Rovers begin new observations on changing Martian atmosphere

This article focuses on recent discoveries by the two Mars rovers, the Spirit and Opportunity. On Mars, seasonal fluctuations in the concentration of atmospheric argon have been detected in the past with instruments designed by the University of Chicago. The changing concentrations of argon indicated that the atmospheric mixing between the polar and equatorial regions was more significant than originally predicted. The rovers Spirit and Opportunity have recently collected atmospheric samples of argon concentration at ground level and in the upper atmosphere.
The article goes on to report the data collection completed by these two rovers. Their activities include soil collection and the exploration of the site of a meteorite impact, (Heat Shield Rock). APXS on Spirit recently found soil with a 90% composition of silica, which is a strong indication that processes involving water were once existent on Mars at the site of collection, Gusuv Crater.
Currently the Opportunity rover has reached the Victoria crater and collected images of the sedimentation as well as soil samples. NASA scientists are attempting to select a potential route for the rover to reach the crater floor, but dust storms hinder its progress.