This paper is devoted to the discussion of the comet mission of Rosetta spacecraft. Rosetta is a space probe that was launched in 2004 by ESA. On its board, Rosetta had a lander Philae. The aim of the mission was to conduct a detailed study of the comet 67P/Churyumov-Gerasimenko. The paper gives an overview of the technical equipment of Rosetta as well as traces the history of the mission that had been lasting for 12 years. In addition, in the paper, the detailed trajectory of the spacecraft and the discoveries made about the comet are given The way the Rosetta mission contributed to the understanding of Tunguska Event and dispelled the theory about comet origin of water on the Earth are discussed as well. The main findings that were made by Rosetta mission have become the significant breakthrough in the whole history of space study missions and space exploration in general.
Keywords: Rosetta, Philae, 67P/Churyumov–Gerasimenko, space mission, comet.
Rosetta Spacecraft Mission
Outer space has always been a subject of interest to humanity. At the age of high technologies, many spacecraft are sent to explore the mysteries of the universe, and each of them brings its invaluable contribution. Types of research, which the spacecraft conduct, are diverse. They range from images to material samples. It allows scientists to create new theories and confirm the old ones. However, sometimes, new data contribute to uncertainty denying the existing opinion. Such cases frequently occur with a small number of tests but then the results should be viewed from the perspective of mathematical statistics, and the number of experiments should be increased. According to BBC, the most important scientific breakthrough of 2014 became an ambitious space project, due to which the spacecraft was able not only to reach the comet but also deliver research equipment directly on its surface for the first time (Hollingham, 2016). Spacecraft Rosetta was successfully launched in 2004, and for more than ten years it has made four gravity maneuvers using gravitational fields of the Earth and Mars, which made it possible to raise the speed of the machine to the orbital velocity of the comet and bring it to the desired point on the trajectory of the motion of the comet (Hollingham, 2016). Rosetta was named after the famous Rosetta stone – a stone slab with three texts in ancient Egyptian and ancient Greek identical in the meaning carved on it. The name of the lander was chosen in honor of the island Philae in the river Nile where the famous obelisk with hieroglyphic inscription was found. These unique archaeological findings have helped scientists to decipher ancient Egyptian hieroglyphics. Modern researchers hope that the results obtained due to Rosetta and Philae work will contribute to further development of the theory of evolution of the solar system and establishment of the origin of water on Earth. It is also expected that the data received during the space mission of Rosetta will be a cornerstone in the construction of the proposed theory. This paper examines the history of space mission of Rosetta probe, its trajectory, and scientific contribution.
Overview of the Research Missions on Comets
Comets can be called remarkable bodies in the solar system due to the fact that they have retained a primordial matter, which our system was formed from about 5 billion years ago, and due to the statement that the evolution of comets is the most dynamic one (Spohn, Breuer & Johnson, 2014, p. 55). A comet is a little planet with a relatively stable orbit. The size of the nuclei of comets is 1-5 km on average (Spohn, Breuer & Johnson, 2014, p. 55). The study of comets is of the great interest to the world of science. It is believed that a comet is one of the oldest bodies in the solar system formed at the period, at which the planets had not existed yet. Since the greater parts of their lives the comets spend away from the Sun, they are composed of very ancient matter and can tell the researchers much about the earliest stages of the Sun and planets life cycles. Another great feature of comets is the fact that they represent huge physical and chemical laboratories, in which it is possible to study various materials in extreme states (Spohn, Breuer & Johnson, 2014, p. 56). Many researchers believe that a comet is a key for understanding the processes that produce life on Earth.
During the first tries to explore the comets, the only aim was to make the units fly near these heavenly bodies and send all possible remote sensing to the Earth. Later, the flight to the nuclei of comets became more complicated. Two main agencies, NASA and ESA, have become the leaders in that field of study. NASA performs multiple projects of varying complexity. First of all, it is a project Deep Impact (Moltenbrey, 2016, p. 89). On July 4, 2005, the station has moved closer to the nucleus of the comet Tempel I (Moltenbrey, 2016, p. 89). The detachable unit made a shot at the comet. The impact on the surface of the nucleus was supposed to provide crater formation and release of the substance from the inner layers. Various devices mounted on a special platform have studied a cloud of ejected materials (Moltenbrey, 2016, p. 90).
