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June 12, 2021
According to Space.com, new estimates show that the Red Planet once held an ocean that covered 20 percent of its surface and up to a mile deep. While most of this water was lost to space, the rest remains buried under the surface and trapped in its icy poles. But the water that could have once kept the planet’s surface habitable was lost over the eons, and scientists are searching for the cause.
Researchers using NASA’s Mars Atmosphere and Volatile Evolution spacecraft, or MAVEN, have learned that powerful dust storms carry water above the hygropause. Here on Earth, the hygropause is a cold layer in the atmosphere that condenses the water from a gas to a liquid, forming clouds and stops the water from escaping into space.
While previous studies suggest that water vapor is transported above the Martian hygropause in a way that allows a steady seepage of water, the new research found a seasonal trend, as well as a link to dust storms. “The classical process is like a slow and steady trickle of hydrogen into the upper atmosphere which varies little from Martian year to Martian year, while the process we describe is like a sudden splash of water into the upper atmosphere,” said Shane Stone, the lead author in the research paper published on November thirteenth in the journal Science.
While dust storms block light and heat from reaching the surface of the planet, they warm the hygropause, weakening it and allowing more water to pass through. The warmer temperatures of the southern summer also heat the atmosphere, making the hygropause more porous. When the water molecules reach the upper atmosphere, they react with charged particles, or ions, and split into hydrogen and oxygen atoms. Because hydrogen is the lightest atom, some of the hydrogen atoms can reach speeds high enough to escape the pull of Mars’ gravity and are stripped off into space.
The researchers estimated that the seasonal process, without taking dust storms into account, would strip Mars of a 17.3-inch-deep (44 centimeters) global layer of water over the course of a billion years. Assuming a global dust storm like the 2018 event occurred once every decade, an additional 6.7-inch (17 cm) depth of global water would be lost in that time, with local dust storms each year contributing even more destruction.
“The seasonal and dust storm-mediated delivery of water to the upper atmosphere could have played a substantial role in the evolution of the Martian climate from its warm and wet state billions of years ago to the cold and dry planet we observe today,” the authors wrote in the new study. “Mars has likely lost enough [water] to cover the planet’s surface with an ocean tens to hundreds of meters deep, and loss rates must have been higher in the past.”
ARTICLE: JOSEPH MODICA
SCIENCE/HEALTH EDITOR: KYLE SMITH
IMAGE CREDITS: NASA