For many thousands of years, a person gazed into the starry sky and asked himself the same question - are we alone in the Universe? Over time, the technologies that humanity possesses have improved. A person could look farther and farther and the further humanity could peer into the cosmic depths, the more it made discoveries and the closer it got to the answer to the question of its loneliness in the world. The first and most important condition in the search for extraterrestrial life forms is to find the necessary conditions for its origin. To determine these conditions, scientists were forced to turn to the only life forms known to us that we have on Earth.
The Earth is simply teeming with various living organisms that are distributed throughout the planet and are able to survive and adapt even to the most unusual places. At the same time, regardless of their habitat, all living things on Earth have a common feature - they can live where there is water. There is no life on our planet without water, there is not a single exception to this rule, no matter what conditions a living organism lives in. This fundamental link between the presence of water and life is at the heart of the search for extraterrestrial life today. The presence of water on space objects is a guarantee that humanity will be able to find manifestations of life on them.
Not so long ago, American astronomers advised NASA to search for extraterrestrial life not on the red planet, but on Europe, the moon of Jupiter, since there may be a whole ocean there. It is on Europe that there is the best chance of detecting extraterrestrial life forms. It is this satellite that we must study in the first place, and we already have a concept of the mission, which NASA considers to be realizable. Robert Pappalardo, an employee of NASA's Jet Propulsion Laboratory, spoke about this on the sidelines of the conference of the American Association for the Advancement of Science.
Currently, the Laboratory of Applied Physics and the Jet Propulsion Laboratory of Johns Hopkins University, on the instructions of NASA, have created a project for a flight to the satellite of Jupiter worth $ 2 billion. According to scientists, the flight to Europe will have to be performed by the automatic space station Clipper, which should enter the orbit of the gas giant and make several flights around Europe. So scientists hope to get a global map of Jupiter's moon.
If this plan is approved, the Clipper project could be launched as early as 2021. In this case, the flight of the space station to Jupiter will take from 3 to 6 years. So far, according to Pappalardo, the implementation of the project is hampered by a lack of funds - earlier, NASA made a statement that no money was provided for the project to study the satellite of Jupiter. At the same time, the American space agency has planned to launch a new robot to Mars in 2020, which is similar to the one that is already working on Mars. At the same time, according to Pappalardo, this strategy is erroneous, since if life once existed on Mars, it disappeared several billion years ago, but life on Europe may exist even now, the scientist believes.
Europa is the sixth moon of Jupiter, its surface is composed of ice, the noticeable youth of which has led to the hypothesis that Europa may have an ocean, and possibly life. At the same time, Europe has a rather rarefied atmosphere, which consists mainly of oxygen. Jupiter's moon has already been explored several times using automatic probes. In 1979 it was Voyager and in 1989 it was Galileo.
Europe is slightly smaller in size than a single earthly satellite. At one time, Galileo, who discovered it, named the satellite in honor of the princess of Europe, who was abducted by Zeus the bull. The satellite's diameter is 3130 km, and the average density of matter is about 3 g / cm3. The surface of the satellite is covered with water ice. Apparently, under the ice crust there may be a liquid ocean 100 km thick, which covers the silicate core of the satellite. The surface of the satellite is dotted with a network of light and dark lines, which can be cracks in the ice crust that have arisen as a result of tectonic processes. Their length can reach several thousand kilometers, and their thickness exceeds 100 kilometers. At the same time, there are almost no craters on the surface of Jupiter's moon, which may indicate the youth of Europa's surface - hundreds of thousands or millions of years.
On the surface of Europa, there are no heights of more than 100 meters, and the estimate of the thickness of the crust ranges from several kilometers to several tens of kilometers. In addition, in the bowels of the satellite, it was possible to release the energy of tidal interaction, which maintains the mantle in a liquid state - an under-ice ocean, which may even be warm. Therefore, the possibility of the presence of the simplest forms of life in this ocean is quite real.
Judging by the average density of Europa, silicate rocks should be located under the liquid ocean. The photographs taken by Galileo show individual fields with irregular shapes and elongated parallel ridges and valleys that look like highways from above. In a number of places on the surface of Europa, dark spots can be seen, which are most likely deposits of matter that was carried out from under the ice.
According to the American scientist Richard Greenberg, the conditions for life on the moon of Jupiter must be sought not in the deep subglacial ocean, but in a large number of cracks. According to him, due to the tidal effect on the satellite, these cracks periodically expand and narrow to a width of about 1 meter. The moment the crack narrows, the ocean goes down, and the moment it expands, the water rises again almost to the very surface of the crack. At this time, through the cork of ice, which prevents water from reaching the surface, the sun's rays can penetrate, which carry with them the energy necessary for living organisms.
On December 7, 1995, the Galileo space station entered the orbit of Jupiter, which allowed scientists to begin unique studies of its 4 satellites: Ganymede, Io, Calypso and Europa. The performed magnetometric measurements showed that there are perceptible perturbations of the magnetic field of Jupiter near its moons Calypso and Europa. Apparently, the revealed variations in the magnetic field of the satellites were explained by the presence of an "underground" ocean, which may have the salinity characteristic of the Earth's oceans. The measurements made allow us to assert that there is an electric conductor on Europa under the visible surface, while the electric current would not be able to flow through solid ice, which is not a good conductor. At the same time, the gravitational measurements carried out by Galileo also confirmed the differentiation of the satellite's body: the presence of a solid core and a water-ice cover up to 100 km thick.
Currently, many scientists hope to send a scientific mission to Europe, however, as history shows, NASA's budgetary problems could seriously hinder these plans. This means that it is not known when exactly humanity will be able to find at least some extraterrestrial form of life in our Universe.
