Thousands of tiny 'ice needles' may explain mysterious stone patterns on Earth … and Mars

Many thousands of tiny "ice needles" created some of the most stunning zen garden designs on the planet. Each delicate design is created by clumping stones of similar size across a landscape.
The Proceedings of the National Academy of Sciences published new research Oct. 5, which shows how ice needles can create intricate patterns of stones in different landscapes. Ice needles freeze and push small rocks to one side or the other. The rocks will become more concentrated over time and form a pattern. Bernard Hallet (University of Washington geologist) co-authored the study. He said that the work confirms over a century of scientific speculation regarding the relationship between stone patterns and ice needles. It might also shed light on the origins and meaning of a more mysterious set patterns, such as those found on Mars.

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When the temperature of the soil is too high, it can cause ice needles. Certain types of dirt "exhale" at night and contract with the temperature drop. The soil's water is simultaneously drawn up by capillary action. Water molecules stick to the sides and corners of the ground's very narrow pores. This water then freezes into a crystal-like needle shape as it rises to the frosty air.

Hallet said that sometimes they can be very striking. They are quite common. You've likely stumbled upon "crunchy" ground in the early morning and crushed some ice needles, even if you didn't know it.

Scientists have long associated tiny ice sculptures and intricate swirls on pebbly ground with the colorful landscapes surrounding Hawaii's volcanoes.

From moist, porous soil, ice needles are formed. Image credit: QuanXing Liu

They didn't know how ice could trace these patterns without living beings. They began to investigate.

Researchers covered a 1 by 1 foot (1.4 meter) square area of soil with evenly-sized, regular-spaced stones. After 30 freeze-thaw cycles were completed, the researchers covered the area with small, uniformly spaced stones. This allowed ice needles form and melt. The rising and falling needles gradually, almost imperceptibly, pushed the pebbles towards one side. This was due to tiny environmental imbalances like the slope of the landscape. A pile of stones weighs more than one pebble so ice needles can't push them once they reach a sufficient concentration. The team observed zen-garden-like patterns begin to form at the end of their experiments: stones on one and bare ground the other.

Left: Soil rings from Svalbard (Norway). Center: Stone lines at Mauna Kea, Hawaii. Right: Thule, Greenland. (Image credit to Bernard Hallet

Hallet stated that stones have a tendency to move towards stony domains. Flat stones tend to form loops and swirls while stones on gentle slopes tend to organize into rows.

According to research published in Arctic and Alpine Research, not all soil is porous enough for ice needles to form. Also, needle ice is not possible in all climates. It will only form where the ground and air are moist.

Experts think that there may be a subtler version to this cycle behind the patterns observed on Mars by NASA's Curiosity rover. NASA's Kennedy Space Center says that although the Martian atmosphere has very little water, some evidence of tiny ice crystals can be found in the Red Planets soil. This dirt expands as it heats up and shrinks when it cools.

A stone circle on Mars. Image credit: NASA/JPL

Although this is less dramatic than ice needles pushing stones aside, it can still cause small pebbles or dust to shift over time. Hallet stated that the intricate patterns created by soil contractions and expansions on Earth might not be noticed. These features are visible on Mars because there is so little else going on than the wind.

Unfortunately, scientists have yet to find any Martian ice needles.

Original publication on Live Science

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