The descent is long, unpowered, unguided, and 30 minutes away in time - if something goes wrong, all they will be able to do is watch, in fact not even that, be

The descent is long, unpowered, unguided, and 30 minutes away in time - if something goes wrong, all they will be able to do is watch, in fact not even that, because there is no data from the lander yet. They're not expecting any data till 1400 or so, and then they'll gradually get some descent data back, but whatever happens, they won't be able to affect the outcome of the descent now. Before the data comes in was probably a good time to get some rest/food.