The baffling case of the tiny craters on the Meridiani dunes

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silylene old

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Ok, I will try one more time.<br /><br />There are baffling microcraters all over Meridiani. What causes them?<br /><br />Here is a very good thread to read on this subject:<br />http://www.unmannedspaceflight.com/index.php?showtopic=943<br /><br />I proposed a sapping mechanism involving melting subsurface ice nodules are the cause:<br />http://www.unmannedspaceflight.com/index.php?showtopic=943&st=105<br /><br />I thought that maybe this would be an interesting SDC discussion subject. Any serious ideas for their origin?<br /><br /> <div class="Discussion_UserSignature"> <div class="Discussion_UserSignature" align="center"><em><font color="#0000ff">- - - - - - - - - - - - - - - - - - - - - -</font></em> </div><div class="Discussion_UserSignature" align="center"><font color="#0000ff"><em>I really, really, really miss the "first unread post" function.</em></font> </div> </div>
 
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vogon13

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Secondary craters caused by ejecta from a nearby crater perhaps?<br /><br /> <div class="Discussion_UserSignature"> <p><font color="#ff0000"><strong>TPTB went to Dallas and all I got was Plucked !!</strong></font></p><p><font color="#339966"><strong>So many people, so few recipes !!</strong></font></p><p><font color="#0000ff"><strong>Let's clean up this stinkhole !!</strong></font> </p> </div>
 
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silylene old

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Unlikely, IMO. but this is NASA's explanation. Read the full thread. <div class="Discussion_UserSignature"> <div class="Discussion_UserSignature" align="center"><em><font color="#0000ff">- - - - - - - - - - - - - - - - - - - - - -</font></em> </div><div class="Discussion_UserSignature" align="center"><font color="#0000ff"><em>I really, really, really miss the "first unread post" function.</em></font> </div> </div>
 
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vogon13

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The sands of Mars sifting into a fault?<br /><br /> <div class="Discussion_UserSignature"> <p><font color="#ff0000"><strong>TPTB went to Dallas and all I got was Plucked !!</strong></font></p><p><font color="#339966"><strong>So many people, so few recipes !!</strong></font></p><p><font color="#0000ff"><strong>Let's clean up this stinkhole !!</strong></font> </p> </div>
 
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JonClarke

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Good to have you with us still!<br /><br />It is an interesting question. I have to go for micrometeorites even though i would have thought that most would have been burnt up in the atmosphere. The craters are too symmetrical to be collapse or secondary impact. <br /><br />Mind you the lighting theory is interesting too. I have never seen craters formed by these on earth but there is theoretical evidence in favour of white high charges being built up in martian dust stroms and devils.<br /><br />It may also be worth noting that the sany nature of the meridiani regolith is very favourable for the preservation of micro craters.<br /><br />Jon <div class="Discussion_UserSignature"> <p><em>Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars</em>  Arthur Clarke</p> </div>
 
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CalliArcale

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It would be nice to see some targeted work on these craters by the rovers.<br /><br />Is it possible they're caused by larger debris flung about in a sandstorm? I realize Mars has a very thin atmosphere, so it might not be able to lift much, even in the strongest winds, but is it possible it can lift something just large enough to make a crater like this if it were going fast enough? Or maybe debris flung out by a dust devil? <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff."</em>  -- The Tenth Doctor, "Blink"</font></p> </div>
 
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vogon13

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I like (on general principles) new fun phenomena. Like dust devil lightning on Mars.<br /><br />However, (sigh)<br /><br />We apparently have had a dust devil or two blow the dust off the solar panels on the rovers.<br /><br />Lightning like discharges powerful enough to blast a hole in the ground, should be more than adequate to deposit 50,000 electrons in the wrong memory address on the rover CPU and kill the vehicle. Especially since (IMO) it wouldn't have been designd to withstand such an event that powerful.<br /><br />The rover in its entirety should be a pretty sensitive lightning detector.<br /><br /><br />Sorry.<br /><br /> <div class="Discussion_UserSignature"> <p><font color="#ff0000"><strong>TPTB went to Dallas and all I got was Plucked !!</strong></font></p><p><font color="#339966"><strong>So many people, so few recipes !!</strong></font></p><p><font color="#0000ff"><strong>Let's clean up this stinkhole !!</strong></font> </p> </div>
 
