Martian spiders explained?

[alexblackwell]

<i>Thanks for that link, Alex. This paper is freely available online. (You may want to download it rather than opening it in a window since it is a rather large file.)</i><br /><br />Thanks for pointing that out. As it happens, I subscribe to <i>Astrobiology</i>, and I'm aware the publishers typically make one paper freely available for newly published issues. They also offer free access to one entire issue. In fact, at one point a couple of years ago, they offered temporary free online access to <i>all</i> of the issues. I almost cancelled my (rather expensive) subscription at that point.

 

[alexblackwell]

<i>While I agree with Jon that the majority of slope streaks, especially as seen as avalanches on crater walls, appear as albedo artifacts due to dry dust avalanches, I do not agree that this accounts for all of them. If it were the case that all light streaks should be similar to dark streaks because the fundamental mechanism is the same as regards dry avalanches, then there should be no difference in the apex angle between them. But Schorghofer did a study over a large sample and found that the light ones have a larger apex angle than the dark ones in general.</i><br /><br />Given the spatial and temporal relationships between the slope streaks, it's likely there is a common origin and/or control mechanism(s). In my opinion, the minor morphological and albedo differences you and others noted could simply be due to differing substrates, as Jon pointed out earlier. Until someone shows me convincing evidence (e.g., SHARAD data) of near-surface liquids, I prefer the "dry dust" explanation.

 

[JonClarke]

Us Brits can be an odd lot <img src="/images/icons/smile.gif" /><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>

 

[JonClarke]

That's a great paper, many thanks. But the avalanches they are talking about there are quite different from the light streaks seen in many images. They are spatially restricted and appear thicker, with destinct relief.<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>

 

[JonClarke]

Alex, do you know if imaging streaks is a high priority for MRO?<br /><br />I assume that if any moisture is involved in the streaks that the highresolution hyperspectral systems like OMEGA of CRISM might be able to detect it. Their best resolution (200-300 m) would probably be adequate to detect larger streaks, I think.<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>

 

[chew_on_this]

I take it this explains the "Banyan trees" per Arther C. Clark.

 

[alexblackwell]

<i>Alex, do you know if imaging streaks is a high priority for MRO?</i><br /><br />I don't know how high a priority the streaks are but, as I understand it, some workers want to use HiRISE's cm-scale per pixel resolution mode to try to resolve the relief at the margins of the streaks. Resolving the point sources at the streaks' apexes has also been discussed.

 

[alexblackwell]

<i>I assume that if any moisture is involved in the streaks that the highresolution hyperspectral systems like OMEGA of CRISM might be able to detect it. Their best resolution (200-300 m) would probably be adequate to detect larger streaks, I think.</i><br /><br />It would defintely be a challenge but it might be possible, especially with CRISM. And given the close spatial clustering of the streaks in some areas, getting a reliable, representative set of spectra with acceptable SNR might not require resolving individual streaks.<br /><br />However, the big problem, as anyone familiar with spectroscopy from martian orbit knows, is the pervasive dust components, both surficial and atmospheric, that must be deconvolved from the signal.

 

[exoscientist]

Alex, does MARSIS on Mars Express have sufficient horizontal resolution to observe the cryptic region?<br /><br /><br /> Bob Clark <div class="Discussion_UserSignature"> </div>