Europe: the hope of astrobiology

The smallest of the four Galilean moons of Jupiter, which has attracted the attention of scientists in many specialties for years, will become a real ... star in the third decade of our century. MEDIA. Probes will fly towards Europa, which will carefully study this extraordinary moon and try to study its insides. First things first.

Opening

Europa, like the other three major moons of Jupiter, was discovered on January 8, 1610. This was done by Galileo of the University of Padua using a 20x refractor. In fact, he had observed Europa the day before, but due to a slight increase in the refractor, he treated Io and Europa as one object, separating them only the next night. Space Exploration The first probes to fly near Europa were Pioneer 10 and 11 - but the photographs taken by them were of relatively poor quality. Scientists were only interested in the flight of the Voyager probes through the Jupiter system in 1979. Photographs of Europa sent to Earth then showed its icy surface. Even then, some scientists began to consider the possibility of the existence of an ocean under the surface of the moon.

In 1995, the Galileo spacecraft entered orbit around Jupiter, launching a scientific mission in which it has repeatedly explored Jupiter's moons over the past eight years and made the most accurate observations to date. New, much more detailed photographs of Europa show cracks in the ice crust that appear to have been flooded from below. On the other hand, in other regions, the impression was that the earth's crust had cracked, released some subsurface water, and refrozen. Unfortunately, the Galileo spacecraft had problems with the antenna and data transmission to Earth. As a result, many of them never reached us, and some parts of the Moon were not photographed at all. 

Photo of Europa from the Galileo spacecraft

The last probe to approach Europe is New Horizons. She took pictures in 2007 on her way to Pluto on July 14, 2015. Nearly two years ago, scientists working with data from the Hubble Space Telescope noticed a large cloud of water vapor over the southern region of Europe. This suggests that Liquid water can seep through the Earth's crust and break away from the Moon's surface when a geyser erupts. Either there are reservoirs under the surface, or there are very deep cracks in the ice.

Ocean

Europa is attracting the attention of scientists because it is widely believed to be under the surface of this moon. layer of liquid water. Despite its distance from the Sun, it may be liquid due to heating due to tidal deformations caused by Jupiter's proximity.

The first assumptions about the existence of an ocean in Europe appeared in purely theoretical works, which took into account the slightly eccentric orbit of the Moon and orbital resonance with other Galilean moons. Even more evidence has reached Earth in images from Voyager and Galileo showing chaotic regions on Europa's surface. Some scientists believe that the subsurface ocean comes to the surface in this area. However, this is still a controversial theory, with most geologists leaning toward the "thick ice" theory, in which the subsurface ocean rarely or never interacts directly with the surface. According to scientists, the outer ice crust is 10-30 km thick, including the so-called warm ice, and the ocean depth can reach 100 km. If these numbers are correct, Europe could be the end twice as much water as on Earth!

Cross-section of the interior of Europa, showing the ice crust, subsurface ocean, and rocky core.

Ever since the Voyager missions passed near Europa 36 years ago, scientists have been trying to understand the composition of the red-brown material that fills cracks and other geologically young regions on the Moon's surface. Spectrographic studies show that these areas may be rich in salts (for example, magnesium sulfate), which can accumulate there due to the evaporation of water flowing to the surface. However, these types of salts are either colorless or white, so some other material must be responsible for the reddish color. In May of this year, a group of scientists from the Jet Propulsion Laboratory reported on experiments in which they were able to recreate the red-brown color of the stripes. They can form when ocean salts reach the surface and are then bleached by Jupiter's strong radiation.

Geysers

In Europe, there may be periodic geysers with a column of water up to 200 km above the surface! They appear when the Moon is furthest from Jupiter in its orbit and disappear as it approaches. This pattern is consistent with the predictions of tidal forcing models. It is worth noting that the tidal influence of Jupiter on Europe is 1 thousand times greater than from the Earth to the Moon. The intensity of water eruptions in Europe is estimated at 7000 kg/s.

Life in Europe

Europa seems to be one of the best places in the solar system for extraterrestrial life seekers. It can exist in the ocean below the icy surface - in an environment similar to the depths of the Earth's ocean, especially near hydrothermal vents. In May 2015, scientists announced that ocean salts could coat some of the geological structures in Europe. This may indicate an interaction between the ocean and the ocean floor, and such an active interaction could be critical for the emergence of life.

The thermal energy of the tides stimulates active geological processes in the bowels of Europe. Like the Earth, the satellite of Jupiter can have an internal source of energy from radioactive decay, but the amount of this energy will be several times less than the energy of the tidal force. Tidal force alone is not enough to support life in such a large ocean, but scientists believe that it can exist, for example, at the interface between the ocean and the ice crust.

Recent studies also show the existence of lakes completely enclosed in Europa's ice crust. They differ from the liquid ocean much lower. If these reports are confirmed, this would be another potential place to look for life.

The future of intelligence

It is thanks to the presence of water, which gives a chance to find life beyond the Earth, that missions to explore this mysterious globe have long been proposed. Currently, the European Space Agency (ESA) is preparing the JuICE (Jupiter Icy Moon Explorer) mission, which will explore Europa, Ganymede and Callisto, and the US NASA is preparing a multiple-fly Europa mission focused exclusively on exploring Europa during a series of flights around it.

ESA project

The selection of the JuICE mission as part of the Cosmic Vision science program was announced on May 2, 2012. The probe is scheduled to launch into space in 2022 on an Ariane 5 launch vehicle. It will arrive in the Jupiter system in 2030. After completion of the Jupiter maneuvers and "Jupiter" in 2033, other satellites will enter orbit around Ganymede, which will be most carefully studied during this mission.

Artist's vision of the Jupiter Icy Moon Explorer (ESA) mission

In the case of Europa, the JuICE probe will focus on the study of chemicals critical to the origin of life (including organic compounds), as well as attempts to unravel the mystery of the formation of characteristic formations on the surface of the Moon and the Moon. the chemical composition of the red substance that fills the cracks on the surface. In addition, it will perform radar measurements of the thickness of the upper ice sheet.

NASA project

In the case of a mission designed by NASA, we are dealing with a task that is entirely focused on the study of Europe. Subsequent missions to this moon have been planned since the days of the Galileo spacecraft. Initial proposals - such as the Europa Orbiter or Jupiter Icy Moons Orbiter - included launching a probe into orbit around Europa, but due to the strong radiation from Jupiter's magnetosphere, this idea was abandoned. The currently planned mission includes launching the probe into orbit around Jupiter and making a series of 45 close flybys near Europa at altitudes from 25 to 2700 km above the surface. Due to this, the probe will be exposed to harmful radiation much less time. During each cruise, he will explore different areas of the surface, analyzing in detail the topography and thickness of the ice crust. Interestingly, the probe can pass through a water vapor geyser at low altitude. This will allow a sample of the subsurface ocean to be explored without having to land on the surface and drill into the ice sheet.

The objectives of the mission include: confirmation of the existence and characterization of waters present under the ice crust and processes occurring at the boundary of the crust and ocean, the study of surface formations with an emphasis on places where recent or current geological activity is visible, and analysis of the chemical composition at the surface.

The launch of the probe is scheduled for 2022-2025, depending on the progress of work on the SLS system. The basic plan is to launch it on an Atlas V 551 rocket. The spacecraft will then use the gravity of Venus and Earth to reach Jupiter six years after launch. In the event that NASA finishes work on the SLS (Space Launch System), this rocket could be used to launch a spacecraft into space and point it straight towards Jupiter. Thanks to this, it would be possible to halve the flight time.