The second project was called CONTOUR (COmet Nucleus TOUR) and aimed at visiting the comets nuclei. It was intended to study comets Encke and Schwassmann-Wachmann 3 (Moltenbrey, 2016, p. 100). However, in 2002, after the launch, the vehicle research station did not reach the estimated flight path. In addition, Schwassmann-Wachmann 3 was divided into three fragments and practically ceased to exist. Subsequently, NASA has decided to repeat the run with a similar task in 2006 (Moltenbrey, 2016, p. 102).
At the same time, the United States are developing another project called Stardust; its mission is aimed at exploring the comet Wild 2 (Moltenbrey, 2016, p. 123). The principal distinguish of this mission from the previous one is the planned delivery of the samples of substance from the comet tail to the Earth. The successful launch of Stardust spacecraft took place on February 7, 1999. In February 2000 and January 2001, the samples were taken from the interplanetary dust. Finally, when on January 2, 2004, the distance between the comet and the spacecraft was about 240 km, the traps captured the dust particles from the tail. On January 15, 2006, the samples were returned to Earth for the detailed investigation (Moltenbrey, 2016, p. 124-125).
In addition, previously, the international community was actively discussing a theory about the origin of water on Earth. The orbital telescope Gretel has carried water composition analysis on the comet Hartley 2 using a heterodyne infrared sensor (Russell, 2007, p. 188). Scientists studying the data calculated the percentage of hydrogen isotopes in comet ice and found that it was almost the same as earthly. It was the confirmation of the theory that water on Earth was of comet origin. However, a recent expedition, the landing of module Philae on the comet 67P/Churyumov-Gerasimenko, exposed the theory to the question. The analysis of water vapor showed that the ratio of deuterium and heavy hydrogen to the normal hydrogen in the comet was much higher than on Earth. This expedition has managed to become the part of the history due to the duration of the flight, which consisted 10 years, and the discoveries made. It continues to the present day (Gulkis, 2012, p. 32). However, not only a scientific sensation but also the devices themselves in conjunction with the flight plan seem interesting.
Rosetta is the latest project of ESA. It includes the flight to a periodic comet, descent to the surface of its nucleus, soil sampling, and its shipping to the Earth. For the first time, the planet has set itself a daunting task. Originally, it was planned that the probe Rosetta will enter the space around the sun and go to the comet Wirtanen (Russell, 2007, p. 197). The start was scheduled for January 2003. However, the failure to start the carrier Ariane-5 a month before the beginning of the mission to the comet made check all equipment again. It took much time, and a “window” for a successful mission to the comet Wirtanen closed. A “window” is the interval of time, during which one can hold the trigger on the calculated trajectory with minor corrections of the orbit. However, the program has not been curtailed since the replacement of Wirtanen was made quickly. It was a comet Churyumov-Gerasimenko (Russell, 2007, p. 199-201).
The astronomers had discovered Churyumov-Gerasimenko relatively recently – in 1969 (Gulkis, 2012, p. 60). By the nature of the current orbits, it refers to the family of comets of Jupiter. Comet Churyumov – Gerasimenko is an ordinary comet with a short orbital period equal to 6.6 years and an average speed of orbital motion of 18 km/s (Gulkis, 2012, p. 33). Its distance from the Sun is less than the radius of the orbit of the Jupiter, and the trajectory is very predictable, which allows the scientists to choose the right window for the launch of the spacecraft. Comet has a mass of about 10 billion tons, the volume of 25 km3, and the rotation period of 12.5 hours (Gulkis, 2012, p. 34-35). Its period of revolution around the Sun is equal to 5 years, and the shortest distance from it is 190 million kilometers. Therefore, the comet has been approaching the Sun and Earth only 5 times after its opening (Gulkis, 2012, p. 35). It is a very significant fact that the nucleus of the comet during this time did not have time to lose much of its gas and dust composition. It is large enough for the comet standards – about 5 km long tail appears when the heavenly body approaches the Sun (Gulkis, 2012, p. 35).
NASA goal was a “shot” of a comet but landing on such a small body, which the nucleus is, has never been planned. It must be remembered that the fire in the nucleus of a comet can be in any part of the trajectory but preferably near perihelion. The landing on the surface of the core unit, on the contrary, can only be conducted away from the Sun, i.e., for this comet, it is possible near Jupiter orbit. It is where the gas component is frozen, and it is hoped that the surface of the nucleus is solid (Schulz et al., 2009, p. 150).
