Europa – Europa, the fourth largest moon of Jupiter, is 3 1 22 km in diameter, almost white in color, and has an extremely smooth surface. This enigmatic planet is in many ways the exact opposite of Earth. At the same time, it is one of the ideal places to search for extraterrestrial life. These two contradictory-sounding descriptions may seem incredible, but that's the way it is. The reason why Europa may become the most important world in the solar system is hidden here.
The mystery of Europa is literally "non-Earth": it is a world carved from ice and snow, unlike Earth, which is carved from rocks. Here, icy crusts replaced drifting continents, saltwater oceans replaced Earth's mantles, and steam fountains replaced volcanoes. The streaks on the surface may have been caused by marine material spilling out to break the ice, which has a similar effect to the ridges on Earth.
From earth's point of view, Europa's structure is absurdly wrong: the hard shell is on top, and the flowing water source is below. But from the point of view of whether there is extraterrestrial life, such an arrangement may be excellent. Under its hard shell, Europa has two times the amount of liquid water in all of Earth's oceans. Astrobiologists often see water as the first element of life, and there are enough water sources on Europa. The environment below the ice line may be similar to the bottom of the Antarctic ice sheet, and there may be an active hydrothermal vent at the bottom of Europa's ocean buried deep under the ice. On Earth, these places are active places where life flourishes.
These icy substances can form strange erosion landscapes without the help of wind and rain, reshaping the shape of the planet's surface.
Mysteriously, Europa's water sometimes escapes from the hard ice. 2 0 1 At the end of 3 years, the Hubble Space Telescope recorded a huge fog eruption near Europa's south pole. The probe confirmed and developed earlier ideas about why Europa was so vibrant. Europa's orbit around Jupiter is slightly elliptical, and under Jupiter's powerful gravity, Europa is sometimes squeezed and sometimes stretched. This flexion creates a strong friction inside Europa, generating enough heat to form a warm ocean beneath Europa's cold, hard shell. The presence of fountains also suggests that europa cracks, which are squeezed everywhere, open and close periodically, causing the seawater hidden deep at the bottom to form an intermittent fountain.
If the geyser is spewing out of the earth's crust all the way out, traces of marine life should be found inside. Moreover, if the height of the fountain spray is high enough, future spacecraft can pass through it and find out whether it contains biological or chemical substances.
At the Exoplanet Review Panel meeting held at NASA's Ames Research Center in February 2017, attendees were dazzled by the reasons for this. The event is a regular forum for discussing the frozen world, known as the Exoplanet Review Panel, or OPAG for short. Here Crouching Tiger, Hidden Dragon, master gathered, some are believers in exoplanet life, some are computer experts, they share the latest scientific and technological achievements, discuss various fantastic ideas, and explore the strategic deployment of space development. With each new bit of data, their confidence increases a little, and they are more adamant that Europa is the best planet to look for extraterrestrial life, not Mars. Finding a fountain on Europa really got them excited. When The Royal Swedish Institute of Technology, Lorenz M. When Ross reported on the other end of the phone about the latest research on such fountain eruptions, people held their breath and listened eagerly.
Another equally sensational piece of news at the Exoplanet Review Panel meeting was a new discovery released five months ago: plate tectonics on Europa. This is similar to Earth, and no other planet we know of does. Plate tectonics describe the movement of the Earth's crust and the cyclical process of surface constituents moving in and out of the Earth's core. Johns Hopkins University's Applied Physics Laboratory's Louis M. Protek was one of the discoverers of such activity on Europa, a phenomenon discovered by meticulously restoring old photographs of Europa taken by Galileo during its flight around Jupiter in 1995 to 2003.
As Protek explained to me at the conference, moving the crust can accomplish two very important things: it wraps around the surface ice, along with all the compounds formed in the sun, and dives all the way down to the depths of the dark ocean, which provide vital nutrients to marine life; in addition, crustal motion can also bring seabed material to the surface so that the probe can see the traces of Europa's ocean on the surface without drilling.
