China’s Mars rover discovers evidence of liquid water on the Red Planet

With an Earth-like climate and an ocean flowing across its surface, Mars was once a very different place to the dry, barren world it is today.

What has remained a mystery, however, is where all this water went, with scientists believing most of it likely became trapped in the planet’s outer layer, or crust.

This led to the widespread belief that it currently only exists in solid form in rocks and as a gas in water vapour, but an exciting new discovery suggests there is also a liquid variation, too.

The breakthrough is important because it could provide the key ingredients to give rise to extraterrestrial life today.

China’s Zhurong rover, which landed on the Red Planet in 2021, detected evidence of this liquid water on sand dunes at low latitudes, i.e. towards the equator and away from its poles.

Arrival: Beijing’s Zhurong rover (pictured) travelled to Mars in an uncrewed Tianwen-1 spacecraft. It then descended from the craft to touch the Martian surface on May 22, 2021

Scientists say the liquid water forms when salts in the dunes cause frost to melt at low temperatures.

However, it is likely to remain in this state for only a short length of time, as Mars is too cold for water to stay liquid on the surface.

Last year an international team of researchers suggested that liquid water may exist beneath Mars’ south polar ice cap, while in 2009 it was detected on a leg of the Mars Phoenix Lander in the planet’s arctic region.

Scientists analysing that discovery said that based on the temperature of the leg and the presence of large amounts of ‘perchlorate’ salts detected in the soil, they believed the droplets were most likely salty liquid water and mud that splashed on the spacecraft when it touched down. 

However, this new study is the first observational evidence of liquid water at low latitudes rather than high latitudes.

The reason this is key is because surface temperatures are relatively warmer nearer the equator, meaning conditions are more suitable for life than those closer to the planet’s poles.

‘This is important for understanding the evolutionary history of the Martian climate, looking for a habitable environment, and providing key clues for the future search for life,’ said Professor QIN Xiaoguang, of the Chinese Academy of Sciences (CAS), who led the research.

He and his team used data obtained by the Zhurong rover’s Navigation and Terrain Camera (NaTeCam), Multispectral Camera (MSCam), and its Mars Surface Composition Detector (MarSCoDe).

This allowed them to study the surface features and material compositions of dunes in the rover’s landing area.

Chinese officials are using the rover, named after the Chinese god of fire, to analyse Martian soil and atmosphere, capture images, chart maps and look for water and signs of ancient life

The Utopia Planitia basin where it was searching is a key target for exploration. However we have not received any new ground-based data from this region for 45 years. The Viking-2 lander touched down touched down in the crater on September 3 1976 and performed soil analysis, took images and searched for signs of life. Pictured: Utopia Planitia basin as seen by the Viking-2 spacecraft

Their analysis revealed that the surface layer of the dune was rich in hydrated sulfates, hydrated silica, iron oxide minerals and possibly chlorides.

‘According to the measured meteorological data by Zhurong and other Mars rovers, we inferred that these dune surface characteristics were related to the involvement of liquid saline water formed by the subsequent melting of frost/snow falling on the salt-containing dune surfaces when cooling occurs,’ said Professor QIN.

The researchers proposed a scenario for how this liquid water comes about.

Unlike Earth, the obliquity (or tilt) of Mars changes substantially on timescales of hundreds of thousands to millions of years.

At today’s 25-degree tilt on Mars’ rotational axis, ice is present in relatively modest quantities at the north and south poles.

However, research has shown that ice builds up near the equator when Mars is tilting more, while the poles grow larger at very low obliquities.

The authors of the new study theorise that low latitudes cool during the Red Planet’s large obliquity, like it is currently, which leads to frost and snow that solidifies dunes and leaves traces of saline water.

That’s despite very low pressure and water vapour content making it difficult for liquid water to sustainably exist on the planet today.

It is for this reason that experts had believed that water could only exist in solid or gaseous forms.

Until now, no evidence had shown the presence of liquid water at low latitudes on Mars, which is why the breakthrough is potentially exciting.