As in previous cases, a missile overtakes a comet and, thus, is closer to the Sun. The main emissions should be in the direction opposite to the movement. However, in these circumstances, the particle emission rate can be much larger: harpoon invasion of a comet nucleus can lead to the appearance of cracks on its surface. The presence of cracks, in turn, when approaching the Sun, leads to the formation of a fistula, in which the speed will be higher than the normal rate of evaporation. There are two models: with particulate emission rates of 2500 m/s and 3000 m/s (Schulz et al., 2009, p. 157). Thus, the only active experiments on the Churyumov-Gerasimenko nucleus offer hope for successful observation of “man-made” meteor shower.
Technical Characteristics and Equipment of Rosetta and Philae
The purpose of the flight is the comet Churyumov-Gerasimenko. The total cost of the project is amounted to EUR 1.3 billion (Schulz et al., 2009, p. 166). The rotation Cycle is 12.4 hours. The weight reaches 10 billion tons, and the volume is 25 km3. The density is 400 kg/m3. The color of the apparatus is charcoal (Schulz et al., 2009, p. 168-169). Rosetta consists of two parts: the probe itself giving the entire system a name and Philae, which is a reentry module. Technical characteristics of the probe include type of construction (a box); dimensions (2.8 m * 2.1 m * 2.0 m); and area of solar panels (64 m2) (Schulz et al., 2009, p. 170). The length of one solar panel is 14 m; the total length of the structure including the length of the two solar cells and connecting portions of the instrument unit reaches 32 m (Schulz et al., 2009, p. 170).
Devices that are in the body of Rosetta include remote sensing instrumentation (OSIRIS (optical spectrographic infrared system for remote imaging), ALICE (a miniature ultraviolet spectrometer with the ability to produce an image), VIRTIS (a thermal spectrometer of visible and infrared radiation), MIRO (microwave for researching the nature of comet nucleus), tools for determining the composition (ROSINA (a spectrometer for ion and neutral analysis), COSIMA (analyzer of secondary ion mass), MIDAS (a microscope for regular dust analysis), radio frequency transmitter for scanning a comet nucleus (CONSERT), particle effect of the analyzer and a dust-keeper (GIADA), ion-electronic sensor (IES), tool for studying the plasma environment of a comet and solar wind interaction (RPC), radio transmitter (RSI), and descent module Philae (Schulz et al., 2009, p. 171-173).
Philae carries different equipment on its board. The devices that are part of the apparatus include APXS (Alpha Proton X-ray Spectrometer), COSAC (COmetary SAmpling and Composition), which is a combined gas chromatograph and mass spectrometer for the analysis of rock samples and evaluation of their content of volatile components, Ptolemy, which is a device for measuring the ratio of proportion of stable isotopes in the volatile key components of a comet nucleus, ÇIVA (Comet Nucleus Infrared and Visible Analyzer) – 6 identical micro cameras for panoramic shooting the surface of the die 1024x1024 pixels each, ROLIS (Rosetta Lander Imaging System) – a CCD-camera for filming during the descent with a resolution of 1024x1024 pixels, CONSERT (COmet Nucleus Sounding Experiment by Radiowave Transmission) – a radar designed to conduct imaging of a nucleus by measuring the spread of a comet in it of electromagnetic waves from Rosetta and determine its internal structure, MUPUS (MUlti-PUrpose Sensors for Surface and Sub-Surface Science) – the sensors for measuring the density, thermal and mechanical properties of the surface, ROMAP (Rosetta Lander Magnetometer and Plasma Monitor) – a magnetometer and plasma detector for studying the magnetic field of a comet nucleus and its interaction with the solar wind, SD2 (Drill, Sample, and Distribution subsystem) – a drill for the extraction of rock samples from depths of 0 to 230 mm and sending them for analysis to Ptolemy subsystem, COSAC, and ÇIVA, SESAME (Surface Electric Sounding and Acoustic Monitoring Experiments) – 3 devices for measuring the properties of the outer layers of a comet. These devices include CASSE (Cometary Acoustic Sounding Surface Experiment) – the experiment on acoustic study of the comet surface, PP (Permittivity Probe) – the study of its electrical characteristics, and DIM (Dust Impact Monitor) – measurement of dust settling on the surface (Schulz et al., 2009, p. 173-174).
