discover the comet’s surface was
group of 11 different science instruOn Oct. 18, 2004, ESA gave the
not as expected. When viewed in
ments aboard Rosetta, all designed
green light for Philae to attempt the
the ultraviolet portion of the specto help unlock the secrets of comet
first-ever soft landing on the surface
trum, they observed the surface to
67P. NASA is also contributing to the
of a comet. After weeks of scrutinizbe darker than charcoal and void
Microwave Instrument for Rosetta
ing images and date from Rosetta,
of any large, icy patches. Due to its
Orbiter (MIRO), the Ion and Electron
the team selected site J, located
location and distance from
on the head of the comet,
the Sun, any exposed waas the primary landing site.
ter-ice would not be vaporFollowing a public conized by the Sun and would
test, the site was dubbed
be present on the surface.
Agilkia, in honor of an island
located on the Nile river.
Alan Stern, ALICE prinAgilkia is located close to
cipal investigator at the
the site where the Philae
Southwest Institute in
obelisk was discovered.
Boulder, Colorado stated:
“We’re a bit surprised at
At 3:35 a.m. EST (0835
just how unreflective the
GMT) on Nov. 12, Rosetta
comet’s surface is and
released Philae, to start its
how little evidence of exseven-hour free-fall to the
posed water-ice it shows.”
comet’s surface. The landing process is a fully auALICE also detected the
tonomous process, with ESA
presence of both hydrogen
supplying instructions to the
Comparing Comet 67P/Churyumov–Gerasimenko with the city of Paris.
and oxygen in the comet’s
Credit: ESA/Rosetta/Navcam/Google/Bluesky
spacecraft and the lander
coma (atmosphere).
prior to release. It takes
The ALICE instrument is
Sensor (IES), a portion of the Rosetta
28-minutes for the signal from Rosetta
packed with over 1,000 times the
Plasma Consortium Suite, and the
to reach us here on Earth, so ESA
data-gathering capabilities of the
Double Focusing Mass Spectromexpected to receive landing confirprevious generation’s instruments,
eter (DFMS) electronics package for
mation at 11:00 a.m. EST (1600 GMT).
while weighing under nine pounds
the Rosetta Orbiter Spectrometer
(4 kilograms) and drawing only 4
Forty-five years ago, the world
for Ion Neutral Analysis (ROSINA).
watts of power. ALICE is part of a
waited, glued to their television sets
Astronomical serendipity
Since 1594, when Johannes Kepler predicted that
there should be a planet between Mars and Jupiter, astronomers had been searching for that “missing planet.”
When Giuseppe Piazzi discovered Ceres in 1801, the
scientific world thought that he had ended the search.
Then Ceres disappeared from sight, only to be recovered one year later. Astronomers breathed a sigh of
relief and celebrated! The “missing planet” was back!
And then there were two
Wilhelm Olbers, an amateur German astronomer who
was a doctor by profession, was again looking for Ceres
about three months after it had been rediscovered. That
was when he saw another moving object nearby! This
“object,”, which was later named Pallas, caused quite a
stir in the astronomical community. Only one planet had
been expected in the space between Mars and Jupiter.
When Gauss calculated this new object’s orbit,
he found that both Ceres and Pallas took 4.6 years
to revolve around the sun. He also found that Pallas could be seen from the Earth for only a small portion of that time. It was incredible luck and timing or,
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maybe astronomical serendipity that Olbers was looking for Ceres during the short period of time that Pallas
happened to be passing near Ceres. Otherwise,