It's improbable that Europe's Jupiter Icy Moons Explorer will discover life. This is why.

 

ItEurope's JUICE spacecraft will make two flybys at Jupiter's moon Europa, which might host microbial life in its subsurface ocean. (Image credit: ESA/ ATG MediaLab)

it's doubtful that we will know for sure whether life is present near the solar system's largest planet by the time Europe's Jupiter Icy Moon Explorer (JUICE) mission is over in more than ten years.

 

According to experts, life can exist anywhere in the cosmos as long as there is liquid water, an energy source, and nutrients. It is more likely for certain of Jupiter's moons than others to offer all three of these components. This week's scheduled launch of the JUICE mission by the European Space Agency intends to aid researchers in better understanding which of these moons has the necessary components to support life and which doesn't.

However, according to scientists, JUICE will not be able to identify life or its immediate traces. We won't know for sure whether life, even if it is simply microbial, exists on any of Jupiter's four major moons until the mission concludes, most likely by crashing into Ganymede, Jupiter's largest moon. What precisely is JUICE going to say, then?

Underneath the ice crust

The moon of Earth is very different from many of the solar system's large planets, including Jupiter, Saturn, and even Uranus. It's possible that these moons are home to large oceans of water, according to data from probes that have flown by them. These seas are covered by shells of ice dozens of miles thick due to the extraordinarily frigid temperatures in these remote regions of the solar system, thus looking within those water bodies is not an easy operation.

Scientists have found evidence of water geysers on some of these moons, including Saturn's moon Enceladus, which shoot water kilometres into space via ice breaches. Europa, Jupiter's tiniest moon, may also emit these plumes, according to Hubble Space Telescope measurements. These plumes suggest that there must be a heat source inside of those moons, which raises the potential that these worlds have the right circumstances for life to exist.

 

The JUICE mission's primary objective, Jupiter's largest moon Ganymede, is thought to have an ocean. The furthest, crater-riddled Callisto may also.

From a height of several hundred miles, JUICE will observe these two moons, primarily measuring the physical characteristics that can be used to establish the existence of these oceans, ascertain their depth, and acquire some understanding of their chemical makeup. Additionally, the probe will conduct two flybys of Europa, the second closest of Jupiter's four major moons. Scientists do not believe that any traces of life could be seen from so far above, despite the useful observations JUICE will make of these moons.

According to Adam Masters, senior lecturer in space and atmospheric physics at Imperial College London and a member of the team that designed one of the scientific instruments for JUICE, "if life exists on these moons, we expect it to be in the water, and that's very hard to access." We don't anticipate finding life on the surface of these moons, and it isn't now practical to drill down to where possible life may exist beneath the ice crust.

The European Space Agency's JUICE mission will explore three of Jupiter's four main moons. (Image credit: Spacecraft: ESA/ATG Medialab; Jupiter: NASA/ESA/J. Nichols (University of Leicester); Ganymede: NASA/JPL; Io: NASA/JPL/University of Arizona; Callisto and Europa: NASA/JPL/DLR)

The wrong moon for life

JUICE has a disadvantage compared to the other two missions that will examine Jupiter's moons in the early 2030s in terms of gathering proof of extraterrestrial life. That's just because Ganymede, the largest moon in the solar system and the third-farthest natural satellite of Jupiter, is JUICE's primary target. Ganymede is Mercury's size. As its emphasis is the tiny Europa, NASA's Europa Clipper mission, which will launch next year but arrive in the Jupiter system one year before JUICE, has a stronger chance of providing ground-breaking findings in that regard. Scientists believe that this moon, which is nearer Jupiter than Ganymede, has a significantly higher likelihood of having all three of the necessary conditions for the birth and continuation of life.

In Europa, behind the ice shell, if you keep diving down into the sea, you will eventually find a rocky bottom, according to evidence from prior missions, theory, and modelling. "This rock is where the nutrients come from. Additionally, we believe there must be some kind of energy source since we believe there may be water plumes on Europa, similar to those on Enceladus. But Ganymede falls into a distinct category.

The ocean on Ganymede, which is nearly 3,200 miles wide (5,200 kilometres), is probably far deeper than the water on Europa, which is much smaller. In fact, according to scientists, the ocean on Ganymede may contain 25 times as much water as the ocean on Earth. But one of the potential reasons why there might not be life on this moon is the enormous depth of this pool of water.

 

If you get far enough into Ganymede, the water is believed to turn back into ice, according to Masters. Therefore, Ganymede's ocean has an ice shell both above and below, which indicates that the water is probably not in contact with the rocky core.

Without a rocky bottom, there is no source of food. The bottom ice layer may have cracks in it, perhaps the result of some sort of thermal activity within the planet-sized moon's core, so all may not be lost for Ganymede, says Masters. Given its size and greater distance from Jupiter (665,000 miles or 1,070,000 km versus 417,000 miles or 671,000 km for Europa), Ganymede is subject to much weaker gravitational forces than Europa, which could lead to less thermal activity inside the moon and a decreased chance of life.

Scientists intend to destroy JUICE by crashing it into the moon at the end of the mission since they are so certain that there is no chance for it to come into contact with anything living near or on Ganymede's surface. By performing this maneuver, JUICE will avoid becoming an unmanageable piece of space debris that might one day collide with the more promising Europa and contaminate it with Earthly pathogens.

"There would need to be a real shake-up of knowledge about Ganymede to put it into a different category," said Masters. "If we for instance find that there isn't such a thick ice shell or if we find that there is material on the surface coming from below and that Ganymede is more like Enceladus and Europa, that might change things."

 

Europe's JUICE spacecraft will directly orbit Jupiter's largest moon Ganymede. (Image credit: ESA/ ATG MediaLab)

Reference: space.com