The Trajectory and History of the Rosetta Apparatus Mission
Flight of the research apparatus to the comet Churyumov-Gerasimenko, which ESA conducted, was very interesting and difficult in execution. The choice of such a long and complicated flight pattern was made due to the scheduled program of the scientific research mission. All previous space expeditions directed to studying comets were on a collision course. Through this scheme, the flight could not only just take a picture of the small comet nucleus section and deliver the samples of dust from its tail to the Earth but also in the literal sense shoot metal bars in the comet and investigate the composition ejected in this matter (Streames, 2016).
For Rosetta, a complex script that used the gravitational fields of the Sun, Mars, and Earth was developed. By its nature, it is similar to the flight to the comet Wild 2 but is more difficult. First, it was planned to make four turns around the Sun while in three cases entering the gravity zone of the Earth in 2005, 2007, and 2009 and once that of Mars in 2007 (Streames, 2016). This convergence should correct the orbit of the ship giving it extra speed to reach the orbit of the Jupiter. Rosetta was following the comet, made one complete revolution, and passed perihelion. They had to meet in May 2014, and probe worked around the comet watching all the changes in its state. Return bay station with all findings had to deliver samples of the substance of the comet nucleus to the Earth first (Streames, 2016).
However, the goal of Rosetta mission was much different from the previous ones: it was planned that the spacecraft would stay near the comet nucleus for quite a long time and make the landing on its surface lander. It is impossible to perform it on a collision course since the comet speed, which can reach tens or even hundreds of kilometers per second, is added to the escape velocity of the device. To conduct the landing on the comet, the relative velocity of the comet and the spacecraft must be as close as possible. Due to the chosen scheme, Rosetta could fly up to Churyumov-Gerasimenko back and stay with it for a long time while moving at the same speed (Streames, 2016).
On board of the three-ton Rosetta, there are one-hundred-kilogram descent module Philae comparable to a refrigerator in size and 11 scientific instruments including a camera equipped with two lenses of 700 mm and 140 mm respectively and a CCD-matrix of 2048x2048 pixels that allow scientists to receive images in the optical and infrared wavelengths (Streames, 2016). The payload of Philae module included ten devices for the study of the morphological, chemical, microbiological, and other characteristics of the comet nucleus involving a pyrolyzer, mass spectrometer for the analysis and identification of gaseous products of pyrolysis, and gas chromatograph for analysis of different mixtures of organic and inorganic substances (Streames, 2016).
During the long flight of Rosetta to the comet, many researches have been conducted. For one and a half years after the start, Rosetta watched the clash of 350-pound metal blanks with the comet Tempel 1 shot by the Stardust apparatus (Streames, 2016). After another six months, it flew in close proximity to the Mars making great shots of Red Planet in different spectral ranges. The images in the ultraviolet part of the spectrum allowed revealing the unusual processes in the Martian atmosphere, which previously stayed unknown.
The spacecraft spent next year and a half in low-power mode. In 2008, it was activated again to capture a six-kilometer asteroid Steins flying by at the distance of 800 km. In early 2010, Rosetta explored the comet-like body of P/2010 A2 discovered in the asteroid belt that demonstrated the abnormal behavior. The proposed data together with information from the space telescope Hubble allowed establishing the cause of the anomaly, which was a clash with 150-meter asteroid splinter. However, the main result of this year's survey was the discovering of100-kilometer asteroid Lutetia at the distance of 3170 km (Streames, 2016). The study of images of its surface gave reason to believe that an asteroid was one of the few remaining from the date of birth of the solar system germs of the planets – planetesimals (Streames, 2016).
Then, for two and a half years, until January 20, 2014, Rosetta was plunged into sleep mode. Despite ten years spent in the space and passing through the asteroid belt, equipment testing has revealed no problems at the spacecraft. In August 2014, Rosetta comet has finally entered the cloud. At this time, the most spectacular images of the approaching and rotating comet nucleus were made (Streames, 2016).
