Martian Gullies Explained By ... Sand
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eldavojohn writes "There's a lot of evidence that a very long time ago some fluid once flowed on Mars, but the primary evidence of water today — gullies inside craters — is explainable by a much less exotic reason: flowing dust and sand. It would now seem that the news from 2006 that NASA had found definitive evidence of flowing water on today's Mars needs to be comprehensively reexamined. The Bad Astronomer lays claim that flowing sand and dust doesn't explain all recent hi-res imagery from the red planet, but it certainly does seem more plausible, considering what we know about Mars."
Re:Terraforming (Score:5, Interesting)
Mass is not the issue; the lack of a magnetosphere is. Without a magnetosphere, the solar wind will strip the atmosphere, leaving you in the same state. We would need to provide some means of creating a field which shields the atmosphere from solar winds.
Did a quick google to find an article - this one was published in 2010: http://science.nasa.gov/science-news/science-at-nasa/2001/ast31jan_1/ [nasa.gov]
"You keep using that word" (Score:4, Interesting)
This actually hits on one of my personal bugaboos - scientists that claim to know something "definitively" while the research or hypothesis is still warm from the metaphorical oven. Unfortunately, the institutions that employ them have figured out that you can get funding through "science by press release" - the initial press release gets the headlines; the retractions are hardly noticed (except on Slashdot). The scientists themselves are certainly culpable as well for going along with this - they should know better. Only a small percentage of theories stand the test of time. Yes, I understand that it's 2010 and we all want answers right now, dammit, but 99.99% of the time life just doesn't work that way.
So anyway, "definitively" - You keep using that word. I do not think it means what you think it means.
Re:no water no life no nothing ..... (Score:4, Interesting)
NASA has definitely found water on Mars already.
They also found a number of minerals in the rocks that can only form in water, as far as we know.
True, that as far as we know bit means it could be something else, but let's stick with known laws until we have evidence of something else before jumping of the cliff labeled "It's got to be caused by an unknown means". Don't forget Occam's Razor. (Especially when the alternative is trying to choose between Known Science and Baseless Denials.)
Does this mean the dust & sand thing is wrong? Not really, but it doesn't mean that water is out either. Funny thing about places that change environments, their primary methods of erosion change as well. Just look at Egypt over the past 30,000 years as a small example.
Thanks
Re:Terraforming (Score:3, Interesting)
Well, if you crash a bunch of asteroids into it, it will likely become molten, creating a new phase of differentiation, and there is a reasonable chance that a new dynamo will form and create a new magnetosphere. It's at least as plausible that that would happen as you could crash a bunch of asteroids into it in the first place. It wouldn't likely last all that long in geological terms given the likely lack of useful radionuclides.
Re:Photo of water on mars. (Score:3, Interesting)
Mars Phoenix Lander dug some up and it sublimated away: http://spaceweather.com/swpod2008/22jun08/ice_gone_blink1.gif [spaceweather.com]
-molo
Re:Terraforming (Score:3, Interesting)
Venus has an induced magnetosphere, created by an ionized layer in the ionosphere. That said, it is theorized that 4 or 5 billion years ago Venus used to have more liquid water on the surface and in the atmosphere, and over time that many of the lighter gases (such as water vapor) have been blown away by the solar wind, and those gases continue to be blown away, resulting in the atmosphere we see today.
As I said earlier, for Mars to have an atmosphere including water vapor, some protective layer would have to be created. I should have been clearer and stated it did not have to be a magnetosphere.
Re:"You keep using that word" (Score:3, Interesting)
The more time I spend in college the more I realize that nearly everything that we "know" is really just semi-educated guesses.
In my experience this applies to just about every science except perhaps math.
Re:Martian Water (Score:4, Interesting)
I share your exasperation with the lack of popsci understanding of Mars' variable temperatures & pressures.
When I used to run planetarium shows for kids, I used to explain the temperature gradient by telling them, "If you stood on Mars, you'd wear sandals and a parka, since your feet would be as warm as a summer day but by the time you reached your head it'd be colder than winter in Antarctica!" which, although on the "tiny lies of oversimplification" side, is true-ish and a vivid enough image that they remembered months later.
Re:Terraforming (Score:3, Interesting)
Huh, so it does. I mean, I'm not the AC, I figured it had a magnetosphere, but thought it was due to having a molten core like Earth.
A quick skim of the wiki link doesn't seem to mention anything about it, but I seem to recall hearing about Venus' molten core with regard to the planet having periodic planet-wide catastrophic volcanic explosions because the lack of plate tectonics does not offer a more gradual pressure release system like on Earth.