By all indications, we have entered the era of new discoveries. Many last year, with a sinking heart, followed the Rosetta mission. Landing on a comet, the first in history, was a very difficult operation, like the entire program as a whole. However, the difficulties that have arisen do not detract from the significance of the event itself, as well as of the data that the space probe has already acquired and is still supplying. Why was landing on a comet needed, and what results did astrophysicists get? This will be discussed below.
Main secret
Let's start from afar. One of the main tasks facing the entire scientific world is to understand what contributed to the birth of life on Earth. Since antiquity, a lot of hypotheses have been expressed on this topic. One of the modern versions says that comets played a significant role here, many of which fell on the planet during its formation. It is believed that they could become suppliers of water and organic molecules.
Evidence start
Such a hypothesis in itself perfectly substantiates the interest of scientists, from astronomers to biologists, to comets. However, there are some more interesting points. Tailed space objects through space carry quite detailed information about what happened at the earliest stages of the formation of the solar system. It was then that most comets formed. Thus, landing on a comet makes it possible to literally study the matter from which our piece of the Universe was formed more than four billion years ago (and no time machine is needed).
In addition, the study of the comet's motion, its composition and behavior when approaching the Sun provides an enormous amount of information about such space objects, allows you to check a lot of assumptions and scientific hypotheses.
Background
Naturally, tailed "travelers" have already been studied with the help of spacecraft. Seven flights were made past comets, during which photographs were taken, certain information was collected. These were just the spans, since long-term follow-up of a comet is a complicated matter. In the 80s, the American-European apparatus ICE and the Soviet Vega acted as the providers of such data. The last of these meetings took place in 2011. Then data on the tailed space object was collected by Stardust.
Previous studies have given scientists a lot of information, but this is not enough to understand the specifics of comets and answer many of the above questions. Gradually, scientists came to the realization of the need for a bold enough step - the organization of the spacecraft’s flight to the comet with the subsequent landing of the probe on its surface.
Mission uniqueness
In order to feel how landing a comet is a difficult operation, you need to understand what this cosmic body is all about. It rushes through space at great speed, sometimes reaching several hundred kilometers per second. At the same time, the comet’s tail, formed when the body approaches the Sun and looks so beautiful from the Earth, is a mixture of gas and dust. All this greatly complicates not only landing, but also movement in a parallel course. It is necessary to balance the speed of the vehicle with the speed of the object and choose the right moment to approach: the closer the comet is to the Sun, the stronger the emissions from its surface. And only then can a landing be made on a comet, which will be further complicated by low gravity.
Object selection
All these circumstances necessitated a careful approach to the choice of mission goals. Landing on the comet Churyumov-Gerasimenko is not the first option. Initially, it was assumed that the probe "Rosetta" will be sent to the comet Virtanen. However, a case intervened in the plans: shortly before the intended departure, the engine of the Arian-5 launch vehicle failed. It was she who was supposed to launch the Rosetta into space. As a result, the launch was postponed and it became necessary to select a new facility. They became the comet Churyumova-Gerasimenko or 67P.
This space object was discovered in 1969 and named after the discoverers. It belongs to the number of short-period comets and makes one revolution around the Sun in about 6.6 years. The 67P is not particularly remarkable, but it has a well-studied flight path that does not go beyond the orbit of Jupiter. It was to her that Rosetta set off on March 2, 2004.
The "stuffing" of the spacecraft
The Rosetta probe carried with it into space a large amount of equipment designed for research and recording their results. Among them are cameras capable of capturing radiation in the ultraviolet part of the spectrum, and devices necessary for studying the structure of the comet and soil analysis, and instruments for studying the atmosphere. In total, Rosetta had 11 scientific instruments at its disposal.
Separately, you need to stop on the descent module "Fila" - it was he who was to land on a comet. Part of the high-tech equipment was located right on it, because it was necessary to study the space object immediately after the landing. In addition, the Fila was equipped with three harpoons for reliable fixation on the surface after it was lowered by the Rosetta. Landing on a comet, as already mentioned, is fraught with certain difficulties. Gravity here is so small that in the absence of additional fastenings, the module runs the risk of being lost in open space.
Long way
The landing on the comet in 2014 was preceded by a ten-year flight of the Rosetta probe. During this time, he appeared five times near the Earth, flew near Mars, met two asteroids. The magnificent photographs taken by the probe during this period once again remind us of the beauty of nature and the Universe in its most diverse corners.
