Seth writes “Mars: Eau What A Find!”

by Keith Rozendal on August 11, 2011

Possible water flows on Mars, a video from NASA Jet Propulsion Laboratory California Institute of Technology

Seth Shostak took a moment to reflect on the recent Mars Reconnaissance Orbiter finding, in between a calls from the media seeking comment on its importance for SETI research.

Water on Mars? “Tell me something new,” you’re thinking.

Claims for evidence of water on the Red Planet seem to be as routine as Tax Day. So, why all the commotion about a recent NASA announcement that the Mars Reconnaissance Orbiter has found dark streaks that appear on crater walls during the martian summer?

Well, to begin with, the streaks – which are a few yards wide and as long as a football field – suggest the presence of liquid water (probably salty) immediately beneath Mars’ sandy surface. That’s a different story than the polar ice caps that seemed so intriguing to William Herschel more than two centuries ago, or the rock-hard ice found by NASA’s Phoenix Lander a few years back. The streaks could signal the presence of cold melt water – water that could support life.

But does it? Are there martian microbes in that soggy, subsurface dirt? We might find out, and fairly soon. Thanks to the fact that the suspected liquid is at shallow depths, it might be possible to build a robotic lander that could ease itself down onto the streaks, and use a drill to retrieve a soppy sample from below. Analyzing the sample chemically – or maybe just examining it with a simple microscope – might uncover alien pond scum. That would be major discovery, as it would imply that biology is rampant throughout the cosmos.

Sure, the idea of water on Mars is not new, but this wet stuff could be the right stuff.

{ 1 comment… read it below or add one }

avatar Matthew von der Ahe August 12, 2011 at 5:37 pm

Provocative images!

In the video, Dr McEwen says that the dark streaks develop each late spring and summer and then disappear, only to re-form the next spring. That makes me wonder a few things:

1.  Do the streaks disappear each autumn and winter because the slope is re-blanketed in dust? If so, how thick would the dust blanket have to be to make those streaks disappear? I assume that the mineralogy of the dust is pretty well characterized, so could the annual disappearance of the streaks suggest an annual deposition rate of the dust?
2.  The rimrock appears to be a much different color than the general colluvium, but nearer in color to the annual streaks. So are the streaks visible in the spring and summer because they are made of FRESH colluvium? Or are the streaks visible because they are made of WET colluvium?
3.  If the streaks are visible because they are made of FRESH colluvium, and if the slope is NOT annually re-surfaced with dust, then that the streaks disappear each year suggests very rapid weathering on those slopes! Remarkably rapid, considering Mars' parched, anoxic atmosphere. Or is their another mechanism possible for their disappearance?
4.  If the streaks are visible because they are made of WET colluvium, and if the slope is NOT annually re-surfaced with dust, then the streaks must disappear because the water sublimes away. So if the water sublimes, would it leave a salty "ring" behind? In very high resolution images, might those annual rings be detectable, kind of like micro-sized, evaporitic, travertine ledges?
5.  Is it likely that the streaks seem to emanate from the dark rimrock because the dark rimrock absorbs heat each spring sol and melts any adjacent ice, and the resultant water then lubricates down-slope movement of colluvium, forming the streaks?
6.  Water is implicated in the formation of the streaks. What is the assumed source of the water? Is the colluvium assumed to be similar to permafrost, with interstitial water?  Or does the water come from fractures in the rimrock? Or is the water dew that condenses  nightly, from the "humid" spring atmosphere, on the cold rimrock ?


Thanks for posting this!

Matthew von der Ahe

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