Has Liquid Water Been Detected On Mars?
Written by Ian O'Neill
Liquid water may have been discovered by the late Phoenix Mars Lander. This astonishing (and controversial) claim comes from some very intriguing images of the lander's leg shortly after Phoenix landed on the Red Planet last year. The series of black and white images appear to show droplets of water hanging off the robot's bodywork in the shade; it seems possible that the water droplets were splashed from the surface during Phoenix's rocket-assisted landing. Far from being static blobs, they appear to grow, much like water droplets here on Earth as water vapour is absorbed from the atmosphere.
But wait a minute, isn't the Martian atmosphere too thin and too cold to accommodate liquid water? That's where the perchlorate comes in…
If liquid water has been found to exist on the surface of Mars, there will be huge implications for our understanding of the planet. Most tantalizingly, liquid water, on or near the planet's surface, could aid the survival of microbial life, reinvigorating the search for extraterrestrial life on out interplanetary neighbour. But on a planet where the atmospheric pressure is 100 times less than on Earth, and temperatures reached a maximum of -20° Celcius during the Phoenix mission, why isn't this "liquid water" candidate frozen?
The perchlorate discovery in the Martian soil was announced by the Phoenix team in August 2008, after an explosion of intense Internet conjecture caused by the "potential for life" announcement by an Aviation Week article days earlier. It turned out that the Phoenix instrumentation had found quantities of a toxic chemical called perchlorate known to be a hindrance to life as we know it. Although follow-up reports were slightly more positive about the presence of the chemical (a possible energy source for microbial life), the mood was fairly sombre. On a planet as unforgiving as Mars, any bad news is a severe knock for the hope of finding life.
However, regardless of perchlorate's toxic effects on life, it may be helping out another one of life's resources to stay in liquid form. If perchlorate is dissolved in significant quantities, water could remain as a liquid down to temperatures as low as -70°C. So could it be that the dissolved perchlorate salt is acting as a very impressive anti-freeze?
Nilton Renno from the University of Michigan and Phoenix team member, thinks it could be. "According to my calculations, you can have liquid saline solutions just below the surface almost anywhere on Mars," he said.
Renno's team carried out a series of laboratory experiments and found that the lander's thrusters would have melted the top millimetre of ice in the regolith. The resulting water droplets may have been splashed onto the landers leg. If the concentration of perchlorate was high enough, the water could have remained in a liquid state during the Mars daytime. As time progressed, atmospheric water vapour may have been absorbed, hence the growing and shifting blobs of liquid on the leg. There is also the possibility that the droplets were splashed from pools of perchlorate-rich water already in a liquid state on the surface.
However, not everyone is convinced. Fellow Phoenix team member Michael Hecht from NASA's Jet Propulsion Laboratory in Pasadena, California, thinks that the photographs actually show water ice, not liquid water. The "frost" changed shape as vapour from the air coalesced and froze to the leg. Renno points out that this is unlikely as any ice on the leg would be more likely to sublime, rather than grow, but Hecht believes this could happen if the leg was colder than its surroundings.
Renno's team will be continuing tests on samples of perchlorate-rich water under Mars-like conditions for the next few months to understand the dynamics of water under these extreme conditions. What makes this even more interesting is that some microbial life on Earth has the ability to survive in very salty fluids, perhaps microbial alien life on Mars evolved in a similar environment where there were pools of liquid water maintained at extremely low temperatures by high concentrations of perchlorate salt…
Source: New Scientist
Filed under: Mars
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February 18th, 2009 at 3:49 am
Once we set foot there we will find life. I doubt machines will, they're stupid, slow and un-living.. Good for taking pictures and doing chemical analysis but that's about all they're useful for really..
To each his own…
February 18th, 2009 at 4:34 am
Frost doesn't normally form big round chunks like the ones in the photos, does it? From my experience (which amounts to scraping the stuff off my windshield) it forms thin crystals. Of course, frost might well behave differently if it's made of perchlorate-laden water in a low pressure environment well below zero degrees, but those blobs sure do LOOK like water droplets to me.
February 18th, 2009 at 6:29 am
The Great Perchlorate Debate resumes.
February 18th, 2009 at 7:40 am
A small piece of dust appears, then goes away.
300 million down the drain.
Never has a mission produced so little data with so many great instruments. The atomic force microscope has returned hardly any information at all… What is the deal?
