Searching for life by going there: NASA programs

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Searching for life by going there NASA programs
The NASA programs searching for life in the sol
ar system are complementary to
the SETI electromagnetic searches.
Since there is no question of other civilization
s in the solar system, the NASA programs focus a
ttention on searches for primitive, probably
microbial, life. For an overview of NASA prog
rams see http//astrobiology.arc.nasa.gov/road
map/
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The targets of the astrobiology program
at NASA were selected on the basis
of criteria we discussed earlier, namely
and primarily the presence of liquid water
and a solid crust. This quite drastically lim
its the possibilities and the current favorites (
none very habitable by earthly standards) are
Mars Europa Ganymede Titan Enceladus
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Some history of the search for life on
Mars. Mars has been a candidate in the search
for extraterrestrial life for centuries. In
the late 1909, the astronomer Lowell
interpreted features he observed on Mars
as canals which he imagined were dug by
Inhabitants. In the 1960s and 70s, resources
made available by the space race with the Soviet
Union made it possible to send probes to the pla
nets to take close up pictures and to take sampl
es and do experiments. The first of these to go t
o Mars was Mariner 4 in 1965.
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The Mariner space craft which took the first
close up pictures of the surface of Mars in 1965.
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First pictures of the surface of Mars, 1965
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The Viking missions to Mars in 1976 sent
two probes to the surface and did numerous
experiments on the soil seeking microbes
or organic molecules. The experiments included
adding water to soil samples and
analysing the resulting gases to see if they
contained chemicals which would be associated
With biological metabolism. A mass spectrometer
Analysed gases exuded by the soil to see if
it contained organic (that is hydrocarbon)
molecules.
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The exobiologist team at NASA was
shocked and very disappointed that
neither microbes nor organic molecules
were found.
Failure of the gas chromatograph-mass
spectrometer to detect organic compounds was dev
astating for those who believed that life on Mar
s was possible. For Jerry Soffen, the
GCMS results were "a real wipe out." Once he
assimilated the fact that the GCMS had found no
organic materials, he walked away from where the
data were being analyzed saying to himself, "Th
at's the ball game. No organics on Mars,
no life on Mars, "But Soffen confessed that it
took him some time to believe the results were c
onclusive. http//history.nasa.gov/SP-4212/ch
11.html
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Venus and Mercury proved equally
disappointing. More recently, the attention of
NASA exo (now called astro)biologists Has shift
ed to the moons of the outer planets
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Galilean Moons of Jupiter
Jovian System
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Studying the moons of Jupiter Galileo space
Probe. Launch 10.18.89 End of Mission 
9.21.03 Jupiter Orbits  34 Total Distanc
e Traveled  4,631,778,000 km Weight  2,223
kg Height  5.3 meters
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Europa
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Europa
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On its first close encounter with Europa,
in early 1996, Galileo took the first images of
this icy moon since those taken by Voyager 2
in 1980. These images, coupled with those taken
on subsequent orbits, began to reveal one of
the most exciting discoveries of the Galileo
mission a cracked, broken surface covered by
ridges and other features, including iceberg-like
areas where the surface seemed to have broken,
moved around, an then refrozen with the pieces
in different locations, like a jigsaw puzzle. Th
is, and other geological evidence, began to sugg
est that Europa could currently possess an ocean
of liquid water beneath its icy exterior.
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Close up of Europa surface taken by Galileo
Satellite. The surface features have been
(tentatively) attributed to effects of an
underground ocean of water.
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The puzzle of whether or not Europa currently had
liquid water found its most compelling piece of
evidence from an unlikely source the magnetic fi
eld instrument onboard Galileo.
This instrument measured evidence of an induced
magnetic field on Europa that changed with Europ
as movement through Jupiters immense magnetic fi
eld. Though Europa does not generate its own mag
netic field, the instrument measured
changes that could only come from a conducting
body moving through Jupiters field. The measurem
ents were consistent with a large layer of liqui
d water similar in composition to terrestrial se
awater located beneath Europas
surface. Other configurations are possible (such
as a large layer of a conducting metal or other
mineral) however geologists consider these unlik
ely.
