The only example of life in the universe is Earth, a rocky planet with over 70% water on its surface. As far as we know, all life on Earth relies on water to survive and thrive, so scientists refer to other planets where liquid water is known to exist as “habitable.”
But scientists also know that a puddle of water alone is not enough to sustain life. Life depends on a constant flow of electrons between molecules, which Electronic GradientTo create energy, electrons move away from areas of high electron density. Reducelow density areas, so-called Oxidize.
Scientists have found several planets and moons in our solar system that have liquid water. Researchers are particularly intrigued by Jupiter's moon Europa, because remote sensing has revealed that it has a salty liquid ocean about 100 kilometers (60 miles) deep on top of a crust of iron-rich rock, with a layer of ice about 10 kilometers (6 miles) thick on top of that.
Europa has no atmosphere to protect it from the sun's radiation, which allows chemical reactions to take place that consume electrons on its surface, creating an oxidizing environment. In contrast, its iron-rich crust creates a reducing environment beneath its oceans. This means that an electron gradient naturally forms along the path from Europa's oxidizing surface to its reduced ocean floor. Scientists want to know if life could harness this electron gradient to obtain enough energy to sustain itself and survive.
Researchers studying Europa From the data Cassini and Galileo The mission found that Europa's ocean temperatures range from 0 to -13 degrees Celsius, or 32 to 9 degrees Celsius. They found that the hottest temperatures are found closest to the ocean floor, where heat is generated by reactions between water and rock, similar to Earth's hydrothermal systems. They also found that some of the most abundant molecules near Europa's surface are all oxide molecules, such as carbonates and sulfates.
Based on these temperature constraints and the amount of energy provided by oxidizing molecules on Europa's surface, a team of researchers from the University of Akron and the University of Southern California calculated the amount of energy available for life in Europa's ocean and investigated whether three types of Earth microorganisms could live beneath Europa's ocean. The microorganisms they tested generate energy using carbonates, sulfates, or iron particles. They reasoned that because all three of these oxidizing molecules are found on Europa's icy surface, if delivered to the ocean floor, the organisms could combine with reducing molecules on the ocean floor to generate energy.
The researchers calculated that in Europa's environment, molten iron near the surface layer of ice would form solid particles when exposed to penetrating radiation from the sun, and slowly fall to the ocean floor — like snow falling from the sky on Earth, except instead of water ice particles, the ocean rains down in the form of rust-like, reddish iron particles.
The scientists calculated that iron oxide snow would provide a larger electron gradient than carbonates or sulfates, ultimately generating more energy for life. They estimated that iron snow could provide up to 2.5×1026 More than 100 microbial cells are found on Europa's ocean floor per year, which represents about 0.1% of the total number of microbial cells currently living in Earth's oceans.
However, the authors caution that only around 10% of the energy produced by organisms on Earth is used to generate cells — the remaining 90% is used to maintain metabolism, meaning that the number of cells that microbial life could actually generate from Europa's underwater iron pathways would be much lower than the authors estimate.
Nevertheless, the authors suggest that these cell count calculations could be used to design missions to search for life on Europa: When future satellites orbit Europa, researchers could estimate how much cell mass we might expect from microbes living in the iron passages on the Europa ocean floor.
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Source: sciworthy.com
