Follow the Water

For several tantalizing months last year, NASA's Phoenix Mars spacecraft sent back images from the Martian Arctic of what scientists were pretty sure was ice.  Water -- the stuff of life -- frozen in the red soil.

Now, a team of scientists, led by Nilton Renno of the University of Michigan, is making a new splash, if you'll pardon the pun.  They have presented a paper saying they think Phoenix saw liquid water -- splashed onto part of its landing gear.  If they're right, it's a big deal.

Or maybe not.

Their paper is HERE, and their wording is pretty bold.  "We show independent physical and thermodynamical evidence that besides ice, liquid-saline water exists in areas disturbed by the Phoenix lander," they write.  A few lines later, "we hypothesize that liquid saline-water is common on Mars.  This finding has important implications for the stability of liquid water, weathering, mineralogy, geochemistry, and the habitability of Mars."

Their theory is that the Martian soil around the Phoenix landing site was rich in perchlorate salts, which act as antifreeze when mixed with water in the thin atmosphere.  The result, they say, is what you see in the following three images:

These pictures were taken 8, 31 and 44 Martian days after the landing last May.  Look at the two highlighted spheroids, and how they appear slowly to merge, a little like droplets on your windshield on a soggy day.

Keep in mind that this was a paper presented at a conference specifically to provoke scientific debate, not a peer-reviewed published paper meant to report a finding.  So the debate is on, and other scientists have their doubts. 

"It's just water vapor moving around," said Michael Hecht, a Phoenix co-investigator at NASA's Jet Propulsion Lab. 

"I completely agree with Nilton that the topic deserves attention," he said to me on the phone.  "I only disagree with him -- strongly -- on whether there was liquid water on the landing struts.  It distracts from some of the more important questions."

Hecht said, "It may just be plain old ice."  Ice is very common in the universe -- think of comets, or the moons of Jupiter.  Water in gaseous form is too.  But liquid water is critical to life as we know it, and so far it seems very rare.

"I suppose sending another ship to get more answers would be nice?" I asked with a laugh.

Hecht answered in the same spirit. "If you know any NASA higher-ups, please let me know."

(Photo credits: NASA/JPL)

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