Jupiter's moon Europa hides an ocean of water beneath its icy
crust that might harbour extraterrestrial life.
Unfortunately, a big price tag has kept alive the fictional
decree in Arthur C Clarke's Space Odyssey series
to leave Europa
alone: No robot has ever landed on, drilled into or orbited the
chilly world. Only a handful of spacecraft have flown by.
A panel of scientists determined
in 2011 that Nasa's plans to explore the moon with a
single spacecraft, called the Jupiter Europa Orbiter, or
JEO, would cost about $4.7 billion (£2.98 billion). That amount of
cash, they wrote, "is so high that both a decrease in mission scope
and an increase in Nasa's planetary budget are necessary to make it
But even before the panel slammed the mission's financial
feasibility, astrobiologist Pabulo Henrique
Rampelotto of Brazil's Federal University of Pampa was
plotting to save exploration of Europa.
In a study published 13 July in Astrobiology,
Rampelotto argues that nixing one large orbiter and instead sending
three small spacecraft -- two orbiters and a probe carrying surface
impactors -- could spread out both the cost and the risk while
hitting all of JEO's science goals, and then some.
"[T]he main advantages are the complete access to the
habitability of Europa, simpler mission design and low cost for
each mission," Rampelotto wrote in an email to Wired.com. "Europa
is considered the prime candidate in the search for life in our
solar system. Its ocean may be in direct contact with the rocky
mantle beneath, where the conditions could be similar to those on
Earth's biologically rich sea floor."
Both Nasa and the European Space Agency hope to explore Europa
and Ganymede, another of Jupiter's moons, sometime in the next two
decades because both bodies may hide a liquid ocean. In the joint
space exploration plan, called the Europa Jupiter System
Mission, Nasa would launch JEO within this decade. Around the
same time that spacecraft launches, Europe would rocket its
own Jupiter Ganymede
Orbiter into deep space.
Budget hawks, however, aren't buying into Nasa's $4.7 billion
dream. Accounting for other higher-priority missions, JEO would
stretch further Nasa's shrinking annual planetary science budget of
"I believe you will not find someone who continues to support
the $4.7 billion … mission concept," Rampelotto said. "And that is
interesting because before the release, no one was considering the
possibility of an alternative mission concept."
Rampelotto beat the panelists to the punch by proposing
his three-spacecraft mission.
If built and launched within the next few years, mission one --
an orbiter to measure the thickness of Europan ice and see how deep
its oceans go -- could reach Europa between 2020 and 2025. A second
orbiter would launch a few years later, map the surface in visible
and infrared light, and determine if any organic chemicals are
"Mission two is technically easier than mission one and could be
launched very soon too," Rampelotto wrote. "After we have those
results from missions one and two, mission three would be mature
enough to be launched."
That mission would pound the
surface with impactors, penetrate between one and ten metres of
ice, and then beam data about the ice's composition to Earth. It's
unlikely any impactor would reach the subsurface ocean, however,
because the thinnest ice may be 2.9km thick. Even below that depth,
only lakes of water far
above the ocean may be locked in the icy crust.
"But, if delivered in potential landing sites where liquid water
from the ocean could have recently reached the surface or near
surface, we could analyze indirectly the ocean composition,
including signals of life," Rampelotto wrote.
Rampelotto's plan to barnstorm Europa offers no concrete costs
for each mission, which he said would require "advanced studies" to
determine. So the idea isn't without its critics. "Nasa team
leaders have advised me that penetrators are difficult and risky to
deliver and the best option continues to be a lander," Rampelotto
Bob Pappalardo, a planetary
scientist who studies Europa and is helping Nasa develop future
missions to the moon, said Rampelotto's scheme is a logical one
during tight budgetary times. But he noted saving money by
splitting up a big mission into smaller ones brings about another
issue: fear of commitment.
"The reality is that Nasa is not going to want to fund or begin
a program of missions, based on the reaction to the Mars sample return
suggestion," said Pappalardo, who wasn't involved in
Rampelotto's study. "That went over like a lead balloon [at the
White House], in terms of being a long-term budgetary
Pappalardo hopes that, if there are signs of a recovering U.S.
economy in the next few years, they will spur the current
presidential administration to open its tight wallet.
"Right now the goal is to do anything at Europa," he said. "I
really hope we'll come back to our senses soon. I don't see the
vision for planetary science that was present in the past."
"We need to be planning on the future," he said. "As it stands,
in a few years, we won't be launching anything. We're in danger of
losing our leadership in planetary science."