spaceSpace and Physics

Saturn's Moons Titan And Rhea Revealed In Stunning NASA Image


Jonathan O'Callaghan

Senior Staff Writer

NASA/JPL-Caltech/Space Science Institute

NASA has re-released a rather awesome snap of Saturn’s moon Rhea passing in front of the moon Titan, captured by the now-dead (sob) Cassini spacecraft.

The image was taken way back on November 19, 2009, from a distance of about 1.148 million kilometers (713,300 miles) from Rhea.


In the image, Rhea is the moon in the foreground, and Titan the hazy moon in the background. Despite both orbiting Saturn, you can clearly see how different these two worlds are from this one snap.

Rhea measures about 1,527 kilometers (949 miles) across, and is Saturn’s second largest moon after Titan. It has an ancient surface, owing to a lack of geological activity. As such it has retained a lot of its craters from impacts over the years, and is one of Saturn’s most heavily cratered moons.

We also think Rhea has a very thin atmosphere, called an exosphere, and also a very faint ring system. All in all, it’s a rather fascinating place.

Then you’ve got Titan, which has an atmosphere so thick that we can’t even see its surface. Here, there are seas and lakes of hydrocarbons – the only place in the Solar System other than Earth known to have bodies of liquids on its surface.


Titan is 5,151 kilometers (3,201 miles) in diameter, slightly bigger than Mercury and twice the size of our Moon. It has rain, wind, and many other Earth-like features. If it weren’t for its poisonous atmosphere, which is 98.4 percent nitrogen, 1.6 percent methane, and less than 0.2 percent hydrogen, it would almost seem like home.

This image above, though, really just highlights the amazing complexity of moons and worlds in our Solar System. Titan and Rhea might be two of Saturn’s 62 known moons, but they couldn’t be more different in their appearance.

NASA is currently considering a return to Titan, after we not only studied it with the Cassini spacecraft, but also sent a lander there – the Huygens probe – in 2005. With the Cassini mission coming to an end in September 2017, many are now hoping for continued exploration of the outer Solar System, and this mission serves as a handy reminder of what’s awaiting us out there.

Maybe there’s some sort of new rocket that might be useful in that regard. Just saying.


spaceSpace and Physics
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  • Saturn,

  • cassini,

  • Titan,

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  • rhea