TORONTO – Are we alone?
It’s the question that has plagued philosophers, astronomers — maybe even yourself — since we first began to understand that there were other worlds beyond our own in the universe.
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The answer to “are we alone in the universe” likely has a “no” answer, if not just simply based on the statistical math behind it: with billions of galaxies and billions of stars, there are potentially hundreds of stars that are able to sustain life in a planetary system.
But when the question is posed closer to home, it becomes a lot more complicated.
First, we can’t possibly know what all life looks like. We can only search for life as we know it.
But where in our solar system can we hope to find the best chances for life?
Mars
Mars has long held a fascination for humanity, since Percival Lowell first spotted what he believed to be Martian-made channels along the Martian landscape. Now we know that yes, they were made, but through eons of geological processes, and even through flowing water.
So, knowing that Mars once had an abundance of water, does that mean that life once existed? Or could still exist below ground?
NASA’s Curiosity rover, which arrived on Mars in August 2012, was designed to answer the question of whether or not life could have existed at one time. And the answer is a resounding “yes.” Billions of years ago the Martian surface was replete with water, with lakes and running rivers.
There’s even the belief that we are the Martians; that after Mars was hit with a large celestial body, its fragments — which contained water and possibly microbial life –travelled through space and eventually landed here on Earth as Martian meteorites, bringing its ingredients for life to our planet.
But what about life today?
In September 2013, Curiosity found that, contrary what Earth-bound telescopes had reported finding, there was very little methane in the Mars atmosphere. Methane is a gas that is given off by living organisms here on Earth. The earlier finding had given some scientists hope that some form of life existed on the planet, but hope dwindled with Curiosity’s finding.
But Mars also has polar caps, and ice below its surface. So that’s not to say that there’s no hope at all for life on Mars. If there is, it may be below the surface. And current rovers on the planet — Curiosity and Opportunity — as well as future missions, will continue the search.
Enceladus
Many astronomers believe that this icy moon of Saturn has a good chance of hosting microbial life. But Enceladus is so bright that it reflects all sunlight back into space, meaning no photosynthesis could take place. It also has no oxygen. So how could life even begin, let alone thrive?
On Earth, scientists have found that in some of the darkest recesses of our planet — devoid of sunlight and with minimal oxygen — life has somehow flourished.
These “extremophiles” have helped scientists understand that maybe what we think is absolutely needed for life may not be all there is. An example of this would be microbes that survive from the chemical processes that take place between particular minerals, such as the single-celled micro-organism, archaea. These bacteria thrive in oxygen-deprived environments, such as the hot springs in Yellowstone National Park.
There is also the chance that some forms of life may even survive off the radioactive decay in rocks.
What makes Enceladus so appealing for harbouring life is the geysers that erupt from the moon. The Cassini spacecraft found evidence of ice particles in the geysers, possibly fed by reservoirs of liquid water.
The moon also has a heat source, believed to be generated by tidal forces as the moon is pulled to and from by Saturn’s enormous gravity (to see this at work, take a foam ball and squeeze it over and over again, and it will begin to generate its own heat).
With heat and water, many astronomers believe that this moon should be high on our priority list for the search for life.
Europa
“All these worlds are yours except Europa. Attempt no landing there.”
It’s safe to say that we can ignore that message from the fictional movie 2010 based on the novel by Arthur C. Clarke.
This is yet another moon with a very good chance at having some sort of life.
READ MORE: NASA planning mission to Jupiter moon that may harbour life
Europa is slightly smaller than our own moon, has water ice, and possibly an iron core. It is even believed to have an ocean of salty water. The only catch is that this ocean surface would be frozen over. However, there is evidence to support the idea of an ocean below the icy surface. And more promising is the belief that this moon-wide ocean could transfer nutrients from the water below to the surface.
The Juno spacecraft is on its way to Jupiter, though it won’t be closely investigating Europa. However, NASA has committed to sending a craft to Europa within the next 15 years.
Titan
Since the Voyager spacecraft passed Titan in 1980, it was a moon that was literally shrouded in mystery.
The thick, cloud-covered moon wasn’t revealing any of its secrets. So when the Cassini mission was designed, it also included the European Space Agency‘s Huygens probe. Huygens would detach from Cassini and head toward Titan, piercing through the cloud of the mysterious moon and landing on its surface.
What we now know is that Titan is quite Earth-like. It has lakes and even rain. However, that’s where the similarities end. The water that exists on the huge moon is made of liquid methane and ethane, meaning it’s not somewhere humans could ever exist.
There is the chance, though, of some other life that thrives on these gases. That’s not to say there isn’t any water at all on Titan — a layer of liquid water is believed to exist below the moon’s surface.
Scientists believe that there are organics in the air, on the surface and even deep in its interior. These building blocks of life could hint at that there could be life on this enormous, cloudy world.
So as our technology advances and our scientific knowledge expands, there is the hope that one day, we will find some form of life in our solar system, though it may not be as sexy as a little green Martian.
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