1. Exploring Mars Pathfinder Rover Electrostatic Charging October 8 th 2002 Joseph Kolecki.

2. Preliminary Activities 1. What surface conditions prevail on Mars? a.Cold, dry, dusty b.Warm, dry, dusty c.Cool, wet, crusty d.All of the above 2.How might the surface conditions on Mars be related to ambient electrical activity? a.Conducive b.Not conducive c.A little conducive d.Conditionally Conducive

3. 3.Which surface element on Mars would you think most likely to develop and carry charge? a.Rocks b.Dust c.Duracrust d.Volcanic glass 4.What charging mechanisms do you believe are operational on Mars? a.Collisional charging b.Triboelectric (frictional) charging c.Photoelectric effect d.None of the above

4. 5.What are some issues associated with surface vehicle and astronaut charging? a.No issues b.Charge is harmless c.Charge could impact operations d.Charge could produce fatal conditions

6. Mars Mount Olympus “Old” Surface - Mantle North Pole Tarsus Mariner’s Valley Northern Desert Cirrus Clouds

7. Tarsus

8. Mount Olympus

9. Mariner’s Valley

10. Martian arroyos as seen from orbit…

12. Fossil Martian Nano-Bacteria? ~100 nm

13. Why go to Mars??? Most earth-like planet Reachable via present day technology Possible future colonization … Simple curiosity – It’s there!!!

14. Why Send Robots to Mars??? Robots are “more durable”/less expensive than humans. Robots can accomplish almost as much as humans. Robots can help us to learn as much as we can about the Martian environment before we send humans.

15. Environmental Issues at Martian Surface Radiation environment Chemistry Toxicity Electrical charge Biology (?)

16. Electrical Charging in the Martian Environment ++++++++++ ----------

17. Why expect charging on Mars? Cold, dry climate – good for charging things up Seasonal winds – good for stirring things up Dust storms – good for keeping things stirred up in a variety of ways

18. What physical mechanisms might be involved? Collisional charging due to turbulent motion in dust clouds & dust storms Triboelectric charging due to vehicle or astronaut motion across the surface Photoelectric charging due to solar UV at the surface

19. Collisional Dust-Charge Exchange Mechanism

20. + - e-e-

21. Effects of Collisional Charging in a Martian Dust Cloud

22. Paschen’s Curve Pressure-Distance Product Electric Potential Difference

23. Paschen Curve Minimum Pressure-Distance Product Electric Potential Difference 100V 5 X 10 -5 atm-m

24. Sojourner Rover: Triboelectric charge = Frictionally generated electric charge

25. Rover Charging Scenario Each wheel rolls over surface dust bearing down with 1/6 of rover weight. Dust beneath wheels becomes compressed. Grains rub together liberating charge. Large grains (-) Small grains (+) Small grains cling to wheel charging rover. Large grains remain behind as charged wheel track.

27. Dust collection in laboratory + - + 150 V - 150 V

28. Clogged wheel Wheel track

29. Clogged Wheels!

31. Theory: Predicts charging Laboratory: Confirms prediction Pathfinder: Similar to laboratory Mars: Does charging actually occur?? Conclusions

32. Because of mass constraints on rover, no instruments were carried to measure charge. Instruments will be carried on future landers and rovers to better characterize Mars’ electrical environment.

36. Some Issues Remaining to be Solved What is the nature of Martian surface electricity? Do electrical discharges accompany dust storms? Dust devils? Can these storms be detected by radio static? Does triboelectric charging pose a hazard to future large rovers? To future astronauts?

37. joseph.c.kolecki@grc.nasa.gov