DISTANT DISCOVERIES
SEARCHING FOR ET... CAREFULLY
As NASA pursues unmanned missions throughout the solar system, the quest
for signs of life on distant planets -- more likely in the past than
in the present -- is gaining increased attention from space agency planners.
The problems are formidable: They must increase their understanding
of how life originated and evolved on Earth; they must deduce the most
likely places where water could have existed on planets like Mars; and
they must develop new techniques for drilling many yards, and later
many miles, beneath the surface of such planets.
Finally, the scientists must be scrupulously careful with every spacecraft
and every tool that lands on any planet to make sure they do not carry
microbes from Earth that would contaminate whatever extraterrestrial
life might conceivably exist now or in the past.
At last week's annual meeting of the American Geophysical Union in
San Francisco, NASA-sponsored scientists from many research institutions
called their search for life on other planets and their moons "a
unifying theme'' for solar system exploration.
"Astrobiology is now the intellectual centerpiece of NASA's efforts
in space exploration," said Bruce M. Jakosky, professor of geology
at the University of Colorado, referring to the new field that integrates
astronomy with the study of life.
Mars and Europa, the ice-covered moon of Jupiter, "appear as potentially
habitable worlds, either today or in the past," he said. "And
the smoggy atmosphere of Saturn's moon Titan may well cover a surface
where intermittent water and organic chemicals might have encouraged
the evolution of living organisms."
As a result of recent discoveries of microbes living in freezing cold,
with no oxygen or light, and the profound pressures of deep underground
mines, Jakosky noted, the extreme diversity of life on Earth makes it
quite likely that life could be or have been widespread in our solar
system.
"We could probably pick up some bugs right now on Earth that would
find themselves quite happy in a Martian environment," he said.
For 30 years, scientists scanning images of Mars from spacecraft have
been tantalized by giant channels, broad basins and sinuous valleys
on the Martian surface that look exactly as if water had flooded and
flowed there billions of years ago.
In coming weeks, three spacecrafts -- one stationary lander operated
by the European Space Agency and two NASA rovers -- will set down on
the Red Planet and search for signs of past and present life, and water.
In an even more ambitious mission, astronomers and astrobiologists
said at last week's AGU meeting that they have begun planning a voyage
to Europa to study what must be deep oceans -- and possibly life --
beneath the icy crust of the Jovian moon.
They envision sending a 300-foot-long, nuclear-powered craft -- called
JIMO, for Jupiter Icy Moons Orbiter -- to spend five years circling
Europa, plus two others, Callisto and Ganymede. Scientists have not
ruled out landing probes or instruments on the surface of Europa to
aid the search.
The mission will fly no earlier than 2010 and could cost as much as
$8 billion.
As the space agency pursues missions to other planets, a major focus
is protecting those worlds and ourselves, said John D. Rummel, who bears
a unique title as NASA's "planetary protection officer'' in Washington.
"As we discover life out there, we don't want to find that we've
already killed it off."
International space treaties require space-faring nations to develop
foolproof techniques for rigorously sterilizing every object -- spacecraft
or instrument -- that is designed to approach or land on a planet, he
said. Similarly, when spacecraft are planned to return to Earth, they
must be built so there is no possibility of unknowingly bringing an
alien organism back to Earth.
Back when the Apollo program was carrying astronauts to the moon, their
samples of lunar rock were quarantined for months, and their instruments
were sterilized. Because the job will be infinitely more difficult for
the robotic planetary explorers, teams of scientists are already developing
the crucial anti-contamination technology, Rummel said.
NASA has created a major "Astrobiology Institute" with its
headquarters at the Ames Research Center in Mountain View, with some
20 universities and research institutions participating.
Geochemist David J. Des Marais, an astrobiology researcher at Ames,
noted the importance of understanding the evolution of life on Earth
if scientists are ever to understand how life might have developed on
planets elsewhere.
His own research into how life developed suggests that water must have
first rained down on the new-forming Earth from comets and meteors as
much as 4.9 billion years ago and that more massive impacts introduced
organic chemicals within an additional billion years.
