object resolved in this image is about 22 miles across.