The Possible Intermittent Wettness of Mars
A new study seems to hint that the idea of a warmer mars with flowing water may have only occurred during repeated yet very brief periods in its history precipitated by volcanism only to disappear when the volcanoes stopped erupting.
It has become an iconic belief about Mars that in its past, water flowed extensively over the planet creating streams, rivers, and lakes whose ancient remains are still detectable today, almost 4 billion years after the fact. NASA’s Curiosity rover strengthened that belief late in 2013 when it provided evidence of an old lake-bed near its landing site.
The reflexive implication of all this watery evidence is that Mars enjoyed great swaths of time during which the water flowed, making it much more earth-like than it is now, dare we say even tropical? Over the years though, this evidence for a warmer Mars with flowing water made less and less sense as we learned more and more about what the planet was like back then.
3.7 billion years ago (when much of the water flowed), the atmosphere of Mars was simply too thin to hold onto enough heat for liquid water to exist. The sun itself did not help matters considering it was a whopping 25% dimmer than it is now. Atmospheric models completed 2 years ago concluded that there wasn’t a single place on the planet warm enough for water. How could a bitterly cold and ice-covered ancient Mars produce water then? Mars’ axis would have to have been tilted 40 degrees or more in order for the planet to be heated sufficiently. Some models actually predict that the planet could tilt its axis by the required amount for millions of years at a stretch but this isn’t the answer since, even if that happened, the wrong parts of the planet would have been warmed. The final word from the model being used was that some other mechanism must have been in play to cause the clear evidence we see today of a warmer Mars.
That mechanism may be just what was found by a team of scientists at Brown University and the Weizmann Institute of Science in Israel.
As it turns out, that mechanism may very well be volcanoes. This is possible because the period in Mars’ history when water was prevalent happened to coincide with tremendous volcanic activity. Not only that, the pattern of ancient lakes and valleys in the lower latitudes make sense in the context volcanic eruptions happening nearby.
You may be thinking, how could volcanic eruptions warm the planet to allow ice to melt and flow. After all, large eruptions of ash on the earth in the past have been shown to cool the earth due to the reflection of light from the sun off the ash and back into space. That however is what happens on Earth, Mars may have been a different story. To explore this option the researchers modeled volcanic activity in the ancient Martian atmosphere and discovered something very interesting. Sulfuric acid particles from the eruptions could have attached themselves to the ubiquitous atmospheric dust causing it to be less reflective and thereby allowing more light in from the dim sun to heat the planet. In addition, Sulfur dioxide gas could have been generated in sufficient quantities to cause a greenhouse effect, further nudging the temperature above freezing in certain areas.
The kicker though is that such events would have been episodic at best, occurring occasionally within a 200 million year window. The warming events would have allowed water to flow only for tens of years or perhaps a meager few centuries. Still however, over the course of such a long time, many of these events would have occurred which could readily explain the proliferation, even billions of years later, of the evidence we see of ancient water on Mars.
Keep in mind that this conclusion is still preliminary and is, as of yet, still just one potential mechanism to explain the curious history of water on Mars.
Regarding this, James Bell III, a planetary geologist at Arizona State University in Tempe said the following:
(The study) “makes a reasonable argument that’s consistent with a lot of data…But there’s still a lot of other data that’s not consistent” (with the idea of water’s limited presence on the planet.)
If this is true though, I can’t help but think what the implication for life on Mars would be. It seems reasonable that a Mars with water on it consistently for millions of years could spawn some sort of simple life forms. An intermittent wetness though seems to greatly lower the odds of this happening. Of course subsurface water could have persisted for far longer than what existed on the surface.
James W. Head, professor of earth, environmental and planetary sciences at Brown University is also optimistic.
“Life in Antarctica, in the form of algal mats, is very resistant to extremely cold and dry conditions and simply waits for the episodic infusion of water to ‘bloom’ and develop…Thus, the ancient and currently dry and barren river and lake floors on Mars may harbor the remnants of similar primitive life, if it ever occurred on Mars.”
This is certainly encouraging but it still assumes life could develop from raw chemistry even in an environment that is only episodically unfrozen. This final reservation would of course be moot if life, already started on Earth, seeded Mars in a spasmodic fit of Panspermia.
Image credits: http://brainmind.com/Mars.html