Rosetta comet probe project just recently defeated a lot of first-class research projects, was named the American magazine "Science" in 2014 the first of the top ten scientific breakthroughs. January 23, "Science" magazine special issue recurrence, to show the world the main results of exploration "Rosetta" made.
Previously, the combination of human Fengyun highest intellectual achievements detector has experienced 10 years of Star Trek, in August 2014 arrived in the destination comet 67P / GC, and on November 12 to launch the lander Philae the surface properties of the gas surrounding the nucleus and the more in-depth analysis.
The "Science" published a special issue of seven new research report, which the comet shape, composition and surface characteristics have been described, the mystery of the comet is being slowly opened.
First, the cost of 1.4 billion euros worth?
Origins "Rosetta" comet formation and our solar system and other secret unprecedented close-exploration. The entire project investment amounted to 1.4 billion euros.
Comets are formed at the beginning of the solar system of ancient ruins, "Rosetta" This line is essential to explore the composition and origin of the solar system comet material. According to the solar system formed, "nebular hypothesis" about 46 billion years ago, a piece of interstellar dust and gas in molecular clouds collapse under gravity, temperature rise, accelerated rotation and flattening into crusts nebula. Where 99.8% of the nebulosity in the center of the astrolabe aggregate to form protostars. Protostar nuclear fusion of stars, at the same time, the astrolabe peripheral temperature decreases, resulting in ice, methane, ammonia and other gases gather with other interstellar particles randomly hyperplasia, the formation of planetesimals. Planetesimals then collide gathered, gradually evolved into our present planetary system. The comet, it can be seen as capable of producing micro planetary coma and tail and other characteristics of the structure. Comets often from the cold darkness of the outer edge of the solar system orbit, it may well save the information at the beginning of the formation of the solar system.
At the same time, the comet will help to reveal the origin of the earth to explore the mystery of life. Comets are composed of water ice and solid matter consisting of "dirty snowballs." According celestial collision hypothesis of the origin, in the early Earth, a large comet hit the Earth's surface, not only brings a wealth of water, forming a primitive ocean, and all kinds of alkanes and comets carry, amino acids, fatty acids, polycyclic aromatic hydrocarbons and other organic porphyrin compound together at a suitable temperature of the Earth, atmosphere and other environmental conditions of the birth of the most basic life. The material composition of the comet's analysis is expected to answer whether the water on Earth come from comets, why on earth are left-handed amino acid form, whether the comet earth opened door key issues of life and so on.
Not only that, understanding comet nucleus structure and material composition, accurately grasp the laws of orbital motion of the comet colliding with Earth will help address catastrophic events. In the evolution of the Earth's history, leading to several small objects hit the Earth's climate catastrophe and extinction events, such as 65 million years ago dinosaurs extinction, Tunguska 100 years ago, and the like. February 15, 2013 as well as small objects hit Russia Chelyabinsk and cause injuries and extensive damage to buildings. We can not rule out the possibility of a comet colliding with Earth once again, it is necessary to increase the understanding of comets.
Second, the 10-year "Starchaser" Road
"Rosetta" in the March 2004 launch, in March 2005 for the first time around the Earth February, 2007 around Mars in November the same year, the second time around accelerated. After three acceleration orbit, "Rosetta" in September 2008 flyby of asteroid Steins. November 2009, "Rosetta" in the last acceleration orbit around the Earth. October 2010 flyby of asteroid Lutetia. Subsequently, the "Rosetta" in June 2011 into hibernation until recovery in January 2014, the same year in August, "Rosetta" comet with the successful docking, November 12 to launch a comet lander Philae. It is calculated that the comet 67P / CG will reach perihelion in August 2015, and "Rosetta" and Philae program will be closely monitoring and analysis of the changes in this period comet activity. The entire project will be December 31, 2015 officially ended.
Scientists originally conceived Exploration comet began in the early 1980s, and in 1986 Giotto spacecraft sent back photos of Halley's nucleus is to promote the Rosetta project was put on the official agenda. "Rosetta," the construction and testing was completed in 2002, the time originally scheduled for launch in early 2003, but the launch pad launch failures found previous month making the "Rosetta" launch postponed to March 2004, the acquisition target also change from the original comet 46P / Wirtanen of 67P / CG.
In the decade after the launch of the tour, the "Rosetta" traveled about 6.5 billion kilometers away, it is not directly from Earth to Comet 67P / CG, but experienced three around the Earth and once around the acceleration Mars acceleration. In addition, the comet is not a "Rosetta," the only object of study, "Rosetta" on the road also skimming two asteroids: Steins (September 2008) and Lutetia (2010 October 2005), provides asteroid about the size, shape and surface characteristics of the information, and increase our understanding of asteroids, but also for the study of comets provides a comparison thereof.
