When night falls on Rosetta’s comet 67P/Churyumov-Gerasimenko, the bizarrely shaped body remains active. This can be seen in new images of the Ma’at region located on the comet’s “head” captured by OSIRIS, the scientific imaging system on board the Rosetta spacecraft. They were taken approximately half an hour after the Sun had set over the region and show clearly distinguishable jets of dust escaping into space. Researchers from the OSIRIS team believe that the increasing heating-up of the comet is responsible for the newly observed phenomenon.
“Only recently have we begun to observe dust jets persisting even after sunset”, says OSIRIS Principal Investigator Holger Sierks from the Max Planck Institute for Solar System Research (MPS) in Germany. In the past months, the comet’s activity originated from illuminated areas on the day side. As soon as the Sun set, these jets subsided and did not re-awake until after the next sunrise. An exception poses an image from 12 March, 2015 showing the onset of a dust jet on the brink of dawn.
Rosetta-Alice Spectrograph Obtains First Far Ultraviolet Spectra Of A Cometary Surface While Orbiting Churyumov-Gerasimenko
NASA’s Alice ultraviolet (UV) spectrograph aboard the European Space Agency’s Rosetta comet orbiter has delivered its first scientific discoveries. Rosetta, in orbit around comet 67P/Churyumov-Gerasimenko, is the first spacecraft to study a comet up close.
As Alice began mapping the comet’s surface last month, it made the first far ultraviolet spectra of a cometary surface. From these data, the Alice team discovered that the comet is unusually dark at ultraviolet wavelengths and that the comet’s surface — so far — shows no large water-ice patches. Alice is also already detecting both hydrogen and oxygen in the comet’s coma, or atmosphere.
“We’re a bit surprised at both just how very unreflective the comet’s surface is, and what little evidence of exposed water-ice it shows,” says Dr. Alan Stern, Alice principal investigator and an associate vice president of the Southwest Research Institute (SwRI) Space Science and Engineering Division.
ESA’s Rosetta spacecraft has found that comet 67P/Churyumov–Gerasimenko is releasing the equivalent of two small glasses of water into space every second, even at a cold 583 million kilometres from the Sun.
The first observations of water vapour streaming from the comet were made by the Microwave Instrument for Rosetta Orbiter, or MIRO, on 6 June, when the spacecraft was about 350 000 kilometres from the comet.
Since the initial detection, water vapour has been found every time MIRO has been pointed towards the comet.
“We always knew we would see water vapour outgassing from the comet, but we were surprised at how early we detected it,” says Sam Gulkis, the instrument’s principal investigator at NASA’s Jet Propulsion Laboratory in Pasadena, California, USA.
“At this rate, the comet would fill an Olympic-size swimming pool in about 100 days. But, as it gets closer to the Sun, the gas production rate will increase significantly. With Rosetta, we have an amazing vantage point to observe these changes up close and learn more about exactly why they happen.”
New observations indicate that the asteroid Lutetia is a leftover fragment of the same original material that formed the Earth, Venus and Mercury. Astronomers have combined data from ESA’s Rosetta spacecraft, ESO’s New Technology Telescope, and NASA telescopes. They found that the properties of the asteroid closely match those of a rare kind of meteorites found on Earth and thought to have formed in the inner parts of the Solar System. Lutetia must, at some point, have moved out to its current location in the main asteroid belt between Mars and Jupiter.
A team of astronomers from French and North American universities have studied the unusual asteroid Lutetia in detail at a very wide range of wavelengths  to deduce its composition. Data from the OSIRIS camera on ESA’s Rosetta spacecraft , ESO’s New Technology Telescope (NTT) at the La Silla Observatory in Chile, and NASA’s Infrared Telescope Facility in Hawaii and Spitzer Space Telescope were combined to create the most complete spectrum of an asteroid ever assembled .
This spectrum of Lutetia was then compared with that of meteorites found on Earth that have been extensively studied in the laboratory. Only one type of meteorite — enstatite chondrites— was found to have properties that matched Lutetia over the full range of colours.
Full Story: http://www.eso.org/public/news/eso1144/
ESA’s Rosetta spacecraft has revealed asteroid Lutetia to be a primitive body, left over as the planets were forming in our Solar System. Results from Rosetta’s fleeting flyby also suggest that this mini-world tried to grow a metal heart.
Rosetta flew past Lutetia on 10 July 2010 at a speed of 54 000 km/hr and a closest distance of 3170 km. At the time, the 130 km-long asteroid was the largest encountered by a spacecraft. Since then, scientists have been analysing the data taken during the brief encounter.
All previous flybys went past objects, which were fragments of once-larger bodies. However, during the encounter, scientists speculated that Lutetia might be an older, primitive ‘mini-world’.