Are there presently any astronauts who are also geologists? After all, who better to evaluate geological evidence on Mars than a geologist?

Hello,

In answer to your question, is that yes there are astronaunts who are geologist. It's not uncommon for some to have some type of degree in geology or in geo-phsysics which is somewhat the same, with some differences. Examples are Jack Schmitt and James F. Reilly.