Unraveling the Secrets of Mars' Transformation into a Desert World
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Chapter 1: Mars – A Former Water World
Once upon a time, Mars was a vibrant planet teeming with lakes, rivers, and seas. However, over the eons, this abundant liquid water has all but disappeared, leaving behind the cold, arid landscape we observe today. Presently, any residual surface water on Mars is trapped in the form of ice, concealed beneath its reddish exterior. Understanding the process that led to this loss of water may hinge on examining the planet's formidable dust storms, which have the capacity to envelop Mars entirely.
Research indicates that these colossal dust storms can generate intense forces, propelling water vapor from typical altitudes of 20 kilometers (12 miles) to heights of approximately 80 kilometers (50 miles). At these elevated levels, water molecules in the Martian atmosphere can interact with ultraviolet rays from the Sun, resulting in the dissociation into hydrogen and oxygen, which eventually escape into space.
Mars may have resembled this image 4.5 billion years ago, during its formative years. Image credit: NASA/GSFC
Geronimo Villanueva, a researcher at NASA Goddard, elaborates, "When water is elevated in the atmosphere, it is far more susceptible to being lost."
Section 1.1: The Thin Martian Atmosphere
Mars’ atmosphere is tenuous and thin, akin to the air found at the peaks of Earth's tallest mountains, containing only delicate clouds of ice. Observations made by the Mars Atmosphere and Volatile EvolutioN (MAVEN) orbiter and the Hubble Space Telescope (HST) have revealed that hydrogen escapes from the Martian atmosphere, especially during dust storms or the summer months in the southern hemisphere. This phenomenon suggests that a "heat pump" mechanism may be responsible for driving water vapor to significant altitudes.
The MAVEN spacecraft is depicted orbiting Mars in this artistic representation. Image credit: NASA
This concept could clarify how liquid water, once abundant on Mars, has been lost to the cosmos. Unlike Earth, where atmospheric water condenses and falls as precipitation, Martian water high in the atmosphere dissociates into hydrogen and oxygen and is lost permanently to space.
Dmitry Shaposhnikov from the Moscow Institute of Physics and Technology (MIPT) explains, “The Sun acts as a pump, becoming active during the day and facilitating water to ascend to altitudes exceeding 60 kilometers. The increased moisture and airflow during dust storms enable this 'pump' to elevate water even higher.”
The first video titled "Are Martian Dust Storms Dangerous?" explores the potential hazards posed by these colossal storms.
Section 1.2: The Unique Orbit of Mars
Mars follows a more elongated orbit around the Sun than Earth. Consequently, during the southern hemisphere's summer, Mars is considerably closer to the Sun, while the northern hemisphere experiences summer at its farthest point from the Sun (aphelion). This variation in distance leads to cooler summers in the northern hemisphere compared to the southern.
As summer arrives in the southern hemisphere, ice sublimates, transitioning directly from solid to vapor and entering the atmosphere. Below 40 kilometers (25 miles), this water remains as vapor, while above this altitude, it condenses into ice clouds. Solar heating generates a temporary updraft between latitudes of 20 and 70 degrees south during local summer, propelling water into the atmosphere. Seasonal winds then transport this water northward, where a portion is subjected to ultraviolet light, leading to its breakdown into hydrogen and oxygen. The remaining moisture typically cools and settles near the north pole, contributing to the formation of the northern polar cap.
The Curiosity rover is enveloped by a dust storm on Mars from June 8, 2018, to September 13, 2018. Image credit: NASA/JPL-Caltech/York University
Chapter 2: The Impact of Dust Storms on Martian Water
Dust storms on Mars can cover areas comparable to the size of the United States for days. Global dust storms, such as the one that rendered the Opportunity rover silent after nearly 15 years, can envelop the entire planet and persist for months. The first global dust storm documented on Mars occurred in 1971 with the Mariner 9 spacecraft, followed by similar occurrences in 1977, 1982, 1994, 2001, 2007, and 2018. The most recent storm saw eight spacecraft—the highest number yet—studying Mars simultaneously.
Astronomers once believed Earth was the only planet with significant bodies of water, but we now recognize that several celestial bodies in our solar system may harbor substantial water reserves, some potentially capable of supporting primitive life. Beyond our solar system, super-Earths orbiting distant stars might also possess vast oceans, possibly nurturing diverse alien ecosystems.
As nations and private enterprises gear up to send humans to Mars, understanding the dynamics of water on the Red Planet and the role of dust storms in shaping its climate is crucial.
The second video titled "The Storm So Big It Can Take Out Satellites" delves into the immense power of Martian dust storms and their effects.