The abundance of water molecules in the meteorite -- about 6,000 parts per million, 10 times more than other known rocks -- suggests water activity persisted on the Martian surface when it was formed.
The baseball size meteorite is officially known as NWA 7034 because of where it was found - Northwest Africa. The basalt rock is from a volcanic past, the same period being studied by the Opportunity and Spirit rovers.
In terms of such space rocks, The Guardian story on the meteorite stated:
About 65 Martian rocks have been recovered on Earth, mostly in Antarctica or the Sahara. The oldest dates back 4.5bn years to a time when Mars was warmer and wetter. About half a dozen Martian meteorites are 1.3bn years old and the rest are 600m years or younger.
Here is the more scientific statement on the meteorite from the authors of a paper titled Unique Meteorite from Early Amazonian Mars: Water-Rich Basaltic Breccia Northwest Africa 7034:
We report data on the martian meteorite, Northwest Africa (NWA) 7034, which shares some petrologic and geochemical characteristics with known martian (SNC, i.e., Shergottite, Nakhlite, and Chassignite) meteorites, but also possesses some unique characteristics that would exclude it from the current SNC grouping. NWA 7034 is a geochemically enriched crustal rock compositionally similar to basalts and average martian crust measured by recent rover and orbiter missions. It formed 2.089 ± 0.081 Ga, during the early Amazonian epoch in Mars' geologic history. NWA 7034 has an order of magnitude more indigenous water than most SNC meteorites, with up to 6000 ppm extraterrestrial H2O released during stepped heating. It also has bulk oxygen isotope values of Δ17O = 0.58 ± 0.05‰ and a heat-released water oxygen isotope average value of Δ17O = 0.330 ± 0.011‰, suggesting the existence of multiple oxygen reservoirs on Mars.
I think my summary was easier to digest.