Encouraged by these new discoveries, the enthusiasm for Europa has surpassed that of the Exoplanet Jury meeting. For example, as early as June 2014, NASA announced that it had begun to develop a probe to visit Europa and would launch in 2020 years to further study Europa. If successful, this exploration project could bring Europa's incredible world of ice and sea to life. At the same time, it can also help scientists better understand the overall situation of such a frozen world. Frozen moons, dwarf planets, and giant asteroids are standard in the vast outer space of the solar system, and if they can replicate Europa's model, they may have more habitable elements. Similarly, there is reason to believe that there are a large number of similar frozen planets around other stars. In summary, the Milky Way galaxy may have tens of billions of livable frozen worlds!
These surprising extrapolations seem to suggest that scientists are already beginning to understand how Europa works. If anyone thinks that, it's a big mistake. Let me sing the opposite: to a large extent, Europa is still a mysterious giant hockey ball.
Almost everything we know about Europa comes from NASA's Galileo Jupiter probe, which arrived on Jupiter in 1995. During the 8-year mission, the telescope it carried captured most of Europa, but each pixel of the photos covered about 1.6 kilometers, which was too blurry. Today, the best Mars photos can reach nearly 1 meter in pixels, and the clarity is relatively high. Elizabeth Tuttle of the Hopkins Applied Physics Laboratory promises that the pixels of NASA's upcoming Europa detector can also be raised to that level. Before that, imagine with a painting of 1. If you explore Europa with a nautical chart that you can't see anything under 6 kilometers, you can understand that scientists still have a long way to go on the road to exploring Europa.
Moreover, planetary scientists do not yet understand the basic workings of geology (perhaps "glaciology") on frozen planets. Because, ice is ice, very ice. NASA's Jet Propulsion Laboratory's Robert M. Papalado, who was in charge of the development of Europa's detector, explained to me the complexity. During the day, Europa's surface temperature is -1 3 4 ° C, and the minimum temperature at night can drop below -2 2 3 ° C, which is a veritable kingdom of ice and snow. In such an environment, water is considered a mineral, and ice is roughly as hard as concrete. As a result, the fractures, faults, and crushing of these ices are very similar to rocks. However, unlike rocks, these surface ices can be directly sublimated from solid to gaseous state even if frozen very firmly. Icy matter boils in dark and warm areas and solidifies in bright and cold areas, thus forming strange landscapes and reshaping the shape of the planet's surface without the help of wind and rain.
In addition, there are other strange things happening on Europa. Jupiter has a large, powerful magnetic field that emits powerful radiation from its moons: an average daily radiation of 5 00 rehms. After exposure to this dose of radiation, people will feel uncomfortable after 1 hour, and after 24 hours, they will die from radiation. Radiation of this intensity can instantly break down any organic compound, making it more difficult for us to find life. Radiation also produces a variety of complex chemicals. A recent experiment conducted by the Jet Propulsion Laboratory showed that the color of the stripes on Europa was caused by sea salt reflecting sunlight. These compounds, along with various other molecules, as well as organic minerals brought about by comet impacts, can return to the bottom of the ocean with circulation. There, any life form can be well protected, acting as a source of energy for life.
If there is extraterrestrial life swimming in Europa's ocean, but no one can see it. So, does it really exist?
Europa's ice shell is another vast mysterious place. Papalado pointed out that in the frozen world, water acts as magma and hot rock deep below the surface, but ice is different from rock after all. The ice under high pressure is warm and soft, slush-like, and flows slowly. With an ice crust thickness of 16 km to 24 km (the actual thickness may be larger or smaller than this number, which is one of the mysteries that need to be explored in the next Europa mission), there may be an unusually complex cyclic pattern throughout the ice crust. In the ice crust there are lakes formed by liquid water, and lakes are separated from the lower ocean by the ice crust. Therefore, it is likely that the surface fountains do not originate directly from the subglacial ocean, but from these transit stations , lakes , very similar to Antarctica's unexplored Lake Vostok.
