And even more surprising, was that his findings revealed answers to NASA’s questions about sediment transport and surface processes on Mars. Those results are published in this month’s edition of Geology.
Leier first studied loose pebbles and rocks, also known as clasts, when he was looking at sand dunes in Wyoming and noticed that the clasts seemed to spread away from each other in an almost organized fashion. It turns out,NASA was examining similar patterns on the sandy surface of Mars. (See figure No. 1 below.)
NASA proposed that wind was moving these rocks around. But Leier, who co-authored the study with Jon Pelletier at the University of Arizona and James Steidtmann at the University of Wyoming, says that would be impossible. They also discovered that rather than being pushed backward by the breeze, clasts actually tend to move into the direction of prevailing winds.
“The wind is less effective at moving clasts on Mars because the atmosphere is less dense,” says Leier. “And for the wind to move the rocks downwind, it would have to be moving on the order of 8,000 kilometres an hour.”
Instead, the loose sand around clasts is removed by the wind, causing scour-pits to form in front of larger clasts. Eventually, the rocks fall forward (or laterally) into the scours and then, the process repeats. Behind the larger grains, the sand is protected from the wind erosion and so a "sand-shadow" develops. This shadow prevents the clasts from being pushed downwind and from bunching up with one another. (See figure No. 2 below.)
Leier and his team first came up with these results through observation but then took them to a wind tunnel at the University of Wyoming to test the theory. Here, a tightly grouped bunch of small pebbles were buried in sand and then the wind tunnel was activated and results photographed. Surprisingly, as the sand was eroded by the wind, the larger clasts moved into the wind and spread out from one another.
Numerical models, based on the physics of wind transport, were run to test these ideas. Just like what was observed in the wind tunnel, the numerical models predict that as the sand is blown away, the large pebbles will spread out from one another, and often move into the direction of the wind, regardless of their initial configuration.
So through a few simple feedbacks, the larger grains on a windy, sandy surface will inherently spread out and organize (or dis-organize) themselves.
“What I find most interesting about this is that something as seemingly mundane as the distribution of rocks on a sandy, wind-blown surface can actually be used to tell us a lot about how wind-related processes operate on a place as familiar as the Earth and as alien as Mars,” says Leier. “It’s chaotic and simple at the same time.”
Leier’s article Wind-driven reorganization of coarse clasts on the surface of Mars is published in the January 2009 edition of Geology. It can be viewed online at www.gsajournals.org/.
Leanne Yohemas | EurekAlert!
GPM sees deadly tornadic storms moving through US Southeast
01.12.2016 | NASA/Goddard Space Flight Center
Cyclic change within magma reservoirs significantly affects the explosivity of volcanic eruptions
30.11.2016 | Johannes Gutenberg-Universität Mainz
A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.
Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...
In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.
“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...
The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.
The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...
Broadband rotational spectroscopy unravels structural reshaping of isolated molecules in the gas phase to accommodate water
In two recent publications in the Journal of Chemical Physics and in the Journal of Physical Chemistry Letters, researchers around Melanie Schnell from the Max...
The efficiency of power electronic systems is not solely dependent on electrical efficiency but also on weight, for example, in mobile systems. When the weight of relevant components and devices in airplanes, for instance, is reduced, fuel savings can be achieved and correspondingly greenhouse gas emissions decreased. New materials and components based on gallium nitride (GaN) can help to reduce weight and increase the efficiency. With these new materials, power electronic switches can be operated at higher switching frequency, resulting in higher power density and lower material costs.
Researchers at the Fraunhofer Institute for Solar Energy Systems ISE together with partners have investigated how these materials can be used to make power...
16.11.2016 | Event News
01.11.2016 | Event News
14.10.2016 | Event News
02.12.2016 | Medical Engineering
02.12.2016 | Agricultural and Forestry Science
02.12.2016 | Physics and Astronomy