Welcome Professor "brine splat" Burt, "a chance to ask questions... or raise objections" Options

[dburt]

Relevant to Emily's boulder observation, the "Gullies and layers" HiRISE image was not the first to show layers with abundant boulders, indicating poor sediment sorting in layered slopes. Previous images included, e.g., PSP_001691_1320 "Gullied trough in Noachis Terra, released on 28 Feb., and PSP_001942_2310 "Signs of fluids and ice in Acidalia Planitia" released on 9 May. That these bouldery layers might represent ancient ballistic impact ejecta seems a reasonable suggestion, because much of the present martian surface is littered with boulders presumed to be ballistic impact ejecta. Other possibilities for boulder deposits might include, e.g., ancient talus or landslide deposits at the foot of slopes, stream boulders in channels, volcanic ejecta near vents, glacial moraines, or iceberg dropstones.

As an aside, the related suggestion that at least some of the fine-grained layers above or below any boulder deposits (or elsewhere on Mars) could likewise represent ancient impact deposits (non-ballistic fine-grained sand and dust distributed over vast areas by fast-moving, turbulent, erosive gaseous density currents - a.k.a. impact surge clouds - or by the winds as later fallout) already seems to have aroused considerable controversy on this forum, but again that's peripheral to Emily's boulder comment.

--Don

[MOD EDIT: "Brine Splat Burt" discussion moved here -> http://www.unmannedspaceflight.com/index.p...ic=4308&hl= -EGD]

[centsworth_II]

As an aside, the related suggestion that at least some of the fine-grained layers above or below any boulder
deposits (or elsewhere on Mars) could likewise represent ancient impact deposits (non-ballistic fine-grained
sand and dust distributed over vast areas by fast-moving, turbulent, erosive gaseous density currents - a.k.a.
impact surge clouds - or by the winds as later fallout) already seems to have aroused considerable controversy
on this forum, but again that's peripheral to Emily's boulder comment.

So you're the dburt of Basal Surge fame?

"ASU geologists L. Paul Knauth and Donald Burt, who along with Kenneth Wohletz of Los Alamos National
Laboratory, say that base surges resulting from massive explosions caused by meteorite strikes offer a simpler
and more consistent explanation for the rock formations and sediment layers found at the Opportunity site."
http://www.asu.edu/news/stories/200512/200..._meteorites.htm

I haven't followed the situation closely enough to ask any good questions, but I wonder if anyone else here
would like to ask about your current views.

for reference, the basal surge thread is here:
http://www.unmannedspaceflight.com/index.p...surge&st=30

[dburt]

Thanks much for the warm welcome. Am I now supposed to feel like an innocent sheep being fattened for slaughter? (Are those knives I hear being sharpened in the kitchen?) In any case, thanks also for the brief compendium of relevant threads, some of which were old enough that I hadn't read them previously. In addition, here's a more recent thread in which a few correspondents dumped on my "mine dump" article from Eos last December:

http://www.unmannedspaceflight.com/index.php?showtopic=3643

Rather than trying to respond at length to all of the comments in these threads, I'd much prefer to make brief replies to specific points or queries. Otherwise, I may start pontificating at random, like I sometimes do in class, and that could get really boring.

Here's a warning sample: Along with many of you, I'm a firm believer in Carl Sagan's famous dictum applied to Mars, that "Extraordinary claims require extraordinary proof." So far we haven't seen that proof for most aspects of Meridiani or Gusev geology. As an example, it would be premature for me to call those enigmatic spherules "impact spherules" (not the same as tektites, BTW, because tektites are not vapor condensates like spherules, but rather are oddly shaped splash droplets) or "accretionary lapilli" or even "hematite hailstones". Of course, it is just as premature for far too many writers to baldly refer to them as "concretions" (some amateurs regard them as biological products, yet another hypothesis). "Spherules" just describes their obvious spherical shape, and "blueberries" and "BB's" describe their uniformly tiny size, without genetic connotations. For this example alone, we have at least three competing hypotheses, but so far none of them has advanced to being a theory (recall that evolution is a theory, as is plate tectonics, and even gravity). In this regard, any valid scientific hypothesis is testable, usually via making various predictions; it can become a theory only after the competing hypotheses fail their tests. Until now I haven't seen any testable predictions made as part of the MER team's remarkably complex and elegant Meridiani hypotheses, so perhaps they feel these predictions should be obvious. Nevertheless, I'd prefer to see them spelled out explicitly.

Here's another: I'm also a firm believer in Occam's razor, which (as reportedly reworded by Einstein) states that the best hypothesis is the simplest one that accounts for all the observations. Although none of us are experts on impacts (Wohletz probably comes closest, through his experience with bomb tests and exploding volcanoes), my co-authors and I settled on the impact hypothesis via the process of elimination - it seemed the simplest one that could account for all of the rover and orbital observations, and it was obviously testable. The hypothesis in one word: Boom! (Is that simple enough?) More complex: Boom, boom, boom, boom... (= multiple impacts). Well - now you've been warned about Herr Doktor Professor. Please stop me before I stick out my gut and begin to pontificate again...

--Don

[dvandorn]

...recall that evolution is a theory, as is plate tectonics, and even gravity.

I respectfully disagree with this statement. The processes are proven. Some of the mechanisms by which these processes function are not proven, and are therefore theoretical. (I have the same argument with my girlfriend... )

...recall that evolution is a theory, as is ...my co-authors and I settled on the impact hypothesis via the process of elimination - it seemed the simplest one that could account for all of the rover and orbital observations, and it was obviously testable. The hypothesis in one word: Boom! (Is that simple enough?) More complex: Boom, boom, boom, boom... (= multiple impacts).

Now, here is where you get closer to some of the mechanisms than many others, I think. While I truly believe that the Merdiani landforms and minerology were formed by groundwater and standing water (among other things), we have to be aware that impacts have modified the Martian surface far more than they have modified Earth. Impact is a primary agent in much planetary surface formation, and I agree that when you invoke Occam's Razor, the first thing you need to look at are impact processes.

...recall that evolution is a theory, as is Well - now you've been warned about Herr Doktor Professor. Please stop me before I stick out my gut and begin to pontificate again...

Hey -- as long as you don't mind our honest responses (and you don't start wearing tin-foil hats), we *love* pontification around here! Please, keep it up. Or, paraphrasing what someone once said, I may not agree with all of your hypotheses, but I defend to the death your right to express them...

-the other Doug