Not to put too fine a point on it, Holy Moley! Updates: As you were

This could be life, Jim

The press conference is scheduled for 2 p.m. EST on Thursday, Dec. 2. Speculation based on who will be present at the press conference has suggested that this is a about Mars, or Titan, or Photosynthesis, or something.
Specifically, NASA has said that they will discuss: "an astrobiology finding that will impact the search for evidence of extraterrestrial life." To me, that could mean that something has been found on another planet or moon that is or was alive, an actual finding out there, or it could mean a new technique or model (the finding) that will unfold as a project (a mission).

Probably fanboy dreaming but it has made me feel pretty weird

UPDATE:

NASA has also brought together a geologist, an oceanographer, a biologist, and an ecologist for a panel discussion at the press conference. That's got peoples' imaginations running wild but props to Kottke.org for doing a bit of online sleuthing into the backgrounds of the invited speakers. They include:

• Geobiologist Pamela Conrad is the primary author of a 2009 paper on geology and life on Mars
• Oceanographer Felisa Wolfe-Simon has written on photosynthesis using arsenic recently
• Biologist Steven Benner is part of the "Titan Team" at the Jet Propulsion Laboratory
• Ecologist James Elser works with a NASA-funded astrobiology program called Follow the Elements

Here
UPDATE II

I'm sad to quell some of the @kottke-induced excitement about possible extraterrestrial life. I've seen the Science paper. It's not that.

 Spoilsport whoever they are
Buggeration Update: it's some bacteria that eats arsenic
Chiz chiz, we might say