A minimal set of knowledge about the latest studies of the solar system and exoplanets that will help you understand the topic
Everyone is worried about the question "Is there life on other planets?" While fundamental research in astronomy and biology is underway, the media continue to publish articles with the headlines "Life Discovered on N". We have selected the most important information about the latest discoveries in this area so that you can critically read the news feed.
Where life can exist
So far we know only one point in the Universe where life exists - this is the Earth. We are looking for conditions under which protein life can exist. This very narrow range was called the habitable zone. The habitable zone, which in English is called the habitable zone, is an area in space with the most favorable conditions for life of the terrestrial type. Suitability for life is determined by the following factors: the presence of water in liquid form, a sufficiently dense atmosphere, chemical diversity (simple and complex molecules based on H, C, N, O, S, and P) and the presence of a star that brings the required amount of energy.
Astrophysicists simply look for planets and then determine if they are in the habitable zone. From astronomical observations, you can see where this planet is located, where its orbit is. If in the habitable zone, then immediately interest in this planet increases. Next, you need to study this planet in other aspects: atmosphere, chemical diversity, the presence of water and the source of heat. This already slightly takes us out of the parentheses of the concept of "potential". But the main problem is that all these stars are very far away.
Looking for traces of life in other stellar systems
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Kepler is an apparatus that NASA launched in 2009 specifically to search for exoplanets. Exoplanets are understood to be all planets outside our solar system. 2015 marks 20 years since the first solar-type exoplanet was discovered. And, of course, one of the most exciting prospects has always been the opportunity to find habitable planets, traces of life from other stars. They are looking for biomarkers - these are chemical compounds of biological origin. The main biomarker on Earth, for example, is the presence of oxygen in the atmosphere.
Kepler-186
On April 17, 2014, NASA announced the discovery of an exoplanet in the Kepler-186 red dwarf planetary system in the constellation Cygnus. Kepler-186f falls into the habitable zone, and if there is an atmosphere (and we don't know this), there may be liquid water there. But the planet does not rotate around a star like our Sun, which is a yellow dwarf, but around a red dwarf, which is colder. Based on this, we assume that it is unlikely that there can be suitable conditions for life. Red dwarfs are highly volatile from a magnetic point of view, with frequent flares on these stars causing X-rays that can harm nascent life.
Kepler-452b
In July 2015, NASA announced the discovery of another exoplanet by the Kepler astronomical satellite, named Kepler-452b. Planets in the habitable zone have been found before, primarily gas giants, which may or may not have habitable satellites. They also found lands. After the NASA conference in July 2015, many media outlets wrote that there is liquid water on this planet, or must be. In fact, we do not know this, and, moreover, neither the planet nor the water owes anything to anyone. So, in our system, Mars is also in the habitable zone, and there was liquid water on it, but now it is a cold, lifeless world.
Water on Mars
On September 28, 2015, the US National Space Agency announced proof of the presence of liquid water on Mars. Before that, we knew that Mars has water in the form of ice (solid state) and in the form of vapor (gaseous state). Perchlorates, traces of which were discovered by NASA researchers on the surface of Mars, are compounds of a salt of perchloric acid with various metals. When they are hydrated, that is, they become wet, water can exist even at very low temperatures. When the temperature rises above -23 degrees, hydration or wetting of perchlorates occurs in such a hypersaline form. This wet, flowing salt flows from the slopes on the surface of Mars and leaves traces - river beds on the hillsides.
Perchlorates are in principle very toxic: they are compounds of perchloric acid. But there are bacteria on Earth that can live at low perchlorate concentrations. Of course, these bacteria, now placed in a perchlorate hydrosolution on Mars, cannot survive. But we now have a space for imagination: using those metabolic chains, their molecules and features of the biochemical cycle, we will design bacteria that can live under such conditions.
Proxima b
In August 2016, confirmation was received of the presence of the planet, dubbed Proxima b, near the star Proxima Centauri. It is the closest exoplanet to us (the star Proxima Centauri is 4.2 light years away from us) and, possibly, the closest celestial body to the solar system, on which life can exist.
Image: The alleged landscape of Proxima Centauri b as seen by an artist (ESO / M. Kornmesser)
A number of scientific teams from the European Southern Observatory (ESO) have observed the star since 2012. Planet Proxima b found itself in the habitable zone of its star and relatively close to Earth. If we, the planet Earth, are 1 astronomical unit from our star, then this new planet is 0.05, that is, 200 times closer. But the star shines fainter, it is colder, and already at such distances it falls into the so-called zone of tidal capture. As the Earth captured the Moon and they rotate together, the same situation is here. But at the same time, one side of the planet is hot, and the other is cold. There are such climatic conditions, a system of winds that exchanges heat between the heated part and the dark part, and on the borders of these hemispheres there can be quite favorable conditions for life.
Three planets in the TRAPPIST-1 system
On February 22, 2017, seven planets similar in size and mass to Earth were found in the TRAPPIST-1 star system. Three planets at once found themselves in the habitable zone, and not just by formal falling into the required range of distances - the possibility of the presence of liquid water was confirmed by modeling their atmospheres. On the other hand, it must be admitted that there are no even preconditions for the discovery of extraterrestrial life: there are several dampening moments. First, the TRAPPIST-1 star belongs to red dwarfs, and these stars are often characterized by strong flare activity (although this may not apply to this particular dwarf). Observations indicate that activity decreases with age, and TRAPPIST-1 may be an older and less active subject. Secondly, the rotation of all seven planets is probably synchronized,that is, they are always turned to their star by the same side, so that they do not have a change of day and night. We cannot yet say how critical or uncritical this is for the origin of life.
Saturn's moon Enceladus
In May 2017, all news outlets wrote that life was discovered on the moon of Saturn. But, in fact, scientists have found another confirmation of research that took decades. Enceladus is one of the inner satellites of the giant planet in our solar system. The satellite itself is small: its diameter is 500 km (this is something the size of the Moscow region). Oceans were discovered under the ice on the satellite. The satellite has hot springs, a lot of water, a rich chemical diversity in this area, and these are almost all conditions for the emergence of life. One of the theories of the origin of life on Earth says that life could arise at the bottom of the ocean, where there are the same thermal springs (black smokers). This small unique object has a semblance of a system that is present on Earth. Now both astrobiologists and astrophysicists believe that this,perhaps the second place in the solar system where life could arise. The object will be a hot spot in solar system exploration in the near future.