Geological Star Trek Review – “Amok Time”

In September 2018 astronomers announced the discovery of an exoplanet with 8.47 times Earth’s mass and twice Earth’s radius in the 40-Eridani star system, distant 17 light-years from our Sun. In the Star Trek universe, the Eridani constellation is mentioned as the star system where the planet Vulcan is located, homeworld of Commander Spock. In the episode “Amok Time”, first aired on September 15, 1967, the Enterprise visits the planet. As it orbits its sun on a very narrow orbit, surface temperatures are higher as on Earth. Also, the atmosphere is very thin, barely breathable, and non-Vulcans have a hard time adapting to the harsh environment. According to Star Trek lore, the desert-planet Vulcan orbits its sun together with the planet T´Khut, a geologically very active lava-planet.

In the movie Star Trek 2, released in 1982, the star 40-Eridani-A is mentioned as Vulcan’s sun. In 1991, Gene Roddenberry, creator of Star Trek, published a short article together with astrophysicists Baliunas, Donahue and Nassiopoulos, arguing that the constellation of Eridani would be the most fitting place for Spock’s homeworld.

The 40-Eridani system is a triple star system, with Eridani-A as primary star accompanied by a red and a white dwarf star, named respectively Eridani-B and Eridiani-C. Only Eridani-A is stable enough to host a hypothetical habitable planet. Eridani-B emits too much dangerous radiation and Eridani-C is prone to flares, sudden eruptions of energy and matter. As Eridani-A is smaller than our Sun, also the habitable zone, where a planet could exist with liquid water, is narrower. Unlike the fictional planet Vulcan, the real exoplanet seems to be a Super-Earth or a small gas giant. According to the published preliminary results, the planet orbits its star in just 39 to 40 Earth days, along the inner limit of the habitable zone.

Famously Commander Spock is the science officer aboard the Enterprise, including some notions on geology.

“Obsession” (1967).

In the episode “The Apple”, Spock immediately notes the lush vegetation of the planet Gamma Trianguli VI. He correctly deduces that soil-nutrients (and therefore geology) plays a role in supporting this peculiar paradise-like world. With his sharp geological eye Spock identifies also hornblende and quartz in a collected rock.

Hornblende, Moos in Passeier, South Tyrol.

Geological Star Trek Review – “The Enemy Within”

During a minerals-gathering mission on planet Alpha 177 by the crew of the Enterprise, a transporter accident creates an evil duplicate of Captain Kirk.

In the episode the malfunction is explained by the interference of a yellow ore, collected on the alien planet’s surface, with the transporter’s circuits. The ore is not identified in the episode, but seems to consist of some alien mineral.

In many episodes of Star Trek the crew of the Enterprise visits mining colonies or is on a mission to search for valuable minerals and crystals. There exists even a geological tricorder, designed for analyzing rock samples and comparing them to the records memorized in the mineralogical database of the federation. By convention, the names of terrestrial minerals end with the suffix “-ite”, the denominations of elements with the suffix “- ium”, “-um”, “-on”, “-gen” or “-ine”. Unfortunately it seems that this nomenclature is not always applied with the necessary scientific scrutiny in the 23th century.

There are around 5,000 to 7,000 minerals known on Earth, but we still know little about the mineralogy of other worlds. Over 300 minerals have been identified in meteorites so far. Meteorites display a mineral composition different to most rocks found on Earth. The most common type are stony meteorites, consisting of silicate minerals like olivine, pyroxene and traces of iron-nickel alloys. Just 1% of meteorites are pure silicate rocks. The smell of some fragments resembles asphalt or solvents, evidence for 4.6 billion years old carbon-compounds preserved inside the rock. 4 to 5% of all space debris is represented by iron meteorites, consisting of an almost pure iron-nickel alloy with eventually embedded small crystals of silicate minerals.

Around 130 minerals were discovered on Mars and 80 to 100 on the Earth’s Moon. Most are also found on Earth, however, as some of those minerals were formed under conditions that don’t exist on Earth, such as low gravity or the complete absence of liquid water, some are indeed unknown, alien minerals.

There are about 15,300 possible ways to combine all known elements, so there may be even more alien minerals out there.

The mineralogy of an exoplanet depends on its chemical composition. By analyzing the light of a star, it is possible to identify the chemical composition of distant star systems. As the star and the planets form from the same accretion disk, knowing the chemical composition of the star can provide also some information on the chemical composition of the planets orbiting the star.

The exoplanet 55 Cancri -e is roughly twice Earth’s radius, but has just eight times its mass. Its specific density is too low if compared to Earth. Earth is composed mostly of iron, oxygen, magnesium and silicon, with some sulfur, nickel, calcium and aluminum added to the mix. Observing the composition of the 55 Cancri-e’s host star, astronomers discovered a high concentration of carbon and oxygen. It’s likely that most minerals on 55 Cancri-e are based on a combination of the two elements, forming minerals with a low specific density. Surprisingly enough, carbon minerals are quite rare on Earth. Just fifty have been identified on Earth, and most are associated with life, forming from decaying organic biomass. It seems that on Earth, life “hijacked” carbon and carbon-minerals formed by pure inorganic processes (like diamonds) are uncommon.