It turned out that the surface of the comet has strongly rugged terrain: there were mountains up to 900 meters and deep craters. The very comet has a loose structure and density of about 470 kg/m3, which is close to the density of the wood (Streames, 2016). The first measurement of near comet brought unexpected results. Considering the albedo (surface reflectivity) equal to 6%, the comet Churyumov-Gerasimenko is one of the darkest objects in the solar system since the corresponding figure for the Moon is 12%, and for the Earth it is about 37% (Streames, 2016). This fact indicates that the comet surface contains minerals including iron sulfides doped with carbon compounds among others; it also shows low content or complete absence of ice water in the external layers of the soil. However, it does not exclude the assumption that the ice can be located at some depth below the surface. In November 2014, Rosetta comet moved closer, to the distance of 3 km, and has performed the launch of lander Philae. It went to the comet at relative velocity of about 1 m/sec and shot two harpoons during the contact with the surface; the weak gravity of the comet could not hold the device. However, neither the engine, which had to press Philae to the surface, nor harpoon system worked, and the machine bounced from the surface twice. At the end, it managed to gain the foothold but the landing place was in the shade since the machine did not receive enough solar energy for the operation of scientific instruments (Streames, 2016).
Despite such dangerous landing, Philae immediately started to transmit images of the surface of the comet and measurement data. Trying drilling was unsuccessful due to very hard nature of rock beneath the machine, so the samples to analyze were taken from the comet atmosphere. In the atmosphere, gas chromatograph recorded organic molecules with a mass of the comet more than 100 nuclear power units. It was done for the first time. Even in the shadow of failed landing and getting energy from solar panels, for scientific instruments it managed to fulfill most part of the planned measurement program. However, most of the results have not yet been published.
One of the few published sensational results of Rosetta mission refers to the isotopic composition of water in the comet nucleus. Interest in these data is linked to the fact that according to current theories, the main source of Earth water had been the comets, which had fallen on the planet since their nuclei are composed mainly of ice. The most suitable candidates for this role have been short-period comets like 67P/Churyumov-Gerasimenko since previous studies had shown the absence of water in the long-period comets. However, the measurement data have not confirmed this hypothesis. It is likely to indicate a more complex mechanism of material moving in the young solar system. Now, scientists hope that the approaching comet close to the sun energy will flow sufficiently to provide complete on-board devices. According to the original plan, the machine should work on the comet surface to the end of 2015 but service life was significantly extended (Streames, 2016).
Rosetta Mission Contribution to Understanding Tunguska Event
Talking about the essence of the comet Churyumov-Gerasimenko contributes to the understanding of the mystery of the famous Tunguska event occurred in 1908 in the Tunguska taiga (Bauer, 2016, p.45). The famous Tunguska meteorite turned out to be not a meteorite but the nucleus of a small comet. The issue is that it was hard to explain the reason for the explosion of the icy comet nucleus. It was unclear why it exploded with a force equivalent to the energy of the explosion of about 10-20 megaton nuclear bombs since it was in 500-1000 times higher than the power of the atomic bomb dropped in 1945 on Hiroshima (Bauer, 2016, p.50).
These astounding assertions are connected with the question of where did the energy of motion of the comet and its domestic energy resources come from. It turned out that a comet cannot be in isolation from the genetic unity of the physical processes of the cosmos and general laws of development of the substance of stars and planetary systems. The most important moments of the origin of comet bodies in terms of the provision of the new concept of cosmogony show that the nature of these celestial bodies is directly related to the activity of the solar flare (Bauer, 2016, p.51).
The analysis of known data about the solar flare activity, the composition of the comet material and kinematics motion of periodic comets, which is significantly added with the results of recent studies of Halley's Comet in 1986, and the observations in 2007 within the Crimean Astrophysical Observatory on the depth of the energy source that heats the solar corona help to define their nature. Emissions of solar material occur near chromospheric flare, on the edge of the solar disk, rising or looping of prominences or type of coronal condensation become visible (Bauer, 2016, p.59). During its stay in the eruption stage, the prominence often performs large-scale movement and can fly in space. Comet has detached from the surface of the solar chromosphere prominence and resulted in the sporadic shallow ejection of solar plasma with the atoms of the synthesized substances that were in it at that point. The comet movement is powered by a chromospheric flare, which is the result of nuclear reactions under the surface layer of the star. This source of its movement causes corresponding speed and tremendous kinetic energy of motion in the gravity field of the Sun allowing flying around the Sun and not falling on it (Bauer, 2016, p.61).
