It may seem odd to think of planets casting shadows out in the inky blackness of space, but it is a common phenomenon. Earth’s shadow obscures the Moon during a lunar eclipse, and Jupiter’s moons cast small shadows onto their parent planet.
One of the best places in our Solar System to spot intriguing and beautiful celestial shadows is at Saturn. On 1 July, the international Cassini mission celebrates 10 years of exploring Saturn, its rings and its moons, an endeavour that has produced invaluable science but also stunning images like this.
Drifting along in the foreground, small and serene, is Saturn’s icy moon Mimas. The blue backdrop may at first appear to be the gas giant’s famous and impressive set of rings, with pale and dark regions separated by long inky black slashes, but it is actually the northern hemisphere of Saturn itself. The dark lines slicing across the frame are shadows cast by the rings onto the planet.
Although we may not associate the colour blue with Saturn, when Cassini arrived at the planet the northernmost regions displayed the delicate blue palette shown in this image. As this region of Saturn is generally quite free of cloud, scattering by molecules in the atmosphere causes sunlight to take a longer path through the atmosphere. The light is scattered predominantly at shorter – bluer – wavelengths. This is similar to why the sky on Earth appears blue to our eyes.
Seasonal changes over the years since this photo was taken have turned the blue into Saturn’s more familiar golden hue. The reverse is occurring in the south, which is slowly becoming bluer.
Image credit & copyright: NASA/JPL/Space Science Institute
Titan is the largest moon of Saturn. It is the only natural satellite known to have a dense atmosphere, and the only object other than Earth for which clear evidence of stable bodies of surface liquid has been found
Titan is primarily composed of water ice and rocky material. Much as with Venus prior to the Space Age, the dense, opaque atmosphere prevented understanding of Titan’s surface until new information accumulated with the arrival of the Cassini–Huygens mission in 2004, including the discovery of liquid hydrocarbon lakes in Titan’s polar regions.
The atmosphere is largely nitrogen; minor components lead to the formation of methane and ethane clouds and nitrogen-rich organic smog. Titan’s lower gravity means that its atmosphere is far more extended than Earth’s and about 1.19 times as massive. It supports opaque haze layers that block most visible light from the Sun and other sources and renders Titan’s surface features obscure.Atmospheric methane creates a greenhouse effect on Titan’s surface, without which Titan would be far colder. Conversely, haze in Titan’s atmosphere contributes to an anti-greenhouse effect by reflecting sunlight back into space, cancelling a portion of the greenhouse effect warming and making its surface significantly colder than its upper atmosphere.
Titan’s clouds, probably composed of methane, ethane or other simple organics, are scattered and variable, punctuating the overall haze.The findings of the Huygens probe indicate that Titan’s atmosphere periodically rains liquid methane and other organic compounds onto its surface. Clouds typically cover 1% of Titan’s disk, though outburst events have been observed in which the cloud cover rapidly expands to as much as 8%. One hypothesis asserts that the southern clouds are formed when heightened levels of sunlight during the southern summer generate uplift in the atmosphere, resulting in convection. This explanation is complicated by the fact that cloud formation has been observed not only after the southern summer solstice but also during mid-spring.
Saturn Moon Titan’s Underground Ocean May Be Super Salty
The subsurface ocean inside Saturn’s largest moon, Titan, could be as salty as any body of water here on Earth, a new study reports.
Gravity data collected by NASA’s Cassini spacecraft suggest that Titan’s ocean must have an extremely high density. Salt water has a higher density than fresh water because the presence of salt adds more mass to a given amount of water.
Comet 67P/Churyumov Gerasimenko, imaged by the Rosetta spacecraft in August 2014. Rosetta is the first spacecraft to orbit a comet, it has been traveling for more than 10 years to reach 67P, which is currently between the orbits of Mars and Jupiter. Later this year Rosetta will deploy a lander named Philae to the surface of the comet to determine its composition. Observations of 67P will continue through its closest approach to the Sun in August 2015, revealing the changes that occur as the temperature of the comet increases.
Markarian’s Chain is a stretch of galaxies that forms part of the Virgo Cluster. It is called a chain because, when viewed from Earth, the galaxies lie along a smoothly curved line. It was named after the Armenian astrophysicist, B. E.
We compress information to generate our laws of Nature, and then use these laws of Nature to generate more information, which then gets compressed back into upgraded laws of Nature. The dynamics of the two arrows is driven by our desire to understand the Universe.