How the water escaped the red planet

Mars once had oceans but is now bone-dry, leaving many wondering how the water was lost. Researchers at the University of Arizona have discovered a surprisingly large amount of water in the upper atmosphere of Mars, where it is rapidly disappearing, explaining part of the mystery of Mars.

Shane Stone, a graduate student at Lunar and Planetary Laboratory in Eurezona and lead author of a new paper published today Science, Describes himself as a planetary chemist. Once a laboratory chemist who helped develop a polymer that could be used to more effectively wrap and deliver therapeutic drugs, he now studies the chemistry of planetary atmospheres.

Since 2014, he has worked on the short NASA Maven mission to Mars atmospheric and volatile evolution. The MAVEN spacecraft began orbiting Mars in 2014 and has been recording the formation of the atmosphere above the Earth’s planetary neighbors ever since.

“We know that there was liquid water on the surface of Mars billions of years ago,” Stone said. “There must be a ga atmosphere atmosphere, so we know that Mars has somehow lost most of its atmosphere in space. MAVEN is trying to characterize the processes responsible for this damage, and a part of it is to understand exactly how Mars lost its water. Has been. “

Co-authors of the study include Eurizo’s professor of planetary science and Stone’s research adviser, as well as Eurizo’s professor of planetary science and research at the Center for Research and Exploration at Space Science and Technology in Maryland.

Looking for water

As Mars orbits, it sinks into the planet’s atmosphere every 4 1/2 hours. The short onboard NGIMS instrument for neutral gas and ion mass spectrometers, about 100 miles from the planet’s surface, is measuring the abundance of water molecules known as ions in the atmosphere of Upper Mars. From this information, scientists can estimate how much water is in the atmosphere.

Past observations using MAVEN and the Hubble Space Telescope have shown that the loss of water from the Martian upper atmosphere varies with the Tuo. Compared to Earth, Mars takes a more elliptical path around the Sun and is closer to it during the summer in the Southern Hemisphere.

Stone and his team found that when Mars is closer to the sun, the planet warms up, and more water seen on the surface in the form of ice goes into the atmosphere above the surface where it is lost in space. This happens every Tuesday in a year or about once every two Earth years. Regional dust storms that occur on Mars every Tuesday and global dust storms that occur on the planet about once every 10 years further heat up the atmosphere and increase the upward movement of water.

Stone said the processes that make cyclic movement possible contradict the classical picture of saving water from Mars, showing that it is incomplete. According to the classical process, water ice is converted into gas and destroyed by the sun’s rays in the lower atmosphere. However this process will play as a slow, steady trick, not affected by dust tuo or dust storms, which cannot mesh with current observations.

“This is important because we didn’t expect to see any water in the atmosphere above Mars,” Stone said. “If we compare Mars to Earth, the water on Earth is confined to the surface due to something called hygroposes. In the atmosphere it is just a layer that is as cold as cold (and therefore closes) and any water vapor traveling above Prevents. “

The team argues that what should be the highgroup ause of Mars is moving water past, which is too hot to stop water vapor. Once in the upper atmosphere, water molecules break down very quickly through ions – within four hours, they count and then the by-products are lost in space.

“Water damage to its atmosphere and space is a big reason why Mars is colder and drier than hot and humid Earth. These new data from MAVEN reveal a process by which this damage continues today,” Stone said. Stone said.

A dry and dusty world

When the team released their findings 1 billion years later, they discovered that the process was responsible for the loss of about 17 inches deep in the global ocean.

“If we take water and spread it evenly over the entire surface of Mars, the new process we describe caused water to get lost in that ocean space,” Stone said. “An additional 6.7 inches will be lost due to the impact of global dust storms alone.”

During global dust storms, 20 times more water can be transported into the upper atmosphere. For example, a global dust storm lasting 45 days released as much water into space as Mars would lose during a quiet Mars year or 687 Earth days.

And while Stone and his team will not be able to do extrapolation more than 1 billion years ago, he thinks the process may not work the same way as before, as Mars may have been hygroposed much earlier.

“Before we can begin the process described, there must already be a significant amount of atmospheric escape into space,” Stone said. “We still need to reduce the effectiveness of this process and when it started working.”

In the future, Stone will want to study Saturn’s moon, Titan’s atmosphere.

“Titan has an interesting atmosphere in which organic chemistry plays a significant role,” Stone said. “As a former synthetic organic chemist, I look forward to investigating these processes.”