At this meeting of the Exoplanet Jury, the seemingly narrow topic of the cycle of ice has led to interesting discussions about the existence of life on Europa and the possibility of life in a large number of such frozen worlds. Spears of Georgia Tech Schmidt was puzzled by the existence of geological (glacial) activity throughout Europa's ice crust. If matter can't circulate between surfaces and oceans, Europa will be a sealed world where life won't be able to get any fresh chemicals from the surface as a food source.
Even if life could survive in these conditions, we would never be able to see them unless a huge hole was cut through the ice. At the meeting of the exoplanet review panel, several researchers believed that the situation required a lander, and others strongly recommended firing a percussion ball, using the impact force to loosen Europa's surface, thereby collecting possible microorganisms.
As for Europa's ocean, its depth may be beyond your imagination. As the experiments have shown, if the stripes on Europa's surface are indeed formed by salt, it suggests that the interaction between seawaters is very strong inside the mineral-rich ocean. The energy of this interaction stems from hydrothermal vents formed by heat action inside Europa that can provide energy for the continuation of life on Europa, just as they did on Earth. But what is the total hydrothermal volume? Are acidity and salinity conducive to the survival of life? How much organic matter is there? Scientists use these provocative questions to make each other difficult, but they can't give answers.
When (or can we) find answers to these questions depends largely on how much of the inner world we can see from outside Europa. The conversation at the Exoplanet Jury meeting is somewhat similar to the argument about existence in a university classroom: If there is extraterrestrial life swimming in Europa's ocean, but no one can see it, does it really exist?
Europa's loyalists have been waiting for a long time, hoping that one day new exploration missions will sweep away these mysteries and controversies, or at least end them with solid data. However, this wait is more of a tug-of-war between optimists and pessimists. NASA adopted the Europa orbiter program in 19999, but the program was terminated in 2002. Since then, NASA has prepared a more ambitious plan to launch a nuclear-powered "Jupiter Ice-Moon Orbiter." This incredible plan was first postponed and finally terminated in 2006. While the Europeans were at the forefront of the project areas for which they were responsible, a joint venture with ESA did not keep up, and they had planned to launch a probe to Jupiter's other frozen moon, Europa, in 2030.
The Exoplanet Review Panel, established in 2004, is a defense organization that supports frozen satellites and aims to give those frozen satellites the attention they deserve. At present, things seem to be going relatively smoothly, Congress has passed the funding plan for the Europa probe project, NASA has customized a number of equipment, and has designated relevant researchers to be responsible.
Europa's probe may include a lander. Both the MPs and the Director-General of ESA supported this. Adam Steltz — the chief engineer in charge of the Curiosity landing vehicle — assured me that it would not be difficult to design a small rocket-equipped probe to achieve a soft landing on Europa on a technical level. Moreover, the detector can even drill on Europa's surface to look for any possible organic compounds under the ice that are not damaged by radiation.
The researchers on the exoplanet review team regretfully claim that the handsome Europa submarine cannot be seen, and NASA has shown the project on its webpage "Future Mission Concept". Diving the probe into Lake Vostok on Earth has been difficult, not to mention the remote control of drilling holes in Europa's ice layer as thick as 16 km (or even thicker) to find an unknown ocean. The difficulties are unimaginable, and NASA's budget for the program is not optimistic.
Never mind. If NASA's current Europa program releases a lot of information about how the frozen world works and how similar they are in supporting life, and the results are as most scientists expect — and as I strongly expect — it will spark enthusiasm for research on Enceladus, Enceladus, and jupiter's other moons. It would also change people's plans to look for habitable planets around other stars. At present, astronauts are mostly focused on finding other terrestrial planets, but these operations may have gone astray in the first place. Because most life in the universe is probably safely locked under the ice, and most of it cannot be detected by the outside world.
Whether or not there is extraterrestrial organism on Europa, it will tell us what life might take and what the worlds they might have looked like.