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Saturn's Moon, Enceladus, Is Our Closest Great Hope For Life Beyond Earth
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Garrison L. Hilliard
Apr 6, 2017, 11:11:37 AM4/6/17
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A mere 790 million miles from Earth, nestled in the diffuse outer
rings of the planet Saturn orbits a small, unobtrusive moon. 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.
This is the mysterious Saturnian moon, Enceladus, 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. Courtesy of NASA
This is the mysterious Saturnian moon, Enceladus, 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.
Enceladus was first discovered in 1789 by the British astronomer,
William Herschel, who was more famous for his discovery of the planet
Uranus. 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.
This was the Voyager mission's best view of Enceladus, 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. NASA / JPL / Ted
Stryk
This was the Voyager mission's best view of Enceladus, 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.
Most significantly, the Voyager scientists noticed that Enceladus has
a surface of smooth, bright ice. Quantitative observations have
confirmed that in unprecedented fashion: Enceladus is the most
reflective object in the entire Solar System. 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: pockmarked and replete with
craters from collisions with asteroids. But not only is it
extraordinarily crater-free, the regions where cracks are deepest and
most active are also the smoothest.
A map of Enceladus' surface geography, shown similarly to maps of the
Earth in a Mercator projection. NASA / Cassini / Imaging Science
Subsystem / Paul Schenk / Lunar and Planetary Institute
A map of Enceladus' surface geography, shown similarly to maps of the
Earth in a Mercator projection.
The high reflectivity, smooth surface, and active, watery jets also
helped Voyager scientists predict that Saturn’s E-ring was formed from
particles spewed from Enceladus’ surface. 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.
Saturn's E-Ring, 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. NASA/JPL/Space Science Institute
Saturn's E-Ring, 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.
Cassini provided scientists with a wealth of data about Enceladus’
surface and the composition of its powerful plumes. 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.
One of the most intriguing -- and least resource-intensive -- 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. NASA / Cassini-Huygens mission / Imaging Science Subsystem
One of the most intriguing -- and least resource-intensive -- 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.
Not only does the existence of this moon give hope for life elsewhere
in our galaxy, but it also could radically redefine our understanding
of biological life. 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.
An image of an eruption on Enceladus' surface (L) shown alongside a
simulation of the curtain-like eruption from Earth-based scientists
(R). NASA / Cassini-Huygens mission / Imaging Science Subsystem
An image of an eruption on Enceladus' surface (L) shown alongside a
simulation of the curtain-like eruption from Earth-based scientists
(R).
Currently, the simplest definition of life is based on 7 requirements.
Life:
Is composed of cells,
Responds to stimuli,
Reproduces,
Has a metabolism and respires,
Passes traits on to offspring,
Grows and changes,
Maintains homeostasis.
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 silicon based life forms (X-Files),
electronic/nanotechnological/artificial intelligence (Star Trek),
non-metabolic DNA-modifying organisms (Speaker for the Dead), and
many, many others. The basic truth is that we cannot truly know what
defines extraterrestrial life until that first discovery is made.
The deep fissures are huge cracks in the crustal ice, caused by
Saturn's tidal forces, which lead to geyser-like ejecta and continuous
resurfacing events Courtesy of JPL
The deep fissures are huge cracks in the crustal ice, caused by
Saturn's tidal forces, which lead to geyser-like ejecta and continuous
resurfacing events
Even if Enceladus doesn’t hold extraterrestrial life, studying its
environment could yield clues about the development of life on Earth
and hints that our understanding of the requirements for life is
incomplete. 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.
A colony of Riftia tube worms surrounding a hydrothermal vent in the
ocean near the Galapagos islands. NOAA Okeanos Explorer Program,
Galapagos Rift Expedition 2011
A colony of Riftia tube worms surrounding a hydrothermal vent in the
ocean near the Galapagos islands.
Unfortunately, the Cassini mission is slated to end with the
spacecraft’s descent into Saturn’s atmosphere later this year.
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.
Follow us on Twitter, Facebook, Google+, Tumblr, and support Starts
With A Bang on Patreon.
