[X] My Assistant

[tdemko]

(alternative topic title: Opportunity lost its lens cap!)

http://umn.edu/home/tdemko/webpage_photos/...tahberries.html

I've put up this small website showing some pictures of spherule-like concretions in the Lower Jurassic Wingate Sandstone from the San Rafael Swell in central Utah that are at least superficially similar to the Meridiani Planum concretions imaged by the MER Opportunity.

The Wingate Sandstone was deposited by large wind-blown sand dunes in the great western Pangaean desert during the Early Mesozoic. It is a totally continental deposit (deposited in a terrestrial desert setting). These concretions are presumably related to groundwater-related cementation during early diagenesis and have been accentuated in these outcrops by weathering in the modern desert environment.

Enjoy!
--
Tim Demko
http://umn.edu/home/tdemko

[djellison]

Now that IS analagous to meridiani - seen lots of people say "isnt this just like..." - when really - it isnt - but your site actually is - interesting stuff

What sort of time-scale does one need the water to be around for, for concretions such as those to form? A few thousand years, hundreds of thousands? Longer?

Doug