New research shows that it is possible to detect life on the icy moon of Enceladus. It would be difficult.
A team of researchers found that it would take more than 100 flybys through the geysers of Enceladus to get a glimpse of a cell. If life is not detected, this finding could help in the design of future space missions to the planets.
The Enceladus surface was the scene of geysers in 2015. The abundance of dihydrogen (H2), which is abundant on the moon, was shown by data from many flybys. The data reflected generous amounts of carbon dioxide and methane, both of which indicated that methane-based life forms or methanogens could be found around the Enceladus.
There are photos of the bright moon.
Researchers have modeled the moon's hydrothermal vent environment to better understand how many cells can enter the ocean.
Antonin Affholder, a research associate at the University of Arizona and the study's lead author, said in a statement that they were surprised that the hypothetical abundance of cells would only be enough to support one whale.
The team estimated cell densities and found that the moon's life-supporting region could be less than 10 tons of carbon.
The definitive evidence of living cells caught on an alien world may remain elusive for generations.
Antonin Affholder, study lead author
According to this new research, an adequate amount of cells and organic material from methanogens would enter the plume, increasing the chances that some of them would be captured by a visiting spaceship.
The Enceladus' biosphere may be very sparse. Our models show that it would be productive to feed the plumes with just enough organic molecule or cell to be picked up by instruments on a future spaceship.
Methanogens are organisms that live close to the vents on Earth. At the moon's surface, at least 100 methanogens blast through cracks in the ice, releasing warm water that rises until it reaches the surface.
There are similar vents on Enceladus. The creation and growth of yeti crabs, tubeworms, and a distinct species of shrimp with light-sensitive cells on its back can be found on Earth. It is possible to find extraterrestrial life in the vents on Enceladus.
Assuming that most of the methane comes from methanogens residing deep in the moon's ocean, researchers say it's possible to sample a cell from an asteroid mission.
Sampling through flythroughs is a time sensitive challenge due to the fact that most of the material falls back onto the moon. Not every cell that enters is able to survive pressure changes. Experiments have shown that depressurization destroys most of the cells.
A more worrying challenge would be the presence of non- living elements. A high risk of false positives can be attributed to the fact that abiotic amorphs have the same signatures as living cells.
In order to overcome these challenges and maximize chances of sampling a real cell, the team found that at least 0.1 mL of a plume must be taken.
The current plan for a NASA Flagship mission shows that it is doable. Over the course of a year and a half, Orbilanders might achieve 1,000 flythroughs through the moon's surface. These samples would be used to find out if there is life on the moon.
The definitive evidence of living cells caught on an alien world may be hard to come by for a long time. The fact that we can't rule out life on Enceladus is the best thing we can do.
The research is described in a paper.
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