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Viking Lander Labeled Release Experiment Archive (PDS)


Availability: At NSSDC, Ready for Offline Distribution (or Staging if Digital)


This data set contains the data returned by the Viking Biology Labeled Release (LR) Experiment carried on the Viking 1 and 2 Landers. The digital data were transcribed from computer printouts and microfilm. Data collected by the LR instruments included radioactivity counts from evolved carbon-14 labeled gas and temperatures of the detectors and the head-end assembly. Radioactivity was counted for 16-minute intervals during an analysis cycle, except for several hours around the time of nutrient injection where intervals of 2- to 4-minutes were used. Detector and head-end temperatures were measured at 16-minute intervals throughout the cycle. Measurements are tagged with the time they were made and are stored in a time-ordered format.

RADIOACTIVITY COUNTS: Radioactivity in the LR data set are given as counts/minute. Counting was generally done over a 16-minute period and then normalized by the length of the counting interval to determine the average number of counts/minute within that interval. Each LR instrument had two solid-state beta detectors and could be commanded to use either one or both detectors. In cases where only one detector was used, radioactivity values were corrected to values equivalent to counting with both detectors. The radioactivity recorded by the LR detectors included a background signal from the Mars environment and from the Radioisotope Thermoelectric Generators (RTGs) that powered the Viking Landers. Background levels were determined from radioactivity measurements made prior to the start of an analysis cycle. Radioactivity values with and without background correction are provided for measurements made during the incubation period of an analysis cycle.

TEMPERATURES: Both detector and head-end temperatures in the Labeled Release data set are given in degrees Celsius. Temperatures were measured every 16-minutes throughout an analysis cycle. Sample temperature are less than those recorded by the head-end temperature sensor because the test cell heaters and temperature sensors are located at the top of the test cell above the sample. See LEVIN&STRAAT1977A for information on correlating head-end and sample temperatures.

TIME: The primary time tag for the LR data set is known as Mars mission time. It is defined as the number of Earth seconds past midnight of Sol 0, where Sol 0 is the day of landing (P. A. Straat, personal communication, 2000). Mars mission time values in this archive have been transcribed from the computer listings or microfilm.

All ancillary time fields in the LR data set were computed from the Mars mission time parameter. The LR data consists of three files for each analysis cycle. Each table has an associated detached PDS label.

The LR data were originally archived on microfilm housed at NSSDC. LR data were also available from a set of computer listings in the personal archives of Co-Investigator Dr. Patricia Ann Straat. All radioactivity , temperature and Mars mission time data in this LR data set were transcribed by hand into data files. The primary data source was computer listings supplied by P. A. Straat. The NSSDC microfilm was used to recover data for gaps in the computer listings. Personnel at the PDS Geosciences Node transcribed the computer listings, whereas personnel at NSSDC transcribed the microfilm. All data entered by hand was checked for accuracy. However, typographical errors may still exist in the data set. See the CONFIDENCE_LEVEL_NOTE for estimates of the data entry accuracy. The data are stored on CD_ROM volume VL-9010, PDS data set ID VL1/VL2-M-LR-2-EDR-V1.0. This data set is also available online at:

Alternate Names

  • PDS VL1/VL2-M-LR-2-EDR-V1.0
  • VL1/VL2-M-LR-2-EDR-V1.0


  • Planetary Science: Biology


  • 75-075C-03G
  • 75-083C-03G

Additional Information



Questions and comments about this data collection can be directed to: Dr. David R. Williams



NameRoleOriginal AffiliationE-mail
Dr. Edward A. GuinnessGeneral ContactWashington

Selected References

  • Levin, G. V., and P. A. Straat, Viking labeled release biology experiment: Interim results, Science, 194, No. 4271, 1322-1329, doi:10.1126/science.194.4271.1322, Dec. 1976.
  • Levin, G. V., and P. A. Straat, Recent results from the Viking labeled release experiment on Mars, J. Geophys. Res., 82, No. 28, 4663-4667, doi:10.1029/JS082i028p04663, Sept. 1977.
  • Levin, G. V., and P. A. Straat, Completion of the Viking Labeled Release experiment on Mars, J. Mole. Evol., 14, No. 1-3, 167-183, doi:10.1007/BF01732376, 1979.
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