On October 28, 2015 Cassini passed below (above?) the south pole of Enceladus at an altitude of 49 kilometers. The probe was flown here in order to get a taste of the water-ice particles that are streaming out into space from Enceladus’ suspected sub-surface ocean in this location. This is the lowest pass Cassini has made through the alien ocean geyser.
This was done in order to help scientists understand the nature of the ocean, how close to the surface it might be, and if the water contained in it could accommodate life. Also of particular interest, the Cassini team is looking for a particular chemical signature of hydrogen that could support the theory that Enceladus has hydro-thermal vents heating water deep in the moon’s ocean.
It’s important to note, however, the instruments Cassini carries on board can characterize the chemical composition of any particles it encounters, but it doesn’t have the ability to directly test for life.
The detailed analysis of the tiny water droplets that Cassini caught as it flew through the plume is now underway (with full results a few weeks away), but some images of the fly-by have already been sent back. And as we’ve come to expect from Cassini, they’re spectacular.
The south polar region of Saturn’s active, icy moon Enceladus awaits NASA’s Cassini spacecraft in this view, acquired on approach to the mission’s deepest-ever dive through the moon’s plume of icy spray. The wavy boundary of the moon’s south polar region is visible at bottom, where it disappears into wintry darkness. CREDIT: NASA/JPL-Caltech/Space Science Institute
A RAW and unprocessed image from Cassini as it flew towards the icy plume at Enceladus’ south pole. CREDIT: NASA/JPL-Caltech/Space Science Institute
During its closest ever dive past the active south polar region of Saturn’s moon Enceladus, NASA’s Cassini spacecraft quickly shuttered its imaging cameras to capture glimpses of the fast moving terrain below. This view has been processed to remove slight smearing present in the original, unprocessed image that was caused by the spacecraft’s fast motion. CREDIT: NASA/JPL-Caltech/Space Science Institute
Following a successful close flyby of Enceladus, NASA’s Cassini spacecraft captured this artful composition of the icy moon with Saturn’s rings beyond. This view looks towards the trailing/anti-Saturn side of Enceladus. North is up. The image was taken in visible light with the Cassini spacecraft wide-angle camera on Oct. 28, 2015. The view was acquired at a distance of approximately 171,000 km from Enceladus and at a Sun-Enceladus-spacecraft, or phase, angle of 141 degrees. Image scale is 10 km per pixel. CREDIT: NASA/JPL-Caltech/Space Science Institute
Over the past week or so we’ve seen a few stories regarding wet bodies in our solar system.
First, there was news about water on Mars. Now the news wasn’t so much that there was water on Mars, since that’s been pretty well understood for a while now (thanks in large part to the rovers Spirit, Opportunity, and Curiosity), rather how much water there was – and it’s plentiful to say the least.
Mars with a vast Northern Ocean (NASA/Goddard Space Flight Center)
Using land-based infrared telescopes (the ESO’s VLT and NASA’s Keck), NASA was able to measure the hydrogen isotopes in Mars’ atmosphere. The results indicate that Mars one had 20 million cubic kilometers of water – more water than is in the Arctic Ocean here on Earth today. Astronomers are also currently suggesting that the Martian water was contained, mainly, in one large ocean surrounding the Red Planet’s north pole. It would have covered proportionally more of the planet’s surface than the Atlantic Ocean does here.
Nowadays on Mars it’s bone-dry, quite a bit different from ~4 billion years ago. Current estimates suggest that Mars’ ancient ocean contained about 6.5 times more water than what is currently observed in Mars’ polar ice caps, meaning that a great deal was likely lost into space as the Martian atmosphere thinned 2-4 billion years ago (though some water could still possibly be trapped in a permafrost layer).
The next news item this week is regarding Enceladus, an icy moon of Saturn. Now again, we’ve understood for a while that this moon had a sub-surface ocean of liquid water, trapped beneath an icy crust, but the news this week is tantalizing: the possibility of active hydrothermal vents in the moon’s southern ocean.
Hydrothermal activity on Enceladus (NASA/JPL-Caltech)
Announced just a couple days ago thanks to data from the Cassini spacecraft, astrophysicists have been able to pinpoint the origin of tiny particles of silica that the spacecraft had been detecting in space as it orbits in the area. And the origin appears to be the southern ocean of Enceladus, a 10km deep body of water. How the silica particles form is a chemical process that takes places when ocean water interacts with volcanic activity on the ocean floor.
Precisely the same process has been observed in only one other place so far: right here on Earth. And on our world, hydrothermal vents are teeming with life.
Jump ahead to today, and NASA announces, using Hubble data, that the largest moon in our solar system has a sub-surface ocean of liquid water of its own.
