Lecture 28. The Viking Lander Missions.

1. Lecture 28. The Viking Lander Missions. reading: Chapter 7

2. Viking Mission Launched in 1975, arrived in 1976. Twin Orbiter and Lander mission. Orbiters operated for 4 and 6 years. VL1 lasted 6 years, VL2 lasted 4 years on the surface. During descent through the atmosphere, landers measured composition of the atmosphere. Landers were sterilized before launch. Goal: Detect life on Mars

3. Orbiters Returned 52,000 images Observed new and puzzling terrain Provided some color and stereo images. Mapped >87% of the surface. Infrared thermal mappers Atmospheric water detectors. Determined that the permanent N polar cap made of water ice. S polar cap made of water ice and CO2 ice.

4. Viking Landers 600 pounds Each lander had 2 RTG (radioisotope thermoelectric generators) convert heat to electricity. Landers require 70 watts of power.

5. Viking Lander Landing Sites Chosen before launch, but orbiters found them too rocky - too dangerous to land. VO1 searched for ~3 weeks before finding landing sites.

6. Camera Each lander had 2. Didn’t use film. Moveable mirror scans up & down, photodetectors measure the amount of light. To create an image, camera is rotated slightly and scanned again. Weren’t originally planned - argued they are a form of life detection. More than 1500 images taken, to note changes in seasons and dust storm activity. First picture of the surface of Mars. VL1

7. Surrounding Rocks vesiculated basalt - caused by gas bubbles as the lava solidifies similar to basalt seen on Earth

8. Martian Weather Meteorology experiment measured on a boom away from the lander P (~7 millibars during summer) T (-58˚C mean summer) wind speed (gusts up to 65 km/hr) wind direction VL1 summer T as high as -14˚C at noon, but -77˚C on sunrise. VL2 winter day/night T’s very similar Lowest predawn T was -120˚C, about the frost point of CO2 Winter produced a thin layer of water frost on the ground. VL1 P varied from 6.8 - 9.0 millibars. LV2 P varied from 7.3 - 10.8 millibars. CO2 freezes out to form polar caps each winter, disappears in the spring.

9. Martian Weather, cont. Wind Speeds slower than expected. Gusts during dust devils and wind storms. Observed ~ 12 small dust storms. Two global dust storms, ~4 months apart. Both hid the planet’s surface from the orbiter’s cameras.

10. Soil Composition Scooped up soil with soil sampler on a boom. Dropped soil into an X-ray Flourescence Spectrometer Exposed to X-rays Each element in the soil absorb X-rays, re-emit at characteristic energy levels. Soil dropped out of the container when done. Soil at VL1 and VL2 similar. Mostly composed of Si and Fe, consistent with basalt. Sulfur content surprisingly high. Magnets on the sample arm attracted soil particles. Soil contains a duricrust.

11. Seismic Experiment VL1 didn’t work. VL2 - only one possible seismic event. Showed Mars has very low seismic activity.

12. Four Biology Experiments - GCMS 1. GCMS - gas chromatograph mass spectrometer GC separates out different gases MS measures their masses and amounts of each mass Scooped soil into oven. Heated soil to 500˚C to pyrolyze (break apart w/ heat) any organics Pass through the GCMS Found no organic compounds Sensitivity: few parts per billion 10 million times less what you would find on Earth soil

13. Four Biology Experiments - Pyrolytic Release Expt PR Expt (also called the Carbon Assimilation Expt) Take 0.25cc soil Add moisture (water vapor) Add 14CO2 and 14CO (radioactive martian atmosphere) Incubate 5 days under a Xenon lamp Flush out the atmosphere Heat soil to 625˚C to pyrolyze any organic matter Pass the broken down organic matter through a 14C detector Test to see if there are ___________________. Results: Found 14C incorporated into the soil. Suggested metabolism is possible.

14. Pyrolytic Release Expt Control What is an experimental control? Pre-treated the soil to kill any potential organisms by heating to 175˚C for 3 hours. Control PR Expt: Also found 14CO2 incorporated into the soil. So, is this due to microbial metabolism?

15. Four Biology Experiments - Gas Exchange Expt Gas Exchange Expt, GEX Take 1 cc soil Partially submerge in broth of complex organic compounds (“chicken soup”) Incubate 12 days in simulated martian atmosphere Monitor for the release of gases that might be due to respiration or fermentation. H2, O2, CH4, CO2 Results: O2 was released in both the dark and the light. Could this be oxygenic photosynthesis?

16. Four Biology Experiments - Gas Exchange Expt, cont. Found O2 released even when just water vapor is added. Control: Pre-heated soil then added broth Saw release of O2 after pre-heating. So, is this evidence of life?

17. Four Biology Experiments - Labeled Release Expt 4. Labeled Release Expt (LR) Take 0.5 cc soil Add 1 cc dilute, simple organic nutrients labeled with 14C (glycine, alanine, formate, lactate, glycolate) Are organic compounds made by Miller-Urey experiments. Look for release of radioactive gases (14CO2) Results: Radioactivity increased, then fell down. If more nutrients were added, radioactivity increased then fell down. Heating the soil to 50˚C reduced radioactivity release. Control: Preheating to 160˚C eliminated radioactivity release.

19. VL1 Panorama

20. VL2 Frost during Northern Winter

21. Meteorological Boom and Trenches made from soil sampling

22. Lecture 29. Jupiter and the Galilean Moons, Tides and Friction. reading: Chapter 8