Bleriot Propeller

The Cassini spacecraft has been monitoring propeller features since their discovery. Here the propeller dubbed Bleriot is seen in a recent image. The bright dash-like features are regions where a small moonlet has caused ring particles to cluster together more densely than normal. Beyond the bright areas are fainter, longer dark linear features. These are believed to be extended regions where the same moonlet has caused particles to evacuate, leaving an under-dense (thus darker) area.

To learn more about propellers, see PIA07792 and PIA07791. For more of Bleriot, see PIA12789.

This view looks toward the sunlit side of the rings from about 33 degrees above the ringplane. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on April 3, 2013.

The view was acquired at a distance of approximately 301,000 miles (484,000 kilometers) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 119 degrees. Image scale is 2 miles (3 kilometers) per pixel.

Photo credit: NASA/JPL-Caltech/Space Science Institute

Earth as a Pale Blue Dot and Saturn's Silhouette

With giant Saturn hanging in the blackness and sheltering Cassini from the sun's blinding glare, the spacecraft viewed the rings as never before, revealing previously unknown faint rings and even glimpsing its home world.

This marvelous panoramic view was created by combining a total of 165 images taken by the Cassini wide-angle camera over nearly three hours on September 15, 2006. The full mosaic consists of three rows of nine wide-angle camera footprints; only a portion of the full mosaic is shown here. Color in the view was created by digitally compositing ultraviolet, infrared and clear filter images and was then adjusted to resemble natural color.

The mosaic images were acquired as the spacecraft drifted in the darkness of Saturn's shadow for about 12 hours, allowing a multitude of unique observations of the microscopic particles that compose Saturn's faint rings.

Ring structures containing these tiny particles brighten substantially at high phase angles: i.e., viewing angles where the sun is almost directly behind the objects being imaged.

During this period of observation Cassini detected two new faint rings: one coincident with the shared orbit of the moons Janus and Epimetheus, and another coincident with Pallene's orbit. (See PIA08322 and PIA08328 for more on the two new rings.)

The narrowly confined G ring is easily seen here, outside the bright main rings. Encircling the entire system is the much more extended E ring. The icy plumes of Enceladus, whose eruptions supply the E ring particles, betray the moon's position in the E ring's left-side edge.

Interior to the G ring and above the brighter main rings is the pale dot of Earth. Cassini views its point of origin from over a billion kilometers (and close to a billion miles) away in the icy depths of the outer solar system. See PIA08324 for a similar view of Earth taken during this observation.

Small grains are pushed about by sunlight and electromagnetic forces. Hence, their distribution tells much about the local space environment.

A second version of the mosaic view is presented here in which the color contrast is greatly exaggerated. In such views, imaging scientists have noticed color variations across the diffuse rings that imply active processes sort the particles in the ring according to their sizes.

Looking at the E ring in this color-exaggerated view, the distribution of color across and along the ring appears to be different between the right side and the left. Scientists are not sure yet how to explain these differences, though the difference in phase angle between right and left may be part of the explanation. The phase angle is about 179 degrees on Saturn.

The main rings are overexposed in a few places.

This view looks toward the unlit side of the rings from about 15 degrees above the ringplane.

Cassini was approximately 2.2 million kilometers (1.3 million miles) from Saturn when the images in this mosaic were taken. Image scale on Saturn is about 260 kilometers (162 miles) per pixel.

Image credit: NASA/JPL/Space Science Institute

Note: For more information, see Cassini Probe to Take Photo of Earth From Deep Space; also, Cassini to Photograph Earth From Deep Space.

Ligeia Mare

Ligeia Mare, shown here in a false-color image from the international Cassini mission, is the second largest known body of liquid on Saturn's moon Titan, and it is one of the many seas and lakes that bejewel Titan's north polar region. It measures roughly 420 km x 350 km, and its shorelines extend for over 3,000 km. It is filled with liquid hydrocarbons, such as ethane and methane. Cassini has yet to observe waves on Ligeia Mare, and will look again during its next encounter on May 23, 2013.

The mosaic shown here is composed from synthetic aperture radar images from flybys between February 2006 and April 2007.

Photo credit: NASA/JPL-Caltech/ASI/Cornell

Note: For more information, see Forecast for Titan: Wild Weather Could be Ahead.

The Formation of Aerosols in Titan's Haze

This illustration shows the various steps that lead to the formation of the aerosols that make up the haze on Titan, Saturn's largest moon.

When sunlight or highly energetic particles from Saturn's magnetosphere hit the layers of Titan's atmosphere above 1000 km, the nitrogen and methane molecules there are broken up. This results in the formation of massive positive ions and electrons, which trigger a chain of chemical reactions that produce a variety of hydrocarbons. Many of these hydrocarbons have been detected in Titan's atmosphere, including Polycyclic Aromatic Hydrocarbons (PAHs), which are large carbon-based molecules that form from the aggregation of smaller hydrocarbons. Some of the PAHs detected in the atmosphere of Titan also contain nitrogen atoms.

PAHs are the first step in a sequence of increasingly larger compounds. Models show how PAHs can coagulate and form large aggregates, which tend to sink, due to their greater weight, into the lower atmospheric layers. The higher densities in Titan's lower atmosphere favor the further growth of these large conglomerates of atoms and molecules. These reactions eventually lead to the production of carbon-based aerosols, large aggregates of atoms and molecules that are found in the lower layers of the haze that enshrouds Titan, well below 500 km.

The formation scenario of aerosols in Titan's atmosphere depicted in this illustration is based on the simulations described by Lavvas et al., 2011 (The Astrophysical Journal, 728, 80); doi:10.1088/0004-637X/728/2/80.

Illustration credit: ESA/ATG medialab

Note: For more information, see Cassini Sees Precursors to Aerosol "Snow" on Titan.