March 25 – Titan

Titan, Saturn’s largest moon, and the second largest moon in the Solar System (behind Ganymede, which is only ever so slightly bigger), was discovered on March 25th 1655 by the Dutch astronomer Christiaan Huygens.  As the first moon to be discovered around Saturn there was no immediate pressure on Huygens to find an impressive name for it, so he settled for Luna Saturni (Saturn’s moon).  It wasn’t until Cassini discovered a further four Saturnian moons that a naming system became an issue, and even then the solution wasn’t particularly imaginative (“Saturn IV” to start off with, then “Saturn VI” after a couple more were found).  It was John Herschellson of the more famous William, who came up with the name Titan, as well as the names of the other six saturnian moons known at the time.

Titan, with Tethys in the background (image: NASA)

Titan, with Tethys in the background (image: NASA)

Titan, as you can see from the picture below, is shy, and doesn’t like to show us a great deal of surface detail.  It is the only moon in the Solar System with a substantial atmosphere, so dense in fact that the surface pressure is about half as great again as on Earth.  It is also suspected of having the potential to support microbial life, making it a very tempting place for Earthlings to visit.

Titan from the Cassini Spacecraft (false colour image in Ultraviolet and Infrared). Image credit: NASA / JPL / Space Science Institute.

Titan from the Cassini Spacecraft (false colour image in Ultraviolet and Infrared). Image credit: NASA / JPL / Space Science Institute.

In the hierarchy of Saturnian moons, Titan is right at the top of the pile.  It has a mass of 1.34 x 1023 kg (that’s about twice the mass of our own lightweight moon) which makes it far and away the biggest, accounting for 96% of the combined mass of all Saturn’s satellites.


1928  –  Jim Lovell (commander of Apollo 13) born today in Cleveland, Ohio. Captain James Lovell, USN, is a veteran of four space flights (he was the first man to achieve the feat) totalling 29 days: Gemini 7, Gemini 12, Apollo 8, and Apollo 13. He is also the only person to fly to the Moon twice without landing on it.


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