11:00 AM - 1:00 PM
[PPS01-P05] Europa's tenuous atmospheric sputtering and surface composition uncovered by plasma irradiation to NaCl samples
Keywords:Europa, space weathering, subsurface ocean, icy satellite, tenuous atmosphere
A jovian icy satellite Europa potentially has a subsurface water ocean with a habitable environment for life. Elemental and molecular compositions of Europa's surface materials tell us that of the subsurface ocean because water and salts may be transported between the surface and ocean(Carlson et al.,2009). Europa's surface materials are continuously irradiated with Jovian plasmas, UV, and micrometeorites from space, driving the space weathering process. Jovian plasmas, which are the dominant energy source of the space weathering, sputter particles from the surface materials. Sputtered particles create Europa's tenuous atmosphere. The residual un-sputtered surface material may change in the elemental and molecular compositions.
However, since this process comprises complex physics and chemistries that are hard to theoretically estimate, it has been a big unsolved problem to quantitatively associate the tenuous atmosphere with the surface compositions accompanying the space weathering.
Here we present the laboratory space weathering experiment that quantitatively associates the tenuous atmospheric sputtering with the surface composition. We irradiated energetic O2+ ions and electrons with an energy of 10 keV and fluence of 5×1018 particles/cm2 to NaCl samples for the first time to model for the sputtering process by Jupiter’s plasmas irradiation to Europa’s surface materials.
We found that the electrons induced more surface spectral change and greater sputtering yield of 26 /incident particle than the O2+ ions (0.9 /incident particle). The electrons likely drive the space weathering more than the O2+ ions for NaCl. We also confirmed that the yield of volatile materials (Cl, Cl2, and HCl) is greater than Na, which demonstrates that Na is more residue than the volatiles on Europa's surface.
Our results suggest that electrons drive the space weathering more rapidly than ions and create Europa's tenuous atmosphere. In addition, Na is likely abundant compared to Cl in the region where electrons dominantly induce the space weathering.
We will compare our experimental results with the previous spacecraft and telescope observations to verify the obtained yields and spectral change of the irradiated samples. We will also conduct the same experiment for other candidate materials to uncover the surface and subsurface ocean compositions.
However, since this process comprises complex physics and chemistries that are hard to theoretically estimate, it has been a big unsolved problem to quantitatively associate the tenuous atmosphere with the surface compositions accompanying the space weathering.
Here we present the laboratory space weathering experiment that quantitatively associates the tenuous atmospheric sputtering with the surface composition. We irradiated energetic O2+ ions and electrons with an energy of 10 keV and fluence of 5×1018 particles/cm2 to NaCl samples for the first time to model for the sputtering process by Jupiter’s plasmas irradiation to Europa’s surface materials.
We found that the electrons induced more surface spectral change and greater sputtering yield of 26 /incident particle than the O2+ ions (0.9 /incident particle). The electrons likely drive the space weathering more than the O2+ ions for NaCl. We also confirmed that the yield of volatile materials (Cl, Cl2, and HCl) is greater than Na, which demonstrates that Na is more residue than the volatiles on Europa's surface.
Our results suggest that electrons drive the space weathering more rapidly than ions and create Europa's tenuous atmosphere. In addition, Na is likely abundant compared to Cl in the region where electrons dominantly induce the space weathering.
We will compare our experimental results with the previous spacecraft and telescope observations to verify the obtained yields and spectral change of the irradiated samples. We will also conduct the same experiment for other candidate materials to uncover the surface and subsurface ocean compositions.