The Koyal Group Info Mag Review - Philae Comet Lander Eludes Discovery

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The Koyal Group Info Mag Review
Philae Comet Lander Eludes Discovery
Efforts to find Europe's lost comet lander,
Philae, have come up blank.
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The most recent imaging search by the overflying
Rosetta "mothership" can find no trace of the
probe. Philae touched down on 67P/Churyumov-Geras
imenko on 12 November, returning a swathe of data
before going silent when its battery ran
flat. European Space Agency scientists say they
are now waiting on Philae itself to reveal its
position when it garners enough power to call
home. Researchers have a pretty good idea of
where the robot should be, but pinpointing its
exact location is tricky. On touchdown, Philae
bounced twice before coming to rest in a dark
ditch. This much is clear from the pictures it
took of its surroundings. And this location, the
mission team believes, is just off the top of the
"head" of the duck-shaped comet. The orbiting
Rosetta satellite photographed this general
location on 12, 13 and 14 December, with each
image then scanned by eye for any bright pixels
that might be Philae. But no positive detection
has yet been made. Rosetta has now moved further
from 67P, raising its altitude from 20km to 30km,
and there is no immediate plan to go back down
(certainly, not to image Philae's likely
location). Even if they cannot locate it,
scientists are confident the little probe will
eventually make its whereabouts known. As 67P
moves closer to the Sun, lighting conditions for
the robot should improve, allowing its solar
cells to recharge the battery system. The latest
assessment suggests communications could be
re-established in the May/June timeframe, with
Philae distributing enough electricity to its
instruments to resume operations around
September. This would be at perihelion - the
time when the comet is closest to the Sun (185
million km away) and at its most active.
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Scientists continue to pore over the data Philae
managed to send back before going into
hibernation. Some of the results - together with
ongoing Rosetta observations - were reported at
the recent American Geophysical Union meeting in
San Francisco. Highlights include a clearer idea
of the nature of the comet's surface. Researchers
say this appears to be covered in many places by
a soft, dusty "soil" about 15-20cm in
depth. Underneath this is a very hard layer,
which is thought to be mainly sintered ice. The
conference had the rare opportunity to see
pictures from Rosetta's Osiris camera
system. These high-resolution images are not
normally shown publicly because the camera team
has been given an exclusive period to study the
data and make discoveries. Among them was a shot
looking into a pit on the surface, revealing an
array of rounded features that the Osiris team
has nicknamed "dinosaur eggs". These features
have a preferred scale of about 2-3m and may be
evidence of the original icy blocks that came
together 4.5 billion years ago to build the
comet. The dino eggs have been seen at a number
of locations, including in cliff walls. Early
interpretations of the general surface of the
comet indicate that many structures are probably
the result of collapse over internal
voids. Although a small body just 4km across,
67P's gravity is still strong enough to shape
depressions and arrange fallen boulders. A good
example of this is in "Hapi" valley - the giant
gorge that forms the "neck" of the comet. It
contains a string of large blocks at its base,
which one Osiris team-member argued very likely
fell from the nearby vertical cliff dubbed
"Hathor". All the surface features on 67P carry
names that follow an ancient Egyptian
theme. Hapi was revered as a god of the Nile.
Hathor was a deity associated with the sky.