China’s Zhurong spacecraft was the first Chinese spacecraft to land on Mars and explored Utopia Planitia, one of Mars’ largest impact basins. The area was visited by Viking 2 in his 1976 year, and advances in technology over the decades have allowed Zhurong to provide new insights into the area. And some of them came from below the surface of the earth. The spacecraft discovered 16 polygonal structures buried beneath the surface.
Researchers believe they formed during freeze-thaw cycles, when cracks formed in the landforms that were originally on the surface. As seen in other landforms on Mars, sublimation and freezing can carve landforms in unique ways (such as so-called spiders), and this process does not appear to be new on Mars. It may have lasted billions of years.
Research from Zhurong’s radar indicates that parts of this cracked terrain and its polygonal structure may become buried. The formation was 35 meters (115 feet) below the surface. Previous studies focused on the vertical layers of the region. This indicates that there were several accidental floods that filled the basin about 3 billion years ago. Instead, the new study revealed what the formations look like horizontally by looking at radar analysis over 1.9 kilometers (1.2 miles).
A scenario for the formation of a polygonal structure buried under Utopia Plain.
Mars was once a volcanic world. The highest volcano in the solar system is on Mars. Some geological activity continues to this day, and Mars earthquakes have been recorded on Mars by NASA Insight.
The researchers therefore considered the possibility that the buried structures originated from lava. There are several examples of these on Earth, such as the Giant’s Causeway. However, there was no evidence of basaltic extrusions at the sites investigated by Zhurong. The researchers believe the structures are deposits, formed by thermal processes in different climates.
And that’s the interesting result of this study. If the polygonal structure required freezing and thawing events, ancient Mars’ climate would have been more variable. The Utopian Plains are located in low to mid latitudes. This region is located 25 degrees north of Mars’ equator. However, the planet’s tilt may have been higher, so this region may have had very different seasons.
Layers indicate that more happened in the past. The polygonal structures were buried in layers of material that looked nothing like them. Perhaps the wet environment that formed them no longer exists, or some other unknown geological event has occurred.
“This polygonal landform, occurring at low latitudes (approximately 25°N), is interpreted to have most likely been formed by thermal shrinkage cracks and provides a convincing indication of the high tilt of early Mars. “The subsurface structure of the overburden covering the buried paleopolygons suggests that there was significant paleoclimate change some time later,” the authors write.
This research natural astronomy.
[H/T: Universe Today]