Monday, April 11, 2005

BBC News: Titan probe's pebble 'bash-down'

The BBC News website has an article up regarding a conference talk given by the Huygens SSP Principal Investigator John Zarnecki at the UK National Astronomy Meeting. He reported that based on test drops run at Open University in Milton Keynes, the probe likely landed on one of the fist-sized pebbles strewn across the Titanian landscape before slipping into the icy sand. Shortly after the probe landing, the SSP investigators reported that the penetrometers results were consistent with a surface that consisted mostly of sand-sized particles covered by a thin crust. This led to the early analogy developed by Ralph Lorenz of the SSP team (and the principal developer of the penetrometer component) of creme brule. While the hard crust-sandy middle model has not been ruled out, from the article:
"A crust is still a possibility, but we now think it's most likely we hit one of those water-ice pebbles you see in the ground image; the biggest you see is about 15cm," Professor Zarnecki told the BBC News website.

"We probably pushed the pebble to one side and then ploughed into the stuff underneath which we are pretty convinced is a 'sand' made of ice," the principal investigator on the Huygens surface science package explained.

The article also reported that the penetrometer results were consistent with a matrix of sand- to gravel-sized particles up to 8 mm in size.

Thanks to paxdan over at the Unmanned Spaceflight forum for the link.

2 Comments:

Anonymous Michael Chisnall said...

Intuitively it seems to me that if you stick something into wet sand there will be a spike in the force required when it makes contact when compared to the force required to drive it in further.

It's not clear to me though if it would still be wet. Methane's lower surface tension compared to water means that it will drain away more readily. On the other hand the temporary conductivity and enduring permittivity changes seen suggest a solvent. Hmmm.

4/12/2005 02:54:00 AM  
Blogger Bruce Moomaw said...

Actually, there's no particular reason (according to both Zarnecki and Jonathan Lunine, in their earlier video appearances) to think that wet sand would produce any more resistance when the tip of the penetrometer first hit it than it would as the spike was pushed further down into it.

I've been wondering for some time whether Huygens might have plopped down in Titanian quicksand (in which, of course, it would have floated, not having seen any of those old "Tarzan" movies).

4/12/2005 10:39:00 PM  

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