It suggests there are certain conditions where liquid water can emerge in some parts of present-day Mars.

Of course, past studies have already shown that the Red Planet could have held enough water to cover its entire surface in a layer measuring between 330ft (100m) and half a mile (1km) deep.

This was more than four billion years ago, when Mars was warmer and wetter and possibly had a thicker atmosphere.

However, when this disappeared the planet’s climate changed dramatically and gave rise to a world hostile to life, which we see today.

The new discovery will add hope to the work of NASA’s Perseverance rover, which is currently searching an ancient crater lake for signs of past life.

It is collecting samples which are due to be returned to Earth for analysis in the 2030s.

The new study has been published in Science Advances.

TIMELINE OF CHINESE SPACE MILESTONES

The Shenzhou-12 spacecraft is launched from the Jiuquan Satellite Launch Center on June 17, 2021 in Jiuquan, Gansu Province of China, carried on the Long March-2F rocket, to Chinese Tiangong space station

July 19, 1964: China took its first official step into space, launching and recovering an experimental biological rocket carrying white mice.

April 24, 1970: The first Chinese satellite, Dong Fang Hong 1, was launched from the Jiuquan launch centre in the northwestern province of Gansu. That made China the fifth country to send satellites into orbit, following the Soviet Union, the United States, France and Japan.

Nov. 26, 1975: China launched its first recoverable satellite.

Nov. 20, 1999: China launched its first unmanned spacecraft, the Shenzhou-1.

Oct. 15, 2003: China became the third country after the United States and Russia to send a man into space with its own rocket. Astronaut Yang Liwei spent about 21 hours in space aboard the Shenzhou-5 spacecraft.

Oct. 12, 2005: China sent two men on a five-day flight on its Shenzhou-6 spacecraft.

Nov. 5, 2007: China’s first lunar orbiter, Chang’e-1, entered the moon’s orbit 12 days after takeoff.

Sept. 25, 2008: China’s third manned spacecraft, Shenzhou-7, was launched into space, where an astronaut clambered out of the spacecraft for the nation’s first space walk.

Oct. 1, 2010: China’s second lunar exploration probe blasted off from a remote corner of the southwestern province of Sichuan.

Sept. 29, 2011: The Tiangong-1, or ‘Heavenly Palace 1’, China’s first space lab, was launched to carry out docking and orbiting experiments.

Nov. 3, 2011: China carried out its first docking exercise between two unmanned spacecraft, the Shenzhou-8 spacecraft and Tiangong-1 module, a key test to securing a long-term manned presence in space.

Dec. 14, 2013: China landed an unmanned spacecraft on the moon in the first ‘soft-landing’ since 1976, joining the United States and the former Soviet Union in accomplishing the feat.

Sept. 15, 2016:China launched its second experimental space laboratory, the Tiangong-2, part of a broader plan to have a permanent manned space station in service around 2022.

Jan. 3, 2019: The Chang’e-4 lunar probe, launched in December, touched down on the far side of the moon. Previous spacecraft have flown over the far side but not landed on it.

June 23, 2020: China put into orbit its final Beidou satellite, completing a navigation network years in the making and setting the stage to challenge the U.S.-owned Global Positioning System (GPS).

July 23, 2020: China launched an unmanned probe to Mars in its first independent mission to another planet.

Nov. 24, 2020: China launched an uncrewed mission, the Chang’e-5, with the aim of collecting lunar material to help scientists learn more about the moon’s origins.

Dec. 1, 2020: China landed the Chang’e-5 probe on the moon’s surface.

April 29, 2021: China launched Tianhe, the first and largest of three modules of its upcoming space station.

May 15, 2021: China became the second country after the United States to land a robotic rover on the surface of Mars.

June 17, 2021: China launched the crewed Shenzhou-12 spacecraft to dock with Tianhe.

October 15, 2021: China launched the crewed Shenzhou-13 spacecraft to dock with the country’s new Tiangong space station.

June 5, 2022: China launched the crewed Shenzhou-14 spacecraft to dock with Tiangong.