Washington State Flood comparison, at last!

From: wecooks@ix.netcom.com
Subject: Washington State Flood comparison, at last!
Date: Wed, 16 Jul 1997 08:48:19 -0500 (CDT)

Someone earlier complained that, Why don't the scientists compare the Mars 
site to flooding in Washington???   Here it is!  From the LFM Questions Site

QUESTION: Please can you tell me if the whole of mars is mapped either 
showing topographic or geologic information and at
what scale it is mapped to and whether or not the maps
are available to the general public to buy or view?
Thank you for your time.

ANSWER from Jim Murphy on July 15, 1997:
Yes, mars is mapped both topographically and geologically, from information
gained with the Mariner 9 orbiter and the Viking orbiters.  

The scale of the topographic mapping is on the order of a kilometer or two,
I believe.  As for the geologic mapping, I'm not sure.   The topography
data set can, I think, be obtained from NASA's Planetary data System (PDS),
which can be accessed via the web.  Additionally, the US Geological SUrvey
office in Flagstaff can be contacted.

As for the geologic map, that might be available on the PDS as well.  USGS
in Flagstaff would probably know where to obtain it.

QA: color of martian sky (is it ever blue)?

I have a
question about the color of the martian sky.  I realize that at least
currently at the Pathfinder landing site the sky is reddish-brown due to
suspended dust in the atmosphere.  However, before the lander touched down,
it was postulated that due to colder, cloudier weather on Mars recently
that the sky would not be so dusty and would in fact be of a dark blue
color.  After the lander touced down it was commented that the atmosphere
was dustier than originally thought.  My question is: does the Martian sky
ever appear blue and under what circumstances and is there any chance of it
turning blue during the Pathfinder mission?  Thanks for your time in
answering this question.

ANSWER from Jim Murphy on July 15, 1997:
This is a great question about martian sky color and suspended dust, and we
here on the Pathfinder meteorology have spent quite a bit of time talking
about it.   If the martian atmosphere were completely clear of dust, I think
that the sky would be quite a bit darker than clear skies here on earth.
If you have ever flwon on a plane at 30,000-35000 feet during daytime, and 
at the sky, you might have noticed that it appears much darker than from
the surface, especially when you look at particular angles away from the 
This darker appearance is due in part to the reduced scattering the light
experiences at these high altitudes (low air pressures..like on the surface
of mars!!) compared the much greater numbers of molecules the sunlight can
'bump' into on its way to the surface.   Blue light is scattered more
effectively by molecules than is the longer wavelength red light, which
is why the sky looks blue.

I don't expect that the martian atmosphere will clear substantially during
Pathfinder's mission on the surface.  In fact, I expect the atmospheric dust
content to increase as summer gives way to autumn.  But, if the atmosphere
were to clear (I've blown forecasts before :-)  ),the sky would be bluer,
but not the light blue that we see on a terrific day here on Earth.  It 
be a beautiful picture of mars, however...

Thanks for the question

Jim Murphy
Mars Pathfinder ASI/MET Science Team

What is the priority for updating the web page
images? Who gets "first crack" at new images and commentary?
ANSWER from Marc Siegel on July 15, 1997:
I think that everybody gets first crack at the images together.
Once images are made public through a press conference or other 
release by the scientists, then folks are welcome to put them online.

I know that the Pathfinder team is lean and mean and they have only
two people to handle all of their web work.  So it is not surprising
that you'll find material on other sites (with bigger staffs).
My suggestion is to use the online resources that work best for you.
If that is USA Today, so be it.

My group is responsible for the Live From Mars site and we don't even
try to stay current with the latest news about Pathfinder.  We think 
that is what links are for.  Instead, we'll continue to focus on the
people of the Mars team: their stories, webchats and email Q&A.
Our site is http://quest.arc.nasa.gov/mars

ANSWER from Marc Siegel on July 15, 1997:
How often is your web page updated with mission information?

