Home Science Hot water flows on Enceladus could trigger life

Hot water flows on Enceladus could trigger life

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Scientists have discovered heating warm ocean and it looks like Saturn’s icy moon Enceladus has an active hydrothermal system.

Researchers found that Enceladus has a vast, underground ocean at
its south pole, just a year ago. It appears to be sitting under a 30- or
40-kilometre-thick layer of ice, and is itself almost 10 km deep. At the
time, there didn’t seem to be much evidence of hydrothermal activity
connected to the ocean, but researchers from the University of
Colorado’s Laboratory for Atmospheric and Space Physics in the US have
managed to find some in the form of tiny, but significant fragments of
minerals
And when we say tiny, we mean tiny. Discovered by the Cassini
spacecraft, these grains are just 2 to 8 nanometres in radius, which
makes them not much bigger than a strand of hair. But they can tell us
so much. Consisting of mostly silica, just like the masses of sand and
quartz particles here on Earth, it’s thought that they are the direct
result of hydrothermal processes  – “the skeletons of evaporated
geyser-flung saltwater”, says William Herkewitz at Popular Mechanics.
The
process that ends up forming these silicate particles begins with the
gravitational pull of Saturn and its other moons on Enceladus. This
causes a lot of friction, which heats its underground ocean to about 90
degrees Celsius. This hot water gradually dissolves the solid minerals
that surround the ocean, and these particles are then carried up towards
the surface by the geyser water, which is being rapidly cooled by the
icy layer above. 
As Sean O’Kane explains at The Verge,
once the dissolved particles make their way to the geyser opening to be
spewed all over the surface of the moon, they become trapped inside
grains of ice. This icy coating will soon be eroded away in the harsh
Enceladus atmosphere, which exposes the silicate particles to the
elements and Cassini’s onboard lab. 
“We now have very strong
evidence that there is a hot hydrothermal environment at the base of
Enceladus’s ocean, perhaps like those where we believe life began on
Earth,” Jonathan Lunine, a planetary scientist at Cornell University who
is involved with Cassini but not this particular study, told Popular Mechanics.
“This is yet another discovery in a series of really remarkable
findings that have come one by one, to tell us that this may be the
place to go look for life in the outer Solar System.”
The
researchers are so good at interpreting this little piece of evidence,
they can actually use the size and chemical make-up of the particles to
figure out just how much salt is in Enceladus’s ocean. Publishing in Nature,
they say the upper limit for salinity in the ocean is 4 percent – 3.5
percent is the average in Earth’s oceans – and its pH is likely higher
than 8.5.

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What’s really special about this discovery is that many
scientists believe hydrothermal vents gave rise to life on Earth – the
repeated contact between the hot sea water and surrounding rocks created
the energy and nutrients needed to produce and sustain single-celled
organisms – so perhaps they will, or have, on Enceladus?

“Today,
Earth’s active hydrothermal vents are seafloor oases, harbouring
ecosystems that flourish in the darkness, isolated from the surface
world. Find someplace else beyond Earth where hot rock and water
intermingle, and even if it’s far from the Sun, life might flourish
there, too. 

Such systems may have been common early in
the Solar System’s history, when rocky planets and icy moons were still
relatively hot and wet from their initial formation. But until now
scientists had no evidence of ongoing hydrothermal activity anywhere
beyond Earth.”

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