Electrostatic Dust Ejection From Asteroid (3200) Phaethon With the Aid of Mobile Alkali Ions at Perihelion

Abstract

The asteroid (3200) Phaethon is known to be the parent body of the Geminids, although meteor showers are commonly associated with the activity of periodic comets. What is most peculiar to the asteroid is its comet-like activity in the ejection of micrometer-sized dust particles at every perihelion passage, while the activity of the asteroid has never been identified outside the near-perihelion zone at 0.14 au from the Sun. From the theoretical point of view, we argue that the activity of the asteroid is well explained by the electrostatic lofting of micrometer-sized dust particles with the aid of mobile alkali ions at high temperatures. The mass-loss rates of micrometer-sized particles from the asteroid in our model is entirely consistent with the values inferred from visible observations of Phaethon's dust tail. For millimeter-sized particles, we predict three orders of magnitudes higher mass-loss rates, which could also account for the total mass of the Geminid meteoroid stream by the electrostatic lofting mechanism.

Electrostatic Repulsion of Dust from Planetary Surfaces

“…This way, large mm-size aggregates are easily lifted in a fraction of a second after sticking to the electrode, while small aggregates cannot gain enough charge for lift-off. In agreement to earlier works by Kok & Renno (2006) and von Holstein-Rathlou et al ( 2012), conduction is one viable mechanism in aeolian transport to reduce the necessary gas drag for lift, but if adhesion is lower it might also provide electrostatic repulsion from atmosphereless bodies (Kimura et al 2022;Hirata et al 2022).…”

“…Also, atmosphereless bodies typically have less gravity. In any case, Kimura et al (2022) and Hirata et al (2022) point out that there are also strong electric fields on the surface of atmosphereless bodies due to photoeffect or plasma charging. So electric repulsion might be present as well.…”

“…In agreement with this, von Holstein-Rathlou et al (2012) showed that the threshold friction velocity in wind tunnel experiments indeed decreased for grains (glass, quartz, copper) on a conductive surface, while the threshold friction velocity necessary for saltation increased for grains on an insulating surface. This electrostatic repulsion mechanism of conducting grains has only recently been suggested for micrometer particles on other celestial bodies like asteroid Phaeton or Saturn's rings (Kimura et al 2022;Hirata et al 2022). Especially the latter works require additional ways to reduce the sticking forces that counteract the repulsive force, but otherwise build on the same electrostatic repulsion.…”

“…On one side, electric fields might influence aggregation of ejected dust grains simply by inducing dipoles which attract each other ). On the other side, the fields might be particularly important in the context of lifting grains from the surface in the first place (Renno & Kok 2008;Kimura et al 2022;Hirata et al 2022;Wang et al 2016).…”