Open thread, Dec. 15 - Dec. 21, 2014

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If it's worth saying, but not worth its own post (even in Discussion), then it goes here.

Notes for future OT posters:

1. Please add the 'open_thread' tag.

2. Check if there is an active Open Thread before posting a new one. (Immediately before; refresh the list-of-threads page before posting.)

3. Open Threads should be posted in Discussion, and not Main.

4. Open Threads should start on Monday, and end on Sunday.

Fluctuating levels of methane, which is what's actually new about the Curiosity measurements, are strong evidence for active replenishment.

Sure, but there are tons of geological processes which produce methane without any involvement of life.

The discovery of methane spikes is certainly interesting, but to go from there to changing the Great Filter estimates is a looooooong jump.