The faster blocks make sense though if you want to protect yourself from Earth miners (see discussion in their forum under "Evil Earth Miner Scenario".
Except it does nothing to protect you...
Earth just needs more hashrate, and their blockchain trumps Mars', no matter how delayed.
It will make it harder as it adds a much higher burden on a co-ordinated attack from Earth. Yes, they will have more hashing power, but to advance such a large blockchain in such a short time frame it will need a concerted effort from Earth to do that.
I don't see how; the terrestials will just naturally create a forked blockchain, and if they have a higher hashrate, it will replace the martian one as soon as it gets far enough ahead...
On top of that, if the Marscoin network adds a timestamping or other security measures that are local to Mars an attack from Earth is impossible due to the distance.
I'm not aware of any such measures that can be taken without centralising the currency.
Regarding the coin supply: it aligns with the departure of the Marscoin blockchain to Mars:
Why is this a good thing? I'd think it make more sense to have most of the coins mined on Mars itself, not most on Earth...
Depends. The idea is to raise the money NOW to actually help make the Mars mission a reality. Thus you increase the incentive for people to get into the currency before the blockchain leaves. Once on Mars, the Marscolonists have better things to do than to put their servers on a mining armsrace - Marscoin on Mars will then mainly become a transaction network. If need be, the minimal mining that will continue could be monopolized by MarsOne or whoever runs the base to pay early Mars settlers to incentivise the growth of the colony.
Raising the money is done with the premine. Beyond that, it doesn't help raise money at all.
If all the subsidy is mined before leaving Earth, then where is the incentive for martians to mine at all, much less maintain the same hashrate as it had on Earth?
Keep in mind that the difficulty needs to be high enough to make it resistant to attacks...