‘Smiley face’ spotted on the surface of Mars could hide an ancient secret about past life on the Red Planet

A ‘SMILEY face’-shaped salt deposit on Mars could be hiding traces of the last-surviving life on the Red Planet, new research suggests.

Mars was once home to sprawling lakes and rivers that evaporated around three billion years ago during a global freeze.

ESA/TGO/CaSSIS

ESA/TGO/CaSSIS

ESA/TGO/CaSSIS

But some very salty pools of water remained, due to their lower freeze point.

While these pools eventually evaporated, they left behind salt deposits that could be harbouring hardy microbes, a new study published in the journal Scientific Data suggests.

At the very least, they could reveal important information about Mars’ past climate and evolution.

“A cold era began when Mars lost its magnetic field and could no longer hold its own atmosphere, leading to water evaporating, freezing, or becoming trapped within the surface,” Valentin Bickel, a planetary scientist at the University of Bern in Switzerland who led the recent research, said in a statement.

“As the water disappeared over time, it left mineral fingerprints on the surface.”

Bickel, and his colleagues explained that people on Earth use a similar method, leaving saltwater pools to dry in the sun, to produce salt for food.

“Very salty waters could have become a haven for life, a beacon for habitable places on Mars,” they added.

“High concentrations of salt allow water to remain liquid at temperatures as low as minus 40 degrees Celsius.”

The ExoMars Trace Gas Orbiter, a Martian satellite from the European Space Agency, captured infrared images of the previously unknown salt deposits.

The salt – referred to as chloride by the researchers – takes on a purple tinge in the infrared-colour image.

“The chloride deposits in the picture above and its direct relation to liquid water make areas such as Terra Sirenum good targets for future robotic missions searching for signs of life,” the researchers continued.

“Chloride-bearing terrain does not stand out in regular black-and-white images but shows up as a distinct purple hue in color-infrared images, making CaSSIS a unique tool to study the distribution of salts across Mars.”

Our paper includes never-seen-before data that helps us better understand the distribution of water in Mars’ distant past.

Valentin Bickel, lead researcher and his colleagues

These salt deposits had been missed in previous research, the team claims.

“Our paper includes never-seen-before data that helps us better understand the distribution of water in Mars’ distant past,” they said.

“The spacecraft is not only returning spectacular images, but also providing the best inventory of atmospheric gases and mapping the planet’s surface for water-rich locations.

“Understanding the history of water on Mars and whether it once allowed life to flourish is at the heart of ESA’s ExoMars missions.”

ESA/TGO/CaSSIS

All you need to know about planets in our solar system

Our solar system is made up of nine planets with Earth the third closest to the Sun. But each planet has its own quirks, so find out more about them all...

• How old is Earth ? Plus other facts on our planet
• How many moons does Mercury have?
• What colour is Venus ?
• How far away is Mars to Earth? And other facts on the red planet
• How big is Jupiter ?
• How many moons does Saturn have?
• Does Uranus have rings?
• How many moons does Neptune have?
• How big is Pluto ?
• How hot is the Sun ?