Earlier this week we wrote about NASA’s announcement that its Mars Reconnaissance Orbiter had beamed back observations that suggested the strong possibility of their being liquid water on Mars. With the office, the country and the world excited by the announcement and the very distant idea of extraterrestrial life, we needed an expert opinion. So we asked Sergio Colafrancesco PhD, Professor of Radio Astronomy at the University of the Witwatersrand, to explain what the NASA findings mean now that the excitement of Monday’s findings have calmed down.
I think that the case of this announcement is a combination of three things:
- An interesting scientific result.
- An interpretation of the results based on a number of assumptions.
- An overstatement of the consequences of these results.
Let me explain why I think so.
An interesting result
Certainly the discovery of these specific set of minerals, perchlorates (hydrated salts) of various species in specific areas near the equatorial regions of Mars is quite interesting although not entirely new. In fact, in May 2008, the Wet Chemistry Laboratory (WCL) on board the 2007 Phoenix Mars Lander performed the first wet chemical analysis of martian soil. The analyses on three samples, two from the surface and one from depth of 5cm, revealed a slightly alkaline soil and low levels of salts typically found on Earth. Unexpected though was the presence of ~0.6% by weight perchlorate (ClO4−), most likely as a Ca(ClO4)2 phase.
These salts, formed from perchlorates discovered at the Phoenix landing site, act as “anti-freeze” and will substantially lower the freezing point of water. Based on the temperature and pressure conditions on present-day Mars at the Phoenix lander site, conditions would allow a perchlorate salt solution to be stable in liquid form for a few hours each day during the summer.
In 2006, a mechanism was proposed for the formation of perchlorates that is particularly relevant to the discovery of perchlorate at the Mars Phoenix lander site. It was shown that soils with high concentrations of chloride converted to perchlorate in the presence of sunlight and/or ultraviolet light. The conversion was reproduced in the lab using chloride-rich soils from Death Valley. Other experiments have demonstrated the formation of perchlorate is associated with wide band gap semiconducting oxides. In 2014 it was shown that perchlorate and chlorate can be produced from chloride minerals under martian conditions.
Further findings by the Mars Curiosity rover in 2012-13 support perchlorates as being widespread, and even inspired a Science article titled “Pesky Perchlorates All Over Mars”. At half-a-percentage of the component of Martian soil (“a fair amount”), Martian perchlorates present a serious challenge to human settlement, and have rendered Kim Stanley Robinson’s Mars trilogy somewhat anachronistic.
An interpretation of the results based on a number of assumptions
The fact that these perchlorate salts “…Confirms Evidence That Liquid Water Flows on Today’s Mars” depends on several assumptions and hypotheses. First that there is briny water already existing on Mars that then melt with increasing surface temperatures and produce liquid perchlorate flows that the produce these dark flows observed on the surface of Mars.
“What we’re observing here is the spectroscopic signature of perchlorates that are hydrated by water,” [Lujendr] Ojha [lead author of a report on these findings] explained to me via phone from France on Sunday, “These perchlorate salts have salt crystals that have molecules of water in them.”
Now having a water molecule needed to form a perchlorate, does not necessarily mean that there are rivers of waters flowing on Mars awakening on hot days and returning in quiescent state in cold days.
Beyond what has been announced, researchers say that “The flows are not dark because of being wet… They are dark for some other reason.” Basically the supposed flow initiated by briny water could rearrange grains or change surface roughness in a way that darkens the appearance. How the features brighten again when temperatures drop is harder to explain.
“The best explanation for these observations so far is the flow of briny water,” said Alfred McEwen of the University of Arizona, Tucson, thus this is a possible and indirect interpretation of the results of the existence of perchlorates in these Martian regions, but certainly not a direct proof and even less a new discovery.
“It’s a mystery now, but I think it’s a solvable mystery with further observations and laboratory experiments,” McEwen said , thus confirming that this is only a possible interpretation of the results and a direct probe for the existence of liquid water on Mars still needs to be found.
An overstatement of the consequences of these results
When it is written that “NASA Confirms Evidence That Liquid Water Flows on Today’s Mars” or that “NASA’s Mars Reconnaissance Orbiter has captured the strongest evidence yet that salty liquid water flows on the planet’s surface during warm seasons” or that “This is the smoking gun,” (as Ojha told CNET) amongst other strong statements, we are bypassing the self-consistent scientific interpretation of experimental results.
There is no definite proof yet for the existence of liquid water on Mars, but only very indirect facts that might be related to that, and this should also not be directly connected with the existence of life on Mars (“If the water is completely saturated with perchlorates [hydrated salts], then life as we know it on Earth wouldn’t be able to survive in that sort of concentrated water,”Ojha says. “But if the water only has a tiny percentage of perchlorates in it, then I think we should be fine.”)
As stated earlier, this [still] presents a serious challenge to human settlement.
It should also be remembered that “extremophile” (from Latin extremus meaning “extreme” and Greek philiā (φιλία) meaning “love”) ie. organism that thrives in physically or geochemically extreme conditions that are detrimental to most life on Earth, have already been found on the Earth and could easily live on Mars, thus announcing extreme forms of “life” in the cosmos.
New sub-types of -philes are identified frequently and the sub-category list for extremophiles is always growing. For example, microbial life lives in the liquid asphalt lake, Pitch Lake. Research indicates that extremophiles inhabit the asphalt lake in populations ranging between 106 to 107 cells/gram. Likewise, until recently boron tolerance was unknown but a strong borophile was discovered in bacteria. With the recent isolation of Bacillus boroniphilus, borophiles came into discussion. Studying these borophiles may help illuminate the mechanisms of both boron toxicity and boron deficiency.
Therefore, life could arise also in the absence of flowing water, even on Mars.
Maybe we should be more attentive at being consistent with the scientific analysis and experimental proofs rather than discussing on aspects that are at the edge of speculative interpretations of scientific facts, and also we should be more open to accept that life in the cosmos is a much more complex phenomenon than just a minuscule stream of salty water.[Main image – NASA]
PS: certainly this field (astrobiology) is an emerging field of interest in South Africa and I personally believe it is a fertile ground of cross-disciplinary research that should be cultivated.