"Rosetta" Upon completion of the asteroid Lutetia observations after a speed of 54,000 kilometers per hour began to comet 67P / CG pursuit, but even such a high speed, "Rosetta" still faces four years long journey, and in the process it approaches the comet, 67P / CG is in aphelion area, which makes the "Rosetta" not collect enough solar energy to maintain its normal operation - scientists have finally decided from June 2011 onwards let "Rosetta" to enter up to two years and seven months of hibernation. In the sleep period, in addition to on-board computer, some of the internal heating system and wake-up "Rosetta" desired timing device, all other devices are turned off, until January 20, 2014, "Rosetta" and the Earth's communication systems It was only re-opened. Before docking with the comet, there were 11 to activate the device 21 and detects "Rosetta" on.
August 6, 2014, "Rosetta" and the comet 67P / GC successfully docked into the comet's gravitational field and become satellites running around the comet. "Rosetta" comet survey tasks include measuring the shape of a comet, rotation speed, direction, gravity field, albedo, coma and coma characteristics table surface temperature, coma gas density and particle eruption rate, etc.
After a tense rounds of screening landing sites, "Rosetta" on November 12 sent a lander Philae to the comet. "Philae" weighing about 100 kilograms, is the "polygon sandwich" detector the size of a washing machine, which loads the Rosetta Lander Imaging System (ROLIS), comet sampling and analytical instrument equipment components (COSAC), multifunction surface and subsurface sensing means (MUPUS), PLT research equipment. "Philae" carried by the battery life of about 64 hours, the "first phase of the research sequence" is carried by the battery runs out before the research tasks, including shooting panoramas comet surface definition map and landing environment, for table coma component in situ analysis, measuring thermal, mechanical and electrical properties of the surface of the nucleus and the like. Contrast is continued until March 2015 "long-term research Sequence" - if "Philae" can receive enough sunlight to recharge the battery, it will work with "Rosetta" comet together monitoring 67P / CG in to perihelion during operation of activity, given the local and global coherent information.
Unfortunately, "Philae" landing for the first time and did not successfully anchored in the surface of the nucleus from the coma but rebounded table twice, namely, three touchdowns. "Philae" final landing site has not yet been determined, but since the final landing point is not adequate lighting conditions, "Philae" in a short time after landing almost impossible to obtain support to continue its work in power. "Philae" In the November 15, 2014 the command center lost contact with the earth, still no news. In any case, "Philae" scientific mission basically completed the first phase, although scientists have pointed out that "Philae" drilling may not successfully embedded comet sample table, but have harvested Philae clear pictures and considerable coma table the experimental data. Experimental data "Philae" obtained is still parsing the contents of "Science" published a special issue entirely from the latest "Rosetta."
Third, to tell you the appearance of a comet
"Science" published special election eight scientific articles, including: reports Holger Sierks and colleagues from Germany's Max Planck Institute for Solar System Research written on the nucleus structure and activity, Fabrizio from Rome's National Institute for Astrophysics Capaccioni and colleagues comet surface of the organic molecular species and moisture content of the report, Nicolas Thomas and colleagues from the University of Bern, Switzerland coma table reports on topographic diversity, also from the University of Bern Kathrin Altwegg coma and colleagues reported on the table isotope ratios, and Samuel Gulkis, Myrtha H? ssig, Alessandra Rotundi, Hans Nilsson's research team were sublimation flux distribution, coma water, carbon monoxide and carbon dioxide from the ice, dust and gas surrounding the nucleus ratio, water and electricity from the aspect of electromagnetic layer, etc. changes made to the active nucleus and its dynamic analysis report.
"Rosetta" in August last year with the comet 67P / GC after their successful docking of the studies carried out. The first surprise scientists harvest is "Rosetta" in visible and infrared remote imaging system OSIRIS (Optical Spectrocopic and Infrared Remote Imaging System) on August 3 taken nucleus quality photos, people came to understand through this photo to 67P / GC shape is the size of the two hemispheres are connected with a narrow neck "toy duck-shaped" rather than previously thought "potato-shaped." This finding implies that the difficulty of selecting a suitable landing site will increase, but at the same time, a special object of study in turn shape our understanding of the formation of comets provide richer information.
Dual hemispherical structure 67P / GC is made from a complete celestial being eroded, or 45 billion years ago by the collision of two small bodies polymerization inconclusive. Scientists according to the image data collected by the 67P / GC surface morphology summed up as dust cover (dust-covered), potholes and cyclic structures formed by rigid material (brittle materials producing fine fragments with pits and circular structures), major depression (large-scale depressions), smooth region (smooth) and the exposed solid surface (exposed consolidated surfaces) five, and according to the geomorphology coma table is divided into 19 different regions (Figure 3). Surface morphology diversity seems to imply 67P / GC may be caused by small bodies or interplanetary debris collision gathered together, especially surface of the nucleus also they found some 3 meters of tumor-like structure known as the "dinosaur egg", It is considered to be incorporated into the rock by striking coma table. On the other hand, in a different wavelength region 550nm tables coma measured albedo are about 5.9%, that is to say, although the uneven shape table coma, but the color is consistent. Therefore, scientists believe 67P / GC's nucleus is slowly gathered interstellar dust (hierarchical accretion) of the original micro-planet formation, but in the long process of evolution, and the sun collide with other stars such as etching action led to the comet surface structure diversity.
