[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

[Shaka]

Re post #86
Prof Don,
At the risk of inflicting on you a horrible typist's RSI, I will ask you for a little more specific detail regarding the deposits left by impact surges (your paragraph #6). Though I have delved extensively into the impact literature, I am not familiar with the "finely laminated sediments" produced by "shear and steam condensation", and I wonder if you can provide me with some paper references that describe these sediments, preferably with photographs, so that I can compare them with the Burns Formation. Thank you,
Cheers,
Shaka

[dburt]

Re post #86
Prof Don,
At the risk of inflicting on you a horrible typist's RSI, I will ask you for a little more specific detail regarding the deposits left by impact surges (your paragraph #6). Though I have delved extensively into the impact literature, I am not familiar with the "finely laminated sediments" produced by "shear and steam condensation", and I wonder if you can provide me with some paper references that describe these sediments, preferably with photographs, so that I can compare them with the Burns Formation. Thank you,
Cheers,
Shaka

Shaka,

Here's a basic reference on volcanic and nuclear explosion surges, by one of my co-authors, Ken Wohletz:
http://www.ees1.lanl.gov/Wohletz/Pyroclastic%20Surges.pdf
A bit technical, I'm afraid, and not the best quality reproduction, but plenty of classic references and diagrams (see, e.g., the sand wave variations on p. 259). If you locate any good references on terrestrial impact surges, please let me know, because they are virtually never preserved on land, and the ones deposited in the sea are altered and reworked, including the spherules (so we are working by analogy from volcanic deposits, mainly). As stated in previous posts, there are plenty of reasons to suspect that Mars may be the best place to study impact surge deposits in the Solar System, and that the two rovers may have been imaging such deposits all along (including exposures in Victoria).

Ken's publications page, here:
http://www.ees1.lanl.gov/Wohletz/Publications.htm
has links to the above paper and many others, including the Wohletz and Sheridan 1983 paper in Icarus that first proposed that rampart crater deposits resulted from surges. I also attach a pdf of our 2005 Nature paper, which has some photos in addition to more discussion. Let me know if you need anything more.

--Don

Attached File(s)

 Knauthnature04383.pdf ( 529.75K ) Number of downloads: 783

 

[centsworth_II]

Here's a basic reference on volcanic and nuclear explosion surges, by one of my co-authors, Ken Wohletz:
http://www.ees1.lanl.gov/Wohletz/Pyroclastic%20Surges.pdf

I'm struck by the pictures and diagrams that do look similar to what the MERs have seen.
I hadn't fully appreciated that this sort of material existed prior to the MER mission. It
gives the whole base surge theory a kind of predictive quality as opposed to reactive.

The picture on page 292 really struck me. The first I had ever heard of a volcanic "bomb" was
when the one at Home Plate was described. This picture looks like my second exposure to
a "bomb". Strangely though, I don't see specific mention of it in the text.

Here is the picture (top) with it's caption. The Home Plate image is below (not to same scale).

"A typical wet-surge
outcrop exposure described
by Sohn and Chough (1992)
showing irregular and scourfill
deposits and massive
bedded deposits. Photograph
from Sohn and Chough"