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).