September 13, 2013
European Space Agency Preparing For Comet Rendezvous
Brett Smith for redOrbit.com – Your Universe Online
The ESA craft is scheduled to rendezvous with and orbit the comet in 2014. After establishing an orbit, Rosetta will release a small laboratory of scientific instruments, called Philae, to land on the comet’s surface.
“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,” said Jessica Agarwal of the Max Planck Institute for Solar System Research (MPS). “ All of this information is vital for the planning of Rosetta’s orbit and Philae’s delivery.”
“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,” added Matt Taylor, ESA’s Project Scientist for the Rosetta Mission. “There are a lot of things we need to know!”
Jean-Baptiste Vincent, a planetary scientist at MPS, has used images and models to study the development of gas jets as the comet becomes active as it approaches the Sun.
“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 kilometers in the coma,” he said. “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 (31 miles per hour),” he added.
Other MPS researchers said that 67P will start emitting a tail of gas and dust by March 2014, a bit earlier than expected and two months after the spacecraft comes out of hibernation on January 20, 2014. The scientists said their predictions are based on 31 sets of images taken between 1995 and 2010, some of which were captured using the Very Large Telescope (VLT) at the European Southern Observatory (ESO) in Germany. The ESA scientists studied changes in the comet’s brightness, and therefore, the activity levels of the comet 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 MPS researcher Colin Snodgrass. “The results were something of a surprise.”
Scientists had previously thought that the comet would begin to form its tail at around 280 million miles from the sun. However, it became active much earlier than expected – at just over 400 million miles.
"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 MPS scientist Cecilia Tubiana.