Featured Research

from universities, journals, and other organizations

How Martian Winds Make Rocks Walk

Date:
January 12, 2009
Source:
University of Calgary
Summary:
At first, figuring out how pebble-sized rocks organize themselves in evenly-spaced patterns in sand seemed simple and even intuitive. But once one researcher started observing, he discovered that the most commonly held notions did not apply. And even more surprising, was that his findings revealed answers to NASA’s questions about sediment transport and surface processes on Mars.

Spirit Rover camera images of the intercrater planes between Lahontan Crater and Columbia Hills illustrating examples of uniformly-spaced clast distribution. a) Portion of NAVCAM image. b) Pancam image.
Credit: Ward et al.

At first, figuring out how pebble-sized rocks organize themselves in evenly-spaced patterns in sand seemed simple and even intuitive. But once Andrew Leier, an assistant geoscience professor at the U of C, started observing, he discovered that the most commonly held notions did not apply.

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 the journal 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.

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.

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.”


Story Source:

The above story is based on materials provided by University of Calgary. Note: Materials may be edited for content and length.


Journal Reference:

  1. Andrew Leier et al. Wind-driven reorganization of coarse clasts on the surface of Mars. Geology, January 2009

Cite This Page:

University of Calgary. "How Martian Winds Make Rocks Walk." ScienceDaily. ScienceDaily, 12 January 2009. <www.sciencedaily.com/releases/2009/01/090107122708.htm>.
University of Calgary. (2009, January 12). How Martian Winds Make Rocks Walk. ScienceDaily. Retrieved July 29, 2014 from www.sciencedaily.com/releases/2009/01/090107122708.htm
University of Calgary. "How Martian Winds Make Rocks Walk." ScienceDaily. www.sciencedaily.com/releases/2009/01/090107122708.htm (accessed July 29, 2014).

Share This




More Earth & Climate News

Tuesday, July 29, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Baluchistan Mining Eyes an Uncertain Future

Baluchistan Mining Eyes an Uncertain Future

AFP (July 29, 2014) Coal mining is one of the major industries in Baluchistan but a lack of infrastructure and frequent accidents mean that the area has yet to hit its potential. Duration: 01:58 Video provided by AFP
Powered by NewsLook.com
Asteroid's Timing Was 'Colossal Bad Luck' For The Dinosaurs

Asteroid's Timing Was 'Colossal Bad Luck' For The Dinosaurs

Newsy (July 28, 2014) The asteroid that killed the dinosaurs struck at the worst time for them. A new study says that if it hit earlier or later, they might've survived. Video provided by Newsy
Powered by NewsLook.com
The Carbon Trap: US Exports Global Warming

The Carbon Trap: US Exports Global Warming

AP (July 28, 2014) AP Investigation: As the Obama administration weans the country off dirty fuels, energy companies are ramping-up overseas coal exports at a heavy price. (July 28) Video provided by AP
Powered by NewsLook.com
Raw: Sea Turtle Hatchlings Emerge from Nest

Raw: Sea Turtle Hatchlings Emerge from Nest

AP (July 27, 2014) A live-streaming webcam catches loggerhead sea turtle hatchlings emerging from a nest in the Florida Keys. (July 27) Video provided by AP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins