ON A POSSIBLE DUST-PLASMA INTERACTION AT MARS

According to present theoretical models, material ejected from the Mar tian satellite Phobos due to meteoroid bombardment and tidal coupling can stay for a long time in circular orbits near the planet, forming a dust belt. The dust particles are moving through various plasma domai ns of the Martian magnetosphere and may undergo electrostatic disrupti on there, producing very fine motes in the range 0.005-0.1 mum which c an stay positively charged for a time comparable with the orbital peri od. A negatively charged spacecraft will attract such particle and an ion spectrometer with wide enough mass range (1-10(8) amu/Q, where Q i s the particle charge) may detect these grains. Our model can explain observations made by the ASPERA mass spectrometer during the PHOBOS mi ssion when signals in the num channels 10(3)-10(7) amu were detected i nside the Martian magnetosphere. The evolution of a grain orbiting Mar s is shown in a diagram of the particle size-particle potential. Such a diagram a qualitative picture of the grain interaction with the Mart ian plasma environment.