[X] My Assistant

[djellison]

http://sfgate.com/cgi-bin/article.cgi?f=/c....DTL&type=books

the success of "Roving Mars" has everything to do with Squyres' amiable writing style -- that and the fact that he has a heck of a story to tell.

[dvandorn]

Markley has a point -- and yet, he doesn't. He seems to see the "Follow the Water" mission as a negative, limiting definition of the MER mission, as the antithesis of the scientific method. "Why look for water, which we know was there, when we should simply be looking for the real story the rocks tell us?" seems to be Markley's basic point.

There are two problems with Markley's question. The first is that we did *not* know for certain that water formed the large-scale physical features revealed by Mariner 9, the Viking orbiters, and so on. There have been very elegant theories put forward that purport to explain every feature we see by the action of CO2 phase changes (the "White Mars" theories). These theories have been more or less discredited by the results of the MERs, true -- but that's why you get ground truth, to prove or disprove various theories about the world we observe.

And that's the other problem with Markley's main point -- you do *not* always just investigate what's there, with absolutely no pre-conceived notions as to what you'll find. Sure, if we could just pull limitless chunks of Mars from wherever we wish on the planet and bring them back to Earth for whatever investigations we can think of to run on them, we ought to just grab whatever we can and follow whatever story the rocks tell us. But we can't do that. We can only place a very few sensors on the surface, and only on one or two spots on the surface, and we have to select those instruments, and those spots, based on *something*.

And so, when we have to make these kinds of decisions -- what instruments to fly, where to land them -- we have to try and base those decisions on our best theories as to what we're likely to find. And we have to drop the high-minded approach of "let's just gather all the data we can about the rocks and let them tell their own story," we *must* try and either prove or disprove current theories.

Hence, we get "Follow the Water." It's the same reason the major part of the Viking landers' science payload was designed to look for extant microbial life that, for the instruments to detect it, must be almost identical to terrestrial microbial life. They designed the instrumentation the way they did because, as with the MERs, the Viking landers couldn't carry enough instrumentation to determine exactly every chemical compound in the rocks and soils, exactly how old each piece of rock and soil is, exactly where each rock formed, how and why... and because it was felt that the most important theory to prove or disprove, at that point in time, was whether or not terrestrial-type organisms lived on Mars.

Viking found a situation that didn't fit into the theories; some of the life detectors got positive results, but others (especially the organics detector) did not. Some, Markley possibly included, might say that the Vikings were a complete waste of time, since they were designed to find things that weren't there. But the mixed results of the Viking experiments did not derail investigations of Mars -- they served to re-define the debate.

So, Squyres and company were given a set of goals, primary of which was to determine ground truth on the issue of Mars having once supported open bodies of liquid water. Prove that, and you can proceed on to further investigations, like looking for organic materials (which is, of course, the primary mission of MSL). *Disprove* it, and you reach another of those points where you must re-define the debate.

While it may be noble to believe that researchers always approach their investigations without pre-conceived notions of what results they will find, the bare reality is that almost all scientific investigation is undertaken, and *designed*, to either prove or disprove a given set of theories. The results achievable by most experiments and investigations are usually defined such that they will either strongly prove, or strongly disprove, whatever theory is being tested.

Methinks Mr. Markley might need to descend from the ivory towers and take a realistic look at how and why scientific investigations work...

-the other Doug