Mars Water Debate Rages (archival thread reposting #4)

[serak_the_preparer]

exoscientist<br />(<b>O</b>)<br />12/19/02 09:31 AM<br /><br /> Good point about the slope orientations. Here's the full article.<br /><br />Slope Streaks on Mars: Correlations with Surface Properties and the<br />Potential Role of Water.<br />Norbert Schorghofer, Oded Aharonson, and Samar Khatiwala<br />Abstract. The Mars Orbiter Camera on board the Mars Global Surveyor<br />spacecraft has returned images of numerous dark streaks that are the<br />result of down-slope mass movement occurring under present-day<br />martian climatic conditions. We systematically analyze over 23,000<br />high-resolution images and demonstrate that slope streaks form<br />exclusively in regions of low thermal inertia (confirming earlier<br />results), steep slopes, and, remarkably, only where peak temperatures<br />exceed 275 K. The northernmost streaks, which form in the coldest<br />environment, form preferentially on warmer south-facing slopes.<br />Repeat images of sites with slope streaks show changes only if the<br />time interval between the two images includes the warm season.<br />Surprisingly (in light of the theoretically short residence time of<br />H2O close to the surface), the data support the possibility that<br />small amounts of water are transiently present in low-latitude near-<br />surface regions of Mars and undergo phase transitions at times of<br />high insolation, triggering the observed mass movements.<br />http://www.gps.caltech.edu/~norbert/Research/water.pdf [Full text]<br /><br />The article argues for liquid water but another possibility is that there is ice there and when above 0C temperatures are reached it undergoes explosive *sublimation* and this triggers dust slides.<br />Still whe

 

[serak_the_preparer]

voyagerwsh<br />(<b><font color="red">M</font>/b>)<br />12/19/02 12:50 PM<br /><br />What can we learn from APEX of Pathfinder on the chemical composition? Excessive oxygen in the rocks.<br /><br />Excessive oxygen implies water in the Pathfinder rocks, they may be sedimentary or metamorphic rocks. Also, no carbon was detected and iron was richer than previous result with lesser silicon content in Pathfinder samples.<br /><br />Chemistry of Mars Pathfinder Samples Determined by the APXS (PDF)--C. N. Foley et al., LPSC XXXII</b>

 

[serak_the_preparer]

borman<br />(<b><font color="blue">B</font>/b>)<br />12/19/02 07:03 PM<br /><br />Caution about the relevance of triple point.<br /><br />Exoscientist, Thanks for links in a prior thread including the Palermo paper which raised some questions that were properly not addressed in the Schorghofer paper. These questions when considered would raise the nature of the paper to being overly speculative. While they certainly are qualified to entertain specific possibilities for water's role, it was not within the scope of the paper to do so. While a triple point scenario is possible, it requires more assumptions to be made. Especially in light of the observation that dark streaks occur at 11 km elevations where pressure drops to 3mbars, a triple point scenario will be challenging as opposed to a melting point scenario. Since water's role here may only be involved as the triggering event, one may more simply consider its role in modulating the co-efficient of friction.</b>

 

[serak_the_preparer]

exoscientist<br />(<b>O</b>)<br />12/20/02 11:18 AM<br /><br />Schorghofer et.al. do mention that liquid water becomes problematical at that high altitude and low pressure. That's why I wondered whether it could just be ice sublimating. However, even ice at this latitude would be important since it suggests there is ice at other low latitude locations where there are lower elevations, such as in Valles Marineris for example, that would allow for liquid water.<br />Another possibility is that if the water is subsurface then simply the overpressure of the regolith may be enough to permit liquid water. I imagine this would depend on the regolith density and porosity, but I would estimate that just a few centimeters would be enough to provide 6.1 mbars or pressure.<br />Doing a little math converting standard Earth pressure of 15 lbs/sq.in, that works out to only about 6.3 g/cm^2.<br />The density of the Martian soil is probably in the range of 1 to 2 g/cm^3 so perhaps 3 to 6 cm of soil depth would be enough to provide pressure for liquid water on Mars. (Actually you might need to take into account Mars lower gravity than Earth so the depth might need to be twice this.)<br />Note this would also apply to the gullies seen in the southern hemisphere. The argument has been made that even if the temperatures did exceed the melting point the pressures would not be sufficient at the higher elevations of the southern hemisphere.<br />However, if the liquid water is subsurface it may allow a groundwater sapping phenomenon to occur which would cause the ground to slump forming the gulllies seen.<br /><br /><br />Bob Clark

