First off, Astrobiology Magazine has posted a great interview with the TEGA (Thermal and Evolved Gas Analyzer – the ovens) principal investigator Bill Boynton. The interview provides a really great overview of how TEGA works, and what the team is hoping to see. The interview pretty much answered all the lingering questions that I had, as well as some that people have posted in the comments recently. In particular, here’s Bill’s response to a question about how the TEGA team will determine whether any organics they detect are martian or terrestrial:

AM: How will you eliminate the possibility of contamination versus a true reading for organics?

WB: Phoenix has a “blank” that we can analyze. The blank presumably has very low organics — we heated it to bake all the organics out of it. If we analyze that and find much lower levels of organic contamination in the blank than we do in the Mars samples, then we can say that what we’re finding in the samples comes from Mars, not Earth. On the other hand, if when we analyze the blank we see the same levels of organics that are detected in the soils, then we can say the organics are coming either from contamination on the instrument or the robotic arm scoop.

Also, here’s a true color version of the images that showed the disappearing chunks of ice (press release):

And finally, one of my favorite images from Phoenix so far, this very artistic shot of the Snow White trench, where the hard ice layer is exposed. If I recall correctly, this is where the team will be trying to grind into and sample the ice layer (via the Phoenix image archive):