We’ve known for some time that water exists in some forms on Mars. The Viking program, which consisted of both orbiter and lander craft, showed that Mars’ surface had many characteristics that must have been shaped by water. Further probes such as Mars Odyssey and the Phoenix Lander showed that much of the present day water that Mars holds is present at the poles, trapped in the vast frozen tundra. There’s been a lot of speculation about how liquid water could exist on Mars today however no conclusive proof had been found. That was until today when NASA announced it had proof that liquid water flows on Mars, albeit in a very salty form.
The report comes out of the Georgia Institute of Technology with collaborators from NASA’s Ames Research Center, Johns Hopkins University, University of Arizona and the Laboratoire de Planétologie et Géodynamique. Using data gathered from the Mars Reconnaissance Orbiter the researchers had identified that there were seasonal geologic features on Mars’ surface. These dark lines (pictured above) were dubbed recurring slope lineae would change over time, darkening and appearing to flow during the warmer months and then fading during the colder months. It has been thought for some time that these slopes were indicative of liquid water flows however there wasn’t any evidence to support that theory.
This is where the MRO’s Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) comes into play. This instrument was specifically designed to detect water on Mars by looking at varying wavelengths of light emitted from the planet’s surface. Once the target sites were identified CRISM was then pointed at them and their surface composition analysed. What was found at the RSL sites were minerals called hydrated salts which, when mixed with water, would lower the freezing point of the water significantly. Interestingly these hydrated salts were only detected in places were the RSL features were particularly wide as other places, where the RSLs were slimmer, did not show any signs of hydrated salts.
These salts, called perchlorates, have been seen before by several other Mars missions although they’ve never been witnessed in hydrated form before. These perchlorates can potentially keep water from freezing at temperatures down to -70°C. Additionally some of these perchlorates can be used in the manufacturing of rocket fuel, something which could prove to be quite valuable for future missions to Mars. Of course they’re likely not in their readily usable form, requiring some processing on site before they can be utilized.
Data like this presents many new opportunities for further research on Mars. It’s currently postulated that these RSLs are likely the result of a shallow subsurface flow which is wicking up to the surface when the conditions are warmer. If this is the case then these sites would be the perfect place for a rover to investigate as there’s every chance it could directly sample martian water at these sites. Considering that wherever we find liquid water on Earth we find life then there’s great potential for the same thing to happen on Mars. If there isn’t then that will also tell us a lot which means its very much worth investigating.
Natural selection has given rise to some incredible things. The diversity of life on Earth is an ongoing testament to that, showcasing that life can sustain itself pretty much anywhere so long as there’s water present. What’s incredibly interesting to see is how parts of nature take on properties of things you wouldn’t necessarily think they would, like the planthopper with gears in its legs. It seems the more we investigate life here on Earth the more weird and wonderful behaviour we come across and none seems to be more stranger than the hive mentality of fire ants giving rise to a substance that’s neither liquid nor solid:
The research paper that this comes from is quite interesting as they performed a whole bunch of materials tests on the fire ants to see what the properties of the giant ball were like. Interestingly the fire ants, whether they’re alive or dead, exhibit properties of non-Newtonian fluids, specifically shear thinning (like when paint doesn’t drip off a brush). However the characteristics of the live fire ant ball don’t directly classify it as either a solid or a liquid although a similar non-live sample acted much more like a solid. That interesting property is most likely due to the way the ants rearrange themselves in response to stress but the actual mechanism of how they do that, especially in large numbers, is still something of a mystery.
It seems that this behaviour likely arose out of a particular selection pressure, namely flooding. The fire ants can bind themselves together in a ball or mat to form a raft that will float on water thanks to the large surface area relative to the fire ants weight. It’s the same principle that allows water skimmers and other insects to seemingly float on top of water, using the surface tension to provide them with buoyancy. The material properties that fire ant ball carries with it are likely a side effect of that adaptation, although there might be other pressure that led to it as well.
I’d totally go out and try this for myself but I value my hands far too much.
Carl Sagan is quote as saying that “life looks for life”. Indeed if our own history is anything to go by we’re in a constant state of searching out other forms of life and just recently we’ve extended that search beyond the confines of the world that gave rise to us. So far our search beyond our home world has proved fruitless as we’ve been unable to find any direct indications of life on any other heavenly body that’s within our reach. Thus we find Earth in what appears to be some great isolation which is a somewhat disconcerting notion given the age of the universe and the number of potential habitable planets in our galactic backyard. We should not be discouraged however as our quest to find life elsewhere is only just beginning.
Of all the other heavenly bodies that inhabit our solar system there’s one that stands out as the best candidate for housing life. Now if I was to ask the question of which body it was most people would respond with Mars as it’s the only planet that resembles Earth in some fashion, with the next closest candidate being the raging hell of Venus. It’s not a bad guess either as we’ve proven several times over that there was once vast amounts of water there and there’s still a very good chance there’s liquid water present today. However Mars is a very inhospitable place so much so that the best hope for life there is nothing above microbial and even that seems like a far reaching prospect.
Europa on the other hand is quite the curiosity. As far as moons go it really is something out of left field being a striking combination of bright whites and browns. It’s surface is also one of the smoothest in the solar system thanks to it being made almost entirely of water ice. That doesn’t mean it’s featureless however as the entire surface is criss-crossed with fracture lines from the giant ice sheet breaking apart and reforming. Many have speculated that this is because the surface actually lies on top of a giant subsurface ocean and when cracks form the ocean rushes up to fill it, forming the characteristic lines. It’s this undersea ocean that makes Europa one of the best candidates for life forming outside of Earth and recent studies show it just got a little better.
The potential ocean on Europa would be some 3KM below the surface, quite a ways away from any direct sunlight or other potential energy sources. It’s theorized then that the ocean is kept liquid by the tidal flexing that Europa undergoes every time it orbits Jupiter which could also drive the same kinds of volcanism processes that gives rise to life in the depths of our oceans. However recent research shows that there’s potential for some subsurface lakes that are much closer to the surface than the great ocean below. These lakes would have a higher rate of churn between water and ice providing a much a habitat that’d be more nutrient rich and hopefully more hospitable to life. Of both these recently modelled oceans and the great subsurface ocean haven’t yet been conclusively proven, but that just makes Europa a really tantalizing target for exploration.
Quite a few missions have swung past Europa already with the most detailed analysis being done by the Galileo craft from 1995 to 2003. However we haven’t been back there recently save for a short flyby by the New Horizons craft that imaged it on its way to Pluto. If we were to go back there my favourite mission candidate would be the Crybot style mission. In essence it’s a probe that’s fitted with a giant heater on the front of it, capable of plunging through several kilometres of ice. Once it broke through it would then deploy a small autonomous underwater vehicle that could investigate the subsurface ocean. This mission hasn’t got past the back of the napkin style planning stages yet, but I’m hopeful that we’ll one day attempt such a mission.
Europa is a curiosity unlike any other in our solar system and there’s so much we could learn from it if we were to send a mission there. Whilst the environment there isn’t really human friendly (the radiation at the surface is quite large, about 450 chest x-rays a day worth) it’s definitely within our current capabilities of robotic exploration. I know that one day we’ll see a dedicate mission there but until then I’m quite content to continue fantasizing about the undersea world that it contains and the tantalizing possibility that as of yet unknown life forms exist there.