Perchlorate, which is 10,000 times more abundant on the dirt on planet Mars than on Earth’s soils and sands, has beneficial properties, but can also spell disaster for future human colonists in a Mars settlement.
Perchlorate allows water to remain liquid on Mars, despite the planet's atmospheric pressure of about 0.6 percent of Earth’s. It can also break down to unleash oxygen that future human explorers on Mars can breathe in.
On the flip side, this negative ion — while it can form different salts — can prove detrimental health effects. Its environmental form, for instance, causes hypothyroidism or an underactive thyroid.
Perchlorate As Mystery Solver
In 2009, The Phoenix lander of NASA identified that this ubiquitous chemical in Martian dirt is practically everywhere. In September 2015, the Mars Reconnaissance Orbiter identified extremely high levels of perchlorate salts within so-called recurring slope lineae (RSL), which are planetary surface features borne out of quite recent flows of water.
The discovery turned out to be the missing piece of the puzzle showing how water on Mars could stay liquid enough to alter the landscape.
The Red Planet’s thin atmosphere allows pure water, depending on a given temperature, to exist only as either ice or vapor. Dissolved salts, however, alter this chemistry and effectively let subsurface liquid water to surface once in a while and manifest as lakes or streams.
Thus, perchlorate could hold the key to understanding underground water, and in turn microorganisms that lend insight into space biology. In addition, it could help determine the right landing sites and positions of human colonies, and “changing” Mars’ design to resemble Earth.
Potential Downsides
Perchlorate is instrumental in maintaining liquid water, but it would be poisonous to drink and would not be supportive of microbial communities.
“On Earth, salt-loving microorganisms thrive in the Dead Sea,” Discover Magazine reported. “However, Dead Sea salts are not perchlorate salts, and Mars’ surface water is far more briny than the Dead Sea.”
The brine levels, for instance, exceed those of Don Juan Pond in Antarctica, which are marked at 44 percent salinity.
And it’s not just hypothyroidism that one has to watch out for. Perchlorate has also been linked to conditions marked by potentially fatal blood cell deficiencies, such as aplastic anemia. On Earth, it is a particular threat to babies who rely on their lactating moms — how much more on the remote, unpredictable Martian landscape?
Added precautions then become necessary to remove this concern from Martian dirt or water, as well as any space crops to be grown in it. For instance, dust would need to be barred from tainting the air that circulates through life support structures.
Perchlorate needs to be captured for its wealth of benefits, including being a likely electricity and oxygen source and serving as a major ingredient of solid rocket propellants. But it could hold certain disadvantages just like space radiation and the physical impacts of low gravity — something human explorers should constantly be on the lookout for.
Just this week, an analysis of data from the Curiosity rover revealed evidence of tridymite on Mars — a mineral linked to volatile volcanoes on Earth and can potentially change our perception of the planet that holds no proof of plate tectonics.
