NASA has called a news conference for Monday about a “major science finding” on Mars, and there’s strong speculation it will announce there’s liquid water flowing on the Red Planet.
Streaks of salt running down cliffs and hillsides on Mars are the strongest evidence yet that modern-day water — a key ingredient in life — exists in important quantities.
The streaks have tantalized Mars-watchers for several years since a satellite photographed them. One study from 2013 suggests they reveal “surprisingly abundant liquid water” at some places on Mars, likely just under the surface where it could nurture life just as moist soil does on Earth.
The dark streaks could be dried salts left by salt water running on the surface. And since the lines fade and reappear over time, the scientists conclude that this water is still flowing regularly today.
Mars has been known to have water for years, but only as ice and snow, not liquid water. Matthew Chojnacki, a planteary geologist at the University of Arizona, says the new evidence was “hidden in plain sight,” unrecognized for 10 years. He describes it in a blog as “narrow, dark-toned streaks that descend steep Martian slopes, beginning in higher-lying rocky outcrops. We have watched them grow, fade, and reappear every year” in photos taken by a satellite orbiting Mars.
“They grow fast, over time scales as brief as a week. Their seasonal behaviour and preference for warm equator-facing slopes suggests that something volatile, like briny water, could be involved.”
Some are on canyon walls, others on smaller mounds. Most are near the equator, the warmest Martian region (though still much colder than Earth, since Mars has very little atmosphere to trap heat.)
These warm slopes facing the sun do reach temperatures warm enough to produce liquid water, he writes on the website of The Planetary Society. But there’s a problem:
“But pure water should rapidly evaporate or even boil in the thin Martian atmosphere. In contrast, liquid brines that would form in the salty soils commonly observed at Martian landing sites have depressed freezing temperatures, and are much more stable in the harsh conditions of the Red Planet.”
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Earth’s own Antarctica offers a “tempting” comparison, he says: “There, similar features, called ‘water tracks,’ form from salty brines on steep slopes.”
Chojnacki presented a paper on the issue of Martian water at a major conference on lunar and planetary science last year. A paper by Chojnacki and others in Nature Geoscience in 2013 summed up the theory this way: “We observe the lineae (dark lines) to be most active in seasons when the slopes often face the sun. Expected peak temperatures suggest that activity may not depend solely on temperature.
“Although the origin of the recurring slope lineae remains an open question, our observations are consistent with intermittent flow of briny water. Such an origin suggests surprisingly abundant liquid water in some near-surface equatorial regions of Mars.”
What look to be salt streaks, left behind by briny running water, have been observed on Mars. And if there’s water, and possibly life, this gives a boost to discussion of a whole related issue: a theory of where life began called transpermia.
In this theory, primitive life could have been moved from one planet to another during some of the many collisions in our solar system. We know there are Martian rocks on Earth; meteorites traceable to Mars show up here all the time. It’s likely that fragments knocked loose from Earth have gone the other way too.
So, could life on Earth have come from Mars? Or could Martian life have come from Earth? It’s a point of eager discussion.
Another implication: Spacecraft sent to Mars are already subject to rigorous cleaning so that we don’t accidentally contaminate another world with Earth microbes. The presence of water could make that demand more urgent.
NASA hasn’t said much about its news conference. But it gives a strong hint: One of the scheduled speakers is Lujendra Ojha, the student who first noticed the dark streaks years ago.
Just maybe. Picture: 20th Century Fox
