Enceladus Could Be a Cosmic Shaker for the Cocktail of Life

NASA/JPL-Caltech/Space Science Institute

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.

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Life: Not So Grim On The Galactic Rim?

M80 -- an old globular cluster in the Milky Way -- is full of metal-poor stars. Do they still have exoplanetary potential? (NASA)
M80 — an old globular cluster in the Milky Way — is full of metal-poor stars. Do they still have exoplanetary potential? (NASA)

The galaxy may be brimming with habitable small worlds and many older star systems could possess the conditions ripe for advanced alien civilizations to evolve. This prediction comes in the wake of new analysis of data from NASA’s Kepler space telescope and ground based observatories by a team of Danish and American astronomers.

Led by Lars Buchhave of the Niels Bohr Institute in Copenhagen, the team has revealed that stars containing low quantities of heavy elements — known as “metal poor” stars — are still capable of nurturing exoplanets with Earth-like qualities.

“I wanted to investigate whether planets only form around certain types of stars and whether there is a correlation between the size of the planets and the type of host star it is orbiting,” Buchhave said.

After analyzing the elemental composition of stars hosting 226 small exoplanets — some as small as the rocky planets in the Solar System — Buchhave’s team discovered that “unlike the gas giants, the occurrence of smaller planets is not strongly dependent on stars with a high content of heavy elements. Planets that are up to four times the size of Earth can form around very different stars — also stars that are poorer in heavy elements,” he concluded.

The Kepler mission, for example, is actively carrying out a search for exoplanets that pass in front of their host stars (events known as “transits”). With Kepler’s sensitive eye, it is capable of detecting exoplanets of similar size to Earth, or even as small as Mars.

Interestingly, as it surveys Sun-like stars, Kepler can detect tiny, rocky worlds that orbit within the “habitable zones” of their stars. It’s no huge leap of the imagination to think alien life may have evolved on some of these worlds.

But a problem facing astronomers hunting for bona fide “Earth-like” exoplanets is that many older stars have low quantities of heavier elements (such as the silicon and iron) that small rocky worlds need to become… well… rocky. But Buchhave’s discovery suggests that stars once considered infertile may in fact have a shot at birthing small exoplanets.

Jill Tarter, Chair of the SETI Institute, points out that this could be a boon for the search for intelligent extraterrestrials. “The idea that very old stars could also sport habitable planets is encouraging for our searches,” she said in a SETI press release on Wednesday.

Tarter also highlights the fact that life took a long time to evolve into an advanced technological state on Earth. Therefore, should there be small habitable rocky worlds orbiting ancient stars (as this research suggests), perhaps alien life far older and more technologically advanced than ourselves are out there.

Although this seems to make logical sense, it may not make biological sense. Metal-poor stars might have the ability to create small worlds, but just because there are likely many small worlds out there, it doesn’t mean life can be nurtured. But then again, regions of the Milky Way once considered to be devoid of exoplanets may now have a stab at providing a planetary habitat for extraterrestrial biology to gain a foothold. Whether or not these metal poor stars host the right ingredients for the building blocks of life probably won’t be known for some time.

In 2009, I wrote an article (see “Life Is Grim On The Galactic Rim“) that grabbed the attention of National Geographic writer Ken Croswell who quoted my Astroengine.com article in the December 2010 edition of the magazine. In the text, I discussed some research that investigated the strange lack of protoplanetary disks around a selection of metal-poor star clusters in the outermost regions of the galaxy. The lack of a protoplanetary disk means a lack of exoplanet-birthing potential and a grim outlook for life to evolve in regions of the galaxy distant from the galactic core.

The conclusion of this 2009 work appears to contradict these most recent findings and the suggestion that advanced alien civilizations may have evolved around metal-poor stars. Whether these stars are the exception rather than the rule, or whether their low metallicity influences the size or visibility of their protoplanetary disks would be an interesting factor to consider.

Although SETI searches have yet to turn up any signal from an advanced alien technology, Kepler is proving that stars — regardless of their metallicity — have the ability to host small rocky worlds. Should life have taken hold on these worlds, then perhaps, some day, we may intercept an interstellar phone call from one of them.

This topic and a myriad of others will be discussed on June 22-24 where the world’s leaders in the field of alien and exoplanet hunting will meet at the Hyatt Santa Clara hotel in California’s Silicon Valley for SETIcon.

UPDATE: After tweeting this article, @spacearcheology retweeted my link with the following comment:

This is something I neglected to consider in the original post. If there are indeed many more small rocky worlds out there — particularly around metal-poor stars that are, by their nature, ancient — why the heck haven’t we detected any ancient extraterrestrial intelligences yet? This has just become the Fermi Paradox PLUS…