Spaceflight Now has an article by the esteemed space writer Craig Covault on the possibility of targeting the Mars Science Laboratory to an area shown to be emitting methane.
In these posts, I try to keep my opinions to a minimum (I'm no smarter or more knowledgeable than most of my readers) and focus on facts and leave the opinions to you. Here I will make an exception. Given the course spatial nature of the emissions of methane observed, I hope that MSL is not re-targeted with the goal of exploring a methane rich area. The area in question, Nili Fossae, is a geologically interesting area, but one that had been dropped from consideration. If further geological analysis raises its priority given the studies that MSL can conduct, then I'm all for it as a landing site.
However, we know very little about the sources of the methane. Are they coming from a broad area or from very small and localized vents? We could send MSL to Nili Fossae and find that we landed a hundred kilometers from any area venting methane.
I believe that the right strategy is to target MSL based on the instruments in its payload, which are tuned to geochemical analysis and the search for signs of past or present life on the surface. I believe that a follow on orbiter to nail down the precise locations of methane venting should fly as early as possible. After that, a rover with instruments tuned to the quest should investigate the methane emitting regions.
You can read the rankings of the proposed landing sites (on science and engineering grounds) in this letter. For extensive analysis of the science potential of Nili Fossae as an MSL landing site, look at the presentations on this site (look under Day 2's presentations).
Your comments telling me that I am nuts are welcome.