Daphnis is a small inner satellite of Saturn. It has an elongated shape, with an average diameter of 8 km. Daphnis orbits in the Keeler gap, a division of the A ring.
Characteristics[]
Daphnis orbits Saturn in 14.86 hours. Little is known about its rotation period, but, based on its shape and frequent interactions with the ring, the rotation must be rather chaotic.
Based on the effects on the ring, Daphnis appear to have a low mass, which can be associated with an average density of 0.3, much lighter then water. Because of this, we can speculate that the tiny moon is made of porous water ice. It certainly is solid. If it were just a pile of rubble, strong gravity from Saturn would have ripped it apart.
Given the small gravity and the fact that it is very close to the Roche limit, an astronaut will be unable to sit on the moon and will escape into orbit around Saturn.
Daphnis was seen in close detail by the Cassini probe. It appears white and elongated, without craters and with small ridges that appear to be made of accreted dust from the ring.
Daphnis maintains the Keeler gap open inside the A ring. The tiny moon has a diameter very close to its Roche limit, so it cannot grow in size by accreting matter from the ring. Very interesting is that Daphnis has an orbit slightly tilted from the ring plain. Because of this, Daphnis forces matter from the ring to move away from the plain, creating majestic waves that are up to 1 km high. These waves gave Daphnis the nickname wavemaker.
As Daphnis advances, it pulls matter outside from the gap, but behind, it forces small trails of dust to enter the gap.
Environment[]
At first, it was thought that Rings of Saturn were a very dangerous place. However, data from Cassini reveal a completely different story. Particles in the rings appear to move very slowly, as compared to other nearby particles. They also rotate very slowly, between 0.5 to 5 times the time needed to orbit the planet. Each wave created by Daphnis is made each time the little moon orbits the planet once(so, every 14.86 hours). Distance between waves is roughly a few tens of km. This implies that the surrounding ring moves with 1 to 2 km/h faster or slower then Daphnis.
The ring is made of water ice. Particle size varies from fine dust to the size of sand grains and to the size of grabble. Larger chunks of matter are usually piles of debris merged by their own gravity, in a fragile equilibrium. They form and break away very easy.
It is possible for larger solid particles to exist in the ring, with a few meters in diameter. Larger pieces, if they exist, are easy to be detected as they create an unique feature on the ring, known as a propeller. No propeller has been detected very close to Daphnis.
Daphnis affects particle movement in the ring and this creates friction, which erodes larger particles further, creating more dust.
A space station built on the surface of Daphnis will be exposed to dust and larger particles from the ring. However, particles will impact the base only with speeds up to 2 km/h. Dust will be frequent, but larger particles will be rare. Collisions will not be powerful enough to destroy the hull and windows of a base.
It is highly probable that the dust will be ionized by friction between particles. Because of this, a layer of dust can accumulate on all surfaces, including windows.
Colony[]
Daphnis is a very small moon, made of water ice with only little impurities. It has no metal or silicate core. So, building a base with materials found on the moon is impossible. Also, the colony will not have all minerals and materials needed to sustain itself. If we add the presence of the ring, which will cause navigation problems, one might ask why should anyone bother to build something on Daphnis.
However, the little moon has some unique advantages. First of all, it is a very good place for tourism. The rings of Saturn are the largest and most known of the Solar System. A base on Daphnis will create some unique advantages and opportunities.
The base must be built for small ships. Large ships cannot travel through the dusty environment surrounding Daphnis. Also, their large mass will create gravity, which in turn will attract matter from the rings. Small ships will ferry between Daphnis and Helene, Saturn's space station. Small, private ships can also come and dock.
The docking protocol will be different from other asteroids and small moons. Ships will have to travel at some distance from the rings, then they will approach the moon from above or from below. The best place for passing through the ring is in front of the moon.
Because Daphnis is so small, it will not have the proper resources to sustain a large ecosystem. Food will be sent from other larger moons. Oxygen can easily be produced from the ring, which is made of water ice.
Because dust will accrete on all large structures, solar panels are not feasible. A nuclear generator will provide the base with all the needed energy.
