Jupiter’s moon sheltering an icy ocean | Final count to Europe

After 20 years of delay, NASA should finally set course for Europe on Thursday. This moon of Jupiter shelters beneath its surface an icy ocean where microbial life could flourish.

Extraterrestrial life specialists have been “dreaming for 20 years” of a mission like Europa Clipper, which is due to take off on Thursday and fly over the surface of Europa 49 times, coming within 25 km of it. At least that’s what the director of NASA’s prestigious Jet Propulsion Laboratory (JPL), Laurie Leshin, said during a press conference on Europa Clipper in September.

This dream was born from the probe’s observations Galileowhich explored the Jovian system (system which brings together the gas giant planet Jupiter and all the objects around it) between 1995 and 2003. Galileo confirmed summary observations of the two probes Voyager of 1979 concerning the stripes on its icy surface, which only the presence of an underground ocean could explain.

Europa Clipper will analyze gases escaping from Europe, notably through geysers observed for the first time by the space telescope Hubble in 2013. “The essential ingredients for life most likely exist on Europa,” said the mission’s deputy scientific director, Bonnie Buratti, during the press conference. We’re going to look for these organic chemical molecules. »

M^me Buratti even mentioned the detection, unlikely, according to her, of “dream molecules”, DNA or RNA, by the probe.

Life on Europa would be located around potential hydrothermal vents, like those fed by terrestrial magma at the bottom of our oceans.

It took more than 10 years for scientists to convince NASA of the relevance of such a mission, 10 years to prepare it, and it will take almost 7 years forEuropa Clipper reaches the smallest of Jupiter’s four largest moons, summarized M^me Fur.

So far, only nine overflights of Europe have been carried out, by seven probes. The closest flyby, at 320 km, was carried out by Juno in 2022. The European probe JUICE (Jupiter’s Icy Moon Explorer) will make two flybys of Europa around the same time asEuropa Clipper.

The fascination with life in Europe is not new. At the end of his book 2010 : Odyssey Twothe sequel to the famous 2001 directed by Stanley Kubrick, Arthur C. Clark concludes with this warning from the extraterrestrials to Earthlings: “All these worlds are yours except Europe. Do not attempt to land there. »

Watch the trailer for 2010 (in English)

Transistors

Takeoff is scheduled for October 10, with a launch window extending from early September to November 6, in the event of a technical glitch or unfavorable weather.

The Europa Clipper team ran into trouble last spring, when tests of the probe’s transistors revealed that they could be vulnerable to the extreme radiation generated by the giant planet, which is 20,000 times more intense than in Earth orbit.

NASA only publicly revealed this problem earlier this summer. “We reassessed the risks posed by these transistors which were wearing out more quickly than expected,” explained the head of mission, Jordan Evans, at the press conference. We went circuit by circuit and determined that there was a margin of safety to complete the primary mission. »

This primary mission must last three years. Very often, space probes last longer than expected and their mission lengthens accordingly.

The mission of Galileofor example, was supposed to last two years, but ended up lasting four times as long.

Every timeEuropa Clipper will approach Jupiter to fly over Europa, it will be exposed to “the equivalent of several million X-ray examinations on humans”, underlined Mr. Evans.

“European” oceans…

The probe’s nine scientific instruments will estimate the thickness of Europa’s icy crust, whose craters and fissures are relatively recent, showing likely interaction with a subterranean ocean.

This “deluge of scientific information”, in the words of M^me Buratti, will make it possible in particular to see if the underground ocean of Europa modifies its gravitational field. Europa Clipper will be able to measure distortions of just a few meters, a sign of this oceanic gravitational influence.

The subterranean ocean could be 100 km deep, and Europa’s icy crust would extend 5 to 100 km, according to NASA. The maximum surface temperature is -160°C, at the equator.

The ocean could be warmed by the heat caused by the attraction that Jupiter exerts on Europa, which is 1000 times greater than that exerted by Earth on the Moon.

…and Antarctic lakes

Europa Clipper involves geophysicists specializing in the exploration of underground lakes in Antarctica and the Arctic.

These oceans have been explored by underwater robots, notably Lake Whillans, which lies 800 meters below the Antarctic ice sheet. Their data makes it possible to model the Europa ocean and its interaction with the ice surface.

“Europe’s analogues in Antarctica and the Arctic are very important to the mission,” says Natalie Wolfenbarger, a geophysicist at Stanford University who works on Europe’s radar.Europa Clipper. “We can, for example, compare the radar signals from Antarctic underground lakes, or measure them remotely, and on site molecules from these lakes which are found on the surface. »

The radar ofEuropa Clipper can reach depths of tens of kilometers.

Such a robot has been proposed for Europe, according to M^me Wolfenbarger. “It would be a probe that would melt the ice in its path. Communication would be by cable or waves. »

For the moment a lander, Europe Countriesis being considered by NASA. But it was excluded from the 2023-2032 program in favor of probes towards Uranus and towards Enceladus, a moon of Saturn.

Ganymede

To avoid contaminating the surface of Europa, Europa Clipper will crash into Ganymede, Jupiter’s largest moon.

Ganymede also has an icy surface and an underground ocean. It is also the only moon in the solar system to have its own magnetic field. It could also support life, but the pressure at the base of its ocean could be too great for hydrothermal vents to exist.

Solar panels

Europa Clipper will break a record for solar panels for space probes. They will extend over 30 meters, to capture the faint light of the Sun at this distance, 5.2 times that between the Earth and our star.

The probe Juno held the previous record, with three nine-meter panels.