Comet 67P/Churyumov-Gerasimenko
Dust Coma
After a journey of almost ten years, the Rosetta mission has just a
few months left to wait before beginning its rendezvous with a time
capsule. Comet 67P/Churymov-Gerasimenko is a dirty snowball of ice and
dust that preserves material from the formation of the Solar System 4.5
billion years ago. During 2014, the European Space Agency’s most
ambitious mission to date will both start to orbit the comet’s nucleus
and deploy a small laboratory of scientific instruments, Philae, to dock
with the comet’s surface. To aid Rosetta in safely achieving its task,
an international group of scientists back on Earth are using
ground-based telescopes and computer models to understand the behaviour
of the comet as it approaches the Sun and begins to form its tail. Their
findings have been presented this week at the European Planetary
Science Congress (EPSC) 2013 at University College London.
“For two or three orbits now, our community has been observing the
comet to determine the shape of the nucleus, the angle at which it spins
on its axis and how its activity varies as it orbits the Sun. All of
this information is vital for the planning of Rosetta’s orbit and
Philae’s delivery,” said Jessica Agarwal of the Max Planck Institute for
Solar System Research (MPS).
“At this meeting, we have discussed everything from the make-up of
the surface layer of the nucleus to the dust production rates, size and
velocity of the particles emitted, the way the comet interacts with the
solar magnetic environment… There are a lot of things we need to know!”
added Matt Taylor, ESA’s Project Scientist for the Rosetta Mission.
Jean-Baptiste Vincent (MPS) has used images and modelling to study
the development of gas jets as the comet becomes active. “We need to
understand the formation and evolution of dust coma structures at all
scales: from tiny filaments only visible close to the surface of the
nucleus, to large structures extending tens of thousands of kilometres
in the coma. Comet 67P appears to behave in a very consistent way, at
least over the last two orbits. The southern hemisphere is more active
than the northern and there are three major active regions from where
gas jets evolve, which can eject dust particles at around 50 kilometres
per hour.”
To safeguard the spacecraft during its long, cold journey through
deep space, Rosetta was placed into hibernation in 2011. Research by a
group led by Colin Snodgrass and Cecilia Tubiana of MPS suggests that
67P will start emitting gas and dust by March 2014, earlier than
expected and just two months after the spacecraft receives its wakeup
call on Monday 20 January 2014.
The scientists have based their predictions on 31 sets of images
showing the comet at different points during its orbit. The images were
recorded between 1995 and 2010 with telescopes including the Very Large
Telescope (VLT) at the European Southern Observatory (ESO). By
subtracting successive images to remove the starry background and making
the comet stand out, they were able to study changes in brightness and
hence the activity levels of the comet was at different points in its
orbit.
"For the first time, we have a meaningful comparison of all data sets
so that we can reconstruct the activity of the comet as it moves around
the Sun," said Snodgrass. “The results were something of a surprise.”
Scientists had estimated that the comet would start to form is tail
at distance of around 450 million kilometres from the Sun, when it would
become warm enough for water ice to sublimate. Instead, it became
active much further out -- at 650 million kilometres.
"Water will still be frozen solid at that distance from the Sun. Some
other gas must be responsible for this earlier activity that we’ve
observed," said Tubiana.
IMAGES AND ANIMATIONS
Image of 67P/Churyumov-Gerasimenko acquired in February 2009,
processed using a numerical filter. Structures visible in the image are
signatures of regions of enhanced activity on the nucleus surface.
