[X] My Assistant

[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

[don]

dburt - not that I’m a “brine splat” or “mine dump” groupie or anything like that but I do recall a question you asked following a MER member presentation at GSA in Salt Lake City a few years ago that raised some reflexive hackles. The question you asked was reasonable and the presenter responded quite persuasively with an explanation singing praises for eutectic brines (or something like that). Yet when you responded by the way (I paraphrase) I’m the one that introduced the concept of eutectic brines to mars the presenter realized who you were and immediately became defensive and curt. That moment for me stood out because it became evident (to no surprise) that it’s difficult being outside looking in when it comes to the MER project, if you don’t tow the party line you can be viewed as a non-friendly.

Regarding sulfide - in the recent (2007) Sqyures et al “Pyroclastic Activity at Home Plate in Gusev Crater Mars”, it’s mentioned that the rock “Fuzzy Smith” had a unique MB Fe mineralogy that’s consistent with a Fe sulfide such as pyrite or marcasite (evidently not detected in any other martian rock). Unfortunately the composition or oxidation state of the Fe was not determined and a sulfide confirmation could not be made. An interesting remark nonetheless.

the other don