We’re now learning that icy worlds seem to be the best places in Solar System where
life could be hiding.
Worlds like Europa and Enceladus, which have vast oceans of liquid water beneath a shell
of water ice.
And just in the last year, astrobiologists announced that hardy forms of Earth life should
be able to thrive in these oceans, feeding off hydrogen gas emanating from deep sea vents.
Clearly we need to explore these worlds, to go deep down beneath the ice to explore the
ocean depths.
But how do you drill through kilometers of ice to reach it?
Sometimes the Universe is trying to tell you something.
I’ve been going back and forth with viewers about how a lander / submarine to Europa would
work.
How would it drill into the ice?
Communicate with the surface?
Etc.
I’ve been giving you bits and pieces, but clearly, this needed to be an episode, so
let’s do it.
Today I’m going to talk about a plan that folks with NASA put together on exactly how
a mission to Europa would work.
It was done as part of the NASA Innovative Advanced Concepts program.
The plan is called EUROPA, which stands for Exploration of Under-Ice Regions with Ocean
Profiling Agents.
“Europa”, get it?
It’s very meta.
The study was originally put together back in July, 2013.
We reported on it for Universe Today, and so did many other sites out there, but it
didn’t get any further.
Which is a shame, because it’s an awesome plan.
So let’s get into it.
Europa is the smallest of Jupiter’s Galilean moons.
It orbits Jupiter at a distance of about 680,000 kilometers, about twice the distance from
the Earth to the Moon, and takes about 3 and a half days to complete an orbit.
Because of the massive gravity from Jupiter, Europa and the rest of the Galilean moons
travel around the planet in a lockstep orbital resonance.
For every orbit made by Ganymede, Europa circles Jupiter twice, and Io goes around 4 times.
This powerful gravity has another effect: tidal interactions with its moons.
In the most extreme, there’s Io, which experiences huge flexing from Jupiter that massive volcanoes
cover its surface, firing geysers of molten rock high into space.
The same tidal forces are happening with Europa, but because it’s farther out, the heating
maintains a vast liquid ocean of water on the world.
When NASA’s Voyager spacecraft flew past Europa, it revealed a world covered in fresh
ice, with very few craters.
Huge dark lines seem to indicate that the ice is shifting and cracking like plate tectonic
activity here on Earth.
And somewhere down there, there’s liquid water.
NASA’s Galileo spacecraft mapped Europa as best it could.
According to estimates from planetary scientists, the interior of Europa consists of a layer
of ice and water that measures 115 kilometers thick surrounding a rock mantle.
The ice probably measures 40 km thick, but there’s reason to believe it could be even
closer to the surface in some areas.
In the last year, astronomers have discovered geysers of water spewing into space.
Most likely, it’s not a solid sheet of ice, but has regions where warm water upwells,
and other areas where the ice goes deeper.
Locally melted areas where asteroids crashed into it, and frictionally melted areas where
cracks are located
As you’ve probably heard me say a few hundred times now, wherever we find liquid water on
Earth, we find life, so the watery depths of Europa (and the other icy worlds in the
Solar System) seem like the perfect place to go looking for alien life.
We’ve done a whole video about the prospects of life on icy worlds, and how there could
be thousands of times more worlds like this than terrestrial worlds in the habitable zones
of stars in the Milky Way.
I’ll link to that here and in the show notes if you haven’t already seen it.
Let’s talk about the practical plan to actually get under the ice on Europa.
In the original study, they proposed using a Space Launch System rocket, which we’re
still waiting to see the first launch.
The Block 1 configuration would be capable of carrying 10 metric tonnes to Europa without
the hassle of gravity assists.
Now, they’d probably use the Falcon Heavy, or maybe even wait for the SpaceX BFR to enjoy
the cost savings.
Flight time from Earth to Europa would take about two years.
The minimal plan would send a single lander, but if the budgets flow, there could be up
to 4 landers, each exploring a different region on Europa.
One of the big risks to a mission to Jupiter is the charged environment around it.
All spacecraft would need to be able to discharge themselves on a regular basis to prevent any
damage to their electronics.
Once they arrived at Europa, the landers would touch down at 45-degrees south of the equator.
Their highest priority would be to start drilling into the ice immediately.
Because it’s so close to Jupiter, Europa receives an enormous amount of radiation from
the giant planet.
The surface of Europa is exposed to 15 kilorads/day of radiation.
Just for comparison, an astronaut on the surface of Mars would accumulate about 6 kilorads
a year.
So, it’s bad.
In fact, the survival of the lander base station in the harsh radiation environment of Jupiter
would probably decide the overall length of the mission.
In a second I’m going to talk about what happens after the landers set foot on the
surface of Europa, but first I’d like to thank:
Hubert Sosniak Branden Loizides
Marsian Organization Andy McCasland
And the rest of our 810 patrons for their generous support.
If you love what we’re doing and want to get in on the action, head over to patreon.com/universetoday.
When last we left our heroes, they had just landed on Europa and were about to deploy
drills to get down beneath the thick ice shell.