(Nice images at website)
https://www.forbes.com/sites/startswithabang/2017/04/04/saturns-moon-enceladus-is-our-closest-great-hope-for-life-beyond-earth/#ed930bb59849
rings of the planet Saturn orbits a small, unobtrusive moon. 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.
This is the mysterious Saturnian moon, Enceladus, 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. Courtesy of NASA
This is the mysterious Saturnian moon, Enceladus, 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.
Enceladus was first discovered in 1789 by the British astronomer,
William Herschel, who was more famous for his discovery of the planet
Uranus. 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.
This was the Voyager mission's best view of Enceladus, 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. NASA / JPL / Ted
Stryk
This was the Voyager mission's best view of Enceladus, 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.
Most significantly, the Voyager scientists noticed that Enceladus has
a surface of smooth, bright ice. Quantitative observations have
confirmed that in unprecedented fashion: Enceladus is the most
reflective object in the entire Solar System. 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: pockmarked and replete with
craters from collisions with asteroids. But not only is it
extraordinarily crater-free, the regions where cracks are deepest and
most active are also the smoothest.
A map of Enceladus' surface geography, shown similarly to maps of the
Earth in a Mercator projection. NASA / Cassini / Imaging Science
Subsystem / Paul Schenk / Lunar and Planetary Institute
A map of Enceladus' surface geography, shown similarly to maps of the
Earth in a Mercator projection.
The high reflectivity, smooth surface, and active, watery jets also
helped Voyager scientists predict that Saturn’s E-ring was formed from
particles spewed from Enceladus’ surface. 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.
Saturn's E-Ring, 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. NASA/JPL/Space Science Institute
Saturn's E-Ring, 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.
Cassini provided scientists with a wealth of data about Enceladus’
surface and the composition of its powerful plumes. 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.
One of the most intriguing -- and least resource-intensive -- 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. NASA / Cassini-Huygens mission / Imaging Science Subsystem
One of the most intriguing -- and least resource-intensive -- 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.
Not only does the existence of this moon give hope for life elsewhere
in our galaxy, but it also could radically redefine our understanding
of biological life. 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.
An image of an eruption on Enceladus' surface (L) shown alongside a
simulation of the curtain-like eruption from Earth-based scientists
(R). NASA / Cassini-Huygens mission / Imaging Science Subsystem
An image of an eruption on Enceladus' surface (L) shown alongside a
simulation of the curtain-like eruption from Earth-based scientists
(R).
Currently, the simplest definition of life is based on 7 requirements.
Life:
Is composed of cells,
Responds to stimuli,
Reproduces,
Has a metabolism and respires,
Passes traits on to offspring,
Grows and changes,
Maintains homeostasis.
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 silicon based life forms (X-Files),
electronic/nanotechnological/artificial intelligence (Star Trek),
non-metabolic DNA-modifying organisms (Speaker for the Dead), and
many, many others. The basic truth is that we cannot truly know what
defines extraterrestrial life until that first discovery is made.
The deep fissures are huge cracks in the crustal ice, caused by
Saturn's tidal forces, which lead to geyser-like ejecta and continuous
resurfacing events Courtesy of JPL
The deep fissures are huge cracks in the crustal ice, caused by
Saturn's tidal forces, which lead to geyser-like ejecta and continuous
resurfacing events
Even if Enceladus doesn’t hold extraterrestrial life, studying its
environment could yield clues about the development of life on Earth
and hints that our understanding of the requirements for life is
incomplete. 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.
A colony of Riftia tube worms surrounding a hydrothermal vent in the
ocean near the Galapagos islands. NOAA Okeanos Explorer Program,
Galapagos Rift Expedition 2011
A colony of Riftia tube worms surrounding a hydrothermal vent in the
ocean near the Galapagos islands.
Unfortunately, the Cassini mission is slated to end with the
spacecraft’s descent into Saturn’s atmosphere later this year.
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.
Follow us on Twitter, Facebook, Google+, Tumblr, and support Starts
With A Bang on Patreon.
(Nice images at website)
https://www.forbes.com/sites/startswithabang/2017/04/04/saturns-moon-enceladus-is-our-closest-great-hope-for-life-beyond-earth/#ed930bb59849
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