Saturn and Methane


Saturn and MethaneThis picture of Saturn was made by the Cassini spacecraft at wavelengths of light that are absorbed by methane. The darker areas are regions where light travels further into the atmosphere, passing through more methane before being reflected off of clouds. The deeper the light goes, the more of it gets absorbed by methane, and the darker that part of Saturn appears.

The small moon just below the rings on the right is Dione.

Image Credit: NASA

Five Planets


five_planets_chartFrom now until around Feb. 20, pre-dawn stargazers will stand a good chance of seeing all five planets known to ancient astronomers simultaneously: Mercury, Venus, Saturn, Mars and Jupiter. Those planets should be visible to the naked eye, but a pair of binoculars may be necessary to pull Mercury out of the pre-dawn sky glow from the Sun.

Jupiter will rise in the evening, then Mars will come over the horizon after midnight, followed by Saturn, then Venus, and Mercury just before dawn. All five should be visible from southeast to southwest between 6:00 and 6:30 am local time.

Image Credit: NASA

Saturn and Tethys


Saturn & TethysAt 116,500 km across, Saturn is roughly 10 times the diameter of Earth. The planet is much larger in relation to its moons than our Earth to its Moon. Saturn’s moon Tethys (which is a bit more than 1,000 km in diameter and could be counted as a dwarf planet it orbited the Sun by itself) can be seen as a speck in the lower right of the picture.

Image Credit: NASA

Bullseye


Enceladus_Tethys_bullseyEnceladus and Tethys line up almost perfectly in this shot from the Cassini spacecraft. Since the two moons are not only aligned, but also at nearly the same distance from Cassini, their apparent sizes are a reasonable approximation of their relative sizes. Enceladus is 504 km across, and Tethys is 1,062 km in diameter.

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

Dione and Enceladus


Dione_EnceladusAlthough Saturn’s moons Dione (in the foreground) and Enceladus are made of more or less the same stuff, Enceladus has a considerably higher reflectivity than Dione. Therefore, it appears brighter against the blackness of space.

Enceladus has a constant rain of ice grains from its south polar jets which cover its surface with a bright snow. Dione’s older, weathered surface has slowly gathered dust and radiation damage, darkening through a process known as “space weathering.”

Image Credit: NASA

Enceladus Close Up


Enceladus close upDuring its close flyby last Wednesday of the active south polar region of Saturn’s moon Enceladus, the Cassini spacecraft grabbed this view of the terrain below. It’s centered on terrain at 57° S latitude by 324° W longitude. The spacecraft was about 124 km from Enceladus. The image resolution is 15 m per pixel.

Image Credit: NASA