Ganymede, a moon of Jupiter, has been theorized to have a sub-surface ocean since the Galileo probe visited the area in 2002. Shifting magnetic fields were a major clue indicating the presence of water, though the data at the time was inconclusive. But now a novel idea has allowed a team of astronomers to make use of the Hubble Space Telescope to study Ganymede’s shifting magnetic fields from afar: patterns in the moon’s auroras.
An illustration of Ganymede’s auroras (NASA/ESA)
By understanding how different materials impact magnetic fields, and how auroras present themselves through those magnetic fields, the astronomers were able to understand Ganymede’s make-up by studying the auroras using Hubble. What they found is an ocean of water. (Edit: not only an ocean of water, but a large ocean. Ganymede could have more water in its salty subsurface ocean than Earth does in all our oceans combined.)
With all this in mind – and not to mention other wet worlds, like Europa – the solar system is starting to look a little more damp than it was once thought to be. And here on Earth at least, it is well understood that anywhere you can find water – in any form – you are virtually guaranteed to find life as well.
So how do these discoveries impact the prospects for finding life in our solar system beyond Earth?
On Mars, I’m not sure it changes much. It’s been understood that the planet was once wet, that it was wet for hundreds of millions of years (if not a billion or more), and that the environment was once life-friendly. This week’s discovery drives home the idea that there was plenty of water, but I don’t know that it’s a game-changer.
For Enceladus, this is a significant discovery. Adding in the fact that geysers have been previously detected with organic chemicals, this icy world now has to be considered one of (if not the most) likely places to harbour life in our solar system. As we understand life, it needs water and an energy source; Enceladus now seems to have both. Contemplating what might be swimming around in that alien ocean right now is an intriguing thought. (Maybe Enceladus leap-frogs Europa as the target for a robotic submarine mission?)
Ganymede? Add it to the list of worlds with liquid water that require more study. (I would similarly categorize Europa.) Questions abound as to the nature of their oceans, if there is any volcanic activity, do they cover the entire world, and could there be life?
Clearly we have some exploring to do.
Astronauts on board the International Space Station capture an image of the Space Shuttle Endeavour prior to docking during the mission STS-130 in February 2010 (NASA).
The frontiers of exploration have had many faces throughout history. In ages past, what is today London, England would have been a striking, though desolate, find. Today it’s a central hub of the Western world.
Ditto my hometown of Toronto, Ontario. Just 300 years ago it was wilderness. And you don’t have to venture very far from the city limits to return to that untamed world.
And there are many places around the world that are still, in the truest sense of the word, frontiers of exploration.
Antarctica, the Amazon rainforest, the ocean floor (a massive ‘new world’ right here on Earth), Madagascar, the high Arctic – all places that most human will never venture and no doubt hold secrets that could both amaze and bewilder our understanding of the world and perhaps life itself.
Overlooking the frozen shores of Lake Nipissing in North Bay, Ontario
Consider for example the extremophiles (life that exists in extreme environments) that live inside rocks many kilometers beneath the surface – far from any sunlight – that use the rock itself as an energy source.
Or the life that flourishes in Lake Vostok – an underground Antarctic lake that has been cut-off from the outside world for perhaps 15 million years beneath 4km of snow and ice.
These discoveries have changed how we think about life, and rightly so. We have learned that life can persist – and proliferate – in places that only a few years ago were considered too harsh.
The goldilocks zone right here on Earth has ballooned.
Places that were once thought of as too extreme in some way – too hot, too cold, too dry, too little sun – are now all environments where there is life.
And significantly, they’re not just places where life is theorized. It’s not just that someone says there ‘could be’ life there.
There really is life there. We have seen it. Measured it. Tested it. Compared it.
Our exploration has taught us an important lesson for Planet Earth: life finds a way.
And as I sit in my chair explore the ice world I see out the window of the house Ashley grew up in, those four words stick with me.
Life finds a way.
I know gazing out the window that my view is teeming with life.
In the sky, under the ice, in the snow.
Everywhere there is life, and it’s abundant. Our exploration of Earth has proven this to be true.
Then I put on my Mars-coloured glasses, and start to think…
When the first people arrive on Mars in the next decades, the view they’ll be faced with may be remarkably similar to what I see here, sitting in North Bay on the shore of Lake Nipissing.
A landscape shaped by the cold, by wind, by water – by weather.
It’s a landscape that is utterly beautiful, but also incredibly harsh.
Lake Nipissing or Mars?
The one I see is a present day lake and the one on Mars will be an ancient lake – one that has long since dried up. But I’d be willing to bet that the first people to visit Mars will touchdown at a place where we’re confident there used to be water (and maybe still is, just trapped under the surface in permafrost).
Our Martian explorers will lift the veil on some of the secrets of the Red Planet. They will walk and rove. They’ll set up camps and hunker down when dust storms approach. They will keep warm on the cold Martian nights.
And as I think about the incredibleness of discovery that awaits our pioneers, it occurs to me that we’ve been here before. This has already happened.
