The recent close flyby, less than 100km from the surface of Phobos by Mars Express,
perhaps resulting in close-up images five times superior to that of the Viking orbiters,
is commendable, but.....why is Phobos more popular with space mission planners
and scientists than Deimos?

I await the day that close-up images of Deimos as good as those taken of
Phobos would be downlinked to John Q Public.

In one way, Deimos, a Carbonaceous Chondritic martian moon, has more practical
appeal if you are a terraformer.

If Deimos is partly composed of carbon at a MINIMUM ratio of a least 100 parts per million
then...crashing that moon onto the martian surface would inject over 100 million
tons of carbon into the martian atmosphere in the form of mostly carbon-dioxide.

I don't know how much carbon-dioxide by weight exists in the martian atmosphere
now....but I suspect a 100, 200, 300 million, perhaps a billion tons of additional carbon dioxide
in the martian atmosphere would increase atmospheric pressure to well over 100 millibars
and generate a powerful greenhouse effect.
Think of rivers flowing on Mars again.