This is a story of the long-forgotten moon of Saturn, named Enceladus. A moon first thought to be a barren world of ice became the most valuable piece of real estate in our solar system.
Enceladus- the Moon of Saturn
Enceladus is the sixth-largest moon of Saturn. It has a diameter of 500km and has a mass less than 1/50,000 that of earth. It was first discovered in 1789 by an English astronomer, William Herschel. It was known as an ice-cold celestial body in our cosmic backyard until the Cassini mission began orbiting Saturn in 2004.
When Cassini’s magnetometer (a device that measures magnetic field) detected something unusual in Saturn’s magnetic field near Enceladus, it was a sign of the moon being active. After multiple passes by Enceladus, it revealed four fissures in a hot spot near the south pole. Massive plumes of water vapours and ice grains were oozing from the cracks. This put Enceladus on the list of “places to look for life.”
Observing the excess wobble over Enceladus’s orbital period confirmed that the icy crust was not connected with the moon’s rocky core. This is possible only when the frozen crust is floating on a liquid-water ocean.
After multiple studies using various tools onboard, Cassini found that the fumes mostly consisted of water and had small amounts of salts, ammonia, carbon dioxide, small organic molecules. This shows that the world underneath the ice is possibly a habitable ocean that is slightly alkaline, with some geothermal energy on the seafloor.
Elements of Life
Cassini Mission established that Enceladus has all three ingredients essential for life: Water, Chemistry, and energy. The first two ingredients could be utilized for forming the molecular machinery of life.
When it comes to energy, it is hard to pinpoint exactly what we mean by the word power here but to put it in perspective, let us talk about what was observed and how it can help our predictions.
It was observed that there are hydrothermal vents present at the seafloor. This is mostly because of the detected methane in the plumes, and it is very well known that methane is a crucial product of the hydrothermal system. This suggests the interaction of liquid water with a rocky core.
Now that we know Enceladus could harbour life once these ingredients get long enough time to form life. How would we detect it? Do we need more advanced tools to catch them?
The answer is no. With the instruments already present on the Cassini spacecraft, it was observed that the ocean floor of this Saturnian moon might have a complex organic soup of molecules. This was done using one instrument following the ice grains from the fumes, and then the scientist on earth analyzed the observations.
Unique Ice Grains
The ice grains were found to be salt poor and organic-rich. Why is that? The formation of these Ice grains could result from the molecules hanging out together, and since they are not a massive fan of salts or water, they push these things to the microlayer.
As the liquid surface at the base boils into a vacuum, it may cause these microlayer bubbles to burst. They generate aerosols that are salt poor and organic-rich. This is something that happens on earth too.
The Quintessential Question
There are future missions planned to collect the samples from these fumes so that we can closely test if the Saturnian moon is home to some life form or not. This is the place in our cosmic backyard, capable of hosting some life form.
The future missions to Enceladus could help us answer the critical question that we have been asking since we first saw the lights above us: are we alone? If at all we manage to find a way to successfully reach and inhabit Enceladus, among several other lifestyle changes, we might also have to learn an entirely new space language.