Salt structures are usually composed of halite, anhydrite, gypsum and clay minerals. Clays may be brought up with the salt, turning it dark. These salt flows are rare on earth. In a more recent discovery, scientists have found that they also occur on Mars, but are composed of sulfates. (Wikipedia)
We never get to see Galactus in Fantastic Four: Rise Of The Silver Surfer, from 2007. Marvel’s coolest villain (IMO) is only shown surrounded by a giant cloud of asteroids.
A tacit acknowledgement that some Marvel-related movies must suck in order that others may not.
But here is what Galactus looks like in the comics, to give you an idea of what to look forward to in the MCU future.
Galactus was originally the explorer Galan of the planet Taa, which existed in the prime pre-Big Bang universe. When an unknown cosmic cataclysm gradually begins killing off all of the other life in his universe, Galan and other survivors leave Taa on a spacecraft and are engulfed in the Big Crunch. Galan, however, does not die: after bonding with the Sentience of the Universe, he changes and gestates for billions of years in an egg made of the debris of his ship that the current universe formed after the Big Bang. He emerges as Galactus, and though a Watcher observed Galactus’s birth and recognizes his destructive nature, the Watcher chooses not to kill Galactus. Starving for sustenance, Galactus consumes the nearby planet of Archeopia—the first of many planets he would destroy to maintain his existence. (Wikipedia)