A few days ago, the
Juno
probe
NASA's crew flew by Ganymede, the largest moon in the Solar System, which orbits Jupiter and has its own magnetic field powered by a molten metal core hidden under a permanent ice sheet more than 500 miles thick. The probe has made the closest flyby of this icy giant in the last 21 years and has taken some of the highest resolution images ever made of this satellite, including its far side. Two black and white images portray a world full of craters and deep crevices under which an ocean of liquid water is hidden, probably trapped between two thick layers of ice. This remote and violent environment of Jupiter's moons is probably the best place to find extraterrestrial life in the Solar System.
"If we make the right decisions, we may be able to confirm the existence of life on one of these moons in about 20 years," says Lucas Paganini, an Argentine engineer born in Mendoza 41 years ago who is a leader in the exploration of the Solar System at the headquarters. NASA general and program scientist for the
Juno
mission
.
The son of a mechanical engineer and a specialist in psychology and education, Paganini defines himself as a “middle-class neighborhood boy”.
He became interested in the study of chemical compounds in the Earth's atmosphere while studying telecommunications engineering in his native country and later specialized in the analysis of atmospheres of other planets.
The Argentine engineer and scientist Lucas Paganini.LP
Juno
explores one of the most dangerous places in our cosmic neighborhood. Jupiter is the largest planet in the Solar System. Its inner layers act like a gigantic dynamo that generate enormous radiation of charged particles that constantly hit the titanium armor of the ship. Paganini recalls that the primary objective of the mission was to focus on the study of Jupiter and fly over its poles for the first time, where it has photographed storms of more than 1,400 kilometers in diameter whose scourge can last for years, even centuries. Completed its "official" mission, NASA has approved an extension of its operations until September 2025, if the veteran
Juno
is able to hold out until then.
"It is very interesting to see how this radiation begins to affect the instruments on board," Paganini emphasizes. "It may mean that we lose some of them, but it is essential knowledge to design our next missions," he adds.
The spacecraft plans one more flyby of Ganymede on July 21 and then turn its cameras toward Europa, another Jupiter satellite much more conducive to searching for life. The first time humanity saw Europa up close it was thanks to the
Voyager
spacecraft
, which 40 years ago showed its icy surface covered in reddish streaks like a huge bloodshot eye. Many years later, Paganini's team used one of the largest optical telescopes on Earth located on top of a Hawaiian volcano to analyze the gases present on this moon. In a historical study they confirmed that there was water vapor and that it could come from the saline ocean hidden behind a thick layer of ice several kilometers thick.
NASA image of Jupiter's moon Europa, taken by the Galileo probe in the 1990s.
In Europe, the subterranean ocean can meet all the conditions for living beings to inhabit: water in contact with rocks, energy, compounds essential for life and time.
Jupiter was the first planet to form after the birth of the Sun about 5 billion years ago.
Europa and Ganymede appeared shortly after from the rubble surrounding the giant planet.
"We really know very little about the history of how Europa and the rest of the Jovian moons formed," Scott Bolton,
Juno's
chief scientist, told this newspaper
.
“What we do know is that this environment is like a miniature solar system, where Jupiter's gravitational force causes Europa to deform and this generates heat inside.
There is also the possibility that in the inner ocean there are hydrothermal vents, places that on Earth are full of microbes despite being in complete darkness ”, he highlights.
The American ship
It plans to fly over Europe in 2022 at just 320 kilometers from the surface. The last time a spacecraft passed this close to this moon was 21 years ago during the
Galileo
mission
.
Juno
plans to map the frozen surface to compare its much more detailed images with those of its predecessor, and to find out if there have been changes that could indicate hydrological processes.
"Until recently," Bolton continues, "it was thought that the only habitable zone in the solar system where there could be liquid water was around the orbit of the Earth." "The fact that we have evidence of the existence of an ocean in Europe and the detection of water opens our eyes," he adds. The only place that could rival Europa in the search for extraterrestrial life would be Enceladus, one of Saturn's moons, where spectacular fumaroles have been discovered that come out of the ice spewing water vapor and particles, who knows if also microorganisms.
One of
Juno's
instruments
shoots radio signals to the surface and allows us to see the internal composition of the ice, explains Paganini. “Depending on the conditions, it could analyze the first 20 kilometers of thickness. We do not know how thick the ice sheet is in Europe, but it is estimated that it is at least five kilometers long and could reach more than 20. What we do think is that there may be small deposits of liquid water in shallower areas and that these they could be connected to the lower ocean by a network of natural aqueducts. In this way, there may be one of these deposits just 200 meters from the surface. It would be much easier in the future to try to reach the surface at this point, drill and get to liquid water, ”he describes.
Juno's
instruments
can search for water in a second way: by detecting fumaroles, a kind of geysers through which the water from the bottom reaches the surface, explains the engineer.
"It is a window to the interior without the need to drill," he adds.
What this mission discovers in these last years of life will be key for the next ones that NASA is already planning.
The first will be
Europa Clipper
, an orbiter that will take off in 2024 and arrive at Jupiter in 2030. The next step would be
Europa Lander
, a mission that is not yet approved and that would be the first to land on this moon. "It would bring a robotic arm to collect ice and use its onboard instruments to measure the mass, analyze it with ultraviolet ray spectrometers and do seismic studies," Paganini explains. For much later, there would be another mission capable of piercing the ice beyond the first meter thick, although it may not be necessary, warns the engineer. “Scientific instruments capable of seeing infrared or ultraviolet light could make indirect measurements that would allow us to assess whether the most plausible explanation for what we see is the existence of organisms. It is as if you hear that a car is coming without having to see it ”, Paganini details
The hypothetical life of the Jovian moons would be unicellular, "as there was on our planet billions of years ago," says Paganini.
"Maybe there is something more complex, like water bear-like extremophiles, which have great resistance to radiation," he adds.
Juno
plans to visit another hellish but exciting moon: Io, a satellite full of volcanoes and lava lakes, the place with the most volcanism in the Solar System.
If it survives its last years of life, the ship will be programmed to commit suicide.
It will plunge into Jupiter's atmosphere until the pressure bursts it completely.
The reason for this end is to protect the planet's moons and the life they may harbor at all costs.
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