Enceladus

Introduction:

If you talk to any planetary scientist you will get their immediate attention when you mention the moon Enceladus. While there are many objects in our solar system that offer beauty and inspiration, there are only a few that have all of the key ingredients that could not only start life, but could encourage and harbor it. Enceladus is one of these objects and as the sixth largest moon of Saturn, it is one of the top locations that are being studied in the entire solar system.

As a planet, Saturn is awe-inspiring, and when you had the 69 moons that are in orbit, it almost appears as if it’s a miniature solar system. With so many moons it might seem that a moon such as Enceladus would get lost in the shuffle. Thanks to the incredibly reflective surface, Enceladus already stands out, but when scientists decided to begin looking at it they were shocked and surprised to see that it may have a liquid ocean below its frozen surface and the samples taken from the hydrothermal vents show that it has most of the chemical ingredients that are required for life as we know it.

Enceladus isn’t very wide; in fact ay around 310 mi/500 km, it’s almost as wide as the state of Arizona. However, it has the distinction of having the most reflective surface in the solar system. As it orbits around Saturn it blasts icy particles out into space and creates its own ring around its parent planet as it circles around. This ring is called Saturn’s E ring.

This moon is completely covered in ice and that reflects any sunlight that hits it. This makes the surface temperatures incredibly cold.

Enceldaus Statistics:

• Orbits: Saturn
• Discovered By: William Hersche
• Discovery Date: August 28, 1789
• Diameter: 504.2 km
• Mass: 1.08 × 10^20 kg (0.1% Moon)
• Orbital Period: 1.4 days
• Orbit Distance: 238,037 km
• Surface Temperature: – 198 degrees C

History:

On August 28, 1789, William Herschel, the famed British astronomer discovered Enceladus in its orbit around Saturn.

His son, John Herschel, suggested that the names for the first seven moons of Saturn be related to Roman mythological characters related to Saturn. In Greek mythology the name is Cronus. Enceladus is a giant in Greek mythology.

Formation, Structure and Surface:

Enceladus is around one-seventh the diameter of our moon and it is spherical, with an equator bulge due to gravity as it rotates. It isn’t huge, and therefore has only a small gravitational effect at the surface.

Enceladus has an orbit that is in between two of Saturn’s other moons, Tethys and Mimas. It completes a single orbit around Saturn every 32.9 hours and is tidally locked so that only one side of the moon ever faces Saturn. The location of Enceladus is in the densest part of the E ring of Saturn and is trapped in what is referred to as “orbital resonance.” This is a condition when two or more moons are lined up with their parent planet at intervals that are regular and have gravitational interaction. In the case of Enceladus, it orbits Saturn two times for every time that the moon Dione orbits one time. The gravity of Dione has stretched the orbit of Enceladus so that its shape is elliptical. In some parts of the orbit it is closer to Saturn and at other times farther away. This has caused tidal heating inside Enceladus.

The surface of Enceladus shows some regions that have a lower number of craters, while other areas have craters that are as large as 22 mi/35 km in diameter. The regions with a percentage of low craters have had some form of activity that has resurfaced and covered the older craters that once existed there. One of the areas that has almost no impact craters is the South Polar region. Although there might not be craters in this region, the surface is covered with ice-boulders the size of houses and areas that have been carved with tectonic patterns.

NASA’s Cassini spacecraft did a flyby of Enceladus in 2005 and found that there was gas and icy water particles spewing from the surface at around 800 mph/400 meters per second. There are at least 101 of the icy geysers. These were continuous eruptions that generated a huge halo around Enceladus of fine ice dust and in turn generated a large halo of the same ice dust to supply Saturn’s E-ring. While only a small percentage of the dust ended up in the ring, the rest fell back to the moon’s surface creating the extremely white brightness.

Cassini discovered that the jets of water were coming from crust fractures that were somewhat warm. Scientists nicknamed these fractures “tiger-stripes.” Examination of the dust and gas allowed Cassini to find that it contained water vapor, carbon dioxide, methane and a small amount of ammonia. The gas mixture was made of carbon monoxide or nitrogen. Also discovered were salts and silica. The organic materials in the plumes were found to be twenty times denser that was expected by the scientists. The silica can only be created with a rock and liquid water interaction at temperatures above 200 degrees F/90 degrees C. This allowed scientists to understand that there were hydrothermal vents that were deep beneath the surface.

Using the Doppler affect to measure the gravity and the moon’s magnitude of the slightly wobbled orbit, scientists realized that the jet plumes were being sourced by an ocean inside the moon. The global ocean is below the ice shell which is believed to be thinnest at the South Pole at around half a mile to 3 miles. The thickest area of the ice shell is thought to be around 12-16 mi/20-25 km.

There are at least five different types of surface terrain on Enceladus including craters that are as large as 22 mi/35 mi across, smooth areas without any marring features, fissures, and crust breaks. The intensity of brightness of the surface is due to icy reflections of over 90% of the sunlight that hits Enceladus. It is one of the brightest objects in our solar system.

The cracks on Enceladus are opened and closed as the moon gets closer to Saturn. Scientists have theorized that it’s possible that the geysers reach down into the ocean. This is an incredible find as a spacecraft could potentially just fly over the geyser and get a sample without ever being required to land.