At this time, the Mars Pathfinder web site is updated daily with new 
information.  The Live From Mars web site is updated less frequently
since it focuses on the people behind-the-scenes (not the latest 
mission information). For mission info, the Live From Mars web site
relies on pointers to the Pathfinder site.
Thanks for asking, Marc

Person in charge

Hello, I am very interested in the Mars missions.  I hope that you can 
clear up a few things for me.

First of all, who is the main person involved in the missions that
are going on now, and the future missions.

Thank you for your help and I appreciate it much.

ANSWER from Mark Adler on July 9, 1997:
>> First of all, who is the main person involved in the missions that
>> are going on now, and the future missions.

There is no "main person involved"--these missions are a team effort by a  
large number of people, all of whom are critical to the success of these  

Perhaps what you're asking is who's in charge of Mars missions currently?   
Well, there's Wes Huntress at NASA HQ, in charge of space science at NASA.   
There's Norm Haynes, head of the Mars Exploration Directorate at JPL.  Donna  
Shirley is the manager of the Mars Surveyor Program.  Tony Spear is the  
project manager for Pathfinder, Jake Matijevic is the Sojourner rover 
and Glenn Cunningham is the project manager for Mars Global Surveyor.

But keep in mind that managers, while they are leaders, are just one part of  
the team.


I have seen and read about the interest in these two peaks in the distance.
Is the rover capable of climbing one of the peaks to take another 360 degree 
panorama? Hence, what is the maximum angle of inclination that the 
rover could climb? And finally, would this "climbing" be too risky in 
the event that the rover could topple over?

ANSWER from Guy Beutelschies on July 15, 1997:
The "Twin Peaks" are probably too far away for the Rover to ever reach.
We have restrictions based on our modem range and our motor life.

The Rover can climb at angles of 30 deg, and more. The vehicle has
accelerometers that sense the Rover pitch and roll, and the Rover will
stop if it exceeds it exceeds predetermined safe limits.


As I understand it, the difference in atmosphere affects our perception
of sensory information (such as depth perseption).  Is this true, and if
so, how different is what we see in the photos of Mars to the reality?

ANSWER from Jim Murphy on July 15, 1997:

The atmosphere can distort our view, but that usually requires a long line-
site through the atmosphere between our eye and what we are seeing.   Stars
appear to twinkle because their light 'bounces' around with the air 
between the top of the atmosphere and our eye before striking our eye.

The perception we all are gaining from looking at the terrific images
being returned by Mars Pathfinder's IMP do a good job of showing us what
the surface would look like if we were there.  There are some variations
between what the camera sees and what we see (we see across the entire
visible wavelength spectrum, while IMP looks at only specific wavelengths,
for instance).  ALso, with dust in the atmosphere, the light striking the 
appears different than if the atmosphere were clear, and as a result some
features might have more intense colors if seen in direct sunlight.

Jim Murphy
Mars Pathfinder ASI/MET Science Team

I have a question about the duration of daylight at Ares Vallis.  The
information supplied on the Web by the JPL stipulated that sunrise on 4
July occurred at 22:00 UT and sunset came at 06:30 UT on 5 July.  That
would indicate only 8.5 hours of daylight at the site.  However, since a
Martian Sol is 24.67 hours, and it is currently summer in the northern
hemisphere where Ares Vallis is located, how could there only be 8.5
hours of daylight?  There should be a minimum of 13 hours shouldn't

ANSWER from Ted Roush on July 15, 1997:
I could not find specific reference to sunrise/sunset but I do
recall seeing a figure showing the data from the sun sensor that
indicated the landing site was in darkness from about 20:30 to about
03:30 the next morning.  This is certainly more consistent with it being
summer in the northern hemisphere.  Perhaps the information at the JPL
web site was incorrectly entered.

QA: Geology conclusions

Two things amaze me.  First, isn't it early to conclude that the
patterns of deposition are necessarily caused by flooding?  What
observations rule out aerobic erosion and deposition?

