Notice that the estimated space exposure age for Zagami is 2.5 million years - in other words, that impact occured 2.5 million years ago, and IF, I repeat, IF this is a chunk of the same stuff, then this area of Mars surface has not changed in 2.5 million years -

That's a long dry spell.

However, given the general lack of meteorite acumulation on the surface of Mars which has been counted so far, (as no money has been appropriated to do it) this date would be far from firm.

Note also the large cometary component in Mars water, even given the differential isotope outgassing rates in the space exposed samples. viz:

http://www-curator.jsc.nasa.gov/curator/antmet/mmc/Zagami.pdf

The reason that any of this has much value at all is solely in terms of establishing Martian surface ages, so that impactor flux estimates may be "refined" (corrected). Maybe NASA will do nothing on this, but then, the Mars Express data continues to accumulate.

Five more months.

ep