Search for life extends to Jupiter’s moons
Is there life in outer space? Does life exist on other planets? Often, the question centers on Mars, one of our neighbors in the solar system. Like Earth, Mars is a rocky planet with moderate temperatures and an atmosphere that could at least plausibly sustain life. There’s evidence that there may have been water on Mars in the past.
In English, we have a word for a creature from Mars: it’s a Martian. There is no such word for life forms on any other celestial body.
But now, the search for life is moving beyond Mars, farther out in the solar system. Jupiter has 95 moons, plus thousands of smaller objects orbiting it. Its four largest moons are known as Galilean moons; they were discovered in 1610 by Italian astronomer Galileo Galilei. Europa is one of these moons.
In the late 1990s and early 2000s, a robotic space mission orbited Jupiter. That mission’s findings suggest that there might be a vast saltwater ocean buried under a layer of ice on Europa. The Hubble Space Telescope showed what appeared to be plumes of water vapor escaping Europa’s surface.
Where there might be water, there might be life. And a new mission to space aims to find out more about conditions on Europa. In October 2024, NASA, America’s space agency, launched a spacecraft called the Europa Clipper. Its mission is to orbit Jupiter and study Europa, the moon.
The Clipper is equipped with high-resolution cameras to take photographs. It has radar, which will search for water beneath the surface. And it has other instruments, which will measure temperature and the composition of Europa’s thin atmosphere. The hope is that the mission will produce a detailed map of the surface and more clues about potential life.
The mission will be complicated by the fact that there are high levels of radiation around Europa—levels so high , they can damage the observational equipment onboard the Clipper. For that reason, the Clipper will orbit Jupiter—it won’t orbit Europa itself —and it will take long loops around the Red Planet, coming close to Europa only fifty times in the whole mission.
It’s a long shot, but there are scientific reasons to think life might be possible on Europa. First, life requires water, an energy source, and life-sustaining chemicals. Europa might have an ocean—in fact, the ocean might be bigger than the Earth’s oceans. There are lots of chemicals on Europa, many of them sourced from Jupiter.
What about an energy source? On Earth, the energy source is almost always the sun, directly or indirectly. On Europa, it would be more complicated. Jupiter gets only about four percent as much energy from the sun as Earth does, so astronomers suspect that there’s not enough solar energy to sustain life.
But there are two other possibilities. First, the gases on Jupiter itself might be a source of energy for ocean organisms on its moon Europa. And second, there are some very few deep ocean organisms on Earth that survive off chemical energy, independent of solar energy. So it’s possible that a different energy source could sustain life in Europa’s frigid oceans.
Speaking of frigid: just how cold is Europa? The surface temperature is minus 160 degrees Celsius. That’s cold! Here on Earth, water freezes at 0 degrees Celsius, but the freezing point depends on the pressure. On Europa, the frozen, surface layer of water could put so much pressure on lower layers that a liquid ocean could exist at temperatures well below zero degrees. It would take a hardy creature to survive in those conditions.
Jeff’s take
So, a Martian is a creature from Mars. What would we call a creature that lives on Europa? Just ponder that for a while.
It’s understandable if you’re anxious for results, but you’ll have to wait a while. The Clipper won’t even reach Jupiter’s orbit until 2030. It takes about five years to get there.
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