Global Storms Launch Dust Towers Into The Martian Sky

 No other planet in our Solar System has inspired the human imagination more than Mars. This is because, historically, the Red Planet was considered the most likely world to be the distant home of life beyond Earth. While this viewpoint has certainly become greatly outdated, Mars still entices Earthlings with its rusty-red surface, etched with small valleys carved into slopes, that are eerily similar in shape to gullies formed by rushing water flowing on the surface of our own planet--and where liquid water exists, life as we know it may also exist. But, today, Mars is a frigid and dry wasteland, where violent dust storms are common--but, every ten years or so, something unpredictable happens, and a series of runaway storms break out that cover the entire planet in a dense shroud of swirling dust. In November, 2019, planetary scientists announced that a fleet of NASA spacecraft managed to get a good look at the life cycle of the enormous--and highly destructive--2018 global dust storm that prematurely ended the visiting rover Opportunity's mission of exploration on the surface of the Red Planet.

At this time, planetary scientists are still in the process of studying the new and puzzling data. However, two papers have recently been published that shed new light on a phenomenon seen occurring within the enormous dust storm--dust towers, which are concentrated clouds of dust that become warm in sunlight and then rise rise high into the air. Planetary scientists have proposed that water vapor, imprisoned by the dense, swirling dust, may be riding them in a way that has been compared to an elevator into space, where radiation from our Sun rips their molecules apart. This suggestion might help explain how the Martian water vanished over the passage of billions of years.

Our Solar System is about 4.6 billion years old. Prior to approximately 3.8 billion years ago, Mars may have had a much denser atmosphere than it has today, as well as higher surface temperatures. These ancient conditions would have permitted vast quantities of liquid water to exist on the Martian surface, including a large ocean covering one-third of the planet.

Almost all of the water on Mars today is in the form of ice, although some of it also exists as water vapor in its atmosphere. The only place where water ice is visible on the Martian surface is at the north polar ice cap. However, a large amount of water ice is also present beneath the permanent carbon dioxide ice cap at the Martian south pole, as well as in the shallow subsurface at more temperate conditions.

More than 21 million kilometers of ice have been discovered at or near the Martian surface. This amounts to enough water ice to cover the entire planet to a depth of 115 feet. It is even more likely that water ice is lurking in the deep Martian subsurface.

Large quantities of dust have formed on the surface of the Red Planet as a result of its currently dry conditions. Dust towers are churning, enormous clouds that climb considerably higher than the normal background dust in the thin Martian atmosphere. Even though dust towers have also been seen under more normal conditions, they appear to form in greater numbers as the result of global storms.

A tower first forms on a planet's surface. It begins as a region of rapidly lifted dust that is approximately as wide as Rhode Island. By the time this dusty tower reaches the lofty height of 50 miles, as observed during the infamous 2018 global dust storm, it may be as wide as the state of Nevada. As the tower begins to lose strength, it can form a layer of dust 35 miles above the surface of a planet that can be wider than the entire continental United States.