Salts on Mars Are a Mixed Blessing

By David Warmflash | June 20, 2016 7:00 am

Perchlorates are abundant on Mars, and they allow liquid water to flow. (Credit: NASA/JPL-Caltech/University of Arizona)

It’s a major component of solid rocket propellants. It allows water to exist as liquid on Mars, despite atmospheric pressure at the Martian surface being roughly 0.6 percent that on Earth. It also can be broken down to release oxygen that astronauts and future colonists in a Mars settlement could breathe.

It’s called perchlorate and it’s abundant on Mars –10,000 times more abundant in Martian dirt than in soils and sands of Earth. That may sound like a good thing, considering the useful properties of perchlorate, but there’s also a flip side.

Being a negative ion, perchlorate (ClO4) forms various salts, but it has detrimental health effects. Potassium perchlorate is used as a drug to treat certain forms of hyperthyroidism (overactive thyroid). But exposure to environmental perchlorate causes the opposite of hyperthyroidism, namely hypothyroidism — an underactive thyroid.

It would be devastating for Martian colonists.

An Ubiquitous Chemical Solves Two Mysteries

Perchlorate is all over the Martian surface. In 2009, NASA’s Phoenix lander identified perchlorate in the Martian dirt pretty much everywhere it looked. Then, last September, NASA’s Mars Reconnaissance Orbiter demonstrated very high concentrations of perchlorate salts within recurring slope lineae (RSL), features on the planet’s surface that were formed from relatively recent water flows. The finding solved a mystery of how Martian water could be liquid long enough to change the landscape.


Recurring slope lineae are seen as dark streaks as salty water oozes from the walls of Garni Crater on Mars. (Credit: NASA/JPL-Caltech/University of Arizona)

Because of the thin atmosphere, pure water on the Red Planet can persist only as ice or vapor, depending on the temperature. But dissolved salts change the physical chemistry, enough that subsurface liquid water can emerge from time to time and stick around as lakes and streams.

Following the perchlorate could lead us to underground water, which in turn could lead to native microorganisms, a long-sought milestone in space biology. But it would also factor into the choice for landing sites for human missions and colonies, plus it would facilitate terraformation – changing the planet to be more like Earth.

A Source of Energy and Oxygen

The oxygen and energy contained in perchlorate make it a potential energy source on Mars, both for generating electricity and for rocket propulsion. Ammonium perchlorate was the main propellant in solid rocket boosters of the space shuttles that NASA flew from 1981-2011. Mars colonization, and even early human landings, will depend on utilization of Mars resources to fuel craft that will ferry people between the surface and orbit, where they will link with larger ships that make the interplanetary voyage.

Having four oxygen atoms per molecule also makes perchlorate useful to life-support systems. Colonists could employ certain microorganisms from Earth that break up the molecule to release O2. The extracted O2 could be pumped through life support systems of enclosed underground habitats.

Later, the process could be scaled up to enrich air that’s pumped into sealed caverns and craters to help achieve paraterraforming — creating Earth-like environments within limited enclosed areas rather than encompassing the entire planet.

Not a Solution for Liquid Water

Although high concentrations of perchlorate will maintain water in a liquid state, it would be toxic to drink and wouldn’t support microbial life. On Earth, salt-loving microorganisms thrive in the Dead Sea. However, Dead Sea salts are not perchlorate salts, and Mars’ surface water is far more briny than the Dead Sea — even more briny than Antarctica’s Don Juan Pond, where salinity is 44 percent.


The saltiest pond on Earth. (Credit: NASA Earth Observatory image by Jesse Allen)

Along with hypothyroid conditions, perchlorate has also been implicated in aplastic anemia and agranulocytosis, conditions characterized by a life-threatening deficiency of blood cells. Perchlorate is particularly dangerous for infants dependent on lactating mothers; that’s enough of a concern on Earth, but especially alarming on a new world that interplanetary colonists might populate.

This means that we’ll have to take extreme precaution to remove perchlorate from Mars water and dirt, or from any crops that we grow in it. Dust will have to be kept from contaminating air circulating through life support systems. Future explores and colonists will have to do all of this, not only as they capture the perchlorate in order to reap its benefits, but also as they confront space radiation, physical deconditioning from low gravity, and other potential Martian threats to human health.

CATEGORIZED UNDER: Space & Physics, Top Posts
MORE ABOUT: Mars, space exploration
  • Uncle Al

    Following the perchlorate could lead us to underground water, which in turn could lead to native microorganism” Were that statement operationally true, NASA would be furiously culturing a vast range of terrestrial genera at 98% perchlorate concentration lethality to evolve perchlorate-welcoming biologies. First, that would remediate so many tens of thousands of US acres wherein rocket solid fuel (e.g., the Space Scuttle) and military propellants have contaminated soils and water tables through manufacture, storage, transport, and use.

    Second, it would give NASA a hint (no easy task, that, in any venue) about what to seek in Martian biology. NASA is budgetarily fueled by studies not successes. Success unemploys research and its unaccountable bureaucratic oversight.

    • zero

      Success leads to new fields of study, expanding the research horizon. Success scores political points, expanding the potential future budget. Make no mistake, government-funded research is as ruthless as any M&A firm. This is what happens when we push for many STEM graduates, then only fund enough research to keep maybe 20% of them employed.
      Our government is not a lumbering bureaucratic behemoth any more; it is a collection of sadistic kids paying homeless people to fight for their amusement..

      • Julia

        Hopefully as orbital sciences/robotics/general need for advanced technology graduates become more and more in demand, this will get fixed, and government can stop subsidizing oldtech such as fossil fuels…

  • zlop

    Lava tubes — perhaps caves formed by other means,
    could be a basis for a Martian outpost?

    • John C

      Once we conquer the Cyclopean Cave Bears.

      • zlop

        Elon the, forgettable, CO2 confused,
        is he in the bloodlines of the Illuminati?

        There could be chemically formed caves similar
        to limestone formations, dried out geysers?

  • Mike Richardson

    Thawing out frozen but relatively fresh water wouldn’t be such a problem. Unfortunately, the need for heavy-duty desalination wasn’t something the original Mars mission planners took into consideration. At least these precursor robotic missions are giving us a better idea what to expect before humans set foot on Mars.

  • zero

    So what you’re saying is:

    – Colonists would have to practice decontamination routines, as already envisioned (though not as rigorous as lunar colonies)
    – Native soil would have to be washed before use in agriculture, which is already planned (or at least considered) in order to leach heavy metals.
    – As a structural material native soil should not be exposed to habitable atmosphere unless processing renders it safe.
    – Outposts should maintain supplies of medicines to reverse the effects of perchlorate exposure

    That doesn’t sound like a big deal compared to the many other problems facing a Mars colony.

  • 12golden

    im prepared to disagree,these are theories and not proof,or fact

  • James Gherson

    ” This means that we’ll have to take extreme precaution to remove
    perchlorate from Mars water and dirt, or from any crops that we grow in
    it. Dust will have to be kept from contaminating air circulating through
    life support systems.”

    As it will more than likely be , a corporate endeavor to colonize Mars…..who can already see measures being taken ,to cut corners and risk peoples lives…. just to save time and money ?

  • Julia

    Answer = genetic engineering…, but you knew this..


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