Second, why are scientists so quick to conclude that there was a
catastrophic flood on Mars and so slow to conclude that the Earth could
have experienced the same kind of event?


ANSWER from Jeff Plescia on July 15, 1997:
The conclusion that the Pathfinder site was in the a large flood
plain was based on the Viking oribiter images.  In fact that is
why the site was chosen, because it was hoped that there would be
a wide diversity of rock types there (carried by the flood).  The
surface features observed in the Pathfinder images (e.g., the
grooves and the imbricated rocks) are consistent with such an
interpretation.  The scale of the erosion is too great to be caused
by the wind and the vertical extent of the erosion (that is above
a certain altitude things are not eroded) require a fluid moving
along the surface.  The rocks in the Pathfinder scene could not be
moved by the wind.

The earth has experienced the same kinds of floods that are suggested
for the Pathfinder site.  The channeled scablands of the state of
Washington are a good analog.  There a large lake formed behind
a glacier.  When the dam broke, water washed across Washington to
the Pacific ocean and eroded the ground.
Jeff Plescia
Jet Propulsion Laboratory
MS 183-501
Pasadena, CA 91109
818 354 7356 (Phone)
818 354 0966 (Fax)
jeff@lithos.jpl.nasa.gov (email)

QA: about imbrication

It has been claimed that the imbrication is due to flow
of water.  Imbrication is consistent with that.  However, you
are right, some of the rocks, particularly the angular ones
and maybe the imbricated ones, could be from the nearby
impact crater.  There has not been time yet to do the details
of the direction of imbrication with respect to the crater and
the flow directions and to measure the size of the rocks.

ANSWER from Jeff Plescia on July 15, 1997:
It has been claimed that the imbrication is due to flow
of water.  Imbrication is consistent with that.  However, you
are right, some of the rocks, particularly the angular ones
and maybe the imbricated ones, could be from the nearby
impact crater.  There has not been time yet to do the details
of the direction of imbrication with respect to the crater and
the flow directions and to measure the size of the rocks.

Mars temperature changes

Is there any hypothesis related to the temperature change on Mars from
the past warm ones (enough to have liquid water) to the actual cold

ANSWER from Jim Murphy on July 15, 1997:
   Yes, there are several hypotheses relating to how mars may have been warm
 and wet in the past but is now colder and drier.  Some theories for a 
 mars in the past invoke a much more massive atmosphere of carbon dioxide
 which generated a significant 'greenhouse' effect which raised surface 
 temperatures above the water melting point.  Additionally, other plausible
 gases could have been present and contributed to greenhouse warming.  If 
 CO2 greenghouse effect were the case, then the question is:  where did all
 that CO2 go?   Some could have dissolved in  oceans (if they were present) 
 formed carbonate rocks, but the evidence for such rocks is not too terribly
 convincing (at least, that is waht I undes`rstand from listening to my
 geologist colleagues).  Some researchers believe that Masr may not have 
 too much warmer in the past, but that impacts and tectonic avtivity might
 have melted and released vat reservoirs of sub-surface ice which then
 'ran' down hill forming the large outflow channels like the one the Mars
 Pathfinder lander is presently located at the mouth of.

  Jim Murphy
  Mars Pathfinder ASI/MET Science Team

ANSWER from Bridget Landry on July 15, 1997:
> What kind of compression software and algorithms did you use ?

We have two main types of compression software, a lossy
version (similar to JPEG) and a lossless version (developed from
the RICE algorithm).  With our lossy compression we have many
different options which include:
Least Cosine Transform, Arithmetic Encoding, Huffman tables,
different quantization tables, and pixel averaging, compression ratios
and quality factors.  Some of these options are used together for a
single image.

> What were your constraining factors and what did you base your
> decision on ?

	Some of the constraining factors were:
	1) Development time / delivery schedule.
	2) Robustness to data loss.
	3) Memory usage.
	4) Image processing time.



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