Scientists decode how Mars lost its water

Scientists have managed to further decode the phenomenon that resulted in loss of water on Mars. The Red Planet lost equivalent of a global ocean of water up to hundreds of feet deep in more than billions of years.

An instrument aboard NASA’s Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft helped scientists discover that water vapour near the surface of Mars is lofted into the atmosphere higher than anyone expected could be possible.

Electrically charged gas particles or ions easily destroy it and it is lost in space. The team wrote in journal Science that the Red Planet continues to lose water because the water vapour goes to high altitudes after sublimating from the frozen polar caps during warmer seasons.

“We were all surprised to find water so high in the atmosphere,” said Shane W Stone, a doctoral student in planetary science at the University of Arizona’s Lunar and Planetary Laboratory in Tucson.

“The measurements we used could have only come from MAVEN as it soars through the atmosphere of Mars, high above the planet’s surface.”

For over two Martian years, Stone and his team tracked the abundance of water ions high over Mars. The team found that the amount of water vapour in the atmosphere at about 150 kms above the surface was highest during summer in the southern hemisphere.

Mars is closest to the Sun during this time and hence warmer and there are more chances of dust storms to occur.

The warm temperatures and strong winds allow the water vapour to reach the uppermost parts of the atmosphere, where it is broken into its constituent oxygen and hydrogen, which are then lost to space.
Scientists previously believed that water vapour was trapped close to the Martian surface.

“Everything that makes it up to the higher part of the atmosphere is destroyed, on Mars or on Earth,” Stone said, “because this is the part of the atmosphere that is exposed to the full force of the Sun.”

“We have shown that dust storms interrupt the water cycle on Mars and push water molecules higher in the atmosphere, where chemical reactions can release their hydrogen atoms, which are then lost to space,” said Paul Mahaffy, director of the Solar System Exploration Division at NASA Goddard and principal investigator of NGIMS.

Other scientists also say that dust storms on Mars can lift water vapour far above the planet’s surface. However, until now it was not known that water would reach the top of the atmosphere.

“What’s unique about this discovery is that it provides us with a new pathway that we didn’t think existed for water to escape the Martian environment,” said Mehdi Benna, a Goddard planetary scientist and co-investigator of MAVEN’s NGIMS instrument.

“It will fundamentally change our estimates of how fast water is escaping today and how fast it escaped in the past.”