Observing the geysers, scientists have noted that some have decreased since the Cassini mission and researchers are unsure why. Enceladus is the third active moon to have been found to have volcanic eruptions. The other two are Jupiter’ Io and Neptune’s Triton.

Atmosphere and Magnetosphere:

The Cassini spacecraft mission accomplished two flybys of Enceladus, finding that the moon has a significant atmosphere. The spacecraft used its magnetometer and researchers have said that there may be volcanism, geysers, or gases that are escaping the interior through to the surface.

The first flyby of Cassini registered a signature in the magnetic field. The second approach was closer and the instruments got additional confirmation evidence. Cassini found that the magnetic field was bending with a slowing and deflection of the magnetospheric plasma by the moon. Cassini also observed oscillations in the magnetic field that were believed to be from ionized water vapor.

The importance of these discoveries can’t be overestimated as the discoveries update the previous 1981 Voyager flyby that was at such a distance that no atmosphere was detected. Finding an atmosphere and a magnetic field, along with the potential of liquid water under the surface is strong evidence that Enceladus has a continued source that are part of the requirements to harbor life.

Could Life Exist?

The current criteria established by science that is the basis for life to form includes: energy, a rich chemical background, and liquid water. So far, other than Earth, Enceladus is the only object in our solar system where all of these things exists. Scientists do suspect that Europa, Jupiter’s moon may also have all three of the criteria, but they haven’t confirmed it.

Enceladus is too cold for liquid water, however, the fact that it has ammonia which acts as an antifreeze could allow liquid water to exist beneath the surface without freezing. The plumes have been analyzed and the acidity doesn’t rule out the possibility of life. Additionally, the Cassini spacecraft did detect other complex organics and chemicals in some of the plumes.

Thus far, Enceladus is the most promising lead that we have in searching for life on other worlds.

Interesting Information:

• Various features on Enceladus have been named for places and characters in the collection of stories known as “One Thousand and One Arabian Nights.”
• It takes Enceladus 1.37 days to orbit around Saturn
• Scientists think that the gravity of Saturn has a great impact on the tidal forces of Enceladus that could be turning a layer under the ice into liquid.
• The erupting ice that escaped Enceladus is traveling at 800 mph/1,300 kmh and goes thousands of miles into space.
• The total surface of Enceladus is just 15% larger than the state of Texas.

Exploration:

Enceladus has been visited by both the Voyager spacecraft and the Cassini spacecraft.

Due to the interests of scientists for potential life on Enceladus, future visits will be made to the moon.

Facts about Enceladus Moon for Kids:

• The Cassini mission used high resolution to map the surface of Enceladus.
• Scientists believe that the core of Enceladus is rock mixed with water ice.
• The water ice particles spewed from the geysers on Enceladus are being caused from cryovolcanic activity.
• It’s believed that the heat inside Enceladus is caused by either decaying radioactive elements called “radioactive heating,” or tidal flexing caused by the intense gravitational pull by Enceladus’ parent planet, Saturn.
• Future missions of exploration are being discussed to bring back samples from the icy plumes of Enceladus and for the study of other Saturn moons and the rings of Saturn.

Pop Culture:

Enceladus has long been the backdrop for many science fiction books, shows, films and games.

The Buck Rogers 1930s radio show had the episode Killer Kane where Enceladus was mentioned. In the story it had an atmosphere as well as humanoid life.

The science fiction novel by Grant D. Callin called Saturnalia included Enceladus as a place that had an alien artifact.

Encedalus was a fortified outpost for a pirate clan in Exosquad.

The renowned book, Time Machine, had a conclusion called The Rings of Saturn where the spacecraft arrives in 2085 to blow up Enceladus before its Earth return.
Dust, written by Charles Pellegrino, has a narrative switch to include a robotic probe that searches for life on Enceladus.

The 2008 The Quiet War by Paul J. McAuley has Enceladus serving as a battlefield as Earth invades the inhabited satellites of Saturn in the 23rd century.

The television series Life After People: The Series, by The History Channel, a storyline shows the Cassini spacecraft crashing into Enceladus and contaminating the moon with bacteria. The bacteria sparks life that eventually evolves into extraterrestrial life.

The television series Futurama has the Cold Warriors episode where Enceladus is referred to as “Saturn’s main dump moon,” and is the place where a 20th century cold virus specimen is sourced.

The web comic Saturday Morning Breakfast Cereal, #1733, Enceladus is shown with fish-like creatures underneath its surface of ice.

In the novel 2312, by Kim Stanley Robinson, there is an occasional reference to the “Enceladian biota” which is a microscopic organism that is ingested by people because they think it has medicinal value.

https://solarsystem.nasa.gov/moons/saturn-moons/enceladus/in-depth/

https://www.space.com/20543-enceladus-saturn-s-tiny-shiny-moon.html

https://www.solarsystemquick.com/enceladus.htm

http://www.unmuseum.org/7wonders/enceladus.htm

https://solarsystem.nasa.gov/news/12323/cassini-finds-an-atmosphere-on-saturns-moon-enceladus/

https://en.wikipedia.org/wiki/Saturn%27s_moons_in_fiction