Space glaciers: Carbon dioxide ice forms glaciers on Mars
In Mars’ thin, cold atmosphere, temperatures drop enough to freeze molecules that are normally gaseous on Earth.Although scientists have already known For decades, carbon dioxide ice has been deposited at the South Pole of Mars, A recent study These sediments were found to form glaciers, flow into basins and survive warm periods, much like their water-based counterparts on our home Earth.
The study was published in April in journal of geophysical research A team of planet and ice modeling scientists.
Mars, the fourth planet in our solar system, has ice caps made of water and carbon dioxide ice at its north and south poles. Image credit: Kevin Gill/Frick
Similar to Earth, Mars has ice caps at its poles, which accumulate ice in winter and lose ice in summer.Unlike Earth, however, winter on Mars could look like -220℉ at its poles— cold enough to freeze molecules on Earth that are always gaseous. For example, carbon dioxide — a gas at room temperature —Freeze at -109°FThe scientists found that about 1 percent of the Martian ice cap’s volume comes from frozen carbon dioxide (dry ice) deposits that accumulate at each pole in winter, while the rest of the ice cap is made up of frozen water.
Scientists are particularly interested in the structure and composition of Martian ice sheets. Decades ago, scientists thought that Mars’ entire southern ice cap was made of carbon dioxide, while the northern ice cap was made of water.However, in one study, a 4-kilometer-thick ice sheet would collapse under its own weight If it were composed entirely of carbon dioxide — forming ice that is weaker than water — scientists would have to reconsider its composition. They started assuming it contained frozen water and frozen carbon dioxide. NASA space mission detects frozen water In the southern ice sheet of Mars in the early 2000s, scientists now believe that the southern ice sheet consisted mostly of frozen water covered with a thin layer of carbon dioxide ice.
Scientists are particularly interested in Mars’ southern ice sheet because of the mixed composition and distribution of carbon dioxide ice.Courtesy of IB Smith
Scientists like Isaac B. Smith, assistant professor of earth and space sciences at York University’s Lasunder School of Engineering, are now modeling deposits of carbon dioxide ice to understand how they form.Smith participated in a 2011 study that used radar technology to identify carbon dioxide ice deposits It is up to a kilometer thick on Mars. At the time, “no one could explain the distribution, but we acknowledged that the ice was in the basin,” Smith said, meaning the ice didn’t have to hold its own shape, so the strength of the ice was less important. Smith is also involved in studies that measure the strength properties of carbon dioxide ice.
This research is April Researchthey found that the sediments on Mars’ south pole, identified in 2011, were formed by carbon dioxide ice flowing into the basin as glaciers.
While scientists know that these deposits cannot come from atmospheric circulation and storms alone, it is not straightforward to prove that carbon dioxide ice deposits come from glacial flows. Smith said he first found that Martian ice matched “several features we’ve seen on terrestrial water glaciers,” including topography and contours and the presence of compression ridges (linear ridges that glaciers form following gravity). This feature analysis is important for laying the groundwork to support the idea that these ice deposits may have come from glacial flows, but it is not enough to definitively declare it.
Smith then worked with 3D glacier modelers to adapt Earth-based glacier modeling software for Mars—which meant changing model parameters such as gravity, heat flux, and ice types. According to Smith, they were able to use the modeling software “to grow glaciers from scratch,” and the model’s output “matches very well the distribution of carbon dioxide ice measured on NASA’s Mars space mission.”
A close-up of the southern ice cap taken by NASA.Courtesy of IB Smith
The characterization and spatial modeling done by Smith and his team explained the distribution of carbon dioxide ice in these basins better than previous models of precipitation and other atmospheric effects. Because carbon dioxide ice has a lower viscosity (internal friction) than water ice, Martian carbon dioxide glaciers are able to flow faster than terrestrial glaciers that freeze water. The slopes on the Martian South Pole ice sheet are steep enough to channel glacial carbon dioxide into the basin, forming thick deposits identified in 2011. The study also found that these deposits were able to survive the warmer periods on Earth (summer), because to their thickness, because only the uppermost parts of the ice experience sublimation, a process in which frozen molecules are transformed directly into a gaseous state, completely jumping past the liquid.
Understanding the distribution of carbon dioxide ice deposits on the southern Martian ice sheet solves the decade-long mystery of the origin of the mysterious anomalous ice.The study emphasizes that many kinds Ice and glaciers in the solar system, such as Methane and nitrogen glaciers Found on Pluto.
More research is needed on alternative ices in the solar system; Smith said the first step is to make more laboratory measurements of exotic ices so that “we can properly model their behavior when we find them.” of other glaciers and ices may help us better understand our own glaciers on Earth and understand the diversity of ice beyond our atmosphere.
