[meteorite-list] Airless Space Weathering Duplicated in Lab Environment

[Ron Baalke]

https://www.psi.edu/news/kimweathering

Airless Space Weathering Duplicated in Lab Environment
Planetary Science Institute
Sept. 3, 2015
 
Tucson, Ariz. -  Using laboratory instruments typically used to make 
semiconductor devices, space weathering of airless bodies in the Solar 
System has been simulated, allowing researchers to better determine the 
ages of their surfaces, states a new paper by Kimberly R. Kuhlman of the 
Planetary Science Institute.
 
"Space weathering" is a catch-all term for what happens to surfaces 
exposed to the environment of space over time. This includes the micrometeorite 
impact damage and redeposition, effects of UV radiation, and the effects 
of implantation of solar wind particles," said Kuhlman, lead author 
of "Simulation of solar wind space weathering in orthopyroxene" that 
appeared in Planetary and Space Science. "More space weathered surfaces 
become redder and darker from the formation of nano-scale particles of 
iron."
 
Bodies in the Solar System that exhibit space weathering include the Moon, 
Mercury and asteroids.
 
Kuhlman shot hydrogen atoms at solar wind speeds into tiny, polished samples 
of the common Solar System mineral orthopyroxene that had been placed 
on top of a silicon wafer.  She then examined the compositional changes 
in the outer 20 nanometers of the implanted orthopyroxene using a scanning 
transmission electron microscope (STEM), and for the first time discovered 
the particles of iron beginning to form. 
 
"This continuing work will allow us to estimate the rate at which these 
'nanophase' iron particles form as a consequence of exposure to the 
solar wind.  Linking this to the spectroscopic effects will allow scientists 
to infer the age of the body surfaces via remote sensing, which in turn 
will inform our understanding of a wide range of physical processes in 
the Solar System," Kuhlman said. 
 
The project was funded by a grant to PSI from NASA's Lunar Advanced 
Science and Exploration Research program.