The problem is getting a DNA sequence through non-invasive imaging. We don't have technology that can do that; DNA in its natural state is incredibly tangled and wrapped around various helper proteins and structural supports.

The most promising technique is one I mention in the article, where you look for microbes visually and extract them with sterile tools. But it's hard to amplify the whole genome with current technology because salt interferes with the process, and the inclusion is concentrated brine.