We don’t have high-resolution pictures of Jupiter from the Juno mission yet, but we do have JunoCam in operation. It’s a color camera working in visible light that has returned data following the spacecraft’s arrival at Jupiter on July 4. This JPL news release tells us that JunoCam was folded into the mission as part of NASA’s public outreach. It is not, in other words, considered a science instrument, and we’ll need to wait until late August for the first high-resolution images. Still, it’s satisfying to see that all is apparently well in Jupiter space.

Image: This color view from NASA’s Juno spacecraft is made from some of the first images taken by JunoCam after the spacecraft entered orbit around Jupiter on July 5th (UTC). The view shows that JunoCam survived its first pass through Jupiter’s extreme radiation environment, and is ready to collect images of the giant planet as Juno begins its mission. Credit: NASA/JPL-Caltech/SwRI/MSSS.

Here we’re about 4.3 million kilometers from Jupiter on the outbound leg of the initial 53.5-day capture orbit, a view that yields atmospheric features including the Great Red Spot, along with three of the Galilean moons. Io, Europa and Ganymede appear from left to right in the image. Bear in mind that as the mission progresses, Juno will at times close to within 4100 kilometers of the cloud tops. Spectacular high-resolution views are ahead.

The View from Ceres

We might well find ice deposits on the surface of Ceres. That’s the word from researchers with the Dawn mission, who have been looking at permanently shadowed areas on the dwarf planet. Areas like these are generally on a crater floor or along a part of the crater wall facing the pole. With temperatures below -151 degrees Celsius (122 K) these areas become cold traps, where water ice can accumulate and remain stable for a billion years.

“The conditions on Ceres are right for accumulating deposits of water ice,” said Norbert Schorghofer, a Dawn guest investigator at the University of Hawaii at Manoa. “Ceres has just enough mass to hold on to water molecules, and the permanently shadowed regions we identified are extremely cold — colder than most that exist on the moon or Mercury.”

Image: At the poles of Ceres, scientists have found craters that are permanently in shadow (indicated by blue markings). Such craters are called “cold traps” if they remain below about minus 151 degrees Celsius. These shadowed craters may have been collecting ice for billions of years because they are so cold. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA.

Using computer modeling in conjunction with Dawn’s camera imagery, Schorghofer and colleagues could analyze surface features in great detail, learning which areas receive direct sunlight and how changes during the course of a year on Ceres (1680 days) affect the solar radiation reaching the surface. Dozens of permanently shaded regions turned up in the northern hemisphere, the largest (inside a 16-kilometer crater) less than 65 kilometers from the north pole. Altogether, these regions make up about 1800 square kilometers.

As opposed to the Moon and Mercury (which, like Ceres, have a very small spin axis tilt, or obliquity), the cold trap regions on Ceres extend much further toward the equator. The permanently shadowed regions have to be close to the poles on the Moon and Mercury to get cold enough for ice to remain stable. But like Mercury, these areas account for about the same fraction — less than one percent — of the surface area of the northern hemisphere, and most of these areas on Ceres are cold enough to serve as efficient cold traps for water ice.

All of this has useful implications if we’re thinking ahead to one day exploiting Ceres’ resources:

“While cold traps may provide surface deposits of water ice as have been seen at the moon and Mercury, Ceres may have been formed with a relatively greater reservoir of water,” said Chris Russell (UCLA), principal investigator of the Dawn mission. “Some observations indicate Ceres may be a volatile-rich world that is not dependent on current-day external sources.”

It’s also interesting to note that we don’t know the origin of the ice in the cold traps of either Mercury or the Moon. A possible source is incoming comets, meteorites or interplanetary dust particles, but as the paper on this work notes, we might also find ice generated from solar wind interactions (a mechanism not fully understood) or even outgassing. We would expect, however, that solar wind-generated water resources would be less common with greater distance from the Sun, while infalling H₂O would be higher on Ceres than on Mercury because of Ceres’ location in the asteroid belt. Which leads us, the paper notes, to a way to investigate further:

…the trapping efficiency on Mercury and Ceres are similar; that is, for the same number of generated water molecules per surface area, the thickness of the ice accumulating in the cold traps should be almost as high on Ceres than on Mercury. Hence, significant differences in the thickness of young ice deposits may reveal the main source of water. A lack of ice deposits in Cerean cold traps would suggest that infall is not a major source of this ice, consistent with a solar wind generation mechanism on Mercury.

We can, the paper argues, expect fresh and perhaps optically bright ice deposits in the cold traps of Ceres, even without any further water delivery. The authors calculate that about 1 out of every 1000 water molecules generated on the surface of Ceres will wind up in a cold trap during a Cerean year. The upshot: Thin but detectable ice deposits over a 100,000 year period.

The paper is Schorghofer et al., “The permanently shadowed regions of dwarf planet Ceres,” Geophysical Research Letters 6 July 2016 (full text). A JPL news release is also available.