Ph.D. in Geophysics while doing an online MS in CS Has anyone had experience working on two graduate degrees at once? 
The goal being to gain mastery in CS, specifically machine learning so that it can be applied to research problems in the earth sciences.

I'm currently a first year Ph.D. student in geophysics focusing on applying machine learning to massive datasets of satellite imagery. I just got accepted to Georgia Techs Online Masters in Computer Science. I'm trying to decide if I should do it while working on a Ph.D. The CS program is part-time designed for working professionals and is low-cost $6,600. 

While I can certainly learn the CS material on my own, I feel a formal credential will be taken more seriously. A tech career would also be a fallback plan, knowing how competitive the academic world is having a plan B is important to me. Any advice is appreciated.
In general, the CS and machine learning community is more interested in what you build than in what diploma's you have. There won't be many companies where a masters degree is going to significantly compliment a phd with relevant practical experience. A masters degree could give you a more solid theoretical foundation and the possibility to work on some other (toy) project giving you more broad experience. However you can also get that using coursera and personal projects.  

The real trade-off is: a more structured program versus a more self-made learning path. The degree program also 'forces' you to do the work, which can be a good thing or a bad thing.