Cd

A section of the synthetic-aperture radar track taken on 26 October 2004 centred at 82°W, 50°N, at a resolution of 300 metres per pixel. It suggested a complex surface geology.

A section of the synthetic-aperture radar track taken on 26 October 2004 centred at 30°W, 45°N covering an area about 150 kilometres square, showing what might be a cryovolcanic flow.

across the Solar System, and our one big fear was that Titan might look like Jupiter's moon Callisto, which is an old dead world covered in impacts.'' As in the infrared, there were features in the radar imagery that looked as if they might be of cryovolcanic origin, including one, 180 kilometres in diameter, that bore a similarity to a Venusian 'pancake' dome.194,195 A very convincing example was a large bright branched and lobate feature on dark terrain.196,197,198 ''It might be something that flowed, or something that was carved by erosion,'' said Lorenz. ''It's too early to say really, but it looks very much like something oozed across the surface.'' The Ion and Neutral Mass Spectrometer found argon-40, an isotope derived primarily from the decay of potassium-40, which has a half-life of 1.28 billion years. The outgassing of this volatile species from the core where the rock (and hence the potassium) should reside, was evidence that Titan had undergone significant cryvolcanic activity during its history.

Although Cassini took movies to study clouds, monitoring by H.G. Roe's team indicated that the mid-latitude clouds cleared up 2 days prior to Cassini's arrival and reappeared 2 days after the fly-by! ''This demonstrates", said Roe, ''how [Earth-based] observations are important for putting the Cassini observations into context.'' That is, the Cassini team would not have been able to infer that Ta had viewed Titan on an unusually clear day.

The radar altimetry was surprising. The area that was scanned was extremely flat, with the range of elevation being confined to 150 metres over a 400-kilometre track,

A section of the synthetic-aperture radar track taken on 26 October 2004 centred at 30°W, 45°N covering an area about 150 kilometres square, showing what might be a cryovolcanic flow.

The radar altimetry track centred at 5°W, 25°N showed this part of Titan's surface to be remarkably level.

and reducing to just 50 metres across the latter part of the track. But since altimetry, radiometry and synthetic-aperture imaging could not be done simultaneously, there was no indication of what this area 'looked' like in terms of albedo. One speculation was that if organic particulates were blown into low-lying areas to form level plains, there might be areas that looked just like dry lake beds but had formed without the involvement of liquid. Might these plains have produced the specular glints detected by the Arecibo radar?

Two views of Tethys: (left) the trailing hemisphere (north to the top) on 28 October 2004 showing the cratered surface and part of Ithaca Chasma, and (right) the Saturn-facing hemisphere on 15 December 2004 with a large impact basin with rings 300 and 130 kilometres in diameter adjacent to another section of Ithaca Chasma.

Was this article helpful?

0 0
Telescopes Mastery

Telescopes Mastery

Through this ebook, you are going to learn what you will need to know all about the telescopes that can provide a fun and rewarding hobby for you and your family!

Get My Free Ebook


Post a comment