Earth used to be the undiscovered country (and in a meaningful way, we’ve only scratched the surface of it).
We are born to explore, and now there is a new frontier that tugs at our souls – and our emissaries are already there. But they are only wetting our appetite.
Only the most anthropocentric among us would seriously argue that Earth, as part of a solar system, is a godsend.
For me, it always made sense intuitively that our solar system is one among many – just as our star is one among many, or indeed our planet is one among many just in our solar system.
We’ve known for a while that our Sun is one amongst, literally, billions in the Milky Way alone. Thousands of years ago though this concept was intuition, and postulation. A lot of ‘what if?’ type statements were made about our Sun, in comparison to the twinkling lights of the night.
“What if we’re just a lot closer to this one, than to others, so it looks bigger and brighter?”
“What if it’s actually not all that different from others?”
Though there was no way to confirm these ideas – even if intuitively they did make a world of sense.
Through the advent of technologies – namely telescopes, invented roughly 400 years ago – data would eventually be provided to confirm the intuition that our little Sun was in fact quite a bit like all those stars that surround us at night.
(Of course to be accurate, the Sun is also dissimilar from many stars in terms of size, temperature, age, and so on — just as Mercury and Jupiter hold some traits in common, they are of course dissimilar in others.)
The Milky Way (Credit: A. Fujii / NASA)
As time marches on, we find that in our solar system there is also a diversity of worlds: planets, moons, asteroids, comets – whatever classification you choose, there’s a multitude of those other bodies out there.
Again through technology – and again, namely telescopes – we’re able to confirm ideas that intuitively made sense to people of ages past: what if those wondering stars are other worlds?
In fact the word ‘planet’ derives from the Greek ‘asteres planetai’ – wandering stars – as the paths of the planets appears separate against the backdrop of the star field in our night sky.
Around the same time that we confirm there are other worlds around our star, folks start to wonder ‘what if those stars have planets, like ours does?’
It makes sense intuitively – just as the concepts of other Suns in the galaxy and worlds in our solar system makes sense.
What’s been lacking though is the technology to confirm this intuition – since let’s be honest, intuition alone is a very lousy way to do science.
We need data to confirm the hypothesis.
The first exoplanet – or extra-solar planet, aka a planet orbiting a star other than the Sun – was discovered in 1992. That’s only 22 years ago.
So on one hand, it might have been forgivable for people to argue that our solar system is unique. There had been, after all, no data to argue otherwise.
On the other, since the mid-90’s, there have been different techniques to detect exoplanets.
Though it wasn’t until 2009 that the rock star took the stage: Kepler.
(if you want to read all about the Kepler mission, go here – those details aren’t what this article is about)
With the Kepler mission taking centre-stage in our planet-hunting endeavour, we were finally able to take the first steps in confirming something that makes sense intuitively: many (if not most) other stars have planets orbiting them, just as ours does.
Exactly how many planets each star has, exactly the nature of those planets orbits, exactly the composition of those planets – and many other details – continue to be open questions in most cases. Though it’s worthwhile to note that in some examples, perhaps a dozen, we have a pretty good understanding of the answers to those questions.
Should it be surprising that we don’t have all the answers? Of course not. We have only confirmed that these things exist in the first place in the last couple decades.
There are planets out there everywhere – and lots of them.
Their makeup is as diverse as the makeup of our solar system.
But now that we have data to confirm the exoplanet intuition, we need data for next big intuition: life.
And just has happened historically, we’ll start in our own solar system with Mars.
We have been investigating Mars from afar for hundreds of years. Over the last few decades we’ve been investigating it close-up. We’ve confirmed the presence of water. We’ve confirmed a hospitable environment (at least historically).
It’s time to go to Mars and search directly for life.
This search will primarily be one for ancient life, though it’s not out of the question that some microbes could exist underground near a water supply today.
Once again, this is an issue where it is intuitively plausible that Mars was home to life. We know the conditions were right, so why not?
But this is a big question, and again intuition isn’t enough – we need data.
I do, openly, speculate that this is another case where intuition will eventually be confirmed by data (whether it’s within the next few years or not though is harder to guess – Mars is a pretty inhospitable place now, and so evidence of past life might be hard to find – if it is there at all).
Speculation aside though, data can confirm for us that Earth is simply one planet amongst hundreds of billions – if not more.
This is a reality that may take some time to sink in, but it is an undeniable truth.
Just as it is equally true that the Earth is round, that we orbit the Sun, and that the Sun is but one amongst a vast ocean of stars.
Harrison lives in Ottawa, Canada. He works in politics and is passionate about many things, including space and exploration. He's worked for a national news outlet, managing the digital products, writing news, and appearing on air to talk about science, technology, and politics. In his spare time he enjoys astronomy, scuba diving, flying airplanes, photography, and sports.