Credit: J-B Vincent/MPS/GP Tozzi/L Lara/Z-Y Lin. http://www.europlanet-eu.org/images/stories/epsc2013/rosetta_jets1.jpg
Image acquired between June 2008 and Feburary 2009. The location of
the dust coma structures are enhanced by different filtering techniques
((1-3) adaptive Laplace-filtered images, (4) adaptive Laplace-filtered
image with the structure geometry indicated by annotations and (5)
dashed lines, (6) Larson-Sekanina filtered image). Credit: J-B
Vincent/MPS/GP Tozzi/L Lara/Z-Y Lin. http://www.europlanet-eu.org/images/stories/epsc2013/rosetta_67p-evolution.jpg
Dust coma of 67P at a distance of 187 million kilometres from the
Sun, shortly before the comet’s closest approach. Image acquired on 18
Feb. 2009. The image (top left) is presented as processed through
various numerical filters to enhance the visibility of the jets. J-B
Vincent/MPS/GP Tozzi/L Lara/Z-Y Lin. http://www.europlanet-eu.org/images/stories/epsc2013/rosetta_dust_coma.jpg
Movie showing modelled dust jets of comet 67P/C-G as they would be
observed by the OSIRIS WAC camera on board Rosetta. Credit: J-B
Vincent/MPS. http://www.mps.mpg.de/homes/vincent/COSSIM.html
Still from movie showing modelled dust jets of comet 67P/C-G as they
would be observed by the OSIRIS WAC camera on board Rosetta. Credit: J-B
Vincent/MPS
Matt Taylor
Rosetta Project Scientist
ESTEC, European Space Agency
Noordwijk, Netherlands
Tel:+31 (0)71 565 8009
mtaylor@rssd.esa.int
Jessica Agarwal
Max-Planck-Institut für Sonnensystemforschung
Katlenburg-Lindau, Germany
agarwal@mps.mpg.de
Jean-Baptiste Vincent
Max-Planck-Institut für Sonnensystemforschung
Katlenburg-Lindau, Germany
vincent@mps.mpg.de
Colin Snodgrass
Max-Planck-Institut für Sonnensystemforschung
Katlenburg-Lindau, Germany
snodgrass@mps.mpg.de
Cecilia Tubiana
Max-Planck-Institut für Sonnensystemforschung
Katlenburg-Lindau, Germany
tubiana@mps.mpg.de
MEDIA CONTACTS
Anita Heward
EPSC 2013 Press Officer
anitaheward@btinternet.com
+44 (0)7756034243
Oli Usher
Communications Manager
MAPS Faculty, UCL
o.usher@ucl.ac.uk
+44 (0)20 7679 7964
NOTES FOR EDITORS
About the European Planetary Science Congress (EPSC)
EPSC is the major European meeting on planetary science. EPSC 2013 is
taking place at University College London (UCL) from Sunday 8 September
to Friday 13 September 2013. It is the first time that the Congress has
been held in the UK. The 2013 programme includes around 75 sessions and
workshops. Details of the Congress and a full schedule of EPSC 2013
scientific sessions and events can be found at the official website: http://www.epsc2013.eu/
EPSC 2013 is organised by Europlanet, UCL and Copernicus Meetings and
the event is sponsored by the UK Space Agency, UCL, Astrium and the
Science and Technology Facilities Council.
To celebrate EPSC coming to London, a ‘Festival of the Planets’ has
been organised across the Capital in collaboration with partners
including the Baker Street Irregular Astronomers, the Bloomsbury
Theatre, the British Astronomical Association, the British
Interplanetary Society, the Natural History Museum, the Open University,
Queen Mary University of London, the Royal Astronomical Society, Royal
Museums Greenwich and University College London. More information about
the events can be found at: http://www.europlanet-eu.org/epsc2013/outreach-activities
Follow #epsc2013 @epsc2013 @europlanetmedia on Twitter
About Europlanet
Europlanet is a network of planetary scientists, whose aim is to
bring together the disparate European community so that Europe can play a
leading role in space exploration. Europlanet’s activities complement
the mission activities of the European Space Agency through field work
at planetary-analogue terrains on Earth, laboratory measurements,
computer modelling and observations from ground-based telescopes.
Founded in 2002 and funded by the European Commission from 2005-2012,
Europlanet has evolved into a community-based organisation that will
carry on this work and plan for future missions and mission support. www.europlanet-eu.org
About UCL (University College London)
Founded in 1826, UCL was the first English university established
after Oxford and Cambridge, the first to admit students regardless of
race, class, religion or gender and the first to provide systematic
teaching of law, architecture and medicine.
UCL is among the world's top universities, as reflected by its
performance in a range of international rankings and tables. According
to the Thomson Scientific Citation Index, UCL is the second most highly
cited European university and the 15th most highly cited in the world.
UCL has nearly 27,000 students from 150 countries and more than 9,000
employees, of whom one third are from outside the UK. The university is
based in Bloomsbury in the heart of London, but also has two
international campuses – UCL Australia and UCL Qatar. Its annual income
is more than £800 million.
