There's a good chance they are due to freeze-thaw cycles.
Dark streaks on Mars might be modeled by Antarctica streaks.
Posted by Robert Clark on 2/8/2007 11:38:52 AM
http://habitablezone.com/space/messages/457107.html
Head et.al. in the LPSC report I cited argue new ones appear after temperatures in the region exceed the melting point of water (they are located near the equator.)
In their LPSC report, Head et.al only give images of analogous streaks in Antarctica. However, since the Antarctica streaks were created by freeze-thaw cycling, analogous streaks probably also exist in other periglacial regions on Earth.
Bob Clark