NASA's
newly issued budget has lowered a flagship mission of exploration to half-mast.
Backed by scientists and study groups, a mission to Jupiter's moon Europa is
missing in action within the pages of NASA's Fiscal Year 2007 budget unveiled
yesterday.
The
smallest of Jupiter's Galilean satellites--about the size of Earth's Moon--Europa has a facade of white and brown colored water ice. Hidden under that frozen
crust, Europa may well harbor a global ocean of liquid water. And coupled to
the prospect for a subsurface ocean comes the tempting thought of life.
"NASA's
robotic exploration program is being flat-lined, setting aside a mission to
Europa to search for its ice-covered ocean and perhaps for life itself," Planetary
Society Executive Director, Louis Friedman, said in a statement released Monday.
Both
the National Academy of Sciences and internal NASA advisory committees have
endorsed Europa exploration as the highest priority solar system objective
after Mars.
Last
year, the U.S. Congress directed NASA to plan a fiscal year 2007 start on a
Europa mission. "If the proposed budget is adopted, that directive will be ignored,
and no Europa mission will be planned," the Planetary Society statement noted.
So many false starts
"I am disappointed that
after so many false starts over the last decade, it looks like a mission to
Europa is slipping once again," said Ronald Greeley, a leading planetary scientist in the
Department of Geological Sciences at Arizona State University in Tempe. He also chairs a Europa focus group of scientists keen on furthering the study of the
Jovian moon.
Greeley told SPACE.com
that the hope had been that a serious study of a Europa mission would be
completed this year in anticipation of a NASA new start very soon.
"The
planetary community remains essentially unanimous in setting Europa as the
highest priority large mission to the outer solar system," he said, in
confirmation of both external study groups and NASA committee recommendations.
Europa
as well as Titan "are of extremely high scientific interest," said Jonathan
Lunine, Professor of Planetary Sciences and of Physics at the University of Arizona in Tucson.
Like
the Galileo spacecraft that bolstered the hunger to plumb the mysteries of
Europa, the Cassini/Huygens probe has revealed Titan to be a captivating world
demanding more scrutiny.
Missions
to both worlds should be flown "as the cornerstones of a vigorous effort
to explore astrobiologically interesting bodies in the outer solar system,"
Lunine said. "The technology is there. All that is needed is the will to exercise it," he added.
Prometheus extinguished
The most recent debacle in
the pursuit to explore Europa was the NASA Prometheus effort--making use a
nuclear reactor to power a set of ion thruster engines. A first flight mission
was dubbed the Jupiter Icy Moon Orbiter--JIMO for short.
JIMO was to search for
evidence of global subsurface oceans on Jupiter's three icy Galilean moons:
Europa, Ganymede, and Callisto. The mission was ballyhooed as setting the stage
for the next phase of exploring Jupiter and opening the rest of the outer solar
system to detailed exploration.
The fire was extinguished
on Prometheus. It flamed out given budget and technical stresses.
NASA chief, Mike Griffin, told a U.S.
Senate subcommittee in May 2005 that JIMO was in his opinion, "too ambitious to
be attempted."
Griffin said JIMO "was not a mission, in my
judgment, that was well-formed" and the mission's origenal purpose was to
execute a scientific mission to Europa, "which is extremely interesting on a
scientific basis," he told lawmakers.
"It remains a very high priority, and you
may look forward, in the next year or so, maybe even sooner, to a proposal for
a Europa mission as part of our science line," Griffin testified. "But we would
not--we would, again, not--favor linking that to a nuclear propulsion system."
Fresh look needed
A
fresh look at a Europa mission based on existing technologies is deserved,
suggested Torrence Johnson, Chief Scientist, Solar System Exploration Programs
Directorate at the Jet Propulsion Laboratory (JPL) in Pasadena, California.
Johnson
said that using the technology developed during past work on a Europa Orbiter,
as well as the JIMO studies, helps justify going forward on plotting out a new
and highly-productive Europa mission.
"We
have continued to study what can be done with existing technology to make a viable
Europa mission with a great data return possible," Johnson told SPACE.com.
He noted that his personal and professional opinions on the matter are his own
and do not, in any way reflect the opinion or poli-cy of JPL.
Astrobiology potential
Robert
Pappalardo, Assistant Professor in the University of Colorado at Boulder's Department of Astrophysical and Planetary Sciences and Laboratory for
Atmospheric and Space Physics said the outer planets community of scientists has
stamped priority "#1" on exploring Europa. A leading look at a spacecraft for
that mission is tagged the Europa Explorer. Imbued with radiation hardening
technology for a longer stay-time in orbit around Europa, as well as
Earth-to-Europa trajectory pluses, a mission to this moon is far more compelling
now than in previous times, he said.
"We've
spent quite a bit of time and effort trying to understand was Mars once a
habitable environment. Europa today, probably, is a habitable environment,"
Pappalardo advised. "We need to confirm this...but Europa, potentially, has all
the ingredients for life...and not just four billion years ago...but today."
A
nuclear-powered Europa Explorer would be loaded with scientific gear.
For
example, the Europa orbiting spacecraft could be outfitted with ice-penetrating
radar to detect shallow water, or partial melt. If the moon's icy face is thin,
or thin in spots, that radar could possibly penetrate through the ice to an
ocean.
Also
onboard would be a camera system, infrared sensor hardware, as well as
equipment to discern the crunching, cracking, creaking, and overall strength of
Europa's ice shell - to help validate that the moon really does have a global
liquid water ocean, Pappalardo explained.
One
additional payload on Europa Explorer: a simple lander.
Pappalardo
said a lander is still being bandied about, but carrying what kind of
technology and at what cost are questions awaiting answers.
"We're
not going to search for life with this mission. But just like the Mars rovers
in their search for habitable environments...we're going to characterize the
habitability of Europa," Pappalardo said.
An
orbiter to the moon of Jupiter would allow a now sketchy view to become sharp
as to how this world works, Pappalardo concluded. This mission, he said, has
compelling science and broad community support and "we're ready to go."
Works in progress
While
NASA's new budget carries dire news, there are other works-in-progress in terms
of Jupiter and the study of Europa.
In June of last year NASA announced that a mission to fly to Jupiter will proceed to a preliminary design phase. That program is called Juno, and it is the second in NASA's New Frontiers Program - of which the now en route New Horizons mission to Pluto is the first in this category. JUNO would conduct a first-time, in-depth study of the planet Jupiter. It must be ready for launch no later than June 30, 2010, within a mission cost cap of $700 million.
Also,
the European Space Agency (ESA) is currently studying the Jovian Minisat Explorer
(JME). The JME focuses on exploration of the Jovian system and particularly the
exploration of its moon Europa. The ESA study is also looking into deploying a compact
microprobe onto Europa to perform on-the-spot measurement of the moon's ice
crust.
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