A little frozen Saturn moon, with a diameter that could easily fit inside the state of New Mexico, holds some big promises for the possibility of finding basic alien life in our solar system.
Enceladus is often overshadowed by its larger distant cousin, Europa, which orbits Jupiter and the Jovian moon’s awesome potential has been widely publicized. But Enceladus has one thing Europa doesn’t — it has been visited very closely by a robotic space probe that could take a sniff of its famous water vapor plumes. And this week, there was much excitement about another facet of the moon’s complex subsurface chemistry, thanks to analysis carried out on data gathered by NASA’s Cassini mission.
But before we get into why this new discovery is so cool, let’s take a very quick look at the other signs of Enceladus’ life-giving potential.
The Cocktail Of Life
Being living, breathing creatures on a habitable planet, it may not come as a surprise to you that for biology to evolve, it needs a few basic ingredients. Liquid water is a definite requirement, of course. Heat also helps. Throw some organic chemistry into the mix and we have a party.
Enceladus, however, is a tiny icy globe, there’s no sign of liquid water on its surface. But when Cassini arrived at Saturn in 2004, Enceladus revealed some of its best-kept secrets. Firstly, it may be a smooth ice ball, but the moon has a large quantity of water under its surface. This water even escapes as geysers, through fissures in its icy crust, producing stunning plumes that eject material hundreds of miles high and into Saturn’s rings.
Before Cassini was launched to Saturn, we had little clue about Enceladus’ watery potential — though this finding explained why Enceladus appeared so bright and how it contributes material to Saturn’s E-ring. Fortunately, the spacecraft has an instrument on board — a mass spectrometer — that could be used to “taste” the watery goodness of these plumes. During its Enceladus flybys, Cassini was able to fly through the plumes, revealing a surprisingly rich chemical cocktail — including a high concentration of organic chemistry.
It’s as if all the building blocks of life have been thrown into a small icy cocoon, shaken up and gently heated from within.
Now, another fascinating discovery has been made. Further analysis of Cassini data from its last 2015 plume fly-through, molecular hydrogen has been detected and planetary scientists are more than a little excited to add this to Enceladus’ habitable repertoire.
Deep In The Enceladus Abyss
“Hydrogen is a source of chemical energy for microbes that live in the Earth’s oceans near hydrothermal vents,” said Hunter Waite, principal investigator of Cassini’s Ion Neutral Mass Spectrometer (INMS) at the Southwest Research Institute (SwRI), in a statement on Thursday (April 13). “Our results indicate the same chemical energy source is present in the ocean of Enceladus.”
This hydrogen could be a byproduct of chemical reactions going on between the moon’s rocky core and the warm water surrounding it. And there’s a lot of hydrogen gas being vented, probably enough to sustain basic lifeforms deep in the Enceladus abyss.
“The amount of molecular hydrogen we detected is high enough to support microbes similar to those that live near hydrothermal vents on Earth,” added co-author Christopher Glein, who specializes in extraterrestrial chemical oceanography, also of SwRI. “If similar organisms are present in Enceladus, they could ‘burn’ the hydrogen to obtain energy for chemosynthesis, which could conceivably serve as a foundation for a larger ecosystem.”
Yes, we’re talking alien microbes. (Also, “extraterrestrial chemical oceanography” — oceans on other worlds! — is one hell of a mind-blowing topic to specialize in, just sayin’.) And did he mention “larger ecosystem”? Why yes! Yes he did.
So, in short, we know Enceladus has a liquid water ocean. We know that it has an internal heat source (hence the liquid oceans). We also know there’s organic chemistry. And now there’s solid hints that there’s water-rock interactions going on that terrestrial microbes living at Earth’s ocean vents like to munch on. If that’s not a huge, blinking neon sign pointing at Enceladus, saying: “We need a surface mission here!” I don’t know what is.
Although the researchers are keen to emphasize that alien microbes have not been found (because Cassini isn’t capable of looking for life), the universe has given us a moon-sized Petri dish where an “ecosystem” may have taken hold. All the ingredients are there, wouldn’t it be cool to find out if Enceladus could be another place in the solar system where life may be hanging out?
There was also some great news about Europa’s habitable potential this week, but you can go here for that piece of cosmic awesomeness.
Want to know more about Cassini’s final months at Saturn, check out my recent Space.com article on the commencement of the veteran mission’s Grand Finale.