A dusty comet for Rosetta

The tools and MIDAS COSIMA aboard the ESA spacecraft have captured the first grains of dust from the comet Churyumov-Gerasimenko and have analyzed the shape and composition. Meanwhile it reduces the distance between the probe and the comet: engineers hope to get to 4 km in February.


Credit: ESA/Rosetta/NAVCAM

At a speed of 20.9 km / s Rosetta probe the European Space Agency (ESA), and the comet 67P / Churyumov-Gerasimenko is closer and closer to the sun. From what we can see in an animation of ESA, in fact, missing “only” 382 million miles a big meeting with our star and in just over a month it have traveled some 47 million kilometers together. The meeting at perihelion (the closest approach to the Sun) will take place on August 13, 2015, when it will pass 183 million kilometers from the Sun in an orbit between Earth and Mars. Rosetta, was launched in 2004 and has traveled 6.6 billion kilometers already in the Solar System, traveling in tandem with the comet now November and continues to send back data and images valuable for the mission, thanks to its numerous instruments on board, three of which are made in Italy (JADE, OSIRIS and VIRTIS).


Credit: ESA/Rosetta/NAVCAM

A few weeks ago the probe revealed that the composition of the Earth and the ice (analyzed by the instrument ROSINA aboard Rosetta) are different and this would mean that the water has come to our planet but not with comets or with asteroids. In addition, the instruments have confirmed that 67 / P is a dusty comet, as you can see from the images posted on the web by ESA. Comets, in fact, are traveling around the sun undisturbed carrying not only ice, but also dust and debris as old as the solar system itself. Some images show streaks and spots around the nucleus that are probably dust grains ejected from the comet.
The probe has reached 27.9 km from the nucleus of the comet (in February, ESA hopes the probe will be able to reach a distance of four kilometers) and it is 521 million kilometers from Earth. On 6 January, the ESA has published a new mosaic of images created with the help of NAVCAM, mounted on board Rosetta, at a resolution of 2.3 m / pixel.


Credit: ESA/Rosetta/NAVCAM

The images show a unique view of the largest lobe (lower panels) and smaller ones (upper panels), taking up the different structures that make up the object, the regions with smooth boulders scattered to rougher terrains and complex. Already in August 2014 VIRTIS, the Visible Infrared and Thermal Imaging Spectrometer had allowed the researchers to say that the comet is mostly covered with a dark and dusty material, forming the famous tail.
A basic tool to study this material is the Micro-Imaging Dust Analysis System (MIDAS) to measure the speed at which the dust reaches the spacecraft and the size of the grains. How does MIDAS? Quite simply it is like capturing mosquitoes: the instrument is provided with an adhesive surface on which are exposed to rest the dust particles which are then analyzed with an atomic force microscope. The first grain was observed last November and was much bigger than expected – about 1/100 of a millimeter in diameter – but with a soft and a non-compact texture, said Mark Bentley, principal investigator of MIDAS and researcher at the Space Research Institute (IWF) in Graz, Austria.
But not only is that MIDAS does the study of cometary dust. Another tool by its friendly name is COSIMA, the Cometary Secondary Ion Mass Analyser that – specifically – studied a grain called “Boris” in which it identified sodium and magnesium. Magnesium is not a surprise in the space given that 95% of the minerals observed in comets resemble common materials in meteorites and in the upper mantle of the Earth. Sodium had already been seen in the tails of comets, but its origin is still uncertain.
The Rosetta mission will go on until the last days of this year, when the comet will be found to 2 astronomical units from the Sun (twice the Earth-Sun distance) during removal. The experts, however, suggest that the solar panels that are attached to the probe will have energy for another two astronomical units and that means that we can follow the comet until mid-2016 and then losing it altogether. Engineers hope that in steps approaching the Sun, it is able to recharge the batteries of Philae so that you can wake up and resume his mission, as it now is in “stand-by” having exhausted the supply of energy.

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