How is it that when the last two rovers did so well, are still working after all this time, we dont just send the same rovers to new locations? Would it not save money to use the same design over again? Would it not save money to use the same teams to run all 4 rovers?
February 18th, 2009 at 7:46 am
Provocative…fascinating… too bad it's inconclusive
February 18th, 2009 at 7:48 am
I think you could probably use the Rover design over and over. You could at the same time put additional instruments with higher technology on board.
February 18th, 2009 at 10:22 am
I wonder if the team considered electrodeposition.
The perchlorate/water conjecture should be easy to determine with some perchlorate, water and an environment chamber – better than a calculation.
February 18th, 2009 at 10:50 am
@ Conic:
Really? Ice, Perchlorate, Carbonate, Silicate, not to mention snow: aren't these news? The atomic force microscope probably found clay particles: not GREAT news?
The data is just beginning to be studied; I'll bet we'll hear about it for years if not decades.
Yes, the rovers are fantastic. But a rover sent there instead of Phoenix would be just as dead now, for the very same reason. And rovers don't dig, don't do chemistry. They never will, unless they get bigger (MSL).
Any mission raises questions it can't answer, the next mission is designed to answer these questions, and raises more.
Just be patient!
February 18th, 2009 at 10:59 am
Manu…
We already knew there was ice on Mars. Touching it is, in astronomy, hardly a requirement.
The rovers could have carried all of the instruments found on this sessile lander, and it could have moved them around. Rovers can dig, and drill (they have already done the latter), and anything else. Obviously any polar lander should have had an RTG based power system, or at least a way to stay dormant and come back to life after the winter. Just one season of science, at this cost, and at a time when money for probes is very hard to get, is inexcusable to me.
Sorry to be this way. I love all missions, and in a perfect world they should all be funded. But until we find that perfect world, we should have a better filter to cut the programs that show little in the way of returns.
Do you see where I am coming from? The next mars rover (delayed sadly) is roving in the right direction.
February 18th, 2009 at 1:37 pm
@Conic:
Yes I see, but then the rover you describe is precisely the next rover!
Phoenix's instruments could never fit on a MER, let alone an RTG. Phoenix is way heavier than MERs, and MSL is way heavier than Phoenix.
MERs don't dig, they don't drill, they scratch. That's great, but we need more, don't we? Even MSL won't drill, only ExoMars will (maybe).
Also, contrary to other regions of Mars, there was no reason to move around where Phoenix landed, because it's all of the same for 100s of miles. That was a strong factor in mission design, which probably allowed packing in more instruments instead of wheels and motors.
Besides, Phoenix has learned a few hard lessons, soil 'clumpiness' for one, that prove helpful to MSL design (another being bureaucratic interference, but that's there to stay I'm afraid).
And I insist that great science has been made there and is going to be made for a while. Being chemistry, it may not be as sexy as roving, but it's just as important. (I absolutely LOVE the rovers, don't get me wrong there!)
One big thing that Phoenix missed is to get that pure ice sample, to determine the isotopic ratios. Touching WAS important there, there's no other (yet) way to get that vital information.
Well, everybody learn from mistakes.
February 18th, 2009 at 3:39 pm
I am curious about the Phoenix lander's legs. What material were they made from? I will assume aluminum with some sort of protective coating – anodize or other? Might one of these materials have reacted with Perchlorate? or water vapor? And if so, how and what would such an oxidation look like? We've all witnessed how oxidized aluminum degrades here on Earth. Given there may have been out-gassing or melting caused by the lander's exhaust, what chemical reations might take place? Another contributing factor may be tribo-electric charges, i.e. electrostatic field induction.
February 18th, 2009 at 3:48 pm
@Manu & Conic:
Throughout the entire Phoenix mission and even to this point, I've shared and swung between both of your viewpoints, sometimes on a daily basis. I've gone from being completely underwhelmed by Phoenix to being stoked on it's achievements to being disappointed by the amount of science being done and back again. I still have mixed feelings about it! In the end, it has done some great science, but I feel like it could have been so much more. But then again, you live and learn. But then again… Arrrghhh!
