Mars

General

1. Where is the "face" on Mars located?

The so-called "face" on Mars is located in the Cydonia Mensae region at roughly 40.9 degrees North latitude and 9.45 degrees West longitude.

2. How many pictures were taken of the "face"?

As many as 18 images of the region were taken by the Viking 1 and 2 orbiters, but only seven have resolutions better than 250 m/pixel. The other 11 images have resolutions worse than 550 m/pixel and are virtually useless for studying the feature. Of the seven "good" images, the lighting and time at which two pairs of images were taken are so close as to reduce the number to five usable, distinct images. All five of these can be seen at the NSSDC Photo Gallery in raw and processed forms as JPEGS. They are also available as TIFF files in the raw form only on the NSSDC Photo Gallery FTP site for Mars images. Finally, they are available in PDS image format on the NSSDC's FTP site for CD-ROMs.

3. Which images have the "face" on them?

The best images of the "face" can be found in the following Viking images/CD-ROMs (cf. Mission to Mars: Viking Orbiter Images of Mars CD-ROMs):
35A72 (VO-1010)
70A13 (VO-1011)
561A25 (VO-1021)
673B56 & 673B54 (VO-1063)
753A33 & 753A34 (VO-1028) The first two images in the list show the "face" clearly (resolutions of 47 and 43 m/pixel, respectively). The others are lower resolution (163, 226, and 233 m/pixel, respectively). Detailed image parameters are available for 35A72 and 70A13. All seven of these images have been made available in PDS format on the NSSDC's FTP site for CD-ROMs.

4. What other interesting features are visible on Mars?

This list is not intended to be comprehensive, but for example frequently requested photos of the so-called "pyramids" (located near the "face") are in frames 35A70, 35A71, 35A73, 35A74 (all on disc VO-1010), 70A11, 70A12, and 70A14 (all on VO-1011). A feature known as the "water spout" is in the images 775A10 and 775A11 (both on disc VO-1029). A feature which resembles a permafrost melt is in images 182B03 and 182B05 (both on disc VO-1054). Finally, a feature called "Inca City covered over" is in image 225B69 on disc VO-1055.
5. What is NASA's official opinion as to what the "face" on Mars is?

NASA has no official opinion on what the so-called "face" on Mars is. Most planetary scientists agree that, although there is insufficient data to make a definitive analysis of the feature, it is highly unlikely to be anything other than a combination of a natural feature and unusual lighting conditions.

6. How far is it between the Viking and Mars Pathfinder landing sites (or other features)?

The answer to this question can be found on the Martian Mileage Guide. The distance in both miles and kilometers between the Viking and Mars Pathfinder sites and some other features is given.URL: http://nssdc.gsfc.nasa.gov/planetary/mars_mileage_guide.html

7. Where can I get Martian Digital Image/Terrain/Elevation Models/Maps?

Digital terrain models of Mars are available in the Mission to Mars CD-ROM set on Volume 7:Global Topography at resolutions of 1/4, 1/16 and 1/64 degree/pixel. This volume also contains mosaicked digital image models at 1/16 and 1/64 degree/pixel and digitized airbrushed maps of Mars at 1/4 and 1/16 degree/pixel. Higher resolution (1/256 and 1/64 degree/pixel) regional digital image models and 1/16 and 1/64 degree/pixel regional digitized airbrush maps are available on Volumes 1-6 of this set. Digital color mosaics are available on volumes 8-14 at 1/64 degree/pixel. More information on DIMs of Mars and other planets and satellites is available on the Digital Image Models Page.URL: http://nssdc.gsfc.nasa.gov/planetary/dims.html

Viking

1. What do the file names for the images and directories on the Viking Orbiter CD-ROMs mean?

Images on the Mission to Mars: Viking Orbiter Images of Mars CD-ROMs (volumes VO_10xx) are given a designation of the form FxxxZyy, where xxx is a three digit number indicating the orbit number, Z is a capital letter indicating the mission: A and S are Viking Orbiter 1, B is Viking Orbiter 2, C and D indicate images taken by Viking 1 and 2 respectively before orbit insertion, X and Y indicate Viking Orbiter 1 and 2 images, respectively, acquired in an orbit with more than 100 images. The last 2 digits, yy, give the sequential number of an image taken within a given orbit. For example, F443A10 is the 10th Viking 1 image taken on orbit 443; F004Y01 is the 100th Viking 2 image taken on orbit 4.

2. Are there CD-ROMs available for any of the other Viking experiments?

Yes, the Viking Orbiter 1 and 2 Infrared Thermal Mapper (IRTM) data are available on CD-ROM from the Planetary Data System.

3. Are the Viking Lander images available on CD-ROM?

No, not at this time. PDS is planning to put the images on CD-ROM for distribution sometime in the near future. However, Viking Lander images are available on-line through the PDS imaging node Viking Lander Image Browser. The Viking Lander images are also available from NSSDC in photographic or digital format.
More information on CD-ROMs available from the NSSDC can be found in the NSSDC CD-ROM Catalog.URL: http://nssdc.gsfc.nasa.gov/cd-rom/

4. Why are the colors different on different Viking Lander images?

The Viking Lander imagers had three visible filters and three near-infrared filters. The visible filters were blue, green, and red multilayer interference filters which had very irregular spectral response, including a response to infrared light. Therefore, producing a "true" color image required the scene to be imaged in all six filters and an integrated spectral solution developed. The saturation levels at each wavelength also had to be estimated. Finally, with three visible filters, the radiance at all wavelengths not covered by these filters had to be estimated based on the response at the filter wavelengths. An array of color chips was mounted on the spacecraft to mitigate some of these problems, but accurate color reconstruction of the array in the final image, though necessary, was not sufficient to guarantee true color. Since many of the images did not have all this information available, the colors can vary significantly from image to image based on the reconstruction techniques used. It is believed that the closest to "true" color images of Mars (i.e., what one would see standing on the surface) show a light orange sky (due to suspended dust in the atmosphere) and a yellowish cast on the surface (due to sunlight filtering through the dust).(Some Viking lander images can be seen in the NSSDC Photo Gallery.)

Mars Observer

1. What happened to the Mars Observer?

An independent NASA review board concluded that the most likely cause of the loss of communication with the Mars Observer was a rupture in a line in the propulsion system during the start of fuel tank pressurization. The board cautioned that "There was no specific evidence about what actually transpired during the pressurization sequence".
On August 21, 1993 the spacecraft transmitters were turned off during the final approach to Mars to protect the components against shock from the pressurization sequence. After the transmitter was turned off the tanks were supposed to be pressurized and then the transmitters turned back on and communications with Earth resumed, but no further signals were ever received on Earth. The hypothesis is that a small amount of nitrogen tetroxide may have leaked through the check valves during the 11 month voyage to Mars and condensed in the pressurization lines. During pressurization, the oxidant would have mixed with the monomethylhydrazine fuel, causing combustion and rupture of the fuel lines. The resultant high-pressure expulsion of gasses through the rupture would have started the spacecraft spinning uncontrollably and making communication with Earth impossible. The reason that this was considered to be the most likely scenario is that the pressure check valves were not designed for a mission in which tank pressurization took place after 11 months, but rather for a pressurization soon after launch. The decision to pressurize just before entering Mars orbit was made after the check valves were already built. It is therefore likely that some oxidant could have leaked past the valves over the 11 month period.
Other scenarios that were considered likely were: 1) A failure of the pressure regulator, causing the oxidizer tank to burst, 2) A massive short in the electrical system, or 3) Damage to the fuel tank caused by an impact from one of the pyrotechnic devices fired to open valves in the pressurization lines