Amazing New Photo of Rosetta Comet
 
This news release is reprinted courtesy of the European Space Agency, which
is leading the Rosetta mission to Comet 67P.
 
August 2, 2014: As the ESA's Rosetta spacecraft closes to within 1000 km of
Comet 67P/Churyumov-Gerasimenko, the Rosetta science team has released a
new image and made the first temperature measurements of the comet's core. 
The temperature data show that 67P is too hot to be covered in ice and must
instead have a dark, dusty crust.
 
The new image was acquired on August 1st at 02:48 UTC by the OSIRIS Narrow
Angle Camera onboard Rosetta at a distance of approximately 1000 km. It
shows the rough surface of the double-lobed core in amazing detail.
 
http://blogs.esa.int/rosetta/2014/08/02/comet-at-1000-km/
 
OSIRIS narrow angle camera view of 67P/C-G from a distance of 1000 km on 1
August 2014. Note that the dark spot is an artefact from the onboard CCD.
Credits: ESA/Rosetta/MPS for OSIRIS Team
MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA Full image and caption
 
Thermal observations of comet 67P/Churyumov-Gerasimenko were made by
Rosetta's visible, infrared and thermal imaging spectrometer, VIRTIS,
between 13 and 21 July, when Rosetta closed in from 14 000 km to the comet
to just over 5000 km.
 
At these distances, the comet covered only a few pixels in the field of
view and so it was not possible to determine the temperatures of individual
features. But, using the sensor to collect infrared light emitted by the
whole comet, scientists determined that its average surface temperature is
about -70øC.
 
Although -70øC may seem rather cold, importantly, it is some 20-30øC warmer
than predicted for a comet at that distance covered exclusively in ice.
 
"This result gives us the first clues on the composition and physical
properties of the comet's surface," says VIRTIS principal investigator
Fabrizio Capaccioni from INAF-IAPS, Rome, Italy.
 
Other comets such as 1P/Halley are known to have very dark surfaces owing
to a covering of dust, and Rosetta's comet was already known to have a low
reflectance from ground-based observations, excluding an entirely 'clean'
icy surface. The temperature measurements provide direct confirmation that
much of 67P's surface must be dusty, because darker material heats up and
emits heat more readily than ice when it is exposed to sunlight.
 
https://www.youtube.com/watch?v=KQL_43SFHzw&feature=youtu.be
 
The ESA has prepared a must-see visualization of what sunrise over the
comet might look like. Play it
 
"This doesn't exclude the presence of patches of relatively clean ice,
however, and very soon, VIRTIS will be able to start generating maps
showing the temperature of individual features," adds Dr Capaccioni.
 
As Rosetta approachs and later orbits the comet, the sensor will study the
variation of daily surface temperatures in order to understand how quickly
the surface reacts to solar illumination. In turn, this will provide
insight into the thermal conductivity, density and porosity of the top tens
of centimetres of the surface--important data to help select a target site
for Rosetta's lander, Philae.
 
It will also measure the changes in temperature as the comet flies closer
to the Sun along its orbit, providing substantially more heating of the
surface.
 
"Combined with observations from the other 10 science experiments on
Rosetta and those on the lander, VIRTIS will provide a thorough description
of the surface physical properties and the gases in the comet's coma,
watching as conditions change on a daily basis and as the comet loops
around the Sun over the course of the next year," says Matt Taylor,
ESA's Rosetta project scientist.
 
"With only a few days until we arrive at just 100 km distance from the
comet, we are excited to start analysing this fascinating little world in
more and more detail."
 
Credits:
Production editor: Dr. Tony Phillips | Credit: Science{at}NASA
 
Rosetta is an ESA mission with contributions from its member states and
NASA. Rosetta's Philae lander is provided by a consortium led by DLR, MPS,
CNES and ASI. Rosetta will be the first mission in history to rendezvous
with a comet, escort it as it orbits the Sun, and deploy a lander.
 
Web links:
European Space Agency home page
 
Rosetta -- from the ESA
 
Rosetta -- from NASA
 
NASA Instruments on Rosetta
 
Rosetta Comet Comes Alive -- from Science{at}NASA
 
 
Regards,
 
Roger

--- D'Bridge 3.99