This is Enceladus –
Saturn’s sixth largest moon.
At around 500 km in diameter,
Enceladus is encased in a crust of ice
up to 40 km thick--
floating atop a vast salty ocean.
From afar, Enceladus looks like a
smooth, white pearl,
but a closer look at its surface
reveals a rougher reality.
Its north pole is riddled with impact craters,
scars left over from run-ins with asteroids
and other cosmic debris.
On Enceladus’ south pole,
we see long, aquamarine
“tiger stripes” --
fractures in the ice
that spew tall plumes of water vapor and ice particles
kilometers above the surface.
Since 2005,
Cassini has been gathering and analyzing
material from these plumes.
We know they contain water vapor
and traces
of nitrogen and methane,
but the current mission
was to look for molecular hydrogen.
Here on Earth,
organisms known as chemolithotrophs
have the ability to harvest chemical energy
from hydrogen--
forming a base of life
independent of sunlight.
In this latest plume dive,
Cassini screamed
past Enceladus’ south pole
at around 8.5 km/sec,
a mere 50 km above the surface
at its lowest point.
Gas captured during the flyby
revealed that these plumes
do contain hydrogen gas
This suggests that Enceladus’ rocky core
is interacting with the warm waters
of the subsurface ocean.
Such an interaction
makes Enceladus a more hospitable environment
for life than any other body in the solar system
--outside of Earth
This was, unfortunately,
one of Cassini’s last missions.
NASA will soon send the satellite
on a series of 22 dives
between the planet and its rings,
a region of Saturn yet to be explored.
These dangerous dives will reveal
new information about
the formation of Saturn's rings--
are they as old as the solar system
or a new addition?
During its last five orbits,
Cassini will dip a toe into Saturn’s atmosphere.
In September,
Cassini is set to plunge into
Saturn--
sending back what measurements it
can before it vaporizes.
Bringing to a close a 20 year exploration
of one our solar system’s largest residents.