To offer the best protection against impacts and against cosmic rays, settlers will stay in apartments built beneath the surface. Also, underground, there will be gardens and parks. Since Daphnis will be a touristic destination, the colony must also include an amusement park, a casino, clubs, restaurants and other places for entertainment.
Because the moon is made of porous water ice, it will offer some thermal insulation. However, every inhabited chamber will need to be well insulated. If too much heat escapes, it can melt the ice. Every inhabited building on the surface must be well insulated, because at Saturn's orbit day temperature is around -150 C. Also, all structures must be built in such a way that they can face impacts and dust.
Around the Earth, impacts with space debris are felt like bullet hits or even worse, because all debris have huge speeds. Around Daphnis, impacts will be felt as if someone is throwing with rocks in a wall. So, the walls and windows will not need to be bullet proof.
Dust will be a major problem. It will block the view that tourists pay to see. In order to clean the windows, we have two options. First, we can equip each window with a dust cleaner (similar to the way we clean windows of a car against rain). The second option requires that all windows will have small electric wires inside and will change electrostatic charge, forcing dust to move away.
Like any base, Daphnis will need to have a communication system. However, antennas will be affected by incoming dust and impacts. Antennas can be covered with a protection sheet, but this will affect radio signals. Another major problem is that the ring (and mostly the waves) will block radio signals to and from other moons.
In order to solve this problem, Daphnis will require two relay stations, one above and one below the ring plane. They will require fuel to remain in such positions.
There will be a lot of tourist ships, ready to take visitors around. All these ships will require air, food and fuel. Food can be loaded from the base. Air can be recycled, if we replenish the oxygen. Also, as fuel, we can use hydrogen and oxygen, which can be produced from the rings, which are made of water ice.
Tourist Attractions[]
Daphnis has many things to show to visitors.
At the station. At first, people will be amazed to see the landscape of the rings. Cassini revealed that the rings of Saturn are extremely narrow, with an average width of only 30 m. However, since Daphnis has a slightly tilted orbit, the rings will appear sometimes very narrow (like a smooth line, except for the waves) and sometimes larger. The image of the waves will be most impressive.
People will also see the surface of Daphnis, with its narrow ridges of dust. They will also be interested to see the structure beneath the surface.
Like any tourist station, Daphnis will provide a lot of entertainment services, including a zero-G amusement park, a casino, many clubs underground gardens and not only.
However, the most interesting and most attractive will be touristic visits to the rings.
Short distance visits. There will be short-range ships that will take tourists around Daphnis, showing the shape of the moon, the Keeler gap and the waves produced in the rings. Some ships will come further and get inside the rings. People will have the opportunity to see how do the rings look from the inside.
Short cruises will take up to a few hours and will make only small incursions inside the rings.
Long distance visits. From time to time, Daphnis is aligned with the other ring moon, Pan, which can also host a touristic station. Also, there are a few propellers that sometimes come close enough to Daphnis. Touristic ships will take people on a cruise above or beneath the rings. People will see the rings illuminated from the Sun or illuminated by Saturn. These ships will keep a safe distance from the rings, to avoid dust contamination. Smaller ships will detach and enter the rings, to give people the chance to see particles inside each ring.
The rings of Saturn have a very complex structure. They have denser regions and gaps (which are not quite empty). Sometimes, gravity between particles form larger clumps of matter which soon break away after getting formed.
Long distance visits will require more then a day. So, passengers will have to sleep in the ship or land at another touristic station.
Rented ships. One of the best attractions will be traveling at low altitude above the rings. Also, some people will like to plunge into the rings and explore the place there. For this purpose, special ships can be manufactured.
Sports. The rings offer unique challenges for speed sports that cannot be practiced anywhere else. Races can be done inside the rings, inside the Keeler gap or at small distance above any ring. Amateur races will be held by tourists, while trained pilots will drive at high speed, risking their lives.
Souvenirs. The rings are made of water ice, but with little amounts of other, heavier materials, including tholins. It could be possible to sublimate the ice in a heated void chamber, then to use the remaining solids to create unique souvenirs, which will be sold to tourists or given to them when they leave.
Space tourism will start to form once colonization of the Solar System will start. There will be touristic attractions on all planets and all moons. However, some places, like Daphnis, will be exclusively touristic destinations.