Friday, July 31, 2015

Maybe this is why the Philae Probe didn't "Stick the Landing"

The Philae lander that made (multiple) contacts with the 67/P comet last November has finally reported back some data on the chemistry at the surface. And it appears that there is a polymer, polyoxlmethylene (POM) amongst the mix. The official report is behind a firewall (which means I haven't read it), but there is also extensive reporting by Carmen Drahl (formerly of C & E News) and C & E News itself.

Whenever I think of POM, two thing immediately come to mind. The first is that this polymer probably has more names associated with it than any other polymer. POM is also commonly referred to as acetal, polyacetal, and Delrin (the latter being a tradename that is well on its way to becoming generic). Most other polymers have only a couple of names associated with them.

But the other immediate thought is POM is well known for it's low coefficient of friction (COF) - it's excellent for making plastic gears and other parts that slide past each other. So is the low COF part of the reason that the probe had such a difficulty in landing and staying landed?

Don't laugh. There may be lots of polymer on the surface

"If the polymer covers much of the comet, it could explain the object’s dark colour..." For such a strong visual effect, the polymer is would have to be more than just a monolayer. Additionally, "The polymer may also be masking signals from other interesting compounds formed earlier in the comet's history...", again, indicative of a thicker layer. (And did you notice how junky polymers are already taking the blame polluting up the comet.)

Landing a probe on any comet will always be challenging since the gravitational attraction is so low. But having a slippery surface is only going to make matters worse. This is still mostly speculative, but if it turns out in the future that there actually is a slippery, thick layer of POM on the surface, well, you read it hear first.

Previous Years

July 31, 2014 - Polyprefixicide

July 31, 2012 - Accelerated Aging, Flash Photography and Museums

July 31, 2009 - "It's all about the Entanglements"


Anonymous said...

I have a jar of the stuff laying on my bench. I'm a synthetic organic chemist, and no, I never thought my C1 synthon was indeed a "proper" polymer, i.e. something attractive for its mechanical properties. I thought it was too labile towards acids to find any useful application. I was wrong.

John said...

The acid hydrolysis is definitely an issue, but still, there are enough applications where that's not concern.