February 19th, 2009 at 1:37 am
If it were a water droplet that had almost immediately frozen onto the leg and then, during the heat of the day, (the leg is in direct sunlight, the droplet is on the opposite side of the leg, out of direct sunlight), the warmth heats the surface of the leg sufficiently that the still frozen droplet has now a surface layer, perhaps an atom thick that has melted such that the droplet, still frozen, slides across the surface of the leg.
That will give you the appearance of a liquid droplet with pure water and no need for any antifreeze.
Food for thought?
February 19th, 2009 at 1:40 am
Oh! And you could try this out for yourselves with your home freezer and a aluminium tube splashed with water. Once frozen, take it out into sunlight on a very cold day and see if it works.
February 19th, 2009 at 6:03 am
I also notice that with many fuels (I do not know the fule that powers the lander) Water is a product of combustion.
February 19th, 2009 at 6:43 pm
Didn't the lander have some trouble getting soil into its analyser because it was "too clumpy"? Soil on Earth tends to be clumpy when it's damp. Could this have any significance?
What's more, the lander finally shook the soil in after a few days. It's conceivable it was only able to do so because it had sufficiently dried out.
Mind you, ice (or dry ice) crystals could likely have a similar effect…
February 20th, 2009 at 12:22 pm
Ah, cool! (Or wet?
I remember Emily Lakdawalla over on Planetary Society blog speculating about those blob after their discovery, only to oversee the report on their putative liquid status when she linked to the 40th Lunar and Planetary Science Conference program. I was miffed at the time. 
IIRC one abstract from the above mentioned cementing as a possibility, from detected in abundance carbonates or so.
I'm not a chemist, but I don't get why Ian O'Neill persists in claiming "hindrance to life", on UT and IIRC on his blog. Googling perchlorates only gets me reports of toxicity for animals with nervous systems – among other things it seems to really mess with fish brains already at low concentrations.
I have no doubt that organisms that have evolved in an environment with a weak oxidizer would be able to benefit from it, especially in a Mars environment where it AFAIU is mostly inert in situ.
After all, earthly organisms have evolved intricate systems to not only handle but actually benefit highly from what I believe to be a much more toxic and potent oxidizer at extremely high concentrations. It is called oxygen…
And at the same time O'Neill glides over the difficulties that organisms have to evolve for extreme environments such as "very salty fluids". Most abiogenesis theories seems to have life starting out in relatively benign conditions since it is hard to envision for example membrane self-assembly otherwise, and it is by later evolving what I understand to be fairly intricate mechanisms for protection and self-repair that organisms can live in the more extreme milieus of an oxygen atmosphere or, seemingly much more difficult, high salinity.
February 20th, 2009 at 5:31 pm
The location of each of the little 'blobs' in the lander images, whatever they are, may be where micrometeors impacted during transit? Those impact sites then exposing raw metal to the Martian atmosphere… Tribo electric chemical oxidation anyone?
March 29th, 2009 at 2:57 pm
There is another new update on The Planetary Society Blog, including comments on why the Phoenix team et al, think the droplets were salty water brines and not just ice or frost and unlikely to be the result of hydrazine, etc. from the engine thrusters mixing in with melted ice:
http://www.planetary.org/blog/article/00001890
Excerpt:
“The first question that comes to mind is “Why don’t they think the spheroids are made of ice, not liquid water?” They argue that ice particles wouldn’t have formed in spheroids, they would have formed a thin, uniform layer, much like the frost coating seen later in the mission. For the spheroids to be ice at the observed weather conditions, the humidity would have to be higher than 100%. Also, toward the end of the mission, when frost was abundant at the landing site, ice spheroids should have grown in volume rather than shrinking. Ice couldn’t form on the lander leg unless the leg was colder than the ice, but engineering data returned from the lander shows warmer temperatures.
The next question that’s most often asked is “Couldn’t the thrusters’ composition have contaminated the landing site?” The answer is that Phoenix definitely disturbed her landing site; however, there is no evidence Phoenix chemically altered the site. If any ice was melted by the thrusters, it would have quickly turned into a vapor and not have turned into a liquid. After landing, several containers were vented, and all were on the opposite side from the spacecraft from where the robotic arm’s workspace, and thus also the leg that showed these spheroids. The engineering data doesn’t show that there was any hydrazine left to vent, and had there been, it would have been a solid at Phoenix’s site due to the low temperature. Any byproduct of the hydrazine would not have caused the spheroids either.”