 

[serak_the_preparer]

AlexBlackwell<br />(<b>A</b>)<br />12/20/02 12:40 PM<br /><br />exoscientist wrote:<br />Another possibility is that if the water is subsurface then simply the overpressure of the regolith may be enough to permit liquid water. I imagine this would depend on the regolith density and porosity...<br /><br />Alex writes:<br />It would also depend on the thermophysical properties (i.e., whether the regolith is insulating enough to prevent the H2O from being in diffusive contact with the atmosphere).<br /><br /><br />Alex R. Blackwell<br />University of Hawaii

 

[serak_the_preparer]

borman<br />(<font color="blue">B</font><br />12/21/02 12:53 AM<br /><br />Is there an alternative for Martian valley formation ?<br /><br />Cometary impacts were addressed recently by Segura et al who proceed from a cold Mars’ initail condition and a potential correlation between the age of craters and valley. This second correlation has been subject of some discussion. Briefly, a comet hits and regolith mixed with ice is vaporised; rock re-emplants and water rains as much as 2 meters/year for 100 years. During this short hot period where larger craters are being made, apparently it is posited that the valleys are carved out due to massive flooding. Certain assumptions about the Martain surface need to be made in order for the model’s results to come about. There are some problems. In Ma’adim Vallis, http://www.nasm.si.edu/ceps/research/irwin/press_maadim_bw.jpg, the bottom of the valley is above the base of the crater but there is clear evidence of flooding in the valley anyways suggesting the crater was a filled resevoir of water until discharged or evaporated. There are no obvious rain streams entering into the crater. There are no tributaries and smaller craters near valley walls give no evidence of rain erosion. There are a number of minerals upon the surface that have somehow evaded aqueous alteration due to rain. Evidence in hand, ALH84001, which predates Segura’s epoch only suffered aqueous alteration once.<br /><br />It is unlikely that just water from the comet could be the long-term source for the millions of years needed to erode valleys to their present depth. Discharge of long term underground water deposits has been forwarded. By all appearances there

 

[serak_the_preparer]

rlb2<br />(<b><font color="yellow">F</font>/b>)<br />12/22/02 09:32 PM<br /><br />Alex and everyone else who would like to publish his or her work someday. This is new resource for you to publish some of your work. Since publishing ones work in a reputable journal is such a costly expense. It is called The Public Library of Science and was funded by a 9 million dollar grant. It is an online service at http://www.publiclibraryofscience.org/<br /><br />I hate to get into the debate on the triple point of water without reading the papers you mentioned. So I will ask the question on what model did they use to explain how water reacts in a carbon dioxide atmosphere? Triple point of water in an oxygen/ nitrogen atmosphere is different than triple point of water in a carbon dioxide atmosphere.<br /><br />There was a presentation at a Mars's Conference about two years ago about this. I don’t know the outcome of the paper that was published on this. It was said that water has a lower triple point in a carbon dioxide atmosphere. Therefore water can stay in its liquid form longer in a carbon dioxide rich atmosphere at a lower temperature and pressure.<br /><br />I don't remember how much difference there was between the two (oxygen/nitrogen vs carbon dioxide atmospheres) but it was an interesting presentation. Again I didn’t read all your post. Someone could have mentioned this.<br /><br /><br /><font color="black">"Reality is merely an illusion, albeit a very persistent one"</font>/safety_wrapper></b>

 

[serak_the_preparer]

spaceseed<br />(<font color="blue">B</font><br />12/22/02 11:01 PM<br /><br />borman: The hypothesis, if I understand it, is that Mars was originally an icy planet (like Europa), and its surface was covered by debris from space, specifically asteroids in similar orbits that it captured. I wonder about the following:<br /><br />1. Odyssey detected more ice than people expected, but not nearly the quantity you are talking about. How far below the surface is Odyssey unable to detect ice? This is the minimum depth for the material covering the ice.<br /><br />2. How do you account for the volume of rock needed to cover the surface to the required depth? I think you are suggesting that Mars vacuumed up a significant portion of the asteroid belt. Is there any evidence for this? Could we test for this in soil samples, eg. ALH840001?<br /><br />3. I thought a large portion of infall was cometary, and this was a major source of water for the inner planets. This would add to water on Mars, not cover it up.

