In the event that NASA experts choose a comet, the agency will send a spacecraft to it, which will have to take samples from its surface and then send them to Earth. This finalist project is called CAESAR. The main purpose of this mission is to collect organic compounds in order to understand how comets could contribute to the birth of life on our planet. It should be noted that earlier a Philae probe, delivered to its surface by the European station Rosetta, had already landed on the Churyumov-Gerasimenko comet. However, the probe managed to transmit only telemetry to Earth, after which communication with the device was lost. At the end of September 2016, the Rosetta station was de-orbited and sent into collision with a comet.
In the event that the choice of NASA is made in favor of Titan, a Dragonfly spacecraft, which has already been called a nuclear helicopter, will be sent to its surface, but outwardly it will resemble a quadcopter. Dragonfly will have to scan Titan's surface in order to determine what exactly it consists of and how it is built. Also, the space helicopter will have to answer the question: what are the atmospheric conditions on this satellite of Saturn. Specialists from the American Space Agency believe that extraterrestrial life forms can exist on Titan.
Titan in natural colors (Cassini photo)
The finalists of the competition for the best space mission project in the framework of the research program of the Solar System New Frontiers were two development teams, in total, 12 candidates took part in the competition. Both projects voiced above will receive approximately 4 million dollars a year to work out the details and concept. They should finalize their programs by July 2019, examine all possible risks of their missions, and then make a final proposal. The winner’s project will be launched at the end of 2025. Approximately 850 million dollars will be required for the development of each mission, the winner will receive this amount from NASA, and the agency will assume all expenses for launching the winning spacecraft into space - another approximately 150 million dollars.
According to experts, the “price tag” announced is approximately twice the cost of “light” space missions in the framework of another program - Discovery, and also 2-4 times less than the budget of the “flagship” NASA space stations and telescopes. The announced budget allows to place on the probes a rather large and extensive set of tools, as well as long-lived radioisotope power sources, but these probes will still be inferior in their capabilities and lifetime to such flagships, which were Cassini, Galileo and Voyager.
It is worth noting that in the framework of the New Frontiers program, the US space agency has already carried out three successful missions. So the Juno probe is studying the orbit of Jupiter, the New Horizons spacecraft is currently heading for Pluto, and OSIRIS-REx is flying to an asteroid to take samples from its surface. According to Thomas Zurbuhen, the agency has not yet made a decision on which launch vehicles will be used to launch one or the other mission. At the same time, he expressed confidence that by the time work began on creating the required stations and probes, the heavy SLS rocket, as well as private space “heavy vehicles”, would be ready for the launch of a new generation of interplanetary American probes.
Nuclear helicopter on Titan - DragonFly mission
“Titan is a unique celestial body with a dense atmosphere, lakes and real seas of hydrocarbons, the circulation of substances and a complex climate. We expect to continue the work of Cassini and Huygens in order to understand whether all the "bricks of life" are on the surface of Titan and whether life can exist on it. Unlike other landing modules, our “dragonfly” will be able to fly from place to place, traveling hundreds of kilometers, ”said Elizabeth Turtle, head of the DragonFly mission.
Comparison of the size of the Earth, Titan (bottom left) and the Moon
Titan is the largest satellite of Saturn and the second largest satellite in the entire Solar System (second only to Jupiter’s satellite Ganymede). Also, Titan is the only body, with the exception of the Earth, in the Solar System, for which a stable existence of liquid on its surface has been proved, as well as the only satellite of the planet, which has a dense atmosphere. All this makes Titan a very attractive object for various research and study.
The diameter of this satellite of Saturn is 5152 kilometers, which is 50% more than that of the Moon, while Titan is 80% more than the satellite of our planet in mass. Also, Titan is larger than the planet Mercury in size. Gravity on Titan is about one seventh of gravity. The surface of the satellite consists mainly of water ice and sedimentary organic matter. The pressure at the surface of Titan is approximately 1,5 times higher than the pressure at the earth's surface, the air temperature at the surface is -170 .. -180 degrees Celsius. Despite the relatively low temperature, this satellite is mapped to Earth in the early stages of its development. Therefore, scientists do not exclude that the existence of the simplest life forms is possible on Titan, in particular, in the existing underground reservoirs, in which conditions can be much more comfortable than on its surface.
Dragonfly - the brainchild of scientists from Johns Hopkins University, it will be a universal landing gear, equipped with several propellers that will provide him with the possibility of vertical takeoff and landing. In the future, this will allow an unusual helicopter to explore the surface and atmosphere of Titan. “One of our main goals is to conduct research on methane rivers and lakes. We want to understand what is going on in their depths, ”said Elizabeth Turtle, the head of the Dragonfly mission. “In general, our main task is to shed light on the mysterious environment of the satellite of Saturn, which is rich in organic and prebiotic chemistry. After all, Titan today is a kind of planetary laboratory at which chemical reactions similar to those that could have caused life on Earth could be studied. ”
Such a project, if it won the competition in the 2019 year, will be very unusual and new even for NASA. Thanks to its two features, the Dragonfly unit will be able to move from place to place. The first is the presence of a nuclear power plant, which will provide it with energy for a very long time. The second is a set of several powerful engines with propellers that can lift a heavy research apparatus into the dense air of Titan. All this makes Dragonfly something like helicopters or quadrocopters, with the only exception that a space nuclear helicopter will be designed to operate in much more severe conditions than earthly ones.
