Rosetta mission The
Rosetta mission was the first mission to include an orbiter that accompanied a comet for several years, as well as a lander that collected close-up data from the comet's surface. The mission launched in 2004, arrived at comet 67P in 2014, and concluded with a touchdown on the comet's surface in 2016.
Advance work As preparation for the
Rosetta mission,
Hubble Space Telescope pictures taken on 12 March 2003 were closely analysed. An overall 3D model was constructed and computer-generated images were created.. The candidate was definitively confirmed as the Philae lander in September 2016, when the Rosetta spacecraft flew close enough to capture very high-resolution images of the probe resting in a dark crevice .
Physical properties The composition of
water vapor from Churyumov–Gerasimenko, as determined by the
Rosetta spacecraft, is substantially different from that found on Earth. The ratio of
deuterium to
hydrogen in the water from the comet was determined to be three times that found for terrestrial water. This makes it unlikely that water found on Earth came from comets like Churyumov–Gerasimenko. On 22 January 2015, NASA reported that, between June and August 2014, the comet released increasing amounts of water vapor, up to tenfold as much. On 23 January 2015, the journal
Science published a special issue of scientific studies related to the comet. Measurements carried out before
Philae batteries failed indicate that the dust layer could be as much as thick. Beneath that is hard ice, or a mixture of ice and dust.
Porosity appears to increase toward the center of the comet. The nucleus of Churyumov–Gerasimenko was found to have no magnetic field of its own after measurements were taken during
Philae descent and landing by its ROMAP instrument and
Rosetta RPC-MAG instrument. This suggests that magnetism may not have played a role in the early formation of the Solar System, as had previously been hypothesized. The
ALICE spectrograph on
Rosetta determined that
electrons (within above the
comet nucleus) produced from
photoionization of water
molecules by
solar radiation, and not
photons from the Sun as thought earlier, are responsible for the degradation of water and
carbon dioxide molecules released from the comet nucleus into its
coma. Also, active pits, related to
sinkhole collapses and possibly associated with outbursts are present on the comet. Measurements by the COSAC and Ptolemy instruments on the
Philae lander revealed sixteen
organic compounds, four of which were seen for the first time on a comet, including
acetamide,
acetone,
methyl isocyanate and
propionaldehyde. Astrobiologists
Chandra Wickramasinghe and Max Wallis stated that some of the physical features detected on the comet's surface by
Rosetta and
Philae, such as its
organic-rich crust, could be explained by the presence of
extraterrestrial microorganisms.
Rosetta program scientists dismissed the claim as "pure speculation".
Carbon-rich compounds are common in the Solar System. Neither
Rosetta nor
Philae is equipped to search for direct evidence of
organisms. The only amino acid detected thus far on the comet is
glycine, along with precursor molecules
methylamine and
ethylamine. Solid organic compounds were also found in the dust particles emitted by the comet; the carbon in this organic material is bound in "very large macromolecular compounds", analogous to the insoluble organic matter in
carbonaceous chondrite meteorites. Scientists think that the observed cometary carbonaceous solid matter could have the same origin as the meteoritic insoluble organic matter, but suffered less modification before or after being incorporated into the comet. One of the most outstanding discoveries of the mission was the detection of large amounts of free molecular
oxygen () gas surrounding the comet. Solar system models suggest the molecular oxygen should have disappeared by the time 67P was created, about 4.6 billion years ago in a violent and hot process that would have caused the oxygen to react with hydrogen and form water. Molecular oxygen has never before been detected in cometary comas.
In situ measurements indicate that the / ratio is
isotropic in the coma and does not change systematically with heliocentric distance, suggesting that primordial was incorporated into the nucleus during the comet's formation. This interpretation was challenged by the discovery that may be produced on the surface of the comet in water molecule collisions with silicates and other oxygen-containing materials. Detection of molecular nitrogen () in the comet suggests that its cometary grains formed in low-temperature conditions below . On 3 July 2018, researchers hypothesized that molecular oxygen might not be made on the surface of comet 67P in sufficient quantity, thus deepening the mystery of its origin.
Future missions CAESAR was a proposed
sample-return mission aimed at returning to 67P/Churyumov–Gerasimenko, capturing
regolith from the surface, and returning it to Earth. This mission was competing in NASA's
New Frontiers mission 4 selection process, and was one of two finalists in the program. In June 2019, it was passed over in favor of
Dragonfly. == Gallery ==