 

[serak_the_preparer]

murmac<br />(<b><font color="black">void</font>/b>)<br />12/25/02 04:17 PM<br /><br />This response is not exactly on point, but it does relate to water and life. I heard recently that the latest theory is that the open bodies of water that existed in the past were extremely short-lived and caused by comet or other impact. If this is so, what does this do to the idea that life may have formed over the many years that the surface of Mars retained liquid water? Obviously, there may have been, and still may be, lower level life existing in wet undergroud pockets. However, my hopes that there may have been higher life forms in the past seem to be fading.<br /><br />MurMac</b>

 

[serak_the_preparer]

borman<br />(<font color="blue">B</font><br />11/04/03 04:46 PM<br /><br />Triple point is still a point<br /><br />rlb2,<br />Triple point of water in a Martian atmosphere can be simulated in an Earth lab, and should be found in a thick tome of physical chemistry. It is still a point though and has no additional degrees of freedom. A model for dark streaks that requires triple point as essential won't cover all the cases where streaks are found and another additional model would be needed for these others. Melting, on the other hand, follows a pressure/temperature line which allows a conitnuum of possibilities. Here is a link regarding Triple point and Gibbs Phase Rule:<br />http://www.sv.vt.edu/classes/MSE2094_NoteBook/96ClassProj/examples/triplpt.html

 

[serak_the_preparer]

paulharth6<br />(<b><font color="orange">K</font>/b>)<br />01/04/03 05:19 PM<br /><br />murmac - liquid water is not necessarily the best medium for chemical evolution. Water combines chemically with many molecules which would be considered on potential pathways to life, thus eliminating the pathway.<br /><br />Some models prefer dry, or wet clay, or concentrating ponds. However, if you research the chemistry obstacles for life synthesis, you will find multiple environments would be necessary. Specific pre-biotic molecules will require specific temperatures, ph (not me, alkaline or acid), and wet or dry. Some molecules require condensing agents in order to spontaneously synthesize.<br /><br />This is why specific amino acids are found on meteorites.<br /><br />There is also the problem of accounting for the necessary L-chiration (left handed polarization), alpha-peptide bonding, and specific 3-d folding such as is required for proper enzyme - receptor interactions.<br /><br />You all - I am interested in this thread, but will mostly lurk since listening is also good.<br /><br />Thank you all for your excellent input and research.</b>

 

[serak_the_preparer]

paulharth6<br />(<b><font color="orange">K</font>/b>)<br />01/04/03 05:26 PM<br /><br />rib2 - I'm gonna have to do allot of research to post intelligently on this thread, but I will add my 2 cents worth:<br /><br />Water reacts with CO2. It forms H2CO3. If metallic ions are in the water, as on earth, carbonates precipitate out. Is there any evidence of these carbonates on Mars?<br /><br />Now, I read somewhere recently about a 6- point form of water, and it was a new discovery. Oh, for a perfect memory! I'll try to find it - although it may be irrelevant.</b>

 

[serak_the_preparer]

borman<br />(<font color="blue">B</font><br />01/04/03 05:47 PM<br /><br />overextending models<br /><br />voyagerwsh,<br />Thanks for the Coleman links. They put forth a reasonable criticism of large scale CO2 weathering. The point is that if large scale CO2 weathering occurs, it should look more like a cryoclastic proccess than flooding. Maintaining so many large CO2 resevoirs over geologic time is also a challenge. This does not refute CO2 weathering, but cautions against over-extending a model, which may still be viable on a smaller scale. I see no problem with investigating extremes of a model, but exttremes often require additional assumptions which may not prove valid. In other words, a model may be valid but its over-extention may not be valid.<br /><br />The isothermal proccess envisioned above is not a planetary-wide or even large scale proccess. The CO2 only takes seconds to liquify and only needs await the arrival of the nearest polar summer. This is hardly a geological time. Just as dark slope streaks implicate water because of temperature, so too CO2 is implicated for the same reason at high lattitudes if insolation is involved in the triggering event.<br /><br />A related question is whether the weatheriing of gullies is a dual CO2/H2O event. In this scenario, the weathering of gullies and aprons are formed primarily by flooding rather than a pure cryoclastic proccess. In this scenario a particular layer, rather than being an aquiclude, is rather water porous and serves as a path for a Carr gun. Here hydrothermal proccesses keep the buried water liquid but there is a frozen wall preventing it from draining into the valley. A liquid CO2 explosion breaks this wall and pressured water shoots out for a short while. Key will be ascertaining whether

