Accessing buried water on Mars might be challenging
Mars may not be as dry as it appears. Billions of years ago, its surface was covered with oceans and rivers of liquid water, but now all that remains seems to be a barren, dusty landscape. Yet, as we've explored the planet using orbiters, landers, rovers, and even telescopes from Earth, evidence of water continues to emerge, according to the New Scientist. Each discovery excites researchers due to the vital role water plays in supporting life and its potential usefulness for future missions.
Water has now been found across Mars in various forms- here are five locations where it has been detected.
Buried Underground
Just beneath Mars's dry surface lies a hidden treasure of water ice. Layers of dust insulate these ice deposits, but erosion and meteorite impacts can expose them, making them visible to our orbiters. Using data from the Mars Express orbiter, one recently identified ice deposit is believed to contain enough water to cover the entire surface of Mars with an ocean 1.5 to 2.7 meters deep.
But it's not just ice buried beneath Mars's shifting sands. The idea of a massive lake beneath the planet's south pole has sparked controversy suggesting it could be wet silt or volcanic rock instead. A new study using data from the InSight lander has pointed to another potential water reservoir near the planet's equator. InSight detected this water buried 11.5 to 20 kilometres underground by measuring how seismic waves from marsquakes travelled through the rocks, revealing that the stones might be saturated with water.
Frosting Over the Poles
Accessing buried water on Mars might be challenging, so perhaps a more accessible water source for future explorers lies right on the surface. Mars has polar ice caps similar to Earth's, known for decades, and many craters also harbour smaller ice sheets within them. These are the only areas on Mars where it remains cold enough for ice to persist.
However, some temporary frost forms at high latitudes, where the air is colder and more humid. On particularly chilly Martian mornings, volcanic peaks also frost over, likely due to water vapour freezing out of the atmosphere.
Floating in the Atmosphere
Due to Mars's extremely cold and thin atmosphere, any surface liquid water would quickly sublimate, turning into gas and drifting into the air. Water vapour in the atmosphere is a sign of water and ice moving across the planet's surface to form frost, though it exists only in tiny amounts. Occasionally, enough water vapour gathers in one area to create a few thin clouds, but overall, it is nearly negligible.
Running Downhill
One of the most debated potential signs of water on Mars is recurring slope lineae-dark streaks that appear periodically running down the sloped edges of craters. First discovered in 2011, these streaks have sparked lively debate about their origin. They mainly occur during the warmest times of the year, leading to speculation that they might result from ice melting and flowing downhill before evaporating, possibly making them the only liquid water ever observed on Mars's surface. However, they might also be simple sand flows. Over time, the sand flow theory has gained traction, but some researchers still hope there might be a trickle of liquid water on Mars.
Trapped in Rocks
If Mars was once covered in water and now has mostly dust, stone, and some ice left, where did all that water go? One possible answer is that it was absorbed into the rocks themselves. Mars rovers have discovered plenty of minerals with water molecules incorporated into their chemical structures across the planet.
This process is irreversible, meaning there's no way to extract all that water, but understanding where it went is key to understanding what Mars was like before it dried out. This knowledge might be our best chance to determine if Mars was ever truly hospitable to life.