Space

Hubble Captures Volcanic Eruption Plume From Io.

Io is the innermost of the four Galilean moons of the planet Jupiter. It is the fourth-largest moon, has the highest density of all the moons, and has the least amount of water of any known astronomical object in the Solar System.

Saturn hexagonal polar jet stream is the shining feature of almost every view of the north polar region of Saturn. The region, in shadow for the first part of NASA's Cassini mission, now enjoys full sunlight, which enables Cassini scientists to directly image it in reflected light.

Although the sunlight falling on the north pole of Saturn is enough to allow us to image and study the region, it does not provide much warmth. In addition to being low in the sky (just like summer at Earth's poles), the sun is nearly ten times as distant from Saturn as from Earth. This results in the sunlight being only about 1 percent as intense as at our planet. This view looks toward Saturn from about 31 degrees above the ring plane.

The image was taken with the Cassini spacecraft wide-angle camera on Jan. 22, 2017 using a spectral filter which preferentially admits wavelengths of near-infrared light centered at 939 nanometers. The view was obtained at a distance of approximately 560,000 miles (900,000 kilometers) from Saturn.

Bleriot Propeller Close-up



This view from NASA's Cassini spacecraft shows Cassini's best image of the propeller feature known informally as Bleriot. The propeller is named after Louis Bleriot, the French engineer and aviator who in 1909 was the first person to fly across the English Channel.

This is the third and final propeller to be targeted for a close flyby observation during Cassini's ring-grazing orbits (the period from Nov. 2016 to April 2017 when Cassini's orbit passed just outside the main rings). Because propellers are seen in the outermost parts of the main rings, the ring-grazing orbits provided Cassini's best opportunity to see them up close.

Many small, bright specks and linear, scratch-like artifacts are visible in the image. These artifacts are due to cosmic rays and particles of radiation near the planet striking the camera detector during the exposure. Bleriot is the largest of the propellers in Saturn's rings. The wavy features embedded in the propeller structure indicate that its central moonlet is some 60 percent wider than that of Santos-Dumont, which means the Bleriot moonlet is about four times more massive. Cassini scientists have been tracking the orbit of this object for the past decade, tracing the effect that the ring has upon it. Because it is the biggest propeller, it is more easily seen in lower-resolution images than other propellers, and thus it can be spotted in the most images by far.

Here, as Cassini moved in close to the rings as part of its ring-grazing orbits, it was able to obtain this extreme close-up view of the propeller, which enables researchers to examine its effects on the ring as never before. These views, and others like them, will inform models and studies in new ways going forward. This image was taken on the unilluminated side of the rings, where sunlight filters through the backlit ring. Like a frosted window, Saturn's rings look different depending on whether they are seen fully sunlit or backlit. On the lit side, the rings look darker where there is less material to reflect sunlight. On the unlit side, some regions look darker because there is less material, but other regions look dark because there is so much material that the ring becomes opaque.

Most dramatically in this image, a dark band cuts deeply through the middle of Bleriot's propeller. It is much more prominent than the similar dark band in the unlit-side image of the Santos-Dumont propeller, indicating that Bleriot stirs up the ring particles to much higher densities than does Santos-Dumont. The dark bands are regions where the density is so high that the ring becomes opaque to the sunlight filtering through the rings.

As in Cassini's other propeller close-up images, the central moonlet itself seems to be obscured by the stirred-up ring material around it, so that it cannot be directly seen. It would be about three pixels across, and lies at the center of the propeller structure.

The image was taken using the Cassini spacecraft's narrow-angle camera on April 12.

Aboard the International Space Station (ISS), the Russian Lada greenhouse provides home to an experiment that investigates plant development and genetics. Space grown peas have dried and "gone to seed."

The crew of the ISS will soon harvest the seeds. Eventually some will be replanted onboard the ISS, and some will be returned to Earth for further study.

Putting Martian Tribulation Behind



NASA's Mars Exploration Rover Opportunity worked for 30 months on a raised segment of Endeavour Crater's rim called "Cape Tribulation" until departing that segment in mid-April 2017, southbound toward a new destination.

This view looks back at the southern end of Cape Tribulation from about two football fields' distance away. The component images were taken by the rover's Panoramic Camera (Pancam) on April 21, during the 4,707th Martian day, or sol, of Opportunity's mission on Mars.

Wheel tracks can be traced back to see the rover's route as it descended and departed Cape Tribulation. For scale, the distance between the two parallel tracks is about 3.3 feet (1 meter). The rover drove from the foot of Cape Tribulation to the head of "Perseverance Valley" in seven drives totaling about one-fifth of a mile (one-third of a kilometer).

The elevation difference between the highest point visible in this scene and the rover's location when the images were taken is about 180 feet (55 meters). This view looks northward.

It merges exposures taken through three of the Pancam's color filters.