 

[serak_the_preparer]

rlb2<br />(<b><font color="yellow">F</font>/b>)<br />01/04/03 11:13 PM<br /><br /><br />rlb2<br /><br />borman, it may be a point but according to the geologist it is a lower triple point on Mars then on Earth. I was talking about what I remember from that conference about three years ago in Toronto Canada. According to the geologist, he was showing numbers of how water would react in a CO2 atmosphere and came up with a lower triple point of water then would be in a nitrogen, oxygen atmosphere. He said he even enlisted the help of NASA on this and after they did some testing there numbers were close to his. As far as the debate of the triple point of CO2 verses the triple point of H2O debate. I found this:<br /><br />"This paradox is resolved here by modeling Mars’ evolution with CO2 as the active fluid, and<br />demonstrating that many otherwise obscure feature the Planet can be explained by interactions of CO2 around its solid / liquid / vapor triple point, rather than that of water."<br /><br />WHITE MARS: A GLOBAL EVOLUTION MODEL FOR MARS’ SURFACE BASED ON CO2. N. Hoffman, WNS GeoScience, 22 Marlow Place, Eltham VIC 3095, Australia (nhoffman@ vic. bigpond. net. au). Introduction ...<br /><br />http://mars.jpl.nasa.gov/mgs/sci/fifthconf99/6001.pdf<br /><br /><br />PRESSURE AND TEMPERATURE EVOLUTION OF MARS’ SURFACE. N. Hoffman, WNS GeoScience,<br />22 Marlow Place, Eltham VIC 3095, Australia (nhoffman@vic.bigpond.net.au).<br /><br />http://mars.jpl.nasa.gov/mgs/sci/fifthconf99/6003.pdf<br /><br />Now some of this may have already been discussed earlier or the authors work on this might not have been widely</b>

 

[serak_the_preparer]

paulharth6<br />(<b><font color="orange">K</font>/b>)<br />01/04/03 11:30 PM<br /><br />borman - please excuse my not responding to your post - I'll need to study it more, then I will comment. But thank you for your excellent, scholarly input!<br /><br />rib2 - That quote does not make sense, carbonate does not indicate origin of life scenarios. You need the geologic carbon cycle to produce carbonate. The problem is those metallic ions in water - they react with many pre-biotic molecules, eliminating pathways for chemical synthesis scenarios. For example, phosphates necessary for life.<br /><br />I'll post more on that later - its past my bedtime!<br /><br />By metallic, I meant Calcium ions, Sodium ions, etc.<br /><br />A primordial soup necessary for chemical evolution scenarios should leave geologic deposits such as nitrogenous cokes, etc. Have these been found?<br /><br />BTW - they haven't been found on earth either, which means.....?<br /><br />Oops, pardon me (I'm sleepy). Carbonates would indicate water, but not life. They are looking for water! No wonder the finding (er - lack thereof) is discouraging!</b>

 

[serak_the_preparer]

[<b>Note from the Mad Archivist:</b><br /><br />The following post appears out-of-sequence. Archiving this entire thread back onto the Space Science & Astronomy forum is somewhat ambitious on my part. Where possible, I'm editing out off-topic items, though I've done very little such editing so far. Though I wavered on it a moment or two, I at first decided to leave out the post copied below. But now, having gotten deeper into the thread, the post takes on some added relevance. It appeared on the original thread in response to Alex Blackwell's <i> Re: Groundwater on Mars?</i> post of 11/26/02 11:43 AM (found earlier on this archived thread), of which the body reads:<br /><br /><br /><i>voyagerwsh wrote:<br />In the December issue of GEOLOGY, M. Gilmore et al. have a paper of Martian gullies and the implication of groundwater. Suggesting that guillies are prime cadidates to search for water and possible life.<br /><br />Alex writes:<br />Well, if one actually reads the full paper, one will note the "possible life" issue is tacked on only in the very last sentence of a four-page paper. The major thrust of the paper is geological, not astrobiological. Specifically, that the "location of these gullies [discovered by Malin and Edgett] is controlled in part by the presence of an impermeable rock layer (aquiclude) and that the depths of the gully heads below the surface should thus be correlated to subsurface geology." For example, the authors study a series of gullies on a segment of Martian channeled plains (unit AHh5). They discern "a single cliff-forming layer" and note that the "[g]ullies emanate from this layer even where the rock layer is faulted or disrupted...signifying a genetic relationship between the gully and the rock layer." This and other examples have led the authors to favor the aquiclude model over others (e.g., confined aquifers, geothermal heating, etc.).</i><br /><br />CubanCat answered with the item copied below, after which this archive will resume it

