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from Forbes Website
indicates the presence and abundance of consistently fresh surface ice, like no other moon in the Solar System. Image credit: NASA / Cassini-Huygens mission
Imaging
Science Subsystem. and the perfect raw ingredients, Enceladus might be the holy grail we've been seeking.
With a diameter about as wide as North Dakota and a maximum surface temperature of approximately -200 degrees Fahrenheit, it seems unlikely that this pale, frigid rock would be of any significance. If you were flying past Saturn in a spaceship, you'd probably write it off as just another rocky moon.
Given it's one of 62 moons orbiting Saturn, it'd be pretty easy to ignore, as it has none of the obvious appeal of other Solar System moons.
It has neither a thick atmosphere like Titan nor massive volcanoes like Io; however, it just might be one of the most habitable places in our Solar System.
Its blanched, lifeless surface belies a complex, possibly life sustaining ocean just 11-14 miles beneath the icy crust. A series of pale blue stripes across its surface indicate the presence of deep fissures, which spew water ices into space.
These jets are responsible for creating the entire E-ring of Saturn, and extend upwards for hundred of miles with every eruption.
with its limb illuminated by the Sun, its face lit up by light reflected off of Saturn, and an eruption directed downward, towards the middle of the image.
Image
credit: Courtesy of NASA.
Ironically named after a Giant in Greek mythology, Enceladus remained an elusive speck for almost 200 years after its discovery. Its small size and the surrounding glare from Saturn's rings prevented it from appearing as anything more than a single pixel on a photographic image.
It wasn't until the Voyager 1 and 2 spacecrafts captured closer images of Enceladus that some peculiarities were noticed.
captured by Voyager 2 on August 26, 1981 from a distance of about 109,000 kilometers. The Voyager images revealed Enceladus to have a tectonized surface that was, in places, wiped clean of craters.
Image
credit: NASA / JPL / Ted Stryk.
Quantitative observations have confirmed that in unprecedented fashion:
The reason its polished surface is scientifically compelling is that it indicates the presence of active resurfacing, like when a zamboni smoothes the ice after a hockey game.
Enceladus' sleek surface tells scientists that there was significant tectonic or volcanic activity (our 'space zamboni') in Enceladus' geological history. Without this resurfacing, we'd expect Enceladus to look more like Earth's moon:
But not only is it extraordinarily crater-free, the regions where cracks are deepest and most active are also the smoothest.
shown similarly to maps of the Earth in a Mercator projection. Image credit: NASA / Cassini
Imaging
Science Subsystem / Paul Schenk / Lunar and Planetary Institute.
Sadly, Enceladus fell back into relative obscurity until the Cassini mission reached Saturn in 2004.
While the landing of the Huygens probe on Titan dominated planetary scientists' research efforts initially, several close flybys of Enceladus in 2005, 2008, and 2009 brought this icy moon, and the ring it generates, back into prominence.
as imaged here by Cassini, is created by it's frozen Moon, Enceladus, ejecting icy material over time. Enceladus is the bright spot at the image's center.
Image
credit: NASA/JPL/Space Science Institute.
This data showed evidence of a deep saltwater ocean with an energy source beneath Enceladus' surface. The presence of water, warmth, and organic molecules are the necessary requirements for sustaining life as we know it.
Water is proven to exist, while the tidal forces from Saturn provide the necessary heat.
Based on observations of other bodies in the Solar System, Enceladus likely contains the raw ingredients for life as well. The suspected existence of all three hints at the possible presence of the precursors to amino acids in this vast subsurface ocean.
Should we find extraterrestrial life on Enceladus - or in the geyser-like plumes erupting into space - the implications are almost incomprehensible.
ideas for searching for life in Enceladus' ocean is to fly a probe through the geyser-like eruption, collecting samples and analyzing them for organics. Image credit: NASA / Cassini-Huygens mission
Imaging
Science Subsystem.
Our current definition of life is based solely on observations of the diverse organisms on Earth.
The discovery of extremophiles - organisms that can live in harsh environments previously thought inhospitable - meant our original definition of the requirements of life was too strict.
Life around deep-sea hydrothermal vents, in sulphurous hot springs, and in the hypersaline, alkaline, and arsenic-rich waters of Mono Lake are all breathtaking examples.
They also gave scientists renewed hope in discovering extraterrestrial life in incredibly harsh locations in space.
shown alongside a simulation of the curtain-like eruption from Earth-based scientists (R). Image credit: NASA / Cassini-Huygens mission
Imaging
Science Subsystem.
Life:
It's easy to imagine that extraterrestrial life could violate one or more of these requirements, as robustly defining life is still an ongoing area of research in science.
Many creative minds in science fiction have pushed back on this definition of life, exploring the possibilities of,
...and many, many others.
The basic truth is that we cannot truly know what defines extraterrestrial life until that first discovery is made.
caused by Saturn's tidal forces, which lead to geyser-like ejecta and continuous resurfacing events.
Image
credit: Courtesy of JPL.
Many scientists theorize that life first began near hydrothermal vents deep in Earth's ocean, though there are contrarian points of view.
If Enceladus lacks any biological life, it may serve as evidence that continents or continental shelves are indispensable in supporting life. Additionally, life may require more than merely water, energy, and certain organic molecules.
Still, even the presence of the most basic unicellular organisms on Enceladus would be the most momentous discovery of our time.
surrounding a hydrothermal vent in the ocean near the Galapagos islands. Image credit: NOAA Okeanos Explorer Program,
Galapagos Rift Expedition 2011.
Although numerous missions have been proposed to follow up on Cassini's observations, there are no current missions planned to return to Enceladus.
Neither a lander nor an orbiter - not even one that would sample the ejected, aqueous plumes - has been greenlit by NASA or any other space agency.
It's heartbreaking for
those who study Enceladus, as the secrets it holds must remain
hidden for the foreseeable future...
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