How important is the presence of liquid water?
It is now widely believed that Mars contains a fairly large amount of water.
However, the surface of the planet is so cold that this water only exists as ice.
In order for life to exist on a planet, many scientists believe it is essential for the world to possess liquid water.
Ever since technology has enabled humanity to look at Mars in detail, humans have been looking for clues that there was water on the red planet.
Did water used to flow on the surface of Mars?
The Mariner 9 mission revealed evidence of water erosion in riverbeds and canyons, as well as evidence of weather fronts and fog on Mars in 1971.
Later missions from the Viking orbiters, first launched in 1975, revealed even more details about how water flowed on the surface and jutted out valleys.
Several studies have examined the presence of liquid water for decades. In 2000, the first evidence of liquid water on Mars was discovered.
It was claimed that the gullies seen on the surface of the planet must have been formed by flowing water.
Scientists cited the debris and mud deposits left behind as evidence of moving water existing at some point in the red planet’s history.
However, the formation of these gullies has been hotly debated in subsequent years.
Evidence of Ice in Geological Samples from Mars
Spirit and Opportunity, the twin robbers, found evidence of water trapped in a rock in 2007 when one of Spirit’s wheels broke and smashed into a chunk of rock.
Analysis of the silica-rich layer discovered in the scratch suggested that it was formed in the presence of liquid water.
In 2008, the Phoenix lander collected geological samples and they disappeared after a few days.
Scientists thought these were pieces of ice. This assessment was confirmed when the lander later discovered water vapor in a sample.
In 2012, Curiosity roamed an ancient Martian seafloor when it examined some rocks exposed to liquid water billions of years ago.
In 2012, Curiosity (pictured) meandered over an ancient Martian seafloor as it explored some rocks exposed to liquid water billions of years ago
Recurring slope lines and debate cause it
Features known as recurrent slope lineae (RSL) were first identified in 2011.
These dark streaks populate the areas of Mars with a sharp slope.
Researchers speculated that these may have been caused by the intermittent flow of liquid water along steep banks on the planet.
In June 2013, Curiosity found strong evidence that water once flowed on Mars that was good enough to drink. In September of the same year, the first shovel of soil analyzed by Curiosity revealed that fine materials on the planet’s surface contained two percent by weight of water.
In 2015, NASA claimed to have discovered the first evidence of liquid water on Mars in the present day.
The space agency said its Mars Reconnaissance Orbiter (MRO) provided the strongest evidence yet that liquid water flows intermittently on present-day Mars.
In 2017, NASA issued another statement reprimanding the initial findings.
Features known as recurrent slope lines (RSL) were first identified in 2011 (pictured). These dark streaks populate the areas of Mars with a sharp slope. Researchers speculated that these may have been caused by the intermittent flow of liquid water
It said the dark features running down steep slopes on the red planet were actually granular streams, where grains of sand and dust slide down to create dark streaks, rather than the ground being obscured by seeping water.
Images from the MRO revealed that the streaks only exist on slopes steep enough for dry grains to descend as they do on faces of active dunes.
Also in 2017, scientists provided the best estimates for water on Mars, claiming that it once had more liquid H2O than the Arctic Ocean — and the planet has preserved these oceans for more than 1.5 billion years.
The findings suggest there was enough time and water for life to thrive on Mars, but over the past 3.7 billion years, the red planet has lost 87 percent of its water, leaving its surface bare and dry.
An underground lake
In a study published in the journal Science, ESO researchers have now found the first concrete evidence of liquid water on Mars.
Using radar images from the Mars Express probe, the ESO team has found a 12-mile underground lake filled with liquid water.