NASA scientists are currently trying to understand a set of images taken by the Phoenix Mars Lander shortly after it landed on the Red Planet in May 2008. The images in question show one of the robot’s legs covered in what appears to be droplets of liquid water. The droplets remain on the lander for some time, appearing to get larger and changing shape.
By now, we know that liquid water (apparently) hasn’t existed on the Martian surface for hundreds of millions of years; the atmosphere is currently too thin and too cold to support liquid water. However, the confirmed presence of perchlorate in the regolith may provide an important clue as to what might be going on…
In August 2008, the Phoenix Mars Lander had discovered something… provocative. It was one of those extremely lucky space blogging days, when I stumbled across an Aviation Week article entitled “White House Briefed On Potential For Mars Life“. Technically, the article was correct, but the added secrecy about some discovery being passed to the President before being made public seemed more conspiracy theory than scientific theory. However, I blogged like I’d never blogged before and got this breaking news onto Astroengine.com and the Universe Today in record-breaking typing speed (yes, 50 words per minute is record breaking for me).
I was immensely happy to be up there in the first few bloggers who had posted the news first, but the web traffic tidal wave that ensued knocked both sites offline. It was mayhem, especially for Astroengine. In the first day, I think I got washed away with 50,000 visits from various social bookmarking sites, I have no clue how many slammed the Universe Today server, but it was a lot.
However, the facts behind the headlines weren’t 100% clear. “Potential for life” didn’t necessarily mean it was going to be news of Martian cockroaches setting up home under Phoenix, it was actually the opposite. A toxic chemical called perchlorate had been discovered, more of a hindrance than an advantage to life as we know it. Bummer.
But like all good Mars research projects, there’s a flip-side to this potentially disastrous news; perchlorate is a salt. What does salt do when dissolved in water? It lowers the freezing point of water. Therefore, if perchlorate exists in the Martian regolith, it may also be dissolved in the water we now know (thanks, also, to Phoenix) exists there. Although the temperature never rose above -20°C at any point during Phoenix’s lifetime, perchlorate turns out to be a very potent antifreeze substance, allowing water to remain in a liquid state regardless of the extreme atmospheric temperatures down to -70°C.
Although far from being conclusive evidence about the existence of liquid water on the Martian surface, these Phoenix images do appear to show droplets of water on the lander’s leg. Before the discovery of perchlorate salt in the regolith, these images would probably have been written off as a curiosity, but now NASA scientists are actually entertaining the thought that liquid water can exist on the surface.
But how did the water get on the leg? Either, the Phoenix rocket landing boosters melted a layer of ice on the surface (possibly pure water-ice, melted and mixed with perchlorate, or a water-perchlorate ice mix), or a pool of existing liquid water (plus perchlorate mix) was already there. The lander dropped right in the middle of the puddle, splashing the leg with liquid water that would not freeze, captured in these images.
If liquid water exists on the surface of Mars, with the help of perchlorate, there could be a profound Martian irony: Although we understand perchlorate to be toxic to life on Earth, it might be provide life-giving liquid water to very basic forms of microbial life that thrive in briny fluids.
Perchlorate might be of some use after all…
For more, check out my article on the Universe Today: Has Liquid Water Been Detected On Mars?