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maxtheknife

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Hehehe, I know exactly what they are. <img src="/images/icons/laugh.gif" />
 
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JonClarke

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That's certainly a nice example. It looks very symmetrical, as you would expect for a high velocity impact, there is also what looks like a raised rim on the down slope sode. Mind you, this is consistent with the crater veing a small slump also, although I would not expect it to be so symmetrical in that case. The crater has been there some time, there is a "pool" of finer grained material in the lowest part.<br /><br />As to them supposedly being on the dune tops, I have no idea! Someone care to do crater counts with respect to position? If they are craters, perhaps the ones in the dune swales tend to be filled in more. But one would balance that aginst the crestal ones being more easily eroded. <br /><br />It would be nice to get a really close look at a fresh one. If formed by impacts one would expect to see aggultinates or even glass spatter, if lunar micro craters are anything to go by.<br /><br />Jon <div class="Discussion_UserSignature"> <p><em>Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars</em>  Arthur Clarke</p> </div>
 
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thechemist

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This might be related to microcraters, and might not. Oppy has just reached a very interesting site filled with outcrops, located right next to Erebus crater.<br />Look at this NavCam image from this place , bottom left.<br />The outcrop looks like it was shattered by an impact (?), there are radial microcracks allover it. <br />I've read elsewhere people suggest microcraters could be secondary impacts from such a primary one. <br />Jon, what do you think ? <div class="Discussion_UserSignature"> <em>I feel better than James Brown.</em> </div>
 
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bonzelite

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i am impressed that many of you have accepted the possibility of the microcraters as being the result of electrical discharges. it has been known that the dust devils, as well as earth-bound tornados, are actually plasma discharges of varying current densities. actually, the dust devils are literally lightning strikes in the martian atmosphere. the circular nature of the "craters," as well, conforms to the characteristic remains of such a strike to the ground. furthermore, much larger cratering seen throghout mars, our moon, mercury, etc, can be argued to be the result of such discharging. <br /><br />to defend the craters as being of an impact origin is to deny the existence of plasma discharges and the relevance of them. to suggest the microcraters, most of which appearing as if they happened last week, as impact sites is nearly laughable.
 
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rogerinnh

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Those aren't micro-craters. They're the visible evidence of "piss-clams". What's a piss-clam you ask? Well it's a kind of sea clam found in mud flats along the shore. They're several inches long and about an inch wide. They burrow themselves in the mud and leave a small crater-like opening on the surface. They get their name from the fact that if you walk near their burrow that react by quickly closing up and ejecting a stream of water up through the hole.<br />So, I say we need to send one of the Mars rovers over to one of those so-called micro-craters and disturb it a bit. I'll bet it squirts.
 
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thechemist

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Gusev crater is packed with DDs for months now, yet we only saw the tiny craters after Opportunity entered the etched terrain at the other side of Mars, where we have seen no dust devils at all.<br />I hope you find the above laughable too. After all, we all come here at SDC to make you laugh, aren't we ? <div class="Discussion_UserSignature"> <em>I feel better than James Brown.</em> </div>
 
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telfrow

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<font color="yellow">Gusev crater is packed with DDs for months now, yet we only saw the tiny craters after Opportunity entered the etched terrain at the other side of Mars, where we have seen no dust devils at all. </font><br /><br />You beat me to it. <img src="/images/icons/wink.gif" /><br /> <div class="Discussion_UserSignature"> <strong><font color="#3366ff">Made weak by time and fate, but strong in will to strive, to seek, to find and not to yeild.</font> - <font color="#3366ff"><em>Tennyson</em></font></strong> </div>
 
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thechemist

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I've left the difficult part for you. I could not find any arguments disproving "piss-clams" <img src="/images/icons/wink.gif" /> <div class="Discussion_UserSignature"> <em>I feel better than James Brown.</em> </div>
 
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telfrow

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<img src="/images/icons/laugh.gif" /> <div class="Discussion_UserSignature"> <strong><font color="#3366ff">Made weak by time and fate, but strong in will to strive, to seek, to find and not to yeild.</font> - <font color="#3366ff"><em>Tennyson</em></font></strong> </div>
 
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igorsboss

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Here's a pretty mundane idea...<br /><br />Perhaps, once in a while, dust devils lift a lightweight dirt clod several tens of meters. When each clod lands, you get a little impact crater.<br /><br />Since we know the composition of the soil, the gravity, and the atmosphere, and the size of the micro-craters, we should be able to get a pretty good idea of how much kinetic energy these micro craters take to form. ...through either simulation or calculation.
 
