Star Wars: The Last Jedi has received a lot of grief from a lot of fans, but one geophysicist has come to the defense of at least one strongly criticized moment. Mika McKinnon recently spoke out regarding people making fun of the idea, seen sometimes in film, of people licking rocks in order to identify them. She says it's a perfectly valid tool to figure out what kind of rock you're dealing with and pointed out a scene in The Last Jedi as a great example of the technique.
As shown in the GIF included in the tweet, the scene in question takes place when one of the remaining Resistance soldiers grabs a few grains of the surface of the planet Crait and put them in his mouth, discovering that the planet is covered in a fine layer of salt. While this moment might be one of the minor complaints that viewers had after seeing Star Wars: The Last Jedi, it was almost certainly the sort of complaint that a geophysicist would notice, thus Mika McKinnon makes a point to call it out because it actually makes perfect sense.
Earlier in her thread, McKinnon talks about how the taste, as well as the texture of different rocks, can actually tell you quite a bit about them and that it's a fairly common test that any geologist would likely do in order to figure out what they were dealing with. She also critiques other pop culture franchises who have pulled the licked rocks bit in the past. For the record, the Tenth Doctor has a solid technique, but Captain Jack Sparrow does not.
There might be some completely decent reasons to criticise the Star Wars: The Last Jedi, but it certainly appears you'll need a better one than this scene, as the opinion of an expert should be fairly definitive. Of course, that doesn't mean that everybody is buying the argument entirely. Still, Mika McKinnon seems to have responses for most critiques. She says the lick test is so basic that anybody who has taken introductory geology (like a soldier may have done) would know it. There's also every reason that a soldier should know it.
It turns out that when you see somebody identify the type of rock or sand they're walking on by tasting, it's not just a silly joke (though it can certainly be that too) but an actual geologist testing technique. You learn something new every day.
