Desert Planets - Planets in SF Notes 2/18/25 Lecture 13
There are two kinds of climates: Desert planets and water worlds
Desert Planets: Characterized by extreme aridity, often featuring vast sandy landscapes, minimal vegetation, and significant temperature fluctuations between day and night. These planets often have limited water sources.
Monochromatic planets: Planets that are single color or single climate.
Singular environments on a planet:
Monochromatic planets are popular in Star Wars.
One approach in writing is to incorporate a desert planet with unique adaptations, such as subterranean water reservoirs, which allow for hidden oases and a diverse ecosystem that thrives in harsh conditions. This could include resilient flora and fauna that have evolved to survive with minimal water, creating a rich narrative backdrop.
One astronomical unit is the average difference between the sun and the earth.
The major effect is the tilt of the Earth’s rotational axis. Sometimes, the northern hemisphere and southern hemisphere are pointed toward the sun during rotation.
Energy being received per unit area is a detail that is important to keep in mind.
Infrared energy is energy that goes back into space. Our atmosphere is really good at absorbing infrared energy, which causes the greenhouse effect, which ultimately keeps Earth from entering another ice age.
Radiation makes it through the clouds and back into space.
The average distance Earth is from the sun is one astronomical unit. Distributing the energy over the earth depends on the earth’s axis.
Energy (flux) received at the top of Earth’s atmosphere from the Sun when located at a distance
of 1 astronomical unit (AU) is 1366 W / m2. This is referred to as the “solar constant”.
The most energy received is in the southern hemisphere, followed by the northern hemisphere.
Why does Earth have many different climates?
Climates are the result of many local factors, including topography and amounts of water.
Most particularly, climates depend on the amount of sunlight received. This assumes that the planet has a thick enough atmosphere to absorb and redistribute energy.
The amount of energy and how it is re-distributed drives the ecosystem that develops in a particular area to adapt to the climate of an environment.
Mars is an excellent place to observe since it is a desert planet, lacking a significant atmosphere, and cannot contain surface water. However, it does have seasons. Mars has a shape in its orbit and a tilt in its axis of 24.9 degrees compared to Earth’s 21.9 degrees, which is somewhat similar.
Mars’ polar caps switch each season. During the summer, its ice caps melt. There is no liquid water when this happens, though, and because of the lack of atmosphere, Sublimation happens. Sublimation is very significant in changing water ice to water vapor. It is believed that much of the ground on Mars contains a great deal of ice.
Desert planets are the most popular in SF because they are extreme environments that create tension for characters and the plot. Another reason is that people aren’t familiar with desert planets, so we can use our imagination more to understand the problems that persist on them.
Why are desert planets so popular?
● Deserts are an extreme environment with which the vast majority of people have no direct
experience.
● The environment is thus an accessible means to create the illusion of an alien environment.
● The harsh environment of deserts can serve as a powerful narrative device to develop
and/or motivate the characters (e.g., the Martians in “War of the Worlds”). The environment
can also level the playing field for opposing characters.
● An explanation for life in a desert world is often a tragic story of planetary degradation,
either through indirect (stars, orbits, etc) or direct (wars) means. Thus, the planet itself
becomes a character in the story, and can even have its own “Hero’s Journey.”
When a story is being told about a planet, create the planet as if it is a character in the story. Give it a history and future. Motivations and dreams can be given to planets within a story. It can have a story arc/hero’s journey and have a triumph at the end. When did a planet have water? Why did the planet lose its water? Will the planet lose its water? Answer what happened to the planet to explore its history and future.
The Vulcan planet is from the Star Trek universe. It is a desert planet with very little surface liquid and most of its atmosphere gone. It has a reddish sky like Mars.
Titan inspired lv-46 from Aliens.
Vulcan lies within the 40 Eridani system, a triple star system located 17 light years from the Sun in the constellation of Eridanus. Vulcan (Star Trek)
ANNOUNCED 2018: A planet that is ~8 times more massive than Earth was claimed to have been detected orbiting 40 Eridani A in a 42 day orbit.
REFUTED 2023: The planetary signature is caused by
stellar activity!!
Vulcan (Star Trek)
Be mindful when a red star and white dwarf are in the same system. Since this is impossible, there can be errors.
There are planets around red stars, but their size will most likely be small.
Arrakis orbits Canopus, a bright star 310 light years away that is 8 times more massive than the Sun, 70 times the radius, and more than 10,000 times more luminous.
A lifetime of Canopus will only be a few tens of millions of years!
Arrakis (Dune) is characterized by its vast deserts, colossal sandworms, and the valuable spice melange, which is essential for space travel and extends life.
Pathways to losing surface liquid water
● Vulcan: flares from one of the Eridanus system stars.
● Arrakis: biological invasive species – sand trout.
● Tatooine: surface bombardment during war with another planet. Alternatively, the
radiation modulations from the binary star may have caused water evaporation.
● How can life remain? Why is there oxygen in the atmosphere? There must previously have
been oceans and a thriving ecosystem. Evaporated water will be broken apart in the upper
atmosphere. Hydrogen will be lost to space, and oxygen will remain.
Can desert planets remain habitable?
Research by Abe et al. (2011) has shown that a dry planet may have increased habitability likelihood because the lack of humidity will decrease greenhouse warming. This results in a more extended period of water retention on the planetary surface.