The Earth's Dust Belt: Fact or fiction?: 3. Lunar ejecta

“…The impactor flux and speeds are amplified due to gravitational focusing by the planet (42,75). At the planetocentric distance of Janus and Epimetheus (2.5 R S ), the mean focusing factors are ∼ 4…”

Section: Impact-ejection Modelmentioning

confidence: 99%

Close Cassini flybys of Saturn’s ring moons Pan, Daphnis, Atlas, Pandora, and Epimetheus

Buratti

Thomas

Roussos

et al. 2019

Science

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Saturn’s main ring system is associated with a set of small moons that either are embedded within it or interact with the rings to alter their shape and composition. Five close flybys of the moons Pan, Daphnis, Atlas, Pandora, and Epimetheus were performed between December 2016 and April 2017 during the ring-grazing orbits of the Cassini mission. Data on the moons’ morphology, structure, particle environment, and composition were returned, along with images in the ultraviolet and thermal infrared. We find that the optical properties of the moons’ surfaces are determined by two competing processes: contamination by a red material formed in Saturn’s main ring system and accretion of bright icy particles or water vapor from volcanic plumes originating on the moon Enceladus.

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“…Através da integral da energia é possível relacionar velocidade da partícula antes (v imp ) e depois (v ∞ imp ) da focalização gravitacional através da equação (Colombo et al 1966)…”

Section: Focalização Gravitacionalunclassified

Orbital evolution of theμandνdust ring particles of Uranus

Sfair¹,

Winter²

2009

A&A

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The μ and ν rings of Uranus form a secondary ring-moon system with the satellites Puck, Mab, Portia, and Rosalind. These rings are tenuous and dominated by micrometric particles, which can be strongly disturbed by dissipative forces, such as the solar radiation pressure. In the region of these rings, the solar radiation force and the planetary oblateness change the orbital evolution of these dust particles significantly. In this work, we performed a numerical analysis of the orbital evolution of a sample of particles with radii of 1, 3, 5, and 10 μm under the influence of these perturbations, combined with the gravitational interaction with the close satellites. As expected, the Poynting-Robertson component of the solar radiation force causes the collapse of the orbits on a timescale between 3.1 × 10 5 and 3.6 × 10 6 years, while the radiation pressure causes an increase in the eccentricity of the particles. The inclusion of Uranus's oblateness prevents a large variation in the eccentricity, confining the particles in the region of the rings. The encounters with the close satellites produce variations in the semimajor axis of the particles, leading them to move inward and outward within the ring region. These particles can either remain within the region of the rings or collide with a neighbouring satellite. The number of collisions depends on the size of both the particles and the satellites, and the radial width of the ring. For the time span analysed, the percentage of particles that collide with a satellite varies from 43% to 94% for the ν ring, and from 12% to 62% for the μ ring. Our study shows that all collisions with Portia and Rosalind have the value of impact velocity comparable to the escape velocity, which could result in the deposition of material onto the surface of the satellite. Collisions between Puck and particles larger than 1 μm also occur at an impact velocity comparable to the value of the escape velocity. The exception is Mab, which is hit by particles with velocities several times larger than the escape velocity. These collisions are energetic enough to eject material and supply material to the μ ring. However, only a few particles (3%) collide with the surface of the satellite Mab at such a velocity.

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The Earth's Dust Belt: Fact or fiction?: 3. Lunar ejecta

Cited by 20 publications

References 6 publications

Cosmic Dust in the Atmosphere and in the Interplanetary Space at 1 AU Today and in the Early Solar System

Cosmic Dust in the Atmosphere and in the Interplanetary Space at 1 AU Today and in the Early Solar System

Close Cassini flybys of Saturn’s ring moons Pan, Daphnis, Atlas, Pandora, and Epimetheus

Orbital evolution of theμandνdust ring particles of Uranus

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