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Preliminary Activities
1. What surface conditions prevail on Mars?a.Cold, dry, dustyb.Warm, dry, dustyc.Cool, wet, crustyd.All of the above
2.How might the surface conditions on
Mars be related to ambient electrical activity?a.Conduciveb.Not conducivec.A little conducived.Conditionally Conducive
3.Which surface element on Mars would you think most likely to develop and carry charge?a.Rocksb.Dustc.Duracrustd.Volcanic glass
4.What charging mechanisms do you
believe are operational on Mars?a.Collisional chargingb.Triboelectric (frictional) chargingc.Photoelectric effectd.None of the above
5.What are some issues associated with surface vehicle and astronaut charging?a.No issuesb.Charge is harmlessc.Charge could impact operationsd.Charge could produce fatal
conditions
Mars
Mount Olympus
“Old” Surface - Mantle
North Pole
Tarsus
Mariner’s Valley
Northern Desert
Cirrus Clouds
Why go to Mars???
Most earth-like planet
Reachable via present day technology
Possible future colonization
…
Simple curiosity – It’s there!!!
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.
Environmental Issues at Martian Surface
Radiation environment
Chemistry
Toxicity
Electrical charge
Biology (?)
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
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
Paschen Curve Minimum
Pressure-Distance Product
Ele
ctr
ic P
ote
nti
al D
iffere
nce
10
0V
5 X 10-5 atm-m
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.
Theory:
Predicts charging
Laboratory:
Confirms prediction
Pathfinder:
Similar to laboratory
Mars:
Does charging actually occur??
Conclusions
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.
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?