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bonzelite

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the craters look recent in terms of days or weeks; at most, months. considering dust storms can transport material globally, regularly, to alter the surface dunes, the craters could be very recent structures. <br /><br />where is the main impact that ejected the secondary material to create the microcraters? i think it is a bit myopic to seriously consider ONLY that the microcraters are impacts or have been there for thousands of years. i don't entirely buy that. even if they are of impact origin, the material could have hit the dunes a few months ago. i'd more likely believe they are from a broken up meteor that entered the atmosphere than secondary impacts from a larger meteorite. <br /><br />why must everything on other planets be "millions of years old?" why can't something on mars be a few days old? as well, electrical discharges do not need to mainfest necessarily as DDs. but they do. <br /><br />
 
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JonClarke

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Dunno! Secondary craters need a primary. Where is the nearby fresh primary crater? We don't see one. <br /><br />Also, secondary craters this small would be from fragments moving at compartively low velocities, I would have thought. I would expect them to be less regular and perhaps have remnants of the impactor within them.<br /><br />Jon <br /><br />Added in edit. That is an interesting image you linked, you could be right, it looks a bit like where a bullet has hit a rock or stone a car windscreen. So perhgaps a micro impact from a small, medium velocity body (those travelling at cosmic velocities would have blasted a crater in the rock). <div class="Discussion_UserSignature"> <p><em>Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars</em>  Arthur Clarke</p> </div>
 
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JonClarke

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You could be right, although I would caution that the materials at Gusev are very different to those at Meridiani. It is also possible that there are less electrostatic effects than has been predicted. There has been so sign of chaging from dust on any of the rovers, although some expected this.<br /><br />Jon <div class="Discussion_UserSignature"> <p><em>Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars</em>  Arthur Clarke</p> </div>
 
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thechemist

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bonzelite,<br />Noone knows at this moment what formed the tiny craters. That is why this thread was initiated, to discuss ideas. It is premature to throw terms like "laughable" and "myopic" to any of the ideas in the discussion, like you have done.<br />Personally, at this moment I cannot disregard any of the proposals. Not even "clams", although I think they are highly unlikely to live in Meridiani. <div class="Discussion_UserSignature"> <em>I feel better than James Brown.</em> </div>
 
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thechemist

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Jon,<br />Oppy is currently standing on a location where the rims of both Erebus and Terra Nova (the almost buried paleocrater) coincide. The cracks in the image I linked above could be <i>really</i> old, this rock garden is weird ! <div class="Discussion_UserSignature"> <em>I feel better than James Brown.</em> </div>
 
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centsworth_II

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After reading everyone's thoughts, my favorite theory is that the microcraters are the result of a meteor that desintigrated as it fell to Mars.<br /><br />I imagine the mini craters are the result of a one time event that occured recently enough that the craters on the drift crests have not been obliterated by sand/dust deposition or drift evolution but those in the troughs have. <div class="Discussion_UserSignature"> </div>
 
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bonzelite

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i'd have to go with this one too:<br /><br />After reading everyone's thoughts, my favorite theory is that the microcraters are the result of a meteor that desintigrated as it fell to Mars. <br /><br />I imagine the mini craters are the result of a one time event that occured recently enough that the craters on the drift crests have not been obliterated by sand/dust deposition or drift evolution but those in the troughs have.
 
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JonClarke

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Perhaps, but it could be a long younger too, the readial crcks seem to be superimposed on the main fracture system, so it could be a lot younger.<br /><br />Where did to get that great map?<br /><br />Cheers<br /><br />Jon <div class="Discussion_UserSignature"> <p><em>Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars</em>  Arthur Clarke</p> </div>
 
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