Broken Rings?

broken ringsThat’s not a gap in Saturn’s rings. It’s the planet’s shadow. During most of Saturn’s year, the planet’s shadow extends well beyond the edge of the rings.  However, with summer solstice fast approaching, the Sun is higher in Saturn’s sky and most of Saturn’s A ring is completely shadow-free.

Saturn’s large moon Titan, its northern hemisphere in sunlight of late spring, hangs above the rings.

Image Credit: NASA

The Mystery of Ligeia Mare

Titan Mare FeaturesThe images above were taken by the Radar instrument aboard the Cassini spacecraft. They show the evolution of a changing feature in the large hydrocarbon sea named Ligeia Mare on Saturn’s moon Titan. The small images in the column at left show the same region of Ligeia Mare as seen by Cassini‘s radar during flybys in (from top to bottom) 2007, 2013, 2014 and 2015.

Analysis suggests that the changes in the bright features are cause by either waves, solids at or beneath the surface, or bubbles. Waves are generally thought to be the most likely explanation, but tides or sea level and seafloor changes might be the cause.

The large image panel shows all of Ligeia Mare which is Titan’s second-largest liquid hydrocarbon sea and has a total area of about 130,000 square km, making it 50 percent larger than Lake Superior on Earth.

Image Credit:NASA

Seasons on Titan

Titan TemperaturesThis animated sequence of maps shows varying surface temperatures on Saturn’s moon Titan at two-year intervals from 2004 to 2016. The measurements were made by the Cassini spacecraft. They show heat coming from Titan’s surface at a wavelength of 19 µm, a wavelength at which the moon’s otherwise opaque atmosphere is somewhat transparent. Temperatures have been averaged around the globe from east to west to emphasize the seasonal variation across latitudes. Regions for which there are no data show up as black.

Titan’s surface temperature changes slowly over the course of the Saturn system’s long seasons, which each last 7-1/2 years each. As on Earth, the amount of sunlight received at any location changes as the Sun appears to move north or south in Titan’s sky over the course of the 30-year-long Saturnian year. Cassini arrived at Saturn in 2004 when Titan’s southern hemisphere was in late summer and was the moon’s warmest region. By 2010, shortly after the 2009 equinox, temperatures were about the same across the northern and southern hemispheres, similar to the situation seen by Voyager 1 in 1980, one Titan year earlier.

Image Credit: NASA

The Surface of Titan

Titian in IRThis composite image was stitched together using infrared views of Saturn’s moon Titan taken by the Cassini spacecraft. They were acquired during the a flyby on last month. The spacecraft’s visual and infrared mapping spectrometer (VIMS) instrument took the pictures. In this false color image blue represents wavelengths centered at 1.3 µm, green represents 2.0 µm, and red represents 5.0 µm. Visible light centered around 0.5µm reveals nothing below Titan’s hazy atmosphere. The near-infrared wavelengths in this image allow Cassini’s vision to penetrate the haze.

Image Credit: NASA

Triple Crescent

Triple CrescentSaturn has many moons. The three shown here—Titan, Mimas, and Rhea—show marked contrasts in their surface features. Titan, Saturn’s largest moon and the largest moon in this image, appears fuzzy because we only see its clouds. Because Titan’s atmosphere refracts light around the moon, its crescent is wrapped just a little further around the moon than it would on an airless body. Rhea (upper left) appears rough because its icy surface is heavily cratered. A close inspection of Mimas, though difficult to see at this scale, would show surface irregularities because of its violent history.

Image Credit: NASA

One more thing … If it’s clear where you are this evening, go outside and look up in the western sky just after sunset. There’s a conjunction of Venus and Jupiter tonight. They will be separated by less than half the diameter of the Full Moon.

Titan—the Hard Way

Six Nightly Views of Titan's SurfaceWe’re used to seeing pictures of Saturn’s moon Titan taken by the Cassini spacecraft. These views of Titan were taken by a ground-base telescope, the Very Large Telescope at the European Southern Observatory in Chile. The image on the right has been enlarged for clarity, and the coordinate grid used Titan overlaid. The images are false-colour renderings coded with red (1.575 μm; surface), green (1.600 μm; surface), and blue (1.625 μm; atmosphere), respectively.

Image Credit: ESO