Dragonfly nuclear helicopter on Titan's surface, NASA illustration
Experts note that this drone will be fully supplied with energy produced by a radioisotope thermoelectric generator (RTG). The fairly dense and thick atmosphere of Titan makes any technology ineffective in converting solar energy into electrical energy, which is why nuclear energy will become the basic source of energy for the mission. A similar generator is installed on the Curiosity rover. During the night, such a generator will be able to fully charge the batteries of the drone, which will help the aircraft to make one or several flights at once, for a total duration of up to one hour.
It is known that the Dragonfly toolkit is planned to include: gamma-spectrometers that can study the composition of the subsurface layer of Titan (this device will help scientists find evidence of the presence of liquid ocean beneath the surface of the satellite); mass spectrometers to analyze the isotopic composition of light elements (such as nitrogen, carbon, sulfur, and others); geophysical and meteorological sensors that will measure atmospheric pressure, temperature, wind speed, seismic activity; it will also have cameras for taking pictures. The mobility of the “nuclear helicopter” will allow it to quickly collect various samples and perform the necessary measurements.
During the entire one hour flight, this unit will be able to overcome the distance from 10 to 20 kilometers. That is, in just one flight, the DragonFly drone will be able to overcome a greater distance than the American Curiosity Mars Rover managed for the 4 of his year on the red planet. And for its entire two-year mission, a “nuclear helicopter” will be able to explore a rather impressive section of the surface of the satellite of Saturn. Due to the presence on board of a powerful power plant, the data from the device, according to Turtle, will be transmitted to Earth directly.
If the project wins the competition and receives final approval from the New Frontiers Solar System research program, the mission will launch in the middle of 2025. At the same time, DragonFly will arrive at Titan only in 2034, where, with favorable developments, he will work on its surface for several years.
On the way to the "Soviet" comet - the mission of CAESAR
The second mission, which is currently claiming victory in the New Frontiers competition, could be the CAESAR probe, the first NASA spacecraft, which will take samples of volatile substances and organic matter from the comet's surface and then return back to Earth. “Comets can be called the most important, but at the same time the least studied objects in the solar system. Comets contain the substances from which the Earth was “molded”, and they were also the main suppliers of organic matter for our planet. What distinguishes comets from other known bodies of the solar system? The comets still contain volatile substances that were in the solar system at the time of its birth, ”said Steve Squires, head of the CAESAR mission.
Snapshot of Comet Churyumov-Gerasimenko taken by 19 September 2014 of the Rosetta camera
According to Jim Green, the head of the NASA Department of Planetology, this mission will be sent to a very well-studied comet, in the vicinity of which another probe has already been visited, this is a European mission called Rosetta. The comet with the 67P index is called “Soviet”, since it was discovered by Soviet astronomers. This is a short-period comet with an orbital period of approximately 6 years and 7 months. Comet Churyumov-Gerasimenko was discovered in the USSR on October 23 1969 of the year. It was discovered by the Soviet astronomer Klim Churyumov in Kiev on photographic plates of another comet - 32P / Comas Sola, which were shot by Svetlana Gerasimenko in September of the same year at the Alma-Ata observatory (the first picture, on which the new comet was seen, was made on September 11 1969 of the year ). The 67P index means that we face the 67-i open short-period comet.
It is established that the comet Churyumov-Gerasimenko has a porous structure, 75-78% of its volume is emptiness. On the illuminated side of the comet, the temperature ranges from -183 to -143 degrees Celsius. There is no permanent magnetic field on the comet. According to recent estimates, its mass is 10 billion tons (measurement error is estimated at 10%), the rotation period is 12 hours 24 minutes. In the 2014 year, using the Rosette apparatus, scientists were able to find 16 molecules of organic compounds on a comet, four of which — acetone, propanal, methyl isocyanate, and acetamide — were not previously found on comets.
According to representatives of the US space agency, the choice of the CAESAR mission, which is sent to a well-studied comet, will kill three birds with one stone - this makes the mission safer, reduces its cost, and also speeds up its launch. According to Squires, the installation of a capsule for collecting and returning earth from the comet will play its role. This capsule was previously created by the Japanese space agency for the Hayabus probe. “The choice of this capsule is explained by the fact that for the CAESAR mission a capsule was needed, which would continue to keep volatile substances from the comet frozen during the entire flight, until it touches the earth's surface. The capsule for the Hayabus probe has a thermal shield that prevents it from heating to several hundred degrees Celsius, which could happen when using our technologies, ”said the American scientist.
Possible view of CAESAR probe, NASA illustration
According to NASA plans, the CAESAR probe is planned to be equipped with an ion engine. It will reach the surface of comet Churyumov-Gerasimenko relatively quickly. Samples of its matter, Steve Squires hopes, could be on Earth in 2038.
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