The landers would start drilling immediately, to get as much of themselves under the ice
as possible.
Just a meter underneath the ice, and they would be exposed to one millionth less radiation.
I say drill, but that’s not exactly the best way to describe it.
Each lander would deploy a “cryobot”, which would be equipped with either a fission
reactor (like the 30 or space missions launched by the Russians), or a radioisotope heating
unit; or RHU, a mass of decaying isotope.
This would concentrate the heat at the tip of the melt probe, creating a thick layer
of melt water around it.
The probe would slowly sink into the ice by gravity.
Guiding the probe down through the ice would be a challenge, but one idea is to use a pool
of mercury at the hot point of the probe.
The heat would keep the mercury melted, but if it tipped over too far, the mercury would
collect at the bottom of the point, and help align it back to vertical.
If this sounds like science fiction, smaller probes like this have actually been built
and tested to help explore the ice in Greenland.
The University of Washington Applied Physics Laboratory has built the “Ice Diver”,
which can descend straight down through ice at a speed of 10 meters per hour, spooling
a cable behind it.
You can even speed this process up, spraying jets of hot water in front of the melt probe.
In the beginning, progress would be slow.
The ice in the borehole would be open to space, and need enough energy to sublimate, but once
it got deep enough, the tunnel would be collapses, the pressure would increase, and then the
cryobot would melt down through the ice sheet.
The cryobot would slowly melt its way down through the ice shell, reeling out a fiber
optic tether which connects to a surface transmitter.
Since radio signals can’t penetrate the ice, this would be its only way to send information
back to Earth.
The tether would come from inside the crybot, and would freeze in place in the borehole.
Trapping and protecting it.
This tether would actually be pretty lightweight, only 5 kilograms for 10 km of length.
A small cryobot, just 25 cm in diameter and 2.5 meters long might need only a year to
descend through 10 km of ice, while a much larger one, 50 cm in diameter and 5 meters
long might need up to 4 years.
Once the cryobot detected that it had reached liquid water and the bottom of the ice shell,
it would deploy underwater gliders called hydrobots.
Assuming the currents aren’t too strong down there under the ice, they wouldn’t
even need a propulsion system, just slowly gliding as they drift through the shifting
water columns.
Underwater gliders have been tested successfully here in the Earth’s oceans, and you can
even buy them in Kickstarters.
Each cryobot could contain up to 4 hydrobots, and each of which would have a specialized
job, examining the ocean, the ice, the sea floor, or searching for life.
Over the course of the mission, the hydrobots would explore their surroundings, mapping
out the movements of the ocean.
The tidal interactions with Jupiter keep the oceans from freezing, but do they create currents
under the ice?
What’s it like right at the boundary between liquid water and ice?
How dense is the ice and how does it shift around?
The hydrobots would dive down to the ocean floor and see what kinds of geologic processes
are going on down there.
And of course, they would perform an exhaustive search for life.
They’d start by identifying the big requirements for life: liquid water, energy sources and
chemical building blocks, and then search for the chemical byproducts of life, finally
looking for actual life forms.
We could expect they could find environments similar to the hydrothermal vents we have
here on Earth at the bottom of the oceans.
Ecosystems which are fully self contained and completely separate from the surface and
top of the oceans.
I’m not saying there’d be Europan space whales, but come on…
“Europan space whales”.
The cryobot could harvest energy from the tidal flows that move across the ice/ocean
region, recharging batteries, which it could then use to recharge the hydrobots.
Using this system, the mission could remain active under the ice for much longer.
It’s important to note that planetary protection is one of the most important considerations
of a mission like this.
Since the oceans of Europa could be so conducive to life, any Earth organisms could get a free
ride to colonize it.
The mission planners mentioned a few important ways to deal with that.
Of course, everything needs to be cleaned as much as possible before it leaves Earth.
Helpfully, the surface of Europa is bathed in the trapped radiation from Jupiter’s
magnetosphere.
You think the Van Allen Belts are bad, Jupiter’s belts are way worse.
It might make sense to remain on the surface for a few months to give the radiation environment
more time to sterilize the spacecraft.
Also, the nuclear power plant on board the spacecraft could be used to further sterilize
everything.
It could jettison its radiation shielding and roast any surviving microbes.
As I mentioned earlier, this proposal was originally written up during the 2013 NASA
Advanced Innovative Concepts series of studies.
Since then, NASA has committed to the Europa Clipper mission, which should launch sometime
between 2022 and 2025.
It’ll take 3 years to get to Europa and then another 3 years to study its surface
and the structure of the ice.
So maybe by the early 2030s, NASA will be ready to follow up with the cryobot/hydrobot
Europa mission to Europa.
I can’t wait.
Well, what do you think?
Is it time to revisit this strategy and send the Exploration of Under-Ice Regions with
Ocean Profiling Agents to Europa?
Let me know your thoughts in the comments.
Once a week I gather up all my space news into a single email newsletter and send it
out.
It’s got pictures, brief highlights about the story, and links so you can find out more.
Go to universetoday.com/newsletter to sign up.
And finally, here’s a playlist.