While there have been more than a few predictions made as to when we will discover life on a planet orbiting some far-flung star, what is only occasionally predicted is whether or not we will find life on one of the other worlds in our very own solar system. While some think that Mars might still support some form of microbial life, the worlds that hold a greater potential of being abodes to extraterrestrial life are the moons of the outer solar system.
On Earth, the primary source of energy is the Sun; this isn’t the case for moons circling the gas giants Jupiter and Saturn. Out there, chemical reactions are possibly the most important source of energy. No place is the likelihood of alien life beyond Earth, but in our own solar system, more possible than on Jupiter’s moon Europa. Europa is covered in ice, and analysis from NASA’s Galileo spacecraft has shown that Europa could sport an ocean (singular) that is greater than all the oceans of Earth—combined.
A recently released paper, published online in the Astrophysical Journal Letters and penned by a NASA researcher, states that hydrogen peroxide, which is rich in the icy Europan crust, could be mixing with the ocean below. This could serve as a potential energy source for alien life forms that dwell in the waters below.
“The Galileo measurements gave us tantalizing hints of what might be happening all over the surface of Europa, and we’ve now been able to quantify that with our Keck telescope observations,” said Mike Brown of the California Institute of Technology. “What we still don’t know is how the surface and the ocean mix, which would provide a mechanism for any life to use the peroxide.”
Brown’s team used the Keck II Telescope, located on Mauna Kea, Hawaii, in 2011. What they discovered was that the concentration of peroxide is found in the “leading” side of Europa, in its orbit around Jupiter. The abundance of peroxide is some 0.12 percent relative to the amount of water. By comparison, the amount of peroxide in the side of Europa that is facing away from Jupiter is virtually zero. What does peroxide mean in terms of life on Europa?
“At Europa, abundant compounds like peroxide could help to satisfy the chemical energy requirement needed for life within the ocean, if the peroxide is mixed into the ocean,” said Kevin Hand with NASA’s Jet Propulsion Laboratory and the paper’s lead author.
Researchers looking into the possibility of life on Europa believe that hydrogen peroxide is a key ingredient to making life even possible on Europa. The reason being is that, when mixed with liquid water, hydrogen peroxide decays into oxygen.
Scientists once thought that these outer moons were too cold to support life. It was later discovered that gravitational forces push and pull on these moons, kneading them like dough—and, in doing so, heating them. On Earth, underwater volcanoes known as “black smokers” have been discovered on the ocean floor, far from the Sun and yet teeming with strange forms of life. It is proposed that this might be similar to what is happening on Europa.
“Life as we know it needs liquid water—elements like carbon, nitrogen, phosphorus, and sulfur—and it needs some form of chemical or light energy to get the business of life done,” said Kevin Hand, the paper’s lead author, based at NASA’s Jet Propulsion Laboratory. “Europa has the liquid water and elements, and we think that compounds like peroxide might be an important part of the energy requirement. The availability of oxidants like peroxide on Earth was a critical part of the rise of complex, multicellular life.”
Europa is not alone in possibly having life. Researchers discovered that Saturn’s moon Titan, long considered to resemble a pre-biotic Earth, has something consuming both hydrogen and acetylene. It has yet to be determined what is causing this to take place; it could be a non-biological process occurring on the moon. Now, while having a life form consume acetylene might seem strange on the hydrological-based Earth, it makes perfect sense for a methane-based life form on a world with a methalogical-based cycle like Titan. One thing is for certain: any creatures discovered on these worlds will likely bear little resemblance to what we have here on Earth.
On Earth, there are creatures known as extremophiles, but don’t expect to see them—unless you have a microscope. These creatures live in locations that would prove the death of most other life here on Earth (nuclear reactors, jet fuel, etc.). Most of them are not complex life forms, and are microbial in nature.
NASA has missions planned for Mars, but the European Space Agency (ESA) is eyeing the icy worlds circling Jupiter for its planned “JUICE” (Jupiter Icy Moons Explorer) mission. The probe will take a closer look at Jupiter’s moons—Europa, Ganymede, and Callisto. It is slated to be launched in 2022 and could fund further evidence that these distant, frozen worlds are teeming with life.
If we do discover that Earth is not the only home for life in this solar system, it could fundamentally change how we look at life throughout the cosmos. If life arose twice (perhaps more) around one star, then how abundant is life in the countless stars that make up our universe?
This article was compiled using a NASA report written by Jia-Rui C. Cook.
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