Astronomy Picture of the Day
August 30, 2012

Migrating Dunefield
Migrating Dunefield

Credits: NASA/JPL-University of Arizona - Credits for the additional process. and color.: Dr Paolo C. Fienga/Lunar Explorer Italia/IPF

In a study of the harsh but beautiful White Sands National Monument in New Mexico, University of Pennsylvania researchers have uncovered a unifying mechanism to explain Dune Patterns. The new work represents a contribution to basic science, but the findings may also hold implications for identifying when Dune Landscapes like those in Nebraska’s Sand Hills may reach a “tipping point” under climate change, going from valuable grazing land to barren desert. The study was conducted by Dr Douglas Jerolmack, an assistant professor in the Department of Earth and Environmental Science; Postdoctoral Researcher Federico Falcini; Graduate Students Raleigh Martin, Colin Phillips and Meredith Reitz; and Undergraduate Researcher Claire Masteller. This Team of Researchers also collaborated with Ryan Ewing of the University of Alabama and Ilya Buynevich of Temple University. Their paper was published in Nature Geoscience (---> published online on February 5, 2012). Much of the study’s data was collected during field trips taken by students in an undergraduate and graduate course Jerolmack teaches at Penn, Geology 305: Earth Systems Processes. Each year, the class has traveled to White Sands to do fieldwork during spring break. “It’s a magnificent place to go, and one of the reasons I take my students there is really because it’s so visually striking and compelling", Jerolmack said.

White Sands National Monument, located near Alamogordo in south-central New Mexico, is an enclosed basin that housed an ancient Lake during the last Ice Age. Unlike most Dunefields, which are composed of quartz sand, it’s the World’s largest Dunefield made of Gypsum. Its blindingly White Dunes cover approx. 275 square miles and the Dunefields’ Groundwater Table is located just about a meter below the Surface. “So it means you’re in a very hot arid place, but when you walk around you feel moisture on your feet”, Dr Jerolmack explained. "The moisture creates a somewhat “sticky” surface" he added, “so, if the Sand blows off a Dune and Lands, it sticks to the Surface and can get deposited and left behind”. White Sands has long been the site of geologic inquiry. Scientists have put forward theories to explain individual elements of the Dunes, including their shape, their movements over time and the presence or absence of plants. The novelty of this study lies in showing how all of these problems are a consequence of the interaction between the Wind and the Dunes. (*)

(*): note: we, as IPF, would like to add that the abovementioned study - as far as we can understand - is also based on the assumption that the Dunes, in order to "move" and "migrate", have to be located on a (relatively sticky) Surface under which, at a very short depth, a Groundwater Table - or another Water Source of some kind - can be found.

Given all the above, as well as the reasonable assumption that there are quite a few similarities between many Geologic, Aeolian and, in general, Physical Processes of Earth and Mars (including this one), would it be possible to speculate that, in a few places of Mars where we see the so-called "Migrating Dunefield" acting either constantly, or during specific periods of the Martian Year, if we were able to dig a little bit in those areas, we might find Groudwater Tables (maybe partially frozen, maybe not...), probably only a few meters onder the Surface of the "frigid", and "extremely arid" Red Planet? We, as IPF, while thanking so very much Dr Jerolmack for his Studies and insights, strongly believe so.

In the end, can we reasonably assume (speculate) that the Subsurface of Mars is litterally filled with Ice and Water (depending on the depth as well as on the considered period of the Martian Year) as we have been suspecting for a long time (think about, for instance, to the deeply insightful results of the - however - shallow digging carried out by the NASA - Phoenix Lander in the Region of Vastitas Borealis)? Well, if the answer were (and, likely, it will be) "Yes", then could it also be possible - and reasonable - to speculate that Mars is not "dead" at all, but just "dormient"? Only time will tell, but one thing is sure: once it has been said and repeated that the robotic exploration of the Red Planet is extremely important, it MUST also be said, repeated and underlined that a Human Presence on Mars, if we really want definitive (and more convincing) answers, is MORE than just important: it is absolutely fundamental.

Mars Local Time: 14:40 (early afternoon)
Coord. (centered): 45,438° South Lat. and 38,835° East Long.
Spacecraft altitude: 252,9 Km (such as about 158,0 miles)
Original image scale range: 50,6 cm/pixel (with 2 x 2 binning) so objects ~ 1 mt and 52 cm across are resolved
Map projected scale: 50 cm/pixel
Emission Angle: 6,3°
Phase Angle: 59,6°
Solar Incidence Angle: 63° (meaning that the Sun was about 27° above the Local Horizon at the time the picture was taken)
Solar Longitude: 15,6° (Northern Spring - Southern Fall)
Credits: NASA/JPL/University of Arizona
Additional process. and coloring: Lunar Explorer Italia

This frame has been colorized in Absolute Natural Colors (such as the colors that a human eye would actually perceive if someone were onboard the NASA - Mars Reconnaissance Orbiter and then looked down, towards the Surface of Mars), by using an original technique created - and, in time, dramatically improved - by the Lunar Explorer Italia Team.

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