Consistent albedo suggests similarity nucleus outer layers of the internal structure of the nucleus can only be understood by speculation and overall density and spin mode. "Rosetta" radio science detector (RSI, Radio Science Investigation) radio frequency signal amplitude, frequency and polarity changes in the internal structure of the gravitational field and orbit the nucleus have carried out a series of characterization. According to RSI measurement, 67P / GC mass of about 1013 kg only six femtoAmps Earth. Small nucleus of "head" of 2.6 2.3 1.8 kilometers, larger "body" of 4.1 3.3 1.8 km with a total volume of about 21.4 cubic kilometers. Based on this calculation, the average density of the nucleus is about 470 kg / cubic meter, with a density similar to wood. This means 67P / GC internal structure is relatively loose, tight mixture of ice dust density was about 1500 to 2000 kg / cubic meter, so estimate porosity 67P / GC nucleus of 70 to 80%. In addition, the nucleus to 12.4 hours cycle of rotation, the direction of its spin axis direction is consistent with the maximum moment of inertia axis at a uniform density of the nucleus assumptions derived. In short, 67P / GC kernel should be loosely structured and uniform density. This again supports the nucleus is composed of gas and interstellar dust in the ice under weak gravity gradually gathered from the hypothesis.
"Rosetta" airborne imaging system OSIRIS shows the diversity coma table structure, radio equipment RSI reflects the homogeneity of nuclear structure, and the visible and infrared thermal imaging spectrometer VIRTIS (Visible and Infrared Thermal Imaging Spectrometer) through characteristic absorption spectrum of the chemical composition of the surface of the nucleus were detected. VIRTIS according to measurement data, surface of the nucleus has a wide variety of hydrocarbon, oxygen, hydrogen and nitrogen, hydrogen molecules, but water ice content is very low. Of particular note is that, VIRTIS infrared absorption spectrum in surface 67P / GC identification of a carboxylic acid amino acid molecules can be used as the front body. This finding is not surprising, because in 2006 NASA scientists from the Stardust spacecraft on discrimination in the 81P / Wild 2's coma zone samples collected earlier in an amino acid, but this "Prather tower "where organic molecules 67P / GC found a more original and varied, suggesting its more ancient origins.
Ion and neutron "Rosetta" on the analyzer ROSINA (Rosetta Orbiter Spectrometer for Ion and Neutral Analysis) isotope detection is very sensitive, measured by comparing the relative proportions of hydrogen and deuterium, we can deduce the Earth's water came from comets - comet 67P / GC surface deuterium / hydrogen ratio was 5.3 0.7 10 -4, three times the value of the Earth, which means that like 67P / GC this comet did not play a major role in the process of formation of the Earth's oceans.
As previously mentioned, the surface structure 67P / GC is very diverse, full of potholes, ravines, faults and ripple like structure. Rock cross-section of the table seems to be the result coma coma shell movement, the material from falling off the edge of the cliff rocks and accumulate in the foot, the exposed section of fresh ice dust potholes and depressions are relatively stable areas, but scientists found in some holes in the delta landscape formed by the effluent is considered to be the nucleus of internal pressure buildup caused by the formation of there interested researchers described as "dinosaur egg" tumor-like structure ...... one problem is, 67P / GC these rich surface structure is formed. Scientists "Rosetta" project Nicolas Thomas noted, "The role of the sun alone is unlikely to cause the nucleus we see today has the layered, surface chemical composition and diversity of all", perhaps in the early solar system comets formed environment than most scientists believe the more confusing turmoil, the composition richer, but this hypothesis is difficult to be confirmed.
Worth looking forward to is in the process of 67P / GC run to perihelion, the "Rosetta" will be continuous observation by analyzing the influence of the Sun in the process of comet activity, scientists may be able to reveal the sun how to play a role in the evolution of comets.
references
. [1] Taylor, MGGT, et al "Rosetta begins its Comet Tale." Science 347.6220 (2015): 387-387.
. [2] Sierks, Holger, et al ". On the nucleus structure and activity of comet 67P / Churyumov- Gerasimenko" Science 347.6220 (2015): aaa1044.
[3] Capaccioni, F., et al "The organic-rich surface of comet 67P / Churyumov-Gerasimenko as seen by VIRTIS / Rosetta." Science 347.6220 (2015):.. Aaa0628 [4] Thomas, Nicolas, et al. "The morphological diversity of comet 67P / Churyumov- Gerasimenko." Science 347.6220 (2015): aaa0440.
[5] Altwegg, K., et al "67P / Churyumov-Gerasimenko, a Jupiter family comet with a high D / H ratio." Science 347.6220 (2015):.. 1261952. [6] Hand, Eric "Comet close- up reveals a world of surprises "Science 347.6220 (2015):. 358-359.
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