Liquid water discovered on Mars

One of the key building blocks of life—water—has been detected on the red planet.

An underwater lake extending 20 kilometres is believed to be underneath the south polar ice cap on Mars.

The discovery was made with radar data collected by Mars Express using radar signals that travelled through underground layers of ice to find evidence of a pond.

The European Space Agency launched the mission in 2003 to orbit Mars  with the assistance of various national agencies, industry, and the scientific community.

"Twenty-nine dedicated observations were made between 2012 and 2015 in the Planum Australe region at the south pole using the Mars Advanced Radar for Subsurface and Ionosphere Sounding instrument, MARSIS," the ESA states on its website. "A new mode of operations established in this period enabled a higher quality of data to be retrieved than earlier in the mission."

There was already evidence of a "watery past" on Mars on its surface. This came "in the form of vast dried-out river valley networks and gigantic outflow channels clearly imaged by orbiting spacecraft".

"Orbiters, together with landers and rovers exploring the martian surface, also discovered minerals that can only form in the presence of liquid water."

The climate of Mars has changed over its 4.6-billion year history, which means that surface water can no longer exist there.

"The presence of liquid water at the base of the polar ice caps has long been suspected; after all, from studies on Earth, it is well known that the melting point of water decreases under the pressure of an overlying glacier," the ESA notes. "Moreover, the presence of salts on Mars could further reduce the melting point of water and keep the water liquid even at below-freezing temperatures."