 

[serak_the_preparer]

AlexBlackwell<br />(<b>A</b>)<br />01/06/03 11:19 AM<br /><br />Hunt for life on Mars dealt another blow<br /><br />Nick Hoffman has been studying the Sisyphi Cavi area of Mars for some time and I've had the chance to read a preprint of his just-published paper in Astrobiology.<br /><br /><br /><br />Alex R. Blackwell<br />University of Hawaii

 

[serak_the_preparer]

spaceseed<br />(<font color="blue">B</font><br />01/06/03 03:52 PM<br /><br />Questions that come to mind:<br /><br />1) Why do the flows happen every spring, then stop when it gets warmer?<br /><br />2) Does this mechanism account for all valleys?<br /><br />3) Is there any evidence for or against the existance of geothermal heat sources that could cause liquid water to reach the surface?

 

[serak_the_preparer]

AlexBlackwell<br />(<b>A</b>)<br />01/06/03 08:31 PM<br /><br />spaceseed wrote:<br />Questions that come to mind:<br /><br />1) Why do the flows happen every spring, then stop when it gets warmer?<br /><br />Alex writes:<br />Well, assuming that Hoffman has in fact documented an actual interannual flow event at Sisyphi Cavi, that would be a key question, especially given the different critical temperatures for CO2 and H2O. If the flows are real, and not just contrast artifacts in inherently noisy imagery, then the contemporaneous TES surface temperatures (which are cryogenic) would tend to favor CO2 over H2O. Note, however, that in his Astrobiology paper, Hoffman is not really describing a true time series for a single gully, but rather he is extrapolating (or interpolating) the flow events and associated temperatures at different sites to give what is, in my opinion, a "quasi-time series" based on the advance and retreat of the seasonal southern polar cap.<br /><br />spaceseed wrote:<br />2) Does this mechanism account for all valleys?<br /><br />Alex writes:<br />I believe you meant to say "gullies" instead of "valleys," which are two distinct constructs. At any rate, the answer, in my opinion, is no. And that, again in my opinion, is a major weakness for the CO2 "thawing snowpack" model being advanced by Hoffman. If one accepts his model for Sisyphi Cavi, then one needs to explain how gullies with similar morphologies are created outside (i.e., more equatorwards) of the maximum extent of the CO2 frost line (e.g., the Malin and Edgett gullies at Nirgal Vallis). To me, it is implausible to posit two separate mechanisms (different erosive volatiles operating at two distinct thermodynamic regimes) to account for features with almost the same geomorphologies.<br /><br></br>

 

[serak_the_preparer]

gbbaker<br />(<font color="blue">B</font><br />01/06/03 09:04 PM<br /><br />Although I am just a layman I would have to say that It would seem to me to be much more plausible that it is Co2 as he has described as a general global model.<br />That would make much more sense to me with the general underground ice model depicted showing the 4 or 5 foot depth of the water ice line which get's closer to the surface as you get closer to the poles which sort of implies that if it's ice and it has been anywhere near (a meter or so) the surface for any short amount of time it's long gone by now.<br /><br />But it also seems to me that we can't really blanket the whole planet with one uniform salt content (despite there being dust storms mixing everything around on the surface) and so I think just as there are places here on earth that don't follow the general model for the triple point of water there should also be places there which have a high salt content and I would suspect that out of all these places, visibly they would most manifest themselves along crater walls as gullies.<br /><br /><br />Globally there should be a variety of areas with slightly different pressures and different salt contents.<br />I think the issue will ultimately be resolved definitively when a rover does an upclose mineral analysis of one of these gullies.

