I thought there was one clear assertion in there: 1) Previously, terraforming was thought to be possible, given there being enough trapped greenhouse gasses to

I thought there was one clear assertion in there: 1) Previously, terraforming was thought to be possible, given there being enough trapped greenhouse gasses to establish an atmosphere 2) Recently, it was shown that there is not enough trapped greenhouse gasses to establish an atmosphere 3) Therefore, terraforming Mars is seen as far less possible (or alternatively, would require much more advanced technology) than before.