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
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