Radiation bombardment at Europa by magnetospheric particles and cosmic rays
Abstract
Jupiter's moon Europa is embedded deep within the Jovian magnetosphere and is thus exposed to bombardment by charged particles, from thermal plasma to more energetic particles at radiation belt energies. Examples of radiation-induced surface alteration include sputtering, radiolysis and grain sintering; processes that are capable of significantly altering the physical properties of surface material. Radiolysis of surface ices containing sulfur-bearing contaminants from Io has been invoked as a possible explanation for hydrated sulfuric acid detected on Europa's surface and radiolytic production of oxidants represents a potential source of energy for life that could reside within Europa's sub-surface ocean.
Accurate knowledge of Europa's surface radiation environment is essential to the interpretation of space and Earth-based observations of Europa's surface and exosphere. Furthermore, future landed missions may seek to sample endogenic material emplaced on Europa's surface to investigate its chemical composition and to search for biosignatures contained within. Such material would likely be sampled from the shallow sub-surface, and thus, it becomes important to know to which degree this material is expected to have been radiation processed. We will present modeling results of magnetospheric electron and ion bombardment of Europa's surface, including interactions between these particles and surface regolith. Previous models have mostly assumed a surface that consists of pure water ice. However, we have strong indications that hydrated sulfuric acid and salts are major surface constituents. Here we will discuss the effect of varying surface composition on the locally absorbed radiation dose in surface regolith. In addition to magnetospheric particles, Europa is also exposed to Galactic Cosmic Rays (GCRs) - highly energetic particles from deep space that constantly bombard its surface. These high energy particles initiate extensive secondary particle cascades that are capable of penetrating to large depths (tens of meters).We have investigated GCR bombardment at Europa by carrying out particle physics simulations of GCR ions incident on Europa's surface ice and we will present a comparison of GCR versus magnetospheric radiation dose.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.P22A..01N
- Keywords:
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- 5215 Origin of life;
- PLANETARY SCIENCES: ASTROBIOLOGY;
- 6024 Interiors;
- PLANETARY SCIENCES: COMETS AND SMALL BODIES;
- 6218 Jovian satellites;
- PLANETARY SCIENCES: SOLAR SYSTEM OBJECTS;
- 6280 Saturnian satellites;
- PLANETARY SCIENCES: SOLAR SYSTEM OBJECTS