However, a logical question may arise: why did Rosetta circulate the solar system for so long? It is clear that the photographs and other data collected during the flight were not its purpose, but rather became a pleasant and interesting bonus for researchers. The purpose of this maneuver is to approach the comet from behind and equalize the speed. The result of a ten-year flight was to become the actual transformation of Rosetta into the satellite of comet Churyumov-Gerasimenko.
Rapprochement
Now, in April 2015, it is safe to say that the landing of the probe on the comet as a whole was successful. However, in August last year, when the spacecraft just entered the orbit of the cosmic body, this was still a matter of the near future.
The probe landed on a comet on November 12, 2014. Almost the whole world watched the landing. Undocking Fila was a success. Problems began at the time of landing: the harpoons did not work and the device could not gain a foothold on the surface. The Fila bounced twice from the comet and was only able to descend for the third time, and it flew about a kilometer from the site of the proposed landing.
As a result, the Fila module was in an area where the sun's rays, which are necessary to replenish the energy charge of the batteries, hardly penetrate. In case landing on a comet does not happen very well, the device was equipped with a charged battery for up to 64 hours. He worked a little less, 57 hours, but even during that time Fila managed to do almost everything for which it was created.
results
Landing on the comet Churyumov-Gerasimenko allowed scientists to obtain extensive data on this cosmic body. Many of them have not yet been processed or require analysis, but the first results have already been presented to the general public.
The studied cosmic body is similar in shape to a rubber duck (landing on a comet was supposed to be in the area of the "head"): two rounded parts of comparable size are connected by a narrow isthmus. One of the challenges facing astrophysicists is to understand the reason for such an unusual silhouette. Today, two main hypotheses are put forward: either this is the result of a collision of two bodies, or erosion processes led to the formation of the isthmus. No exact answer has been received at this time. Thanks to the research of "Fila" it only became known that the level of gravity on the comet is not the same. The largest indicator is observed in the upper part of the nucleus, and the smallest - just in the area of the "neck".
Relief and internal structure
The Fila module found various formations on the surface of the comet that looked like mountains and dunes. In their composition, most of them are a mixture of ice and dust. Hills up to 3 meters high, called goosebumps, at 67P are quite common. Scientists suggest that they formed in the early stages of the formation of the solar system and can cover surfaces of other similar celestial bodies.
Since the probe on the comet did not descend in the most successful way, scientists were afraid to begin the planned surface drilling. However, it was nevertheless carried out. It turned out that under the upper layer is another, more dense one. Most likely, it consists of ice. An analysis of the vibrations recorded by the device during landing also speaks in favor of this assumption. At the same time, the spectrographs show an unequal ratio of organic compounds and ice: the former are clearly larger. This does not agree with the assumptions of scientists and casts doubt on the version of the origin of the comet. It was assumed that it was formed in the region of the solar system, near Jupiter. The study of the images, however, refutes this hypothesis: apparently, 67P was formed in the Kuiper belt, located beyond the orbit of Neptune.
Mission continues
The Rosetta spacecraft, which closely monitored the activities of the Fila module until it fell asleep, has not left Comet Churyumov-Gerasimenko so far. He continues to observe the object and send data to Earth. So, his responsibilities include fixing dust and gas emissions, which increase as the comet approaches the Sun.
It was previously established that the main source of such emissions is the so-called comet neck. The reason for this may be the low gravity of this region and the effect of the accumulation of solar energy reflected from neighboring areas arising here. In March of this year, Rosetta also recorded an emission of dust and gas, which was interesting because it occurred on the unlit side (as a rule, such phenomena occur as a result of heating the surface, that is, on the solar part of the comet). All these processes and features of the 67P have yet to be explained, while data collection continues.
The first landing on the surface of a comet in the history of mankind was the result of the work of a large number of scientists, technicians, engineers and designers for almost forty years. Today, the Rosetta mission is recognized as one of the most ambitious events of the space age. Naturally, astrophysicists do not intend to put an end to this. The ambitious plans for the future include the creation of a descent module that will be able to move around the surface of a comet, and a spacecraft that can approach the object, collect soil samples and return to Earth with them. In general, the successful Rosetta project inspires scientists to increasingly challenging programs to master the secrets of the universe.