Deuterium was found in the composition of the comet Churyumov-Gerasimenko; the kernel and helium-3 were found in the composition of tree resin, which survived a terrible explosion in the Stony Tunguska River as will be shown later. Therefore, the probability of hitting the comet as an unfinished product of tritium fusion of elements of the first period is very high (Bauer, 2016, p.68). Then, immediately, the enormous energy of the Tunguska explosion that shook the taiga in 1908 finds its explanation. People have always been intuitively afraid of comets, which have been called space aliens. Rapid deceleration in the Earth atmosphere of comet nucleus led to the release of enormous amount of heat and hot material of the comet nucleus, which exploded a hydrogen “bomb”(Bauer, 2016, p.68). There was a reaction between deuterium and tritium as the intermediate structures of the nuclear fusion of the first period of the elements in the star, which was completed at the time of the explosion in the Earth atmosphere.
The hydrogen bomb is sometimes compared with the Sun. The Tunguska miracle has appeared over the southern part of Central Siberia as a huge fireball with the rumble and roar of flying across the sky and crashed into the hangar. Thus, a comet Churyumov-Gerasimenko, which has discovered in its composition as seemingly unremarkable deuterium, helped to understand the features of the mysterious cosmic event of 1908 (Bauer, 2016, p.69).
The actual abundance of helium-3 in the Stony Tunguska was conclusive evidence, first, of comet origin of the heavenly stranger in 1908. Second, the presence of unfinished products of synthesis of elements was an illustration of the processes occurring in the upper solar membranes of two comets. Knowledge of these processes makes it possible to show the nature of the Tunguska phenomenon as a nuclear explosion at the end of the reaction of synthesis of helium-4, which has not had time to occur on the Sun and, by random circumstances, resulted in the atmosphere of the Earth.
The End of Rosetta Mission and Main Findings
On September 29, the automatic station Rosetta has started rapprochement with the comet 67P/Churyumov–Gerasimenko (Wilkinson, 2016, p. 205). In fact, it could be called a fall from a height of 19 kilometers but closure rate was only 0.5 m/s. After planting, all devices on Rosetta were switched off, and the unit ended the mission. It had lasted for 12 years (Wilkinson, 2016, p. 205). The probe is likely never contact the Earth. In fact, Rosetta was the first spacecraft that managed to complete the mission of that type. Now, the comet Churyumov–Gerasimenko is farther away from the Sun. The solar panels no longer generate the necessary for the proper functioning of the unit amount of electric power. Small breakdowns and failures, which have accumulated during the 12-years mission, affect the performance of the probe.
However, the staff of the European Space Agency has designed clever completion of the mission. It has been called “the great final” (Wilkinson, 2016, p. 256). Its essence lied in the fact that starting with a reduction in the height of 19 km above the surface of the comet, Rosetta sit on the surface of the comet. During the descent, it maintained continuous photographing of the comet from close range. It helped with getting the highest resolution images of all missions. The place for landing was a region of Ma'at (at 67P/Churyumov–Gerasimenko, all parts of the relief have ancient Egyptian names). This place was selected for two reasons. First, it was done due to its unusual topography, Ma'at has been attracting the attention of researchers for a long time. There is a large number of different basins, the origin of which is not clear. There is an assumption that the emissions of gas and dust often occur there. Scientists would like to look at this place closer. Then, Ma'at is one of the few areas where Rosetta could gently fall and not to crash. Unfortunately, after the landing of the spacecraft, antenna did not longer point to the Earth, and communication with it became impossible (Wilkinson, 2016, p. 211).
Despite the completion of the mission, the data obtained by the automatic station will last more than one year. Nevertheless, one can already say that Rosetta completely changes the understanding of the nature of comets. The density of the comet material was lower than that of water ice. It suggests that the comet material from 67P/Churyumov-Gerasimenko is probably porous. At the same time, the surface is covered with a very dark material. Sometimes, the reflectivity is compared with black velvet. The structure of the comet surface should be similar to the dirty snowdrifts melt and formed at spring as a result of melting of snow (Wilkinson, 2016, p. 222).
As it is seen from the Earth, astronomers have often noticed that the comet may change very rapidly its brightness but the question why it is so remained a mystery for a long time. However, on February 19, 2016, in 67P/Churyumov-Gerasimenko, a real collapse occurred. From beneath the outer layer of the comet, layers of ice were exposed, which began to evaporate in direct sunlight. Everything happened quickly leading to the massive release of material from the surface, and, in a short time, the comet became much brighter (Wilkinson, 2016, p. 234).