"Proto-cells" then began to form on the warming Earth. And
finally by 3.7 billion years ago, the first life appeared along the
coasts of small, new continents in the form of "biofilms"
and layers of microbial mats whose fossil forms have been discovered
in recent years.
Within a few hundred million years, those microbes had learned to use
sunlight for energy, growth and reproduction. After a few million years,
more advanced life forms emerged. And after that, the pace of evolution
and growth of diversity increased swiftly, he noted.
"Understanding the nature and timing of this ascent of life is
crucial for discerning our own beginnings," Des Marais said. "This
understanding also empowers our search for the origins, evolution and
distribution of life elsewhere in our solar system and beyond."
Source: David Perlman, San Francisco Chronicle Science Editor
http://www.sfgate.com/cgi-bin/article.cgi?file=/c/a/2003/12/15/MNGNV3NFRI1.DTL
JIMO JOURNEYS TO JUPITER
NASA plans to dispatch a hulking nuclear-powered spacecraft to determine
whether three of Jupiter's icy, planet-sized moons have the potential
to harbor life.
The Jupiter Icy Moons Orbiter, or JIMO, would spend monthlong stints
circling the moons Callisto, Europa and Ganymede, which are believed
to have vast oceans tucked beneath thick covers of ice.
The unmanned craft, far larger and more powerful than any other sent
to explore the outer solar system, would spend years studying the moons'
makeup, geologic history and potential for sustaining life, as well
as Jupiter itself.
Besides water, the moons appear to contain two other ingredients necessary
for life: energy and the right chemicals. Along with Mars, they are
considered the most likely places to have extraterrestrial life within
our solar system.
"We don't know if life is there. But this mission will allow to
ask that question with some pretty sound tools," said Christopher
McKay of the National Aeronautics and Space Administration's Ames Research
Center.
Jimo won't launch until at least 2011. On Monday, scientists at the
fall meeting of the American Geophysical Union briefed reporters on
the mission's progress.
The spacecraft would be the first in a series of robotic NASA probes
that rely on uranium-fueled fission reactors to generate large amounts
of electricity. While probes such as Galileo and Cassini have made do
with hundreds of watts of electricity, Jimo might have thousands of
watts to power its thrusters and instruments.
The reactor conceivably could produce enough electricity to power several
U.S. homes. That could provide Jimo a hundredfold boost over previous
missions in the amount of data it would be able to beam back to Earth.
Jimo would carry high-resolution cameras and other instruments, including
radar and lasers to map the thickness and elevation of the ice that
envelops each moon.
Scientists are keen to study the Jovian system because of its complexity.
The planet and its stable of moons represent, in many ways, a miniature
solar system.
"These are worlds in their own right," said Ron Greeley,
of Arizona State University, Tempe.
The spacecraft is envisioned as being 60 to 100 feet in length. Early
conceptions place its nuclear reactor at the end of a boom to shield
the scientific instruments from radiation.
Jimo also would bristle with fins to dissipate the intense heat from
its reactor.
JIMO Website:
http://www.jpl.nasa.gov/jimo/
PROMETHEUS POWER
NASA is expected to begin stepping up use of nuclear power in its exploration
of the solar system through it's Project Prometheus (formerly the Nuclear
Systems Initiative) - harnessing nuclear energy to usher in a new era
of Solar System exploration.
Prometheus calls for fission power reactor research, advanced heat-to-power
conversion hardware, as well as power management and distribution equipment.
The major poster child for Prometheus is JIMO. JIMO would orbit three
different moons of Jupiter where earlier spacecraft discovered evidence
for vast saltwater oceans hidden beneath icy surface layers: Europa,
Ganymede and Callisto.
Government agencies are powering up to support the effort. U.S. aerospace
firms have started assessing how to build nuclear-powered probes. And
scientists are sketching out an unprecedented "power-rich"
research agenda using potent suites of space science instruments.
Rockets lobbed off Earth carrying nuclear reactors on space science
pilgrimages are not embraced by everybody. Opponents see the Prometheus
program as dangerous and risky, dismissing it as a front for military
star warriors.
Source:
http://spacescience.nasa.gov/missions/prometheus.htm
NASA: Nukes to Power Spacecraft
http://www.wired.com/news/technology/0,1282,57555,00.html
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