re: "Bright Chunks At Phoenix Lander's Mars Site Must Have Been Ice."
The TECP instrument is supposed to be taking measurements at the current trenching site. This may be able to answer more definitely if there is water there:
Thermal and Electrical Conductivity Probe for Phoenix Mars Lander.
http://www.nasa.gov/mission_pages/phoenix/multimedia/mh4-tecp_prt.htm
Bob Clark