http//www.space.com/searchforlife/seti_europa_060
928.html
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Of the other moons of Jupiter, Io
Has a lot of volcanic activity and appears
In hospitable. There is no evidence for any
liquid water on Callisto or Ganymede
Moving out, astrobiologists are looking at the
Moons of Saturn
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Titan's orbit (highlighted in red) among the
other large inner moons of Saturn. The moons out
side its orbit are (l-r) Iapetus and Hyperion t
hose inside are Dione, Tethys,
Enceladus and Mimas
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Exploring Titan Cassini-Huygens
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Dimensions 6.7 meters (22 feet) high
4 meters (13.1 feet) wide Weight 5,712 kilogram
s (12,593 pounds) withfuel, Huygens probe, adapt
er, etc 2,125 kilograms (4,685 pounds) unfueled
orbiter alone Orbiter science instruments co
mposite infrared spectrometer,
imaging system, ultraviolet imaging spectrograph
, visual and infrared mapping spectrometer, im
aging radar, radio science, plasma spectromete
r, cosmic dust analyzer, ion and neutral mass
spectrometer, magnetometer, magnetospheric imagi
ng instrument, radio and plasma wave science P
ower 885 watts (633 watts at end of mission)
from radioisotope thermoelectric generators
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Titan
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Titan's diameter and mass (and thus its density)
are similar to Jovian moons Ganymede and Callist
o.17 Based on its bulk density of 1.88 g/cm³,
Titan's bulk composition is half
water ice and half rocky material. Though similar
in composition to Dione and Enceladus, it is den
ser. Titan is probably differentiated into severa
l layers with a 3,400 km rocky center surrounded
by several layers composed of different
crystal forms of ice.18 Its interior may still
be hot and there may be a liquid layer consistin
g of water and ammonia between the
ice I crust and deeper ice layers made of
high-pressure forms of ice. Evidence for such an
ocean has recently been uncovered
by the Cassini probe in the form of natural
extremely low frequency (ELF) radio waves in Tit
an's atmosphere. Titan's surface is
thought to be a poor reflector of ELF waves, so
they may instead be reflecting off the liquid-ic
e boundary of a subsurface ocean.
Surface features were observed by the Cassini
spacecraft to systematically shift by up to 30 k
m between October 2005 and May 2007, which sugge
sts that the crust is decoupled from the
interior, and provides additional evidence for an
interior liquid layer.
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Titan is the only known moon with a fully
developed atmosphere that consists of more than
just trace gases. Atmosphere thickness
has been suggested ranging between 200 km21 and
880 km.22 Compare these figures to Earth's bou
ndary, which lies at 100 km, with 99.999 of atm
ospheric mass lying below that altitude
The atmosphere is 98.4 nitrogenthe only dense,
nitrogen-rich atmosphere in the solar system asi
de from the Earth'swith the remaining 1.6 comp
osed of methane and trace amounts of
other gases such as hydrocarbons (including
ethane, diacetylene, methylacetylene, acetylene,
propane, cyanoacetylene, hydrogen
cyanide), carbon dioxide, carbon monoxide,
cyanogen, argon and helium
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Based on the observations, scientists announced
"definitive Evidence of lakes filled with methan
e on Saturn's moon
Titan" in January 2007
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Image of the surface of Titan taken by the Huy
gens
lander from Cassini in 2005.
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Life on Titan?
suggestion that enough organic material exists
on Titan to start a chemical evolution analogous
to what is thought to have started life on Eart
h. While the analogy assumes the presence
of liquid water for longer periods than is
currently observable, several theories suggest t
hat liquid water from an impact could
be preserved under a frozen isolation layer.77
It has also been observed that liquid ammonia oc
eans could exist deep below the surface978
one model suggests an ammoniawater
solution as much as 200 km deep beneath a water
ice crust, conditions that, "while extreme by te
rrestrial standards, are such that life could in
deed survive".10 Heat transfer between
the interior and upper layers would be critical
in sustaining any sub-surface oceanic life
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Well, probably not.
there are formidable obstacles to life on Titan,
and any analogy to Earth is inexact. At a vast d
istance from the Sun, Titan is frigid (a fact ex
acerbated by the anti-greenhouse effect of its
cloud cover), and its atmosphere lacks CO2. Given
these difficulties, the topic of life on Titan m
ay be best described as an experiment for examin
ing theories on conditions necessary prior
to flourishing life on Earth.
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Overview Probes of planets during the last 45 y
ears have, to the considerable surprise and disa
ppointment of many scientists,
yielded absolutely no evidence of life or
even of prebiotic chemistry. Remaining candidat
es for biology in the solar system are the moons
Europa of Jupiter and Titan of Saturn, each of wh
ich may have subsurface water oceans. The abse
nce of liquid water may be the reason
for this absence of biology, but it is also
consistent with the possibility of a low
probability of initiation of life.