So do tthe Antartic and the Sahara desert
And those pieces of Mars can be had for a lot less than the cost of launching a rocket. Why I even have dust from Mars meteorites sitting on my desk, waiting for Christmas.
If you're flying to Phobos, what you want is pieces of Phobos, not Mars.
What I found interesting in the MRO images searching for Mars Global Surveyor was the large amount of junk in orbit around Mars. Is this ejecta, or other captured material? Who knows.