 

[serak_the_preparer]

rlb2<br />(<b><font color="yellow">F</font>/b>)<br />01/06/03 10:53 PM<br /> <br /><br />AlexBlackwell<br /><br />Nick Hoffman has been studying the Sisyphi Cavi area of Mars for some time and I've had the chance to read a preprint of his just-published paper in Astrobiology.<br /><br />Rlb2<br /><br />Thanks Alex I always enjoy reading your views on this. I read some of these claims and don’t know the credibility of the people who wrote them. Still credibility doesn’t mean there right. The best way to settle this is to get hard data from the surface.<br /><br />Although I do want it to be water and still think it is, Hoffman does seem to make a good point for CO2. Of course if you are talking about millions and possibly billions of years of dust storms covering everything up. If you saw some of the dust kicked up by sojourner you can easily see how it cakes up. The dust cover might be shielding the real evidence they are looking for. We had good data from the sojourner on the chemical makeup of the dust. Can we duplicate the chemistry of the dust in a lab in an environment similar to Mars and mix it with water or liquid CO2 to see what the results would be?<br /><br />The planets is constantly being struck by the solar wind, ultraviolet rays and cosmic rays over billions of years. So we may have to go much more then 3 meters down to find out. A good place to start would be at the poles with core drilling like we do on Earth. This way most of the surface under the ice layer was shielded from the Martian dust storms and from the constant bombardment of radiation from space. Of course the kind of drilling required on Mars at the poles will require humans explorers.<br /><br />Again I hope I'm not repeating someone else's thought<br /><br />gbbaker<br /><br />I think the</b>

 

[serak_the_preparer]

voyagerwsh<br />(<b><font color="red">M</font>/b>)<br />01/07/03 01:09 PM<br /> <br /><br />Gullies in crater at 39.0°S, 166.1°W, MGS/MOC<br /><br /><br />What is your pick to carve this gullies or channels?<br /><br />1. Avalanches of gaseous carbon dioxide and rocky debris.<br /><br />2. Outburst of groundwater flowing down with liquid water or brine beneath thin layer of ice on top.<br /><br />My pick is #2.</b>

 

[serak_the_preparer]

serak_the_preparer<br />(<b><font color="orange">K</font>/b>)<br />01/07/03 06:49 PM<br /> <br /><br />VoyagerWsh, I must agree in part with the person here who said, 'I <i>want</i> it to be water, but....'<br /><br />We know there is a pattern of circulation between the two polar caps, that the southern cap is currently loaded with frozen CO2 while the northern has more water ice. I know it is very simplistic for me to base my opinion mainly on this single fact, but I suspect this to be the proverbial tip of the iceberg. That is, I'm betting on both 1 (CO2 - 'White Mars') and 2 (H2O - 'Blue Mars').<br /><br />Blue-white Mars then. Perhaps the question will ultimately be: How 'blue,' how 'white'? How much of what we see on Mars represents water, how much represents CO2?<br /><br />I'm still willing to bet, however, that life exists on at least one other body in the Solar System besides Earth. As far as I can tell, Mars remains a leading candidate.<br /><br />Rlb2, thanks for the Windsurfer images. : )</b>

 

[serak_the_preparer]

AlexBlackwell<br />(<b>A</b>)<br />01/07/03 11:39 PM<br /> <br /><br />rlb2 wrote:<br />Although I do want it to be water and still think it is, Hoffman does seem to make a good point for CO2.<br /><br />Alex writes:<br />Nick and I have corresponded for over two years, beginning shortly after he published his original White Mars model in Icarus. Many in the Mars community find his ideas trending a bit towards the fringe; however, and despite the fact that I favor the H2O-based models, I've always felt that Nick was a definite asset to the debate. At the very least, he has sharpened the discussion and pointed out many holes, some of them rather glaring, in the Blue Mars models. He plays by the rules and submits his work for peer review. I don't agree with his interpretation but I do respect his work, and more importantly, I'm still listening. This is the way that True Science is supposed to work.<br /><br /><br /><br />Alex R. Blackwell<br />University of Hawaii

 

[serak_the_preparer]

AlexBlackwell<br />(<b>A</b>)<br />01/07/03 11:43 PM<br /> <br /><br />voyagerwsh wrote:<br />My pick is #2.<br /><br />Alex writes:<br />Ditto. And I do not even think it's a close call in this case.<br /><br /><br /><br />Alex R. Blackwell<br />University of Hawaii