How the water reaches the upper atmosphere is still a mystery.

Although the weather is cold and dry today, Mars used to flow through liquid water. That's all we know. Roughly speaking, we also know the reason for the loss of this water: sometime about 3.9 billion years ago, an internal generator deep in Mars called it out. The planet’s magnetic shield was removed and the charged particles of the solar wind began to strip it. atmosphere.

"To make the water liquid, you need enough atmospheric pressure," planetary scientist Shannon Curry at the University of California, Berkeley, told Inverse. As the Martian atmosphere burns and the atmospheric pressure decreases, the liquid water on the surface "will begin to evaporate-it cannot remain in an unstable liquid form."

The surface is beginning to dry up, but there is still a lot of water hidden in the form of underground ice.

George Mason University planetary scientist Erdal Yiğit published a new opinion article in the journal Science on Thursday that the interaction between the upper atmosphere and the solar wind can only partially explain how Mars loses surface water. An understanding of atmospheric waves, dust storms, and convection will be the key to telling the story of Martian dehydration.

This is a story related to us on Earth, because Mars may represent an untaken road. "Earth, Mars, and Venus formed at similar times, but their evolution is quite different," Curry said. "I think Mars is the planet most likely to have habitable conditions at some point."

What's new? — Yiğit started with the discovery of several recent space missions to Mars orbit: the European Space Agency’s ExoMars Trace Gas Orbiter, or TGO; NASA’s Mars Reconnaissance Orbiter, or MRO; and NASA’s Martian Atmosphere and Volatile Evolution or MAVEN Task.

These missions jointly discovered that Mars is still losing water to space, mainly during the sandstorm season when Mars is closest to the sun in summer. "Low-level atmospheric dust storms are a key component of Martian weather and have a wide-ranging impact on the entire Martian atmospheric system," Yiğit wrote. Storms can circulate hydrogen through solar radiation—solar flares, ultraviolet radiation, and coronal mass ejection—separated from oxygen—into the upper atmosphere, where it escapes irretrievably into space.

"This is a very exciting result for all of us," said Curry, who became the lead researcher of the MAVEN mission earlier this year. "Frankly, if you ask me, I would think that dust will make things drier. I never thought that during a sandstorm, water would lose twice as fast."

However, Yiğit believes in the paper that one step is missing in this process, namely how to couple the upper and lower atmospheres of Mars so that the water can reach a height where it can escape. He suggested that future three-dimensional climate models should consider the effects of gravity waves and tides in the atmosphere in addition to the data still being collected by MAVEN and other missions.

Why is this important? -Understanding how Mars lost surface water-and still losing a small amount of water-is directly related to the biggest problem in planetary science. Livability, the origin and unique qualities of life on earth.

"I think this is almost a metaphysical question. This is crucial to who we are: Why is life formed on the earth, and as far as we know, not anywhere else? At least in the solar system?" Curry said. "I think Mars is definitely the first place to start answering this question."

What's next? --Although scientists are working on climate models of the Martian atmosphere, MAVEN and other missions will continue to collect data to plug into these models and provide some exciting opportunities for upcoming new observations.

Curry pointed out that the sun has experienced 11- and 22-year cycles of activity. "Six months ago, we were at the bottom of the cycle, which means the sun is really quiet," she said. But around 2024 and 2025, solar activity will peak, which means more solar storms, solar flares, and coronal mass ejections-all of which occur in the middle of the Martian global dust storm season.

"In the next few years, we will see very extreme situations," Curry said.

At the same time, she doubts that MAVEN, other existing orbital missions, and climate models can fill the gap that Yiğit wants to explain the continued water loss of Mars. Curry said that scientists may need new instruments, ground instruments that can study the lower atmosphere. In any case, this is something NASA is considering before sending humans to Mars.

"When we put our boots on the ground, we want to have landing assets, not just a few detectors sticking out of the cabin, or whatever," she said. "If you live near the Earth's equator, you want to know when the hurricane will come. It's no different on Mars, right?"