During the mission, Rosetta was able to find a large number of different organic compounds on 67P/Churyumov-Gerasimenko. Scientists still have to find whether these organic substances are involved in the origin of life on Earth. Incidentally, carbon compounds are due to the black color of the outer layers of the comet. However, perhaps, one of the most important results missions was the discovery of the fact that the water on the comet was very different from the earthly one. The fact is that the content of heavy water (deuterium atoms with water – heavy hydrogen) on the comet is three times higher than that of the hydrosphere of the Earth (Wilkinson, 2016, p. 238). It crosses a very common theory that the water in the world is of cosmic origin. At least, a comet brought it not on this planet.
Another interesting scientific result is that 67P/Churyumov-Gerasimenko has changed the period of rotation around the axis. If at the time of arrival of the mission the period was 12 hours 24 minutes and 14 seconds, now, it would rotate significantly faster – for 12 hours 3 minutes and 18 seconds (Wilkinson, 2016, p. 240). It is achieved due to the action of jets of gas emission from the surface of 67P/Churyumov-Gerasimenko. Comet untwisted as a result of evaporation of the active substance at perihelion passage. When Rosetta only began to study the rate of loss of substance by the comet, it was estimated that several tens of thousands of kilograms per day got from the surface into space.
Analysis of Significance of Rosetta Mission
Space mission Rosetta can be called the most outstanding event in space exploration over the past decade. The successful implementation of the space mission Rosetta is a truly grand event of the new XXI century. Without exaggeration, it can be compared only with the launch of the first satellite, Yurii Gagarin’s flight, and landing on the moon. One might argue that for the time elapsed since the beginning of the space age, dozens of interplanetary stations, not counting the hundreds of orbiters and space programs, were launched. Space crafts have flied and continue to fly to Venus and Mars, Saturn, Jupiter and its satellites, to distant planets of the solar system. They have already got to Pluto and beyond. Nevertheless, Rosetta mission is still exceptional. The magnitude of the comet’s nucleus under consideration is about 3 to 5 km. Moreover, it has irregular shape. The spacecraft had to find and catch it, gain a foothold in its orbit, and then put it on the surface of a small lander. ESA ballistics calculated flight path so perfectly that Rosetta almost did not use its own engines before meeting comet.
Surely, the success of the mission depends not only on the flight system and landing of the module, though it is also a great achievement. There is an enormous number of images of the comet and the data on the substance from which it consists of. There were compounds such as carbon monoxide and carbon dioxide, acetone, acetamides, propanal and methyl isocyanate. Polymer molecules, molecular oxygen and water are present. It was found that the comet's mass is of 10 billion tons. The comet was discovered to have even own “sound.” Transforming the recorded fluctuations of the electromagnetic field of the comet in the audible range, the scientists have enabled people to hear its “voice.” Thus, Rosetta project proves that science is a supranational category. Considerable success in it can only be achieved by uniting the efforts of many countries. It was proved by Rosetta mission, which became the property of the entire planet.
Rosetta was the first spacecraft that managed to reach an orbit of a comet. In the coming years, the scientists have to study the entire file of the information received from the device. Rosetta had been following the comet Churyumov-Gerasimenko for over 6 billion kilometers. In total, the spacecraft has been staying in the orbit of the comet for two years – nearly one-third of the full cycle of a celestial body. The probe of Rosetta, module Philae, was launched into space in 2004. It overcame 6.4 billion kilometers before reaching the comet Churyumov-Gerasimenko, which was near the orbit of Jupiter. In November 2014, Philae was undocked from Rosetta. Thereafter, for several hours, the descent to the surface of comet 67P Churyumov-Gerasimenko has been conducted. The unit has collected a vast array of scientific data on the composition of the gas shell 67P, its morphology, geology, and internal structure. The module has suspended work due to lack of solar energy. However, the scientists managed to determine the fact that the comet was the same age as the solar system and, thus, kept the information about the conditions, in which a planet was. It is able to refute the hypothesis that the water on Earth arose due to comets since the isotopic composition of ice water on Churyumov-Gerasimenko is markedly different from the earthly one. What is more, it contributed to the solving of the Tunguska event.