Solar wind powered hoover at work?
http://science.nasa.gov/science-news/science-at-nasa/2008/21nov_plasmoids/
http://www.universetoday.com/21315/mars-atmospheric-bubbles-carried-away-by-the-solar-wind/
Theory is that Mar's magnetic spots could react with the solar wind resulting in Mars's atmosphere being hoovered off.
Maybe we just witnessed such an event?