Scientists have a new theory explaining liquid water on Mars

The Martian Riviera was once a lush place of limpid lakes and mighty rivers — a much more, so the theory goes, hospitable planet. But here’s the problem: Mars is very cold, too cold for liquid surface water. So how to square the mounting evidence there was liquid water on Mars and the less than ideal conditions for that to even be possible? Geophysicist Edwin Kite has a theory.

Kite is an assistant professor of Geophysical Science at the University of Chicago. He’s been pondering what — in addition to carbon dioxide — might warm Mars enough to keep the water flowing.

Mars receives 44 percent of the sunlight that beams down on Earth. But in the past, Kite and his team believe, Mars not only had liquid water but a different climate entirely.

INVERSE is counting down the 20 science discoveries that made us say “WTF” in 2021. This is #11. See the full list here.

The discovery — A study they published earlier this year in the journal Proceedings of the National Academy of Sciences reconstructs the Red Planet’s early history. Using data from the Mars Reconnaissance Orbiter to look back into the planet’s history, Kite and his colleagues propose clouds once warmed the planet just enough to sustain patches of liquid water at the surface.

Why it matters — The idea Mars once had water isn’t new. There’s plenty of evidence that water used to flow there — Perseverance Rover, for instance, is in the Jezero Crater, which scientists believe is actually a dried-up, ancient lakebed. But what’s less obvious is the conditions that allowed for liquid water. That matters because the answer could lead us to discover earlier conditions were suitable for life to thrive on Mars — confirming another grand theory about the Red Planet’s past.

How they did it — On Earth, low-lying clouds cool the Earth’s surface while high clouds warm the planet. The same is true for Mars — water-ice clouds grace its skies for much of the Martian year. Water-ice clouds are, as the name suggests, not warm, but in the planet’s early history, cloud cover may have been more substantial and could have provided significant greenhouse warming.

Kite and his team made a global climate model of Mars simulating the ancient greenhouse effect clouds would have generated on the planet. The model suggests temperatures would have been warm enough for surface water to exist, but it would have been in discrete areas, like ponds and lakes, rather than in huge seas, like on Earth.

“Our models produced a warm, arid climate, but only if the spatial distribution of surface water is quite patchy,” Kite explains.

What’s next — Mars is the planet most similar to Earth in our Solar System. Looking at the potential for liquid water on the Red Planet can tell us about the planet’s habitability, but it could tell us about Earth’s ancient history, too.

Part of the answer to these questions is to do with working out what happened to Mars’ atmosphere. In 2014, NASA sent the Mars Atmosphere and Volatile EvolutioN (MAVEN) mission to reconstruct Mars’ declining atmosphere. Rover data also helps paint a more holistic picture. Of particular interest is Jerezo Crater under the purview of the Perseverance rover.

Most recently, the European Space Agency announced new evidence for water hiding in the meter of soil beneath the Martian surface in a huge canyon called Candor Chaos — this water is thought to be trapped in minerals or ice grains, so not a flowing river, like the Colorado that flows through Earth’s Grand Canyon.

“We found a central part of Valles Marineris to be packed full of water — far more water than we expected,” co-author Alexey Malakhov, a researcher at the Space Research Institute of the Russian Academy of Sciences, says in a statement.

“This is very much like Earth’s permafrost regions, where water ice permanently persists under dry soil because of the constant low temperatures,” he explains.

INVERSE is counting down the 20 science discoveries that made us say “WTF” in 2021. This is #11. Read the original story here.