Once, Mars was a warm planet that could potentially support life and water on its surface. But something changed about 3.5 billion years ago and it lost most of its atmosphere.
Only a thin atmosphere exists today, allowing gases like water vapor to escape. And if water were to be on the surface now, it would instantly evaporate.
In the Martian upper atmosphere, sunlight breaks water molecules down into hydrogen and oxygen, which then pass from the thin atmosphere into space.
A new study published this week in the journal Science reveals that more water vapor is accumulating in the upper atmosphere of Mars, allowing more of it to escape into space. This means that Mars is losing water more quickly than anticipated.
Researchers used data from the Atmospheric Chemistry Suite on the ExoMars Trace Gas Orbiter, which is operated by the European Space Agency and Roscosmos, Russia’s space agency.
The accumulation of unprecedented amounts of water vapor is occurring about 50 miles up from the Martian surface. The orbiter revealed that parts of the atmosphere actually act like pockets, reaching supersaturated level. These pockets contain anywhere between 10 to a hundred times more water vapor than the atmospheric temperature should allow.
During the planet’s warmer seasons, the water vapor loss is even greater. Dust storms also occur during the warm seasons, contributing to the loss of water vapor.
The loss of water vapor, which likely contributed to the shift from a warm, wet planet to a cold desert billions of years ago, “controls the rate of the planet’s continued desiccation” according to the researchers.
Just below the surface
Overall, the majority of Mars’ water is locked up in its polar ice caps. Water vapor and clouds only represent a tiny fraction of the planet’s water.
And a recent study in the journal Geophysical Research Letters shows a map of water ice that could be just an inch beneath the dusty surface.
Data from NASA’s Mars Reconnaissance Orbiter and the Mars Odyssey Orbiter have also been able to detect the signature of water ice beneath the surface.
“You wouldn’t need a backhoe to dig up this ice. You could use a shovel,” said Sylvain Piqueux, study author at NASA’s Jet Propulsion Laboratory. “We’re continuing to collect data on buried ice on Mars, zeroing in on the best places for astronauts to land.”
Water exists on Mars in the form of ice beneath the surface, both at the poles and the planet’s mid-latitudes. The polar ice is the most well-known because the orbiters have imaged it. Meteors even helped increase understanding of the polar ice because they impact it, allowing the orbiter to take pictures of the disturbed ice.
NASA’s Phoenix Lander was even able to scrape and sample the polar ice to confirm that it was water ice in 2008.
In addition to the water ice they already knew about at the poles and equatorial region, the data also revealed areas where water ice may be just below the surface.
The new map reveals water ice less than a foot beneath the surface in a region of the northern hemisphere called Arcadia Planitia. There is also evidence of water ice two feet deep beneath the surface. The researchers want to learn more about the subsurface ice and if it varies across the Martian seasons.
“The more we look for near-surface ice, the more we find,” said Mars Reconnaissance Orbiter Deputy Project Scientist Leslie Tamppari. “Observing Mars with multiple spacecraft over the course of years continues to provide us with new ways of discovering this ice.”