How Ice Needles Create Spontaneous Zen Gardens
Some of the most breathtaking zen garden patterns on the planet owe their existence to an unlikely artist: thousands of tiny "ice needles."
Credit: Quan-Xing Liu of East China Normal University
Credit: Quan-Xing Liu of East China Normal University
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TechTranscript
00:00In high-latitude permafrost environments and high-altitude mountains, there are a large
00:12number of mysterious regular surface patterning, also known as patterning, such as the Qinghai-Tibet
00:20Plateau and other freezing regions in China, the Svobod Islands in Norway in the Arctic
00:27and the Alpine regions in Ethiopia. The patterned ground is made up of different kinds of stones
00:34and soils, some arranged in polygonal net, stone circles, and others in strapped spatial
00:43patterns. The origin of these regular patterns has long been puzzling scientists, but recently
00:51this enigma is starting to be solved. Scientists now attribute the spontaneous regular patterns
01:00to a process called spatial self-organization. In the periglacial environment, winds gathering
01:08together with soil-freezing thawing cycles are speculated to drive the aggregation and
01:14separation movements of granular particles in the soil, which eventually result in a
01:20sordid spatial patterns of stones on the land surfaces.
01:32This idea has been sparked by theoretical and empirical studies in physics, chemistry,
01:38biology and ecology. However, it is notoriously difficult to test this idea in the field.
01:47The geomorphological systems in cold regions often evolve at extremely slow rates, largely
01:54forbidden human observers to record the processes. Many existing numerical models have suggested
02:02that differential frost heave and radial expansion of the fine-grained soils can lead to the
02:08movement of surface particles to the margins of the plugs and the formation of the self-organized
02:14patterns. This mechanism can reproduce a variety of large-scale sordid patterns, such as polygons
02:22and sordid circles, but direct experimental evidence for this model is still lacking.
02:30Scientists have long speculated that needle ice formed in the permafrost layer could play
02:35a role. A new research led by an international team from China, Japan, the US and the Netherlands
02:43revisited this old idea with brand new evidence and theory. The researchers designed an elegant
02:51experiment system that allows for the formation of needle ice in well-controlled lab conditions.
02:58This system can mimic a time machine with which the observers can push the fast-forward
03:04button to speed up the process of land surface evolution within a microcosm. Within a couple
03:10of weeks, the researchers can now observe the years or even decades-long process happening
03:16in nature. They use video camera and computer program to automatically track the movement
03:24trajectory of every single stone and reproduce such observed processes in computer with mathematical
03:31models. The researchers found that driven by the freezing-thaw cycles in soils, the
03:36granular particles migrated towards the stone-rich areas from stone-poor areas. This is exactly
03:43the process where a variety of older spatial patterns of stones arises from.
03:50This group of scientists have replicated the experiment numerous times with all kinds of
03:56settings of needle ice properties and stone field concentration. They put together these
04:01nonlinear relationships between different needle ice height and stone field concentration
04:07to demonstrate that the geomorphological pattern formation process has the same physical principle
04:13as that underpins the water-oil separation process.
04:27Known as phase-separation mechanism, the phase-separation theory perfectly reproduced
04:32the different types of sorted patterns and found that the activity of needle ice plays
04:37a dominant role in shaping this pattern ground. What makes the scientists more exciting is
04:44that their phase-separation model can also perfectly reproduce the similar sorted patterns
04:50found in the Martian boulders by curiosity. Can this seen as another evidence reinforcing
04:57the existence of soil-water on Mars? Does this mean freezing-thaw cycles also drive
05:03the evolution of Martian landscapes? It's still too early to answer this question, but
05:10the study does open many opportunities to look into geological and geomorphic evolution
05:16of Earth-like planets.
05:27NASA Jet Propulsion Laboratory, California Institute of Technology