This is a very old talk from around 1999 that I gave to my department at the Free University of Amsterdam. It\'s very out of date now, but still interesting.

2. A comparison of Mars and Earth 23.9 24.6 Rotation period (h) Yes (71%) ??? Surface water Yes No Magnetic field Yes No (ancient) Tectonic activity 1 2 Moons N 2 78% O 2 21% Ar, CO 2 , noble 1% CO 2 95.3% N 2 2.7% Ar 1.6% Atmospheric composition 1 014 7 (1-9) Atmospheric pressure (mb) 287 218 (140-300) Surface temperature (K) 1 0.38 Gravity 1 1.52 Distance from Sun (AU) 12 756 6 794 Diameter (km) Earth Mars Property

3. Astronomical observations of Mars 1877: Schiaperelli describes “canali” 1906: Lowell writes “Mars and its Canals” 1997: HST view of dust storms on Mars

4. Mars, life and science fiction

5. The history of Mars exploration

6. The Mariner 4 flyby, 1965

8. Orbiter images 1: Valles Marineris

9. Orbiter images 2: Olympus Mons

10. Orbiter images 3: dust storm

11. Orbiter image 4: the Cydonia region Viking orbiter image Close up of “face” MGS image “ Happy face” crater from MGS

12. Lander image 1: Viking 2 landing site

13. Lander image 2: frost at Viking 2 landing site

14. GEX/LR/PR: gas exchange experiment Soil sample incubated in complex organic medium for 12 days under CO 2 , He and Kr Head space analysed by GCMS for CH 4 , CO 2 , H 2 , N 2 , O 2 Results: O 2 was evolved. However, this occurred in a heat-sterilised sample. An inorganic oxidant is the preferred explanation.

15. GEX/LR/PR: pyrolytic release experiment Soil sample incubated with 14 CO and 14 CO 2 for 5 days under xenon lamp illumination Sample pyrolysed at 625 °C and 14 C detected in gas sample Results: Some 14 C was fixed. However, some fixation was also seen in a heat-sterilised sample. An inorganic oxidant is the preferred explanation.

16. GEX/LR/PR: labelled release experiment Soil sample incubated with 14 C-labelled formate, glycine, D/L alanine, D/L lactate and glycolate 14 C in evolved gases is detected Second application of labelled medium. Both responses are compared to a heat-sterilised control. Results: 14 C-labelled gas was evolved. Levels fell initially after the 2 nd application, but then increased. No gas evolution in heat-sterilised samples.

17. Typical LR response using Martian soil

18. Comparison of LR experiments on Earth and Mars

20. The principal objections and refutations Current thinking on this differs to that of 1970s Independent origin of life Gas was reabsorbed-terrestrial soils have show similar response Decrease in gas evolution on 2 nd injection Kinetics are similar to several terrestrial soils from extreme environments “ Too much too soon” Recent physical data suggest liquid water can form and persist at the surface No liquid water at surface Samples taken from under rocks show identical LR response Effect of UV light at surface Recent data suggest H 2 O 2 levels much lower than postulated Presence of inorganic oxidants, especially H 2 O 2 Viking GCMS shown not to detect organic compounds in some Antarctic soils with a positive LR response. Martian meteorites contain organic compounds. No organic matter detected by GCMS Counter-argument Objection

22. Was there life on Mars? Meteorite ALH84001 is one of 18 known meteorites from Mars