Mars...The Big Picture

People who know me, know that I like to talk about the "Big Picture" a lot. So perhaps the best place to go with this is to outline Mars surface science from the Biggest picture I can imagine (that still retains some sort of usefulness). I want to preface this by saying that I'm not attempting to be comprehensive here, I'm just trying to lay out things from my perspective. So sorry geophysicists, there isn't going to be alot about differentiation and planetary evolution.

I think the biggest picture question in my view is the question that most papers are ultimately addressing, and that is the "Warm, wet early Mars" idea. This idea is not well defined and as such discussions of this idea without clear delineations of what exactly is being discussed can be confusing. In my mind the question is:

Was early Mars warm enough, and wet enough, for a long enough period to allow for life to evolve?

This of course leaves a lot to be desired since we don't know how long it takes for life to evolve, or how warm or wet it needs to be. So many people have simply focused on a simpler version:

How warm, how wet, and for how long?

I think most Mars scientists would say that early Mars was warm and wet for at least very short periods - either in short impact induced periods, or in longer ocean forming epochs with rain and an active hydrological cycle.

I think many people would point to the results from the Opportunity rover, as well as the photos of outflow channels and valley networks, to say that Mars had an extended period where it resembled a terrestrial desert. Playa lakes formed inside craters, rainfall was limited but present, hydrology was mainly in the subsurface, and oceans may or may not have been present.

There are others, including myself, who tend towards the idea that Mars has been primarily cold and dry throughout its history, never resembling terrestrial environments, and rarely if ever being warm enough to allow for rain.

So in my mind, the most interesting martian science is that which ultimately addresses these questions through testing our various hypotheses about features on Mars.

Anyways, that is the short version, comments are of course encouraged.