Mars may harbor subsurface liquid water

I wrote this piece as my “Discovery Story” assignment for En84, “Writing About Science,” at Caltech, and got an A. The press release I drew information from is here and the original paper is here.

 

Ancient Mars was a warm and wet place, coursing with rivers and lakes. Though the lakebeds are now dusty and the water long gone, researchers have recently discovered evidence that the present-day Mars may not be as dry as we thought. The evidence suggests that a thin layer of salty liquid water may exist just under the Martian surface, condensing in the cool hours of night and evaporating in the morning.

Conditions on Mars are not favorable for liquid water — Martian temperatures and atmospheric pressures only allow water to exist as ice or vapor. However, the Curiosity rover recently detected a chemical compound in the Martian soil that could make it possible for water to exist in a liquid form.

The compound, called calcium perchlorate, lowers the freezing point of water, acting like an anti-freeze by allowing water to exist in a liquid state even under temperatures where it would normally form ice. Under particular humidity and temperature conditions, perchlorates can also absorb water vapor from the atmosphere, forming salty liquid solutions called brines that can then trickle down into the soil.

While perchlorates are abundant in many places on Mars, this is the first time they have been detected along with the right humidity and temperature for brines to form. Additionally, these conditions were detected at the equator — the driest and hottest region of Mars. If the delicate brine-forming conditions can exist even on the harshest region of the planet, it’s likely that milder regions can stably support brines as well.

The authors measured air humidity and temperature at the equator using Curiosity’s Rover Environmental Monitoring Station (REMS) over a Martian year. They describe the brines as “transient” because the proper humidity and temperatures for brine formation don’t last throughout a full Martian day. The salty solutions only have one night to condense before evaporating with the sunlight.

Liquid water is considered a crucial building block for life, but these brines are unlikely to harbor it — they are simultaneously too short-lived, too cold, and too exposed to solar radiation to support terrestrial organisms.

“Conditions near the surface of present-day Mars are hardly favorable for microbial life as we know it, but the possibility for liquid brines on Mars has wider implications for habitability and geological water-related processes,” says the lead author on the study, Javier Martin-Torres of the Spanish Research Council in Spain and Sweden’s Lulea University of Technology. He is also a member of Curiosity’s science team.

Though for now this finding seems to have few extraterrestrial implications, it is part of a collection of Curiosity’s discoveries that are transforming our perception of Mars. Last year, Curiosity measured sharp spikes and drops in atmospheric methane concentration, implying that somewhere on Mars is a source producing the organic chemical. Scientists have also observed dusty geysers of carbon dioxide erupting from the polar ice caps in the warming of spring. Mars is turning out to be a much more diverse and dynamic planet than we thought.

What you’ve all been waiting for: The Experiment

After several weeks of soldering wires and sealing leaks, Rita and I were finally ready to get some Martian simulation going. Because the scientific process should always be transparent, here’s your personal guide to making those lovely irradiated magnetite samples you’ve always wanted.

Now don’t try this at home, kids.

1. Flush the glove box with nitrogen, three times for 15 minutes each. By filling the glove box with nitrogen, we ensured that in the unlikely case of a leak in the chamber, the surrounding atmosphere was unreactive. Rita and I made sure to stand in the hallway when the nitrogen was on, to avoid any unintended unconsciousness.

2. Put the magnetite on the tray and place it into the transfer chamber. We created a vacuum in the chamber, then filled it with nitrogen from the glove box. We did this vacuum-and-fill process three times to make sure no external atmosphere got into the glove box when we transferred in the sample tray. This is important – it’s not a very good Mars simulation chamber if there’s a ton of Earth’s atmosphere in it. We used a glove box that looks like the one below. (Image from Wikimedia Commons.)

 

  • How do you move things around when they’re already in the glove box? The glove box is totally sealed, so we use these awesome built-in gloves to handle the samples once they’re inside. But use caution: wearing these seemingly-invincible contraptions may make you feel and act like a true mad scientist.

3. Take the samples from the transfer chamber, and put them into the simulation chamber. Using our invincibility gloves, we sealed the sample tray inside the small Mars chamber. These are the magnetite samples we used: a chunk from Greenland, a chunk with olivine inclusions, and a very fine powder.

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4. Suffocate the samples. We vacuumed the chamber using first the back pump, and then the turbomolecular pump, so it’s nice and airless. We then let in 18 millibars of CO2 (a millibar is a unit of pressure – one millibar is about the pressure exerted by a penny lying flat). Remember, only the chamber that becomes a vacuum – the surrounding glove box is still filled with nitrogen.

5. Turn on the UV light. You wouldn’t bake a cake without turning on the oven, so why would you even think about doing this experiment without the radiation?

6. SCIENCE HAPPENS! We left the samples under the radiation for two weeks, checking the pressure and UV lights daily to make sure everything was working properly.

On August 11, we removed the samples to be analyzed. I know you’re dying to find out if the radiation mutated our magnetite into miniature Martians, but you’ll just have to wait for the next blog post.

Mechanical Mars – An Interactive Post

When I first saw the Mars chamber I would be working with, I felt just the tiniest sense of utter bewilderment, and possibly a hint of panic. I am not an engineer, and this thing looks mega intimidating.

Thanks to the awesome Rita Kajtar, who made major contributions to the chamber’s construction as part of her masters thesis, I began to understand its various bits and pieces. But still, I knew I’d have a hard time explaining it to you without some visuals. And so, since hands-on learning is the best learning, I made you an interactive photo! Mouseover for some enlightenment.

And here’s the sample tray that goes inside of the Chamber. 

Since science and technology are ever-updating fields, there are of course a few improvements that still need to be made. For example, even though experiments are run under a near-perfect vacuum and condensation is unlikely, a humidity sensor needs to be added. And even though we can use the ideal gas law to make a rough estimate of the temperature during the experiments, it would also be helpful to have a temperature sensor.