Terraced Hills of Mars
(1 of 3)
In article , "Rick"
writes:

Date: Wed, 24 Dec 2003 00:36:34 -0800
Beside a liquid lake or ocean, what other possible explanations
could account for these terraced hills?
http://antwrp.gsfc.nasa.gov/apod/astropix.html

Hi Rick, and Greetings Y'all.

First let me note that the above URL link to the APOD (Astronomy Picture of the
Day,) shows different daily pictures.

Here's the Archive link to the Terrace pictu
APOD: 2003 December 24 - Layered Hills on Mars
http://antwrp.gsfc.nasa.gov/apod/ap031224.html

And the small (on that page) jpg picture and larger gif it links to:
http://antwrp.gsfc.nasa.gov/apod/ima...shills_mgs.jpg
http://antwrp.gsfc.nasa.gov/apod/ima...ls_mgs_big.gif

RC7-note: The larger gif includes landscape (north?) of the terraces which
looks a little like glacial (ice age) geology, (sort of like the "Land of
Lakes" area of Canada,) but it looks even more like what would result from
massive tidal surges resulting from oceanic asteroid impacts.

But let's re-read the PICTURE CAPTION from that page:

"Explanation: Why are some hills on Mars so layered? The answer is still under
investigation. Clearly, [dark windblown sand] surrounds outcropping of light
[sedimentary rock] across the floor of crater [Arabia Terra]. The [light rock]
clearly appears structured into many [layers], the lowest of which is likely
very old. Although the [dark sand forms dunes], rippled dunes of lighter
colored sand are easier to see surrounding the stepped [mesas]. Blown sand
[possibly] itself eroded once-larger mesas into the layered hills. Most of the
[layered shelves] are wide enough to drive a [truck] around. The [above image],
showing an area about 3 kilometers across, was taken in October by the [Mars
Global Surveyor spacecraft] currently orbiting [Mars]."

RC7-note: Square brackets were added to Caption to signify links on the
original web page. These links from that page have additional info:

Link: Arabia Terra
http://www.msss.com/mars_images/moc/dec00_seds/8N7W/
Link: layers
http://science.nasa.gov/headlines/y2000/ast04dec_2.htm

RC7-note:
The Arabia Terra link above indicates roughly 8 degrees North Latitude and 7
degrees West Longitude for the area, making it close to the present day
equator. Note also that the hills are within a larger "crater" area, meaning
the crater was made, before the area was under water, when the "sedimentary
rock" was formed - possibly a crater lake/sea for awhile, and erosion of the
crater rim gradually allowed water to escape? Of course, there would have to
have been a lot more atmosphere then, as well as warmer climate for liquid
water. (I remember swimming in a water filled bomb crater in Vietnam - What
people do to be cool.

RC7-comments:
There are at least two impact tidal surge possibilities that could result in
sedimentary layers that come to mind. One would be that this area was under
water when this crater area was made, and the suspended dirt and silt settled
directly into place. The other, as hinted at the beginning of this message, and
seems more likely - is that an oceanic impact(s) elsewhere sent one or more
tidal surges into this area, filling the (later to be) terraced area with
sediment and producing the washed out streaked area at the upper part of the
larger gif. Note the 4 nearly parallel almost evenly spaced streaks in the
upper right.

RC7-comments:
I probably shouldn't mention this, but when I first saw the Terrace picture, my
first thought was "STRIP MINING", and the caption did say -most- of the shelves
are wide enough to drive a -truck- around. (Oh, oh, did I just give the "Mars
Face" Folk more ammunition? Nah, they'll probably interpret it as an equatorial
hanging gardens paradise resort.

(This one looks more like a strip mine though
http://antwrp.gsfc.nasa.gov/apod/ap030815.html

Clear Skies! --Richard

(Please see also my next message. Thanks.