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. ******************************************************* QUESTION: 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 lod 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 sun. 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 would be a beautiful picture of mars, however... Thanks for the question Jim Murphy Mars Pathfinder ASI/MET Science Team ******************************************************* QUESTION: 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 ******************************************************* QUESTION: 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 missions. 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 Manager, 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. mark ******************************************************* QUESTION: 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. Matt ******************************************************* QUESTION: 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- of- site through the atmosphere between our eye and what we are seeing. Stars appear to twinkle because their light 'bounces' around with the air molecules 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 surface 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 ******************************************************* QUESTION: 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 there? 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. ******************************************************* QUESTION: 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? Thank-you. 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) ******************************************************* QUESTION: 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. ******************************************************* QUESTION: 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 temperatures? 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 warmer 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 this 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) and 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 been 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. Chris ******************************************************* ------End forward message---------------------------