Actually, as I found in this answer [here](http://scifi.stackexchange.com/a/92077/68872), and from Valorum's [answer](http://scifi.stackexchange.com/a/137320/68872) to [this question](http://scifi.stackexchange.com/q/137300/68872). People surrounding this book and film can be pretty responsive to emails. So I emailed Andy Weir (I hope you don't mind me blacking out my name), but this was his reply:
[![Andy Weir responds to my email stating that Mark uploaded his logs and transmitted them to Earth using the Ares 4 MAV.][1]][1]


So according to him, Mark uploads the logs and sends them using the Ares 4 Mav, although I have no recollection of that happening.

  [1]: https://i.sstatic.net/ySOaem.png