Mars experiences a cold and otherworldly winter season, marked by cube-shaped snow, frozen landscapes, and frost. The planet’s poles experience some of the coldest temperatures, reaching as low as minus 190 degrees Fahrenheit (minus 123 degrees Celsius). The Martian winter is a fascinating phenomenon that has been studied extensively by NASA and other space agencies, providing insights into the planet’s climate and geology. The presence of snow and ice on Mars also raises questions about the potential for water and the possibility of habitable environments on the planet.
This image acquired on July 22, 2022 Ƅy NASA’s Mars Reconnaissance OrƄiter shows sand dunes мoʋing across the landscape. Winter frost coʋers the colder, north-facing half of each dune. Credit: NASA/JPL-Caltech/Uniʋersity of Arizona
As mentioned earlier, Mars does not receive snow drifts as large as those found in the Rocky Mountains. Most regions of the planet receive only a few feet of snow, and this typically falls over extremely flat areas. Additionally, due to the planet’s elliptical orbit, winter takes many more months to come around, with a single Mars year lasting around two Earth years.
Despite these limitations, NASA’s robotic Mars explorers have been able to study and discover a range of unique winter phenomena on the planet. For example, they have observed the formation of frost and ice on the Martian surface, the movement of sand dunes across the landscape, and the sublimation of carbon dioxide snow. The study of Martian winters has provided valuable insights into the planet’s climate, geology, and potential habitability, furthering our understanding of the Red Planet and its place in the solar system.
HiRISE captured these “мegadunes,” also called Ƅarchans. CarƄon dioxide frost and ice haʋe forмed oʋer the dunes during the winter; as this starts to suƄliмate during spring, the darker-colored dune sand is reʋealed. Credit: NASA/JPL-Caltech/Uniʋersity of Arizona
The HiRISE camera aboard NASA’s Mars Reconnaissance Orbiter has captured stunning images of “megadunes” on the Martian surface, also known as barchans. These dunes are covered in carbon dioxide frost and ice during the winter months, creating a visually striking contrast when the darker sand is revealed as the frost begins to sublimate during the spring. The study of these megadunes has provided valuable insights into the Martian climate and geology, including the planet’s wind patterns and how the dunes move and evolve over time. These findings have contributed to our understanding of the complex and dynamic environment on Mars and the potential for future exploration and study of the planet.
Two kinds of snow
Martian snow comes in two varieties: water ice and carbon dioxide, or dry ice. Due to the thin Martian atmosphere and extremely cold temperatures, water-ice snow sublimates, or turns into gas, before it even reaches the ground. In contrast, dry-ice snow actually does reach the ground.
According to Sylain Piqueux, a Mars scientist at NASA’s Jet Propulsion Laboratory in Southern California, “enough [dry-ice snow] falls that you could snowshoe across it.” However, skiing on Mars would require finding a crater or cliffside where snow could build up on a sloped surface. Piqueux’s research includes a variety of winter phenomena on Mars, and the study of these phenomena has provided valuable insights into the planet’s climate and geology, furthering our understanding of this fascinating world.
How we know it snows
Snow on Mars is a rare occurrence and only happens at the coldest extremes of the planet, such as at the poles, under cloud cover, and at night. Unfortunately, cameras on orbiting spacecraft cannot see through these clouds, and surface missions cannot survive in the extreme cold, so no images of falling snow have ever been captured. However, scientists know that snow occurs on Mars thanks to a few special science instruments.
For example, NASA’s Mars Reconnaissance Orbiter uses its Mars Climate Sounder instrument to peer through cloud cover and detect carbon dioxide snow falling to the ground. Additionally, in 2008, NASA’s Phoenix lander detected water-ice snow falling to the surface near Mars’ north pole using a laser instrument. These detections of snow on Mars provide valuable insights into the planet’s climate and geology, furthering our understanding of this fascinating world.
The HiRISE caмera captured this image of the edge of a crater in the мiddle of winter. The south-facing slope of the crater, which receiʋes less sunlight, has forмed patchy, bright frost, seen in Ƅlue in this enhanced-color image. Credit: NASA/JPL-Caltech/Uniʋersity of Arizona
CuƄic snowflakes
The shape of snowflakes on Earth is determined by the way in which water molecules bond together when they freeze, resulting in six-sided crystals. Similarly, the shape of crystals in general is determined by how atoms arrange themselves. In the case of carbon dioxide, molecules in dry ice always bond in forms of four when frozen, resulting in cube-shaped snowflakes.
According to Sylain Piqueux, dry-ice snowflakes on Mars would also be cube-shaped due to the symmetry of carbon dioxide ice. However, thanks to the Mars Climate Sounder, scientists have been able to determine that these snowflakes would be smaller than the width of a human hair. The study of Martian snow and ice provides valuable insights into the planet’s climate and geology, furthering our understanding of this fascinating world.
Jack Frost nipping at your roʋer
Water and carbon dioxide can each form frost on Mars, and both types of frost appear far more widely across the planet than snow does. The Viking landers, which studied Mars in the 1970s, observed water frost on the planet’s surface. Additionally, NASA’s Odyssey orbiter has observed frost forming and sublimating away in the morning sun. These observations provide valuable insights into the planet’s climate and geology, and help scientists better understand the processes that shape the Martian surface. The study of frost on Mars is an ongoing area of research, with new findings regularly shedding light on this fascinating world.
HiRISE captured this spring scene, when water ice frozen in the soil had split the ground into polygons. Translucent carƄon dioxide ice allows sunlight to shine through and heat gases that escape through ʋents, releasing fans of darker мaterial onto the surface (shown as Ƅlue in this enhanced-color image). Credit: NASA/JPL-Caltech/Uniʋersity of Arizona
Winter’s wondrous end
One of the most fascinating discoveries related to Martian winter occurs at the end of the season when the ice built up begins to sublimate into the atmosphere. As this process occurs, the ice takes on bizarre and beautiful shapes that have been compared to spiders, Dalmatian spots, fried eggs, and Swiss cheese. These unique formations provide scientists with valuable insights into the Martian climate and geology.
Additionally, the thawing of ice during spring causes geysers to erupt, creating fans of dust that are sent onto the surface. These fans are being studied as a way to understand the direction of Martian winds. Translucent ice allows sunlight to heat up gas underneath it, which eventually bursts out in a geyser-like eruption. The study of these geysers and dust fans provides researchers with valuable information about the planet